Based on PMs I've received there seems to be some interest in DIY STM32 USB-I2S boards. Earlier I have published designs and software for I2S input board mainly for ADCs (https://www.diyaudio.com/community/threads/diy-adcs.419922/). So let's up the ante and do the same for I2S output board for DACs. Over the last few years I've made several board designs with STM32F7 and STM32H7 having both I2S output and input or I2S output/I2S input only. I believe the STM32H7 based design presented here is quite versatile and should work well with most DACs.




HW specs:

• STM32H723 running at 550MHz
• USB3343 USB HS PHY. USB connector is mini-B.
• 16-pin header for output
  • I2S with 4x SD (digitally isolated). All I2S signals are buffered and routed through same number of gates/buffers to maintain timings. Digital isolators are lowest jitter 6-channel isolators currently available.
  • I2C bus (digitally isolated)
  • 3 output GPIOs (digitally isolated). In addition unused SD lines can be used as output GPIOs as well.
  • Isolator power (3.3V)
• MMCX connectors for I2S and external clock.
• 6 GPIO pin header for jumper configuration or I/O.
• 2x audio clocks (size 2520/3225) with independent enable control. Clocks can be either 22M/24M or 45M/49M. I use NZ2520SDAs.
• External clock input (MMCX). Digitally isolated clock selector GPIO for external clock.
• 20-pin header with 2x SPI (for touch screens) and encoder interface for display/control.
• I2C bus for displays etc. (independent from output I2C)
• Battery for backup memory and RTC.
• 6-pin header for SWD
• 4 status LEDs
• Powered either from USB or external 5V supply
• Board size 75x50mm (without outer mounting holes)

Currently supported protocols:

• I2S
  • 2 channels up to 768kHz/32bits (with 45M/49M clocks)
  • 4 channels up to 384k/32
  • 8 channels up to 192k/32
• DSD up to DSD512 or DoP256. Native DSD only in Linux as no ASIO driver yet.
• TDM
  • TDM128 (4 channels) up to 384k/32
  • TDM256 (8 channels) up to 192k/32
  • TDM256x2 (16 channels) up to 96k/32
  • TDM256x4 (32 channels) up to 48k/32 (not tested).
• PCM
  • 2 channel single ended or differential up to 768k/32
  • 4 channels up to 384k/32
  • Format: 2's complement, offset binary, simultaneous (also 16fs)
  • Bit depths: 16, 18, 20, 24, 32.

Other:

• HID interface for configuration
• DFU interface for firmware upload.

What is missing:

• ASIO driver. I've read that a 3rd party "universal" open source ASIO driver may be available later this year.
• GUI for HID interface. I have used simpleHIDwrite (linkhttps://github.com/benbaker76/SimpleHIDWrite).

The board works "out-of-the-box" with stand-alone DACs. For DACs requiring I2C or GPIOs a "driver" can be implemented. Currently I have driver implementations for ES9038Q2M, ES9039Q2M, AK4490, AK4493, AK4499+AK4191.

Connection to DAC can be made either through the 16-pin header or using MMCX for I2S with separate wiring for I2C, GPIOs and isolator power. In my DACs I have "sandwiched" the USB-I2S board with DAC board as all my DAC boards have same format and connector placement.




With display/control board, power supply (e.g. SilentSwitcher) and headphone amp board it is possible to build a compact DIY USB DAC having versatile functionality and good performance. Even bettering commercial offerings.



Attached are the gerbers, schematic and BOM. BOM has Mouser part numbers except for the NZ2520SDAs which are available from Digikey. Board is quite challenging for hand soldering. Smallest resistors are 0402 size and some ICs are leadless. I have assembled lots of these boards but I have a reflow oven. If there is larger interest it would probably be easiest (and most economical) to organize a group buy and have the boards manufactured professionally.

For sofware development I recommend STM tools which are excellent and license-free. For uploading software to an empty MCU a ST-Link programmer is needed. Easiest is to use a STM32 Nucleo development board which are available for about 15 EUR in Mouser. After initial programming DFU interface can be used for software updates. I will not publish the software source code here but it is available directly from me. If interested send me PM. Sorry, not for vendors.

Hello Swap-Meet Community,


Many years ago I designed and built my own passive crossover pairing a RAAL ribbon tweeter with Scanspeak drivers (see my old thread: https://www.diyaudio.com/community/threads/passive-crossover-for-raal-and-scan-speak.227199/). Life intervened —but now I’m ready to dive back in and I’m looking to source the following parts or kits:

1. RAAL ribbon tweeter
   – Any SR1a / 140-15D models (new or gently used)
2. Scanspeak top-of-range drivers
   – Beryllium-dome tweeters (e.g. Illuminator series)
   – Revelator midranges / woofers
3. Accuton ceramic drivers
   – C-series tweeters or high-end ceramic woofers
4. Passive crossover boards or component kits
   – Specifically configured for RAAL + Scanspeak or RAAL + Accuton combinations
5. DIY crossover parts
   – Toroids, air-core inductors, film capacitors, resistors, PCBs—ideally matched to the above drivers

If you have any of the above sitting on your shelf, please PM me or if you have full speakers that would be nice too.

I’m not a big fan of digital and prefer distorted and noisy sound of vinyl to compressed sound. I was struggling with digital for 20 years and went through dozens of speakers and similar quantity of amps and at least half a dozen of preamps, CD players and similar quantity of DACs but once I switched back to vinyl I hardly change anything and I’m happy with my analog sound, indeed every time I listen to it I’m impressed.

I do like convenience of streaming music for background listening and have been using Tidal with iphone10+ Dragon Fly black. Dragon Fly does not measure well and does not sound well either so I decided to try some Chinese DACs that measure well and have some good reviews. So far I have tried Topping E50 III, E30II l and SMSL U1. I could not make E50 III working with iphone. E30 works partially as it does not work in DAC mode only and SMSL-U1 works without any issues. Both E30II and SMSL-U1 have a tendency to sound vety harsh with some music, Stan Getz Bossa nova for example sounds harsh almost like if I was playing MP3 file. If I play music loud my ears are literally bleeding. Also the sound is wide but flat (no 3D).

I know what a lot of people are going to say “ you get what you pay”. I will disagree as I’ve been involved with materials for RF communication for many years with China being the biggest market and saw the transformation of Shenzhen Fab over the years. First of all, Shenzhen is Mecca for electronics manufacturers when it comes to supply chain, talent and cost. Secondly the economy of scale of manufactures of Toppings and SMSLs and likes is totally different than the ones of Chords or others of high priced Western boutique manufacturers. Chinese internal audio market is humongous not only because of the population size but also because Chinese like music. If we add to it the market outside, Topping and SMSLs outsale Chords or similar Western DAC s buy the factor of 100s if not 1000s. Finaly the component base used in DACs is not expensive, at least don’t have to be. Therefore, I expect that if one factor in R&D and manufacturing costs, Chinese cost of DAC manufacturing will be 5-10 times cheaper. Hypothetically Chinese manufacturers can deliver very inexpensive digital products that will easily outperform Western ones. However, both SMSL U1 and E30 sound bad. Unfortunately the only product that I can compare to is Dragon Fly which is not a great product.

Does anybody has good luck with mid priced Chinese digital gear and had a chance to directly and properly (level and gear matching) compare to decent Western product?. Considering that my analog front end cost more than 10K I would not mind to spend some dough on the DAC but only if I can really hear the improvement. I’m considering used RME ADI-2 or Chord qutest, at least I can easily resell them if I don’t like but I suspect that there are must be some Chinese products that outperforms them at a fraction of cost.

By a timerelated fluke (no pun) I got stuck with 150 pcs of this wonderful transistor. As any symmetry ridden person knows it needs its sibling, one that I haven’t got.

My loss is your gain.

$2/pcs, min 50.

Shipping at cost.

R

I need to know if this is normal or not. When aligning the 737, things go fine until T5. T5 couples the mixer into the ceramic filters. I find adjusting it has almost no effect on the signal amplitude, even though I'm right down near the noise where I peaked everything else. Anybody done one of these or similar?

For sale is a Gainclone amp I built some years ago and hardly used. It's a little dusty but fully functional except it needs RCA jacks and binding posts. It could also use a better enclosure than the one you see in the picture. Uses the LM3875 chip. Asking $75 OBO including shipping to CONUS only.

I would like to have something that can increase (I already know how to decrease) the damping factor without adjusting the amplifier feedback, such as filtering, preamp, DSP algorithm, or similar... I have seen a DSP algorithm that can increase DP but don't have access to it. I would be grateful if someone could provide even a little information

Hi,
I have a salvaged EI transformer from old boombox. AC voltage details are as follows

• 235 AC input at primary
• There are three isolated secondary windings (0-5 v) (13/10.7 -0- 10.7/13 v) (40.7-0-40.7 v)
• The middle one has multiple voltage with common center tap
• I need approx 25-0-25 or any range between 20 to 30 v center taped for example 30-0-30 will also do.
• When I measure secondary voltage by connecting multimeter prongs to output shown in two cyan color dots I get 0-23.7 v

My questions are
1) Can I buck the transformer by using one of the isolated secondary winding of lower voltages (A or B) ?
2) What if I discard the center tap of winding B shown in middle (10.7/13 v ) and short two 10.7 v points to use as center tap ? See pic below ... What voltage I will be getting ?


thanks and regards.

A 12" woofer that I've never seen measured in the @Hificompass.com way (sine sweep, 20mm, low self noise, high SPL capable microphones)


Manufacturer page:
https://www.products-peerless.com/en/transducer/207
Here's one view:



If we change the view of the website, it can look like this:


Lesson 1:
Scale matters!

Here's the VituixCAD2 Enclosure simulation:



Here it is in my actual cabinet, a 1cu foot sealed cabinet with medium fiberglass filling. Note the close correlation at 100Hz, but slightly more output at 20Hz due to the fiberglass filling.

Here is the log chip / exponential sine sweep at 2.83V drive:



Lesson 2: VituixCAD2 Enclosure simulation is very close to practice!

Now at 8.95V (+10dB)




Now at 28.3V (+20dB)



Yes yes, you say. But how can we compare to other woofers?

We'll need to equalize for the same SPL, surely! Here it is at ~85dB, between 40Hz and 262Hz.



There is a low pass filter for an acoustic LR4 @380Hz, which is how it was used in my system, hence the drooping high end.

Here it is again, with harmonics shown: -20 to -100dB down between 40Hz and 262Hz:










What happens when one doesn't do their homework properly*, and decides to install two into a 100L cabinet?
Part 2: *as implemented during COVID-19:

Simulation:
Two 12" woofers in 100L with 2.83V (~2W into 4 ohm)
vs
One 10" little engine that could in 22L with 9V: (~10W into 8 ohm)




What the upper 2 lines show is a 8dB advantage for excursion limited maximum SPL for the pair of 12" woofers...
On the other hand, the two lines are almost superimposed- the 10” in 22L plays with virtually the same frequency response as the pair of 12" woofers in a 100L box, ut it needs more voltage/power to do so- 9V into 8 ohms (~10W) vs 2.83V into 4 ohms (~2W)

Here's the measurement comparison:



Lesson 3: this David vs Goliath battle to bend Hoffman's Iron Law is interesting to this author...

Conflict of Interest Disclaimer:
I hereby declare that I have no financial, personal, or professional conflicts of interest that could influence the content, opinions, or decisions expressed in this post. My views and statements are made without external influence.

Edit: April 29, 2025:
Standard twin vs Double reverse inverted

March 2025 marks the 20th anniversary of Mauro Penasa's "modest contribution to this forum" (his own words) - the "MyRef" composite LM3886 amplifier. I thought the anniversary is a good excuse to design a new board for the MyRef. It turned out pretty nice, so I'm sharing the results.

The MyRef remains one of the few published composite chipamp designs. I built my first MyRef back in 2011 - on Mauro's original board, with my own relay-based 96-step volume control - but I always wanted to build a better version.

Here it comes, mounted on a 2U (80mm) heatsink:


The board for one channel is 90x50mm, all through hole, with two layers. The schematic (see post #3 below) closely follows Mauro's original Rev.C. However, I took the liberty of adding regulators to the LM318's power supply; the two TO-220 regulators are visible in the photo above. The board includes neither raw power supply nor speaker DC protection, both of which I implemented separately.

The linearity is pretty nice for such a simple amplifier:

More spectra are attached to the post #14 below.

Also, while developing the above board, I designed another, for a simple non-inverting LM3886 based amplifier according to the datasheet schematic:

Mechanically, this board is identical to the other one. My objective was to test some ideas for board layout and routing, but this board also turned out quite nice in its own right. The schematic is attached to the post #15 below, measurements - to #16.

I have been looking around for a 15" driver for a new OB/dipole project. A driver that is not really a subwoofer with high Xmax but rather a pro audio driver with decent specs and good HF extension that could be used down to 70-80Hz. I found the SB Audience 15MWN700D, which was just released in mid-to-late 2024:
https://www.sbaudience.com/index.php/products/woofers/nero-15mwn700d/
This is a bit of a head scratcher for a pro audio driver. Qts is not low and Xmax is not all that high. I suppose it could be used in certain applications but it doesn't quite fit the mold in my mind. But it does have very low Le and uses a copper sleeve in the motor. It seems this driver has been designed more for clean performance than outright SPL, etc. and its passband extends up to almost 4kHz with only mild breakup. With its open basket it seems like a good prospect for OB use even if it is not designed or intended for that purpose.

I did some modeling about what I could expect if the driver were used in a small baffle as part of an OB system. As part of the modeling I included series impedance of 6.8mH + 4 Ohms to both flatten out the dipole response and reduce the distortion produced by the motor. With 200W input power and a modest baffle the system can produce over 110dB SPL from around 80Hz to 300Hz, which is perfect for my use. At this power level, the 15MWN700D will exceed Xmax below 55Hz without a HP crossover, however, I would use a subwoofer below 70-80Hz so the size of the main speakers remains modest. I typically cross over to a nude midrange driver around 300Hz and I am thinking of using the Satori MW19TX plus a large AMT tweeter to complete the system (I already own these drivers).

I have not seen any testing or measurements of this driver, but given the MFG description of the design I am optimistic.

I thought I would toss this thread into the wind in case others have been eyeing this new offering from SB Audience.

Hi all,
I got two of these kits off ebay http://www.ebay.com

It all came very well packaged, and everything was there, except for a cap, which was the wrong value (220/63v instead of 150/80v). No big deal, i changed them all to 220/80v just for the heck of it. The PCBs look very robust and very well made, they're thick and heavy, almost glass like! They are, alone, totally worth the money. The output transistors (KEC D1047/B817) don't inspire a lot of confidence, but they should be ok for domestic music.

I assembled the kits and hooked them up to a 33v-0-33v beefy power supply for some testing. Both kits seem to work ok, and they sound just fine. I tried a 4Ω/100w sub woofer, and it quickly reached it's xmax. The heatsinks got warm after 2 minutes, but not hot...

Now the problem is, despite the good sound, i can measure no bias current at the outputs. The heatsinks are cold as beer even after an hour of being turned on with no signal at the input. I used 10Ω power resistors at each rail, and i calculated an idle current of about 13-14mA per rail, per amp module. It seems very low😕.

With inputs shorted, the emitter resistors (0.15Ω) all measure dead zero mV (0.0). The voltage across R26(200Ω) is about 850mV. I think thats about half the optimal voltage to even begin conduction at the output transistors.

What baffles me, is that the amp sounds just right with no apparent output bias. Even the top end sounds smooth, no signs of being grainy or harsh at all. Is that normal?

Could it be that the rail voltage is rather low? The optimal voltage per rail, according to the designer, is around 65v. I will test again with the power supply which i intend to use permanently (57v rails). I hope the higher dc voltage will affect the, almost non existing, standing current.

Here is a (not very revealing) schematic i lifted from another thread. I haven't checked for errors, but it seems close enough.

By popular demand, here is a new thread devoted to PETTaLS flat panel speaker simulation software, developed by Dr. David Anderson. Flat panel speakers may also be referred to as bending wave speakers, or DML speakers.
Let's use this thread to discuss topics specific to the use of and improvement of this great new tool. Topics could include, but are not limited to:

• new release announcements
• questions about how to use it
• features you'd like to see
• possible bugs
• interpretation of results
• other....

The free version of the software is available here:

PETTaLSFree

Some videos about the software are here:

PETTaLS Videos

Eric

Is it feasible to make a voltage divider at the input of a tube amp by using the grid leak resistor and another resistor forming a voltage divider to reduce input signal voltage ?
A bandage I suppose for a preamp with a bit too much gain.

Hello.

I'm looking for the top midrange drivers for open baffle, to be used approx 400 to 3000 Hz in an active system.
I am now using B&C 8PE21 and considering Radian LM10n plannar. I like AMT tweeters - using Beyma TPL-150H open back now.

The Purifi 6.5" midrange looks appealing too, but haven't seen comments about them for OB.

What are the better OB mids out there, for this range?

Thanks in advance!

(I posted this on the AK forum, and so far nobody can give me a good answer, so a gold star to the one who can . . .)

So I'm thinking for my next tube amp build I would really like to do a little integrated 6AQ5 push-pull, so I was researching some of the greats, and apparently the Voice of Music 1404 integrated amplifier (581 console) really stands out as a super performer based upon many comments I have read.

I have a one page schematic, as well as a pdf copy of the SAMs posted below for the model 581 console, which used essentially the same chassis. It very clearly shows that the left and right output transformers are different- one has a primary impedance of 5700 ohms, the other is 7000 ohms. This is confirmed in the schematic, which indicates a different DCR for each primary (325 vs 340 ohms per side). These are not two "alternates" or an accident, this is a deliberate design choice to use a different load line (but same operating point) for left versus right.

Does anyone know why this would be done? I have never seen that before.




BTW I think the super cheap 6AQ5 (essentially a 6V6 in a 7-pin peanut) will be very fun to play with- guitar amps are using them like crazy but still seem to be quite overlooked in new audio builds.

Happy New Year !

to Papa - ( I don't wanna bug ya on personal e-mail ) :

I wish ya many more .....

to all spoiled kids - good Health ....... and mucho active brain cells in next year 😉


(I'm going now , and dunno when I'll be able to post again ; I have plans to drink good Rakija ..... without net )

Please bear with me. I do not have a strong grasp of the complex interactions of my audio equipment. I have never designed or built a new circuit from scratch.

I have been considering adding a tube output to my Philips CD880 for about 10 years now. I have spent a many, many hours trying to learn the technical requirements of I/V conversion and how to build a working tube output. Today, I ran across Regal's thread from 2011 https://www.diyaudio.com/community/threads/new-look-at-tube-analog-for-tda1541.194134/ and a light went on.

Why has everyone focused on building line level outputs instead of MC phono level outputs? I have never seen any discussion of a MC cartridge level output. My Ortofon Cadenza Black cartridge only has an output of 0.3mv and my CAT preamp and ARC D70 MkII have no problem driving my Martin Logan Sequel speakers to good volumes.

It seems to me that there would be more options to build a low level I/V conversion output that outputs 0.3V than 2.0V. What are the technical barriers to converting the TDA1541A's 0.4ma PP to 0.3mv and outputting that to the phono in of my preamp? Is there an insurmountable impedance mismatch problem between the chip and a preamps phono in? Even if I cannot eliminate the tube output, wouldn't I have more options for which tubes I use and which amplification cuirt I use if I am trying to build a phono level output?

I hope someone who has the knowledge will help me with this.

To answer various instigations from forum members in the polemic of 'does THD..' I re-open this subject by submitting samples of audio recorded through the ADC of the Emu0404 to try to hear any differences in the various outputs of :
1. Dac of computer
2. Dac Ak4396 through ecc88 tube of Broskie unbalancer
3. Through Ak4396 + 6BL7 8 Watt tube amp.
4. Through Ak4396 + SS JLH modified amplifier
5. Through computer + SS JLH modified amplifier

Everything will be done at optimal levels for fairness and quality, (amps same power, dacs same output voltage, ADC same gain)

As a continuation of work by Esa Merilainen and Pascal Brunet, as well as my previous work, an approach with a deeper feedback circuitry has been tested. The deeper feedback indeed lowers harmonic distortions by 20dB and more, including the most stubborn 3rd harmonic, in a somewhat unexpected (by me) way.

Introduction​

In the previous experiments, a degree of improvement was reported by applying series resistors 6/12/24 Ohms, which corresponds to the feedback depth of only 6…20dB. The results were promising but it was not clear what you would get with deeper feedback.

Method​

Measuring a driver impedance​

A few drivers from different vendors have been measured using Feeltech FY3200S-20M generator and Rigol DHO802 oscilloscope.



The driver impedance lump was modelled as Zeq = (L+RDC)||C||Rres:



Contrary to the statements of previous researchers, it was found that the p grade of Lp is neither 0.5 nor 0.55 but varies from driver to driver, from 0.6 to 1.0.

Feedback loop structure​

To start with, Dayton Audio SIG150-4 was used. An equivalent of 0.1*Zeq[SIG150] was used as a feedback discriminator, to get a voltage amplifier (LM3886, simplicity’s sake) with a gain in the range between 20 and 30dB. Of course, the feedback network cannot be universal. For SIG150-4:






A reasonable amount of RF care was taken. The amplifier is stable. Measurements were taken by an 12dBA AudioTechnika 4040(Or 2020?) cardiod condenser microphone calibrated by ECM8000 calibrated by AZ8930, at 0.5m from the cone, while being adjusted to 1m loudness (60..85 dB SPL), in a moderately damped living room (RT60 ~= 250ms for f>200Hz). In the signal processing, frequency resolution was traded off to benefit precision and dynamic range (i.e. the curves have been denoised). Dotted lines correspond to the resulting noise floor for the given harmonic and excitation levels. The curves are positioned on the originating frequency, i.e. they correspond to the frequency that produces the harmonic, rather than where it appears, and are properly normalized for the cone frequency response (FR).

Results​

Voltage Drive​

Current Drive​

Discussion​

For LM3886, the depth of feedback is higher due to GBP=200kHz (46 dB on 1kHz). Most decent DIY Class A/B amplifiers have GBP over 1MHz. The depth of feedback can be improved by using second-degree astatizm and/or nested feedback. It is not entirely clear how to implement the current drive with non-self-oscillating Class D amplifiers efficiently.

Note that an open-air inductor serves as an antenna and gets lots of interference, even after turning most of the switching PSUs in the vicinity off. In a real product, the inductor must be shielded.

If seen as necessary, the f<2Fs distortions can be dealt with by motion feedback. However, here the focus of the efforts is on the midrange drivers. Here, you do not need to worry about Fs lump.

90 dB @ 1m is as loud as SIG150 (sensitivity 91.1 dB @ 2.83V / 1m) can get without producing obnoxious distortions, both voltage and current drive. Sig150 is not capable of producing clean sound for f < 2*Fs, and multiple saturated resonances appear all the way through the passband, which is fairly typical for non-professional drivers.

The current sensing network is too sensitive to power and temperature variations. Thicker wire shall be used for the inductor and all resistors must be high-power rated. Satisfying the destruction limit is not sufficient distortion-wise.

It is not clear how far you can get with the current drive because you are limited by the cone distortions.

Conclusion​

More experiments with different drivers, both Fe and Nd, both chirp and music to follow. The effect on Barkhausen noise (non-repeatable-in-details discretization of non-linear de/re-magnetization distortions) is most interesting for magnets that are never fully saturated because of the back current of the magnetizer and some domains are easier to flip than others.

The drivers are implicitly optimized for voltage drive. The current-drive-optimized drivers may turn out to be quite different. It’s a terra incognita, for you to discover.

Waiting for the missing components to be shipped and delivered…

Copyright © Michael Zrull, 2024/09/19. All rights reserved. Released under GPL 3.0. I won't patent it nor restrict DIY by any means.

Hello all - I am new to this site, looks really great! I was granted a 20 year Utility Patent last year for my Folded Horn Acoustic Guitar. Patent # 10,777,172, can find on Google Patents of course. I have two five foot long folded horns inside an acoustic guitar. The horn is exponential and has a 1:8 ratio from throat to horn, with a speaker mounted to each compression chamber. This is long enough to capture the lowest frequency on an acoustic guitar at 1/4 wavelength. The true acoustic sound is a captured by a mic, not a pickup. Check it out and let me know what you think. CNC programming is complete, and will build a partial proto next week. Thanks!

Want to buy HYPEX NILAI.

My Toshiba XR-Z70 CD player lost the right channel and it turns out the DAC chip is faulty.
If anyone has it (yes it's a long shot because it's very old), I'd be happy to buy it.

Electronic Schema Power Amplifier LJM L20SE

Electronic schema and analysis

Schema: Amplif_L20SE.pdf - Google Drive

Project: Amplif_L20SE.ms14 - Google Drive

I am not marketing this product and I am not the author of the project. I did the schematic circuit for analyzing and sharing information.

This single rail power supply is an improvement over R21 power supply add-on module. It has an active rectifier, RF filter and super-regulator on a single compact PCB (120 x 70 mm). Performance is comparable to R21, except for the PSRR at high frequency, where this new supply maintains > 60 dB PSRR far into MHz range. It doesn’t have, for now, negative voltage counterpart.

It works, as is without any changes, from 10 to 60 V output voltage for a version without RF filter. Max. output voltage for a version with RF filter is 50V. Output current is up to 10 A (20 A short term), with dropout voltage of 0.15 V for 10 A load. Headroom voltage for 10 A load is 0.5V.

PSRR is greater than 110 dB @ 100/120 Hz and supply self noise is about 2 µV.



Measured performance:

• 110 dB PSRR @ 100/120 Hz at 0.3 V headroom and 2 A load
• 2 µV total noise @ 2 A DC load or 15 nV/rtHz noise density
• 0.002% load regulation @ ΔI = 5 A (< 0.5 mV output voltage change for the 5 A load increase at 25 V output)
• 0.00008 %/V line regulation @ ΔV = 30 V (< 0.5 mV output voltage change for the 30 V input voltage rise at 25 V output)
• 1.4 mΩ output impedance @ 20 kHz (including output PCB tracks resistance!)

PCB
1 oz copper is fine for dynamic loads up to 10A. For max performance and high current capability, 2 oz is better. All measurements were taken on 2 oz PCB version. Take a note that it may be cheaper to order 2 oz + ENIG finish PCB than just 2 oz and standard finish one, at least when JLCPCB is in question. It depends on other orders in the momentary queue, so you’ll have to check.

Parts
Worst shortages are behind us and I tried to reduce number of different semiconductors anyway. Everything is available but main heatsink is available in limited quantity. I may need to find another one soon.
C2 should be, depending on required voltage, biggest capacitance type that physically fits the PCB. Diameter up to 40 mm is OK. In the BOM, I’ve put the biggest available with 63 V rating.
For output voltages up to 30V, use at least 33.000 – 47.000 uF capacitors. Rule of thumb is that to have max.1 Vpp ripple at the voltage regulator input, we need 10.000 uF per every A of output current. As less input ripple is better, using large capacitors is better.

At 50-60 V output voltages, it would be good to replace R8 & R9 with 4K7 & 3K9 values, to avoid high dissipation and temperature.
More details about required changes at 50-60V output are at posts #245 and #246.
For output terminals, Fast-On connectors or terminal blocks with 5 mm, 5.04 mm or 6.3 mm pitch can be used.

Shared Mouser cart for one click order:
https://hr.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b48c6947bd

Building
Proposed assembling order from the R21 build guide still applies in general. Add parts by height order, starting with diodes. However, as there are several more SMD parts, best method would be to put all SMD components first, except opamp, and then proceed with TH components. All SMD components are situated on the PCB B side. Place opamp as last or after most TH components surrounding it, has been soldered.
Murata RF filter is part to be mandatory soldered by hand. Don’t try to use hot air tools! Upper cover will melt. How do I know? 🙂
Common Q7/Q8 heatsink is required only above 30V output. At 50-60 V output, you can attach token heatsinks to Q5 & Q6 as well.
I’ve build 3 samples for verification purpose, so everything should work reliably.

Start-up behavior
Contrary to the R21 module, which was designed to ignore any amount of capacitance downstream, this regulator is not designed with driving capacitors bank weighting 10 kg in mind. Though, any decoupling capacitance in powered circuits is fine. This enabled to have regulation from the start and output voltage has slow ramp-up or soft-start, reaching nominal output only after several seconds.

Transformer secondary voltage
There is little or no difference in required transformer AC voltage, compared to a regular CRC or CLC supply. Voltage regulator part can work with full performance at only a fraction of single V drop. However, there is mains voltage variation and reservoir capacitor ripple we have to account for. So, usual voltage drop across regulator should be 1 - 1.5 V. Active rectification provides some 1.5 V higher rectified voltage than a diode rectifier. If replacing a classic power supply with this one, you are good.
For new builds you can use transformer with 1 V more at the secondary.

EDIT
08/12/24 - Added shared Mouser cart for easy parts ordering
10/12/24 - project.zip replaced with a new one because of BOM correction (just one 1800 uF capacitor less)
20/12/24 - Shared Mouser cart and Excel BOM updated with correct C6 (220 uF/35V) part. 'Wrong' one can be used as well.
12/01/25 – BOM update with correct trimmer resistor that has inline pins. ‘Wrong’ one can be still used with little contacts bending. Used the opportunity to switch LT4320 for a lower priced one as well.
Do not use BOM inside the project zip file. Always use the latest date separate BOM or link to the shared Mouser cart.
https://hr.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b48c6947bd

11/02/25 - Recommended changes required for operation above 50V at posts #245 & #246

As the title suggests, I have a Victor Meldrew moment whenever I hear this appalling (and meaningless) phrase. It's just waffle. It was bad enough when its early perpetrator (David Coulthard) used it when commentating on F1; after all, something is needed to fill the time when nothing interesting is happening on-screen, but now I find the pretentious phrase appears when this computer boots.

So, is it the most irritating phrase ever, or are there other candidates? (Probably from the field of management-speak.)

Light fantastic​

“The P1 power amplifier requires a super clean high current power supply to turn the low voltage line level music signal into hundreds of watts of output power. To do this, Siltech designed the Apollo Light Drive. A super-strong AC-powered light source is used to drive a photo-electric cell, giving a totally noise-free, galvanically isolated DC output. This then drives the amplifier’s output stage, keeping it absolutely immune from mains-born distortion. The idea behind this is not new, but its execution in a high powered amplifier is extremely challenging. The result is ultra-clean, low distortion power – and lots of it.”

Has anyone tried DIYing this concept?



https://www.siltechcables.com/saga-amplifier-system/

Well, the tubes forum has a photo gallery, so how about one for full range speakers?

Shamefully, I have none of my own to post yet...

I've been working on a waveguide project where I would develop high performance waveguides for some popular tweeters, and than share the files for anyone to print or CNC as they are able. The discussion started here: 3D printed waveguides - Techtalk Speaker Building, Audio, Video Discussion Forum for more details. The short summary is starting with the SB26ADC and a 5" waveguide, I varied flare radius, phase shields, depths, etc. I've started to find some best practices (at least with this dome/horn combo) and all future guides will have elliptical mouths, and with and without phase shields. I then skipped to 8" designs to verify those best practices scale, so anything in between should be trivial to design and still have the expected performance. Tweeters that I'm currently designing for are: SBA SB26ADC, SBA SB19ST, Satori TW29RN, and Transducer Labs N26C-A.

To get some frame of reference, here measurements of the Kef Reference 5 prototype, and Revel Concerta2 (which I suspect also uses the SB26ADC):





Here is my "C" waveguide with SB26ADC, with and without phase shield:





Quite good results I think, better than Revel achieved with the same tweeter! Anyway, the reason I am posting now though this project is still in its infancy, is I've connected with a couple gentleman with the ability to model waveguides. This could speed things up considerably, as waveguide design is extremely iterative otherwise because 90% of the performance happens at the dome/throat interface and this is not easily modeled.

We've started with verifying that the sim can accurately predict reality. With as close a representation as possible of the dome here are the results:





Extremely encouraging! I'd like to do some additional verification - particularly of the 8" guides I've started working on - and then I hope to push the sims to the max, and start producing some really excellent guides for popular tweeters.

I would like to announce CamillaDSP, a general purpose tool for routing and filtering sound. It can be used for example for building crossovers for active speakers, or for performing room correction.

You can find the source code here: GitHub - HEnquist/camilladsp

The documentation for all published versions can be found here: CamillaDSP

There is a second repository for configuration help here: GitHub - HEnquist/camilladsp-config: Help for setting up CamillaDSP, example config files etc

Quick summary

• For Linux, macOS and Windows
• Written in Rust
• IIR filters (BiQuad)
• FIR filters (Convolution via FFT)
• Built-in sample rate converter
• Filters can be chained freely
• Flexible routing
• Alsa, PulseAudio, Wasapi, CoreAudio, File and stdio input/output
• Simple YAML configuration
• All calculations done with 64-bit floats

I have been using BruteFIR for crossovers for quite some time, but there were two main things I wanted to improve upon. Firstly BruteFIR only supports FIR filters, and I wanted the ability to also use BiQuad without having to make an overly complicated setup. Secondly when BruteFIR encounters a buffer underrun it always exits with a "broken pipe" error instead of just trying again. This can get somewhat annoying. I also thought that the BruteFIR configuration is unnessecarily complicated.
I have also been using the excellent tool EqualizerAPO that does all I want, but it's for Windows only.

When using Alsa for both input and output, CamillaDSP can work almost as a drop-in replacement for BruteFIR. I run a 2048 tap stereo 2-way crossover at 44.1kHz, and this consumes less than 2% of a single cpu core on my HTPC (dual core Intel Skylake).

To help with configuration CamillaDSP checks the configuration and tries to give helpful error messages when there is a problem. In addition there is a Python script to visualize the whole pipeline from a config file.

Sample output:


To try it, download a pre-built binary for your system from the "Releases" page:. Click "Assets" to view the available files.

Instead of using a pre-built binary it can also be built from source. The "Cargo" tool makes this very easy as it will download and compile all dependencies automatically. See more instructions in the README.

Hi all, a while ago I purchased a very lightly used set of, all Morel, ET 338, CAW 538 and CAW 938. My intention was and still hopefully is to pack these drivers into a nice 3 way speaker.

I have been learning VituixCAD but am a bit stumped with designing an enclosure for the CAW 938. I have a few questions about this regarding simulated SPL, Xmax and overall rules around these topics.

• • What SPL should these speakers be able to play up to, as in max db SPL for loud listening in a medium to large lounge at between 3-5m listening distance? Or if there is a standard for general high end home audio speaker I would be happy to aim for that.
  • In terms of woofer roll off at what point do you not need to worry about cone excursion, weather that's referencing the SPL roll off, the power dip at the impedance spike, cone force or velocity. I have looked around but cannot find any solid information on what is safe in terms of Xmax, everything from sealed enclosure to bass reflex and band pass all pass the rated Xmax of driver even at fairly low wattage, why is this not a big concern. What are some good rules or parameters to follow in terms of this while getting the desired SPL output.
  • I really want to do a nice job with these speaker as it will be the first I have designed myself and will be my daily drivers. Keeping this in mind they will be mainly used for music and watching movies. I would ideally like the qtc to be reasonably balance around 0.707 to avoid sloppiness or compression.
  • I have built and done some measurement on some test enclosures. The volumes and dimensions are listed below:
  • CAW 938: 320mm x 730mm x 436mm, built in 18mm OBS, the volume is 76.5L with a qtc around 0.71.
  • CAW 538: 260mm x 320mm x 210mm built with the same 18mm OBS, the volume is 10.5L giving a qtc of 0.5 to hopefully keep the mids nice and dynamic.
  • Finally, is the CAW 938 not suited for a low range woofer, my initial goal was anywhere from 500 to 250Hz down to the driver roll off with no HPF. If this does not seem viable I could definitely use it for a 2 way using it with a beyma compression driver.

Please correct me if I'm wrong with anything above. Please see some enclosure simulations below and also some nearfield measurements of the CAW 938 and 538 test enclosures, these measurements are also gated from memory.

Hopefully this data is enough to go on, let me know if not or you need any more info. All measurements in REW have 1/24th smoothing applied.

EDIT: Sorry I also forgot to add the nearfeild accuracy cut off's.

• CAW 938: 655Hz
• CAW 538: 1023Hz

I will also not these measurements where not measured at a specified power level, 1 watt for example, they are quick and dirty just to give an idea of what the drivers are doing. The 538 enclosure has been filled with polyfil but the 938 enclosure doesnt have any.

Thank you!

Hey all! I've been a lurker on these forums for some time now but decided to register. I recently built a vacuum tube amp from a kit and thought I would dust off my long-unused EE skills and try to build a solid state amp next. I am currently working on an F5M build to start with but after that I plan on building some kind of Aleph (I like the First Watt designs). Anyway, this seems like a nice community and I'm looking forward to posting my progress. Cheers!

This thread is for discussions about any of the chassis. For more information on this product, please see the product page below.

• Chassis Product Pages
• Original Announcement and Request for Feedback

Threads on diyAudio or elsewhere on the internet that show off what can be done with these chassis or give creative ideas:

• List of dimensions for all chassis in one PDF

I have this speaker that stopped working and put my Yamaha into protect mode . I took it apart once but couldn’t find a x over or anything??? It seems a cord got loose and i attached it to the wrong spot .

This thread is for people to discuss their builds, build issues, and parts for the DIY Class A/B "Wolverine" Power Amplifier.
The boards are currently available through group buy's when they are held.
@jjs is servicing the USA and Canada regions.
@stuartmp is servicing the other regions.

Main Thread:

Wolverine 57v & 64v Schematic:
Please see the attached PDF files. These schematic show.
The Wolverine IPS - V3.7 (1st Group Buy) & V3.8 (2nd Group Buy)
The Precision EF3 - Both

BOM and Build Guide documentation:
Currently only available to group buy members.
In time will all be posted publicly once the group buy members have had time to order parts.

YouTube Build Link

Google Photos - Wolverine Build Album

Review Attached by @fireanimal 30-06-22
Review Attached by @richbandit 05-08-23 or at post #2,493

Posts of Interest
#

There is also a distortion sweep plot of the Wolverine below with the values listed for 1K, 10K and 20K.
A big thank you to Andy for taking this measurement for us. 🙏

17-3-23
we finally have 20k distortion measurements.
0.000095% THD 80 watts 8 ohm load.
Thanks again Andy for providing these amazing results
More test results can be found at the end of the build guide.

-------------------------------------------------------------------------------------

Announcing the Wolverine 5th Group Buy - Pre Order Open Now!​

Register for the Wolverine 5th group buy

Does anyone have a simple schematic using just CE, CC which can output 15W @ 4 Ω load with efficiency >40% and the input resistance higher than 20k using ± 12V.
Thank you very much.

As the title states, this is a thread dedicated to dome midrange drivers, specifically any larger dome driver at least 50mm or 2" in diameter intended to be used in a 3 way or larger speaker design.

Being there isn't a good collection of data on this rather rare type of driver and its use, it would be nice to have it all in one thread. My goal was to give anyone interested in the successful design of a speaker using a dome midrange a solid starting place to gather or share the info necessary to design a new speaker or to modify an existing design to use them ie. xover, baffle modifications, etc.

If you have any specific or technical info (measurements, graphs, data, xover design, pictures, links etc) regarding your favorite dome midrange or a specific technical question, please feel free to share it in this thread.

Please keep your post to the point and avoid any strong subjective opinions. I was hoping this thread could accumulate as much relevant info as possible. Thanks in advance for any productive shared info.

Here is my latest build an Ultra Linear / Triode Mode KT66 / KT88/6550 . ( the AirTight M101 clone when KT88 / 6550 installed )

Output transformers used in the past projects are Hashimoto ,Tamura , Electra Print , Finemet , Amorphous , Grain Orientated Steel both EI and C cores M6, M4 and M3 often called HiB and Super HiB

After many builds including Single Ended 45 , 2a3 , 300B, PX4 , EL84 , EL509 and now launching into KT66 and KT88/6550 both Ultra Linear and Triode strapped .

My latest build was inspired by the now obsolete AirTight M101 Kitset Single Ended KT88 .

I saw a number of pictures on the net including under the Chassis and pretty much reverse engineered the circuit , quite a simple affair of 12AX7 plates strapped togeather and a KT88 biased with a 600ohm cathode resistor starting with the premise of a B+ rail of 400v DC .

It looked as though the 12AX7 input tube with plates / grids and cathodes strapped together was biased at about 1.3mA , I lifted mine to 2mA .

I first tried the Amplifier with a power transformer B+ 400v output and B+ 385v under load with a SE KT66 triode Plate 373V bias -43 V 63mA 470R Cathode Resistor and Ultral Linear at 70mA Plate 363v bias -27V 380 ohm Cathode R , always seems the tubes don't bias up exactly to publish data !!

The KT66 was first designed back in 1937 by MOV in the UK for Audio Used from its inception to work both in Kinkless Tetrode and Strapped in Triode from day one .

With the latest Muse Coils custom design for me a primary of 4.6K / 3.3K /2.25K / - 4 / 9 and 16 Ohms with %40 Ultra Linear tap for the 4.6K load 70mA max at 4.6K and 80mA at 3.3K / with UL tap

Model MinotauR OTSE - 060NHY-046 is the first Alexander had made of this model and very useful for experimenting with many tube types .
I also have a custom set of 4.3K 20 watt UL Single Ended transformers from https://www.thermioniclab.com/ and a new set of Tamura F915 with a UL tap which
I will also try in the Amplifier also ,the Tamura would be a much closer clone to the original AirTight M101 sound .

The Triode KT66 after the run in period was very pleasing indeed as MOV designed this tube in triode to emulate the highly regarded PX25 directly heated triode the British answer to the 300B .

In triode mode the sound had excellent transparency , full and extended bass and high frequencies , the midrange had all the qualities of a 2A3 but nearly twice the power at 5.8 watts .

The overall impression was excellent with Muse Coils transformer s( https://musecoils.com/?bot_test=1) , Single HiB cut C core with double coils similar design to Lundahl and the best Japanese Nogushi and the Tamura F2007 .

In Ultra Linear at 7.2 watts the KT66 exhibited more bass slam and high frequency dominance , the midrange was neutral but to match the 2A3 I will remove the Jupiter Copper Foil capacitor and replace with a Toshin DUCT Paper in Oil Vita Q capacitor from the Hifi Collective UK to get more of the AM101 original sound .

Next after this will be the GE KT88 / 6550 although labelled GE KT88 it looks certainly to be a 6550 which is a highly regarded NOS GE tube .

The 12AX7 I decided to use was a NOS Japanese Toshiba 12AD7 the very low noise closely matched version the the 12AX7 with very close matched plates suitable for strapping together .

All my signal wiring is point to point copper foil at present and resistors I have chosen are mainly Amtram AMRT carbon resistors and capacitors from mainly Vishay Sprague ATOM and a full bridge rectifier using HEXFREDs bypassed with 0.01 uf 1200v ceramic capacitors .
The LM317 has been replaced with wire wound resistors .

NOW are few pictures of the chassis and woodwork ( almost finished ) to be fitted and Muse Coil Transformer Plots 15Hz - 52Khz -1dB 1K driving impedance

I'm new here. I thought that some of you might be interested to know that while I love audio equipment and listening to great music, I am a professional musician...a violinist. I am the lead violin with the Fox Theater in St. Louis and I played in the Saint Louis Symphony Orchestra for 20 years. Very few of my colleagues have high quality systems and sit down to listen as I do. Perhaps performing is enough for them.

Adrian

So after 30+ years of sitting in the basement, I pulled my old equipment out to resurrect for my son's car. In a bonehead move while hooking up the 2150AM (Board Rev K) I somehow reversed the input voltage and released some of that magic smoke from the amp. I pulled the amp apart and found the Q50 MOSFET was smoked. I removed that Mosfet and applied power back to the amp. The power light turned on and all components were cool.

In the next bonehead move I decided to see if the amp would still function. I hooked up the input and a 12" to the left channel. Surprisingly the amp was working as it should even without this FET. As I was bragging to my son how they "just dont make em like they use to" something happened and I pulled the power lead. I again touched the power lead to the battery and the power light began blinking then just a bit more smoke came from the FET side of the amp. I removed all 10 FETs from the amp and most are shorted and the others dont seem to test correctly. I had the cover off the back so I am guessing they overheated without being pressed to the heatsink, and the fact it probably is also not intended to work with the missing Mosfet. 🙁

The original ones are labeled as PPI25N06 I cannot seem to find these anywhere. I ordered substitutes from Digikey that seem to be a replacement? FQP30N06FS-ND. Does anyone have any idea if these will work properly with this amp?

https://www.digikey.com/en/products...?s=N4IgTCBcDaIGIEUAKBmADAOTQNjgZQFoMAREAXQF8g

What are the chances anything else was blown during this show? I checked the output transistors, and they all seem to test good.

Thanks for your time! Justin

I have this cheap little class AB amplifier. I am getting a hiss through any speaker I connect it to. Both channels. I'm thinking bad transformer but I will run through my troubleshooting steps. It is HIGHLY likely it is a just a bad design and there is noise between signal and power on these boards, however, many have used this amplifier without this issue. BOTH channels hiss.

I do not have the schematic

Findings:

1. When it is whole and you power it up you can hear the power supply transformer hum. The soft start relays kick on once the caps are charged and then you start to hear the hiss. The sound from the transformer isn't that different from the sound through the speakers which is why this is suspect #1. The transformer makes no noise unless it is hooked up to one of the boards. I know class AB is always on and pulling some power even at rest so this makes sense.
2. The hiss seems less noisy with the 120V input ground disconnected which is strange. If you scratch the 120V input ground on the chassis you can hear the scratching come through the speakers. This seems to point to a grounding issue in the design. This ground only goes to the chassis. This is suspect #2
3. There is a 3 pin volume pot for each channel. If I spin the volume pot with my head up to the speaker I can hear the sound of the pot turning coming through the speaker. I do not know how to bypass a 3 lead volume pot. I have disconnected the pot from the boards which seems to default it to the lowest volume level. The hiss is still present.

Things I have tried:

1. Disconnecting the volume pot - no difference
2. Separating the boards and moving them far from the transformer - no difference
3. Attaching the incoming 120V ground straight to the chassis and then to the building's conduit. I know the buildings conduit is a good ground as we have had to test this for other things we have built in the shop.
4. I soaked the transformer in polyurethane. I was hoping to quiet the actual mechanical noise of the transfomer. This also did not help.
5. I took a pencil and started tapping all of the components while it was powered and I could hear the hiss. Touching the components had zero effect on the hiss. I was hoping it might have been a badly seated/soldered component but that does not seem to be the case.

I open to try any suggestions at all. I have hooked this up in both my shop and my house and I get the same noise. I don't think its DC on the AC line since I have another class A amplifier that uses a toroidal transformer and I hear zero hiss coming out of that one. That one is about half the power but it has abosolutely no hiss at all.

The transformer is outputting 12v as well as two 35V leads to the board. Right now I am thinking its the transformer. Could be a bad batch of these cheap filter caps. I really do not have enough experience with class AB amplifiers to give any type of informed guess. Thoughts?

I got lucky last weekend, & found a pair of KEF C40s on the side of the road. Someone had stuck a piece of veneered chipboard on the top of each, presumably so they could put a nice pot plant there, and they had obviously been stored somewhere damp, given the light coating of mould.

I didn’t want them in the workshop in this condition, so when I got home immediately wiped them down with vinegar to kill the mould (fortunately no moisture damage), cleaned them with detergent, and the hot day made it easy to remove the ‘pot plant stands’. I removed the components, and then attacked the sticky residue left on the vinyl with solvent.
The boxes ended up in usable condition, with some nicks & chips, and obligatory spatter of white paint droplets. There was a convenient date stamp inside showing them to be from Apr 1987. Someone must have told KEF to get stuffed, these were sealed and absolutely chocka with polyfill.

The components: the crossover were clean, although with 38 years under their belt it’s time for a recap of the five electrolytics. The woofers cleaned up nicely and are in good condition; the tweeter coatings were bad, almost completely gone from one, seriously cracked on the other.

The plan: take measurements, re-cap the x-over, and re-coat the tweeters, Re-assemble to see how speakers from the ‘Golden Age’ sound, keep them if I like them, otherwise flog them on Gumtree (I need more speakers like a hole in the head).

The plan is to use this thread to document my integration of a Zenductor 2 stereo pair into a Modushop Galaxy 1GX388 2U chassis.

Except for removal of the tall Mosfet heatsinks, relocation of the transistors to the chassis sidewalls and reuse of the speaker posts I tried to leave the Zenductor 2s unmodified, and make the assembly as modular as possible. DC power and RCA input connections are via connectorized jumper cables. A preamp mounted to the front panel can be optionally looped into the signal path via rear panel RCA input and output connectors. I integrated two digital bias current displays and a large illuminated push button power switch into the front panel.

Heatsinks and transistors after removal:

They look a bit sad, with their legs cut off. Will they ever run again? ;-)

The amps just fit with the jumper cable connections:




Transistors mounted on sidewalls (1.4 K/W heatsinks, tested in https://www.diyaudio.com/community/...galaxy-1gx388-2u-chassis.426972/#post-7997356):


A quick test to see whether the Mosfets survived:

The 3-digit display shows the bias current. All four transistors survived, and get warm, but not hot. Definitely an improvement over the original heatsinks.

A thermal image:


Lots of filing for the bias display cutouts:

It's been a while since I had to do 'precision filing'; maybe I'll fill the gap later.

Almost finished (except for the preamp connections):




With top cover:


Rear panel, still with empty holes for preamp connections:

Well done. Just like my name.
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Please I need music fidelity k550 service manual

I have the following phase splitter designed for a 12AU7.





What components would I need to change for it to use a 12AX7 so it can drive a quad of 6V6 in push pull parallel unless with feedback I can get a 1V input sensitivity for 25 watts out with the 12AU7?

The 6V6 has a max grid resistance of 100k when operated fixed bias so the load on each output of the phase inverter will be 50k unless it's ok to use a single 100k grid resistor for two 6V6 in parallel.

Trying to fix a broken amp I bought. The issue is intermittent, but it's happening with increasing frequency. On power up or after a few minutes, the power amp module for one of the two channels quickly gets extremely hot. Sometimes it's the channel 1 module, other times it's the channel 2, never both simultaneously; tried swapping the modules, but it didn't make a difference. I rarely keep it on for more than a few seconds once the problem starts, but that's enough to get it to where you can barely touch the heat sink. Sometimes powercycling the amp resolves the issue, other times not.

The bias on the module experiencing the thermal problems, as it is experiencing them, is all over the place, from 200 to 600mV! I didn't adjust it. On the occasions when powercycling gets the module to operate normally, the bias is a few mV, which is correct, per the specs.

Any suggestions for things to try, or how to narrow down the problem? Perhaps this is a common failure mode? Amp is '97 vintage.

I've tried disconnecting the input board from the main board, to no effect on the thermal issue. Measuring the input DC voltage on the main board fingers where the power modules plug in, it is +/- 61.3V when the amp is on and the power modules are disconnected. When they are connected and working properly, it is +/-59V. When the thermal problem starts, the voltage drops to +/-45V. That could just be because of the power draw of the power transistors.

Schematic attached.

I built a bridged F5m which I am calling the F5mX. It is pretty minimal for a bridged amp.

It is pretty much a F5m that is bridged plus a few little tricks. The most interesting thing is that it has CCS resistors on the OS stage. They are oriented on opposite rails on the opposing phases to hopefully break a little bit of symmetry and give us a little 2nd harmonic distortion.

The Schematics and the BOM are in the 2nd and 3rd post.

The power supply has the bridge rectifiers integrated in the board. You can see I snip the terminals after soldering. Keep in mind that snipping the terminals off is easier without the caps mounted. Snipping them off also makes it a bit easier to desolder the bridges if ever needed. The PSU has 70uF film caps bypassing the last stage of the CRC cap bank. The EL caps are 24x10,000uF 35v. Ground lift is on the board and connects through the standoff. there is also a Quasimodo Snubber circuit on the board which I recommend using. My transformer required a 7 ohm resistor for RS1 and RS2. A 8-10 ohm resistor would work as well.





The front end connects to the output stages with two 16 pin (2 rows of 8) female to female ribbon cables. I bought the ribbon cables and sockets from Amazon. I did have to shorten them as they are very long. It is not very difficult to do.

Each channel on the front end pulls it's power supply from the output stage via the ribbon cables. There is a single ground wire connecting to the PSU which you can see in the pic below. The front end mounts to the standoffs that the power supply mounts to the bottom panel with. So you have short standoffs under the PS, then tall standoffs going from the PS to the front end. I made the standoff holes on all the boards large enough to accomodate #6 thread so you can use either your typical metric standoffs or larger #6. The OS simply mounts by being soldered to the leads on the IRFP140/9240 mosfets. When you assemble the front end, it is good to reduce the resistance of the pots to their minimum setting. This will make it so that they are not biasing the output stage upon first startup. I used Dale resistors as there are so few, and they are convinient for troubleshooting so long as you are careful to face the value labels upwards.

There are spots for source resistors on the JFETs (the 10 ohms) but you can jump as you see in the photo below (between the JFETs). These are there to allow a bit of flexibility in the event that someone wants to experiment.










The front end takes one quad of J74/K170 Toshiba JFETs per channel. The outputs are two pairs of IRFP140/9140 (one pair per phase). However, there are spots for 4 pairs of output devices per channel so you can experiment. I used 0R36 source resistors and it behaved great. However feel free to use the standard 0R47. If you are only using the four mosfets per channel, feel free to skip the gate resistors just like on the regular F5m. There are spots for thermistors on the OS board to make the bias more agressive at a cold startup but I haven't tested this yet. It works just fine without them. As you can see, I have four of the 2.2k CCS resistors populated per phase. I like this amount but you can try more or less. I use ceramic insulators on the mosfets but feel free to use the stores insulators. They are great!



I have had it biased at about 50-60 watts of class and have tested it up to about 110 watts in class B. Assuming you are using a quad of outputs per channel, and have a 5u chassis, with your 0R47 source resistors, use the normal say .500v per mosfet and see how hot things get. If you use 0R36 resistors, you can set it to 0.380v accross a source resistor. Then lower or raise it accordingly. If you are using 4 pairs of mosfets per channel, drop the bias per device in half and tune for temperature.

The transformer that I am using is a 22vac 800va which is giving me around 26.5vdc rails. Antek gave me simple instructions on others ordering this same transformer.



The boards are set up for UMS spacing. The power supply board and the soft start board has the holes set to 10mm spacing so they should bolt right up to the preferated bottom plate that DIYaudio sells. One board set includes:

Front end board
two output supply boards
one power supply board
one soft start board



Okay, the sound. Well, the F5m is excellent! The F5mX is cleaner, more detailed, and can make more power... I have been enjoying it quite a bit. Due to the CCS, it is not steril. However, if you have a good tube source you really like, then that is just wonderful. I have a tube DAC which really plays well with this amp. The highs are very very detailed. In the highs, the F5mX is all telling. But overall still a bit relaxed like the F5m. The bass is fairly tight but doesn't make a point of itself. For me, what I appreciate is the interaction between the mids and highs. It has no problem commanding a large space with my 89dB sensitive floorstanders.

The boards are $45 a set. If you have a DIYaudio paid membership, you get a $5 discount! 🙂 I will have my first 10 sets in about a week.

Great album, has anyone else done the cryptic crossword which came with the original album cover, or rather, the newspaper?

I completed about 80% of it but some clues didn't make sense - which was probably intentional.

Geoff

Thought it best to consolidate the inquiries re the Elsinore Project into a single thread, so issues can be dealt here.

We are currently as of June 7th, 2024, up to page 298, click on this link.


March 1st, 2023. Elsinore Mk6 "ULD" Version. These are very expensive Purifi Audio "ULD" drivers.


There are three variations of the Elsinores:

The "MFC" uses arguably one of the best polycone drivers. Very high sensitivity.

The "NBAC" is the latest variation, uses the same driver but with black anodised aluminium cones. The "NBAC" requires a more powerful amplifier, roughly about double, but is still incredibly amplifier friendly, as all Elsinores are.

The "ULD" is the premium Elsinores, using extreme Purifi Audio drivers that are of the highest quality available. As high sensitivity as the "MFC" and around 20% more efficient. One manufacturer and friend has said that to manufacturer and sell the "ULD" would mean around $50.000 retail.

Nobody manufacturer make a speaker that measures anything like below:


This speaker looks like a resistor to the amplifier. As close as possible, above 25 Hertz, the amplifier will draw the same current at all frequencies. This makes the amplifier's output impedance largely cancelled out. These speaker can be driven by all amplifiers with an impedance from zero to infinity. They are also suitable for so-called current-drive which is becoming more common and has an increasing following. All Elsinore variations are suitable with amplifiers like Nelson Pass First Watt amplifier. This is the most amplifier friend speaker designer ever! Until somebody starts using this approach to speaker design.

This is the place to post known good spice models, and links to libraries, and/or library files. This should help to make good spice models more generally accessible to the membership. General discussion of modeling and measurement issues welcome.

1. The Motivation and Story Behind It​

As electronic engineer and audiophile, I've always dreamed of building an amplifier that would satisfy my own standards. This would not only test my professional knowledge but also be a way to combine my hobby with my work. Though the idea sounds wonderful, the reality was far from easy. Constant interruptions and delays kept pushing back this grand plan.

In truth, the delays weren't just because I was busy, but also because I was unsure of what kind of amplifier I wanted to DIY. Common designs on the market—whether tube, BJT, or MOSFET—didn't seem to be the answer I was looking for. After years of indecision, I finally made a choice in the summer of 2020: to build a no-feedback amplifier that would meet the standards of high-end amplifiers. When I made this decision, it even shocked me. As an electronics engineer, my instinct told me it was an almost impossible task. Despite countless thoughts of giving up, my competitive spirit kept bringing me back. I was too curious to know what a no-feedback amplifier would sound like. This question lingered in my mind for a long time. Out of curiosity, I asked ChatGPT, and here's the response I got (Oh, how I wish ChatGPT had been around back then):



Thus began my DIY journey, filled with challenges and joys, to experience the sound of a fully no-feedback amplifier.

Since Bell Labs engineer Harold S. Black introduced the concept of negative feedback in 1927, it quickly gained widespread application in audio amplifiers, achieving great success. For example, the Williamson feedback high-fidelity amplifier, released in 1947, used deep global feedback to significantly reduce distortion, extend frequency response, lower output impedance, and increase damping factor. These improvements made the Williamson amplifier the benchmark for high-fidelity sound systems at the time and a classic cherished by audiophiles today. Most modern amplifiers are still designed with appropriate feedback to improve measurable data.

However, humanity never lacks pioneers who dare to challenge conventions. Many engineers have been working to reduce the amount of feedback, hoping to achieve better sound through shallow feedback. Products from brands like First Watt, Pass Labs, and NAT Audio are successful examples of this approach. These amplifiers remove global feedback and only use local feedback to maintain performance, aiming to reduce the negative impact of global feedback on sound quality. Though their test data may not be perfect, they focus on sound performance and have been well-received in the market.

The success of these products greatly inspired me. I believe that following in the footsteps of earlier engineers can take me further. As an engineer, I value objective data, but as an audiophile, I also think subjective listening experience is crucial. After all, good test data doesn’t always guarantee good sound, and if the sound is pleasant, why worry about perfect data? The quality of an amplifier cannot be entirely defined by one set of parameters, at least not with today’s technology. Objective data gives engineers direction, but subjective listening remains the ultimate measure of an amplifier's quality.

So why did I ultimately choose to challenge myself with the “hell-level” difficulty of a no-feedback amplifier? There’s a small story here. I had a friend who was an audiophile. He once told me that he had listened to amplifiers without global feedback and found the sound more natural, lively, and impactful. He asked if I could build a fully no-feedback amplifier for him to try. At the time, I just smiled and didn’t give it much thought. But his words planted a seed in my mind, which eventually led me to make this decision and explore the mystery myself.

In fact, I wasn’t sure what a no-feedback amplifier would sound like either, or if it would really be as natural and lively as ChatGPT suggested. But debates in technology often have their complexities. Feedback indeed brings many benefits but can also introduce issues like transient intermodulation distortion and dynamic errors caused by feedback delay. Could these distortions negatively affect subjective listening? Perhaps building a no-feedback amplifier with excellent parameters is the best way to answer these questions.

This is the story and motivation behind my DIY no-feedback amplifier, as well as my views on audio technology and subjective evaluation. In the upcoming posts, I’ll share why I chose Class D as the main architecture, and the challenges and results I encountered during simulation, production, and debugging. This DIY journey took four years, and some details may have faded from memory, but I’ll try to consider readers of all backgrounds, using analogies and simplified technical details to help everyone understand. I hope my sharing will bring you some inspiration.

for a "multi-path" DAC - but will it really do 162 dB N when level is, say -44 dBfs?

I say: no.

I call bogus 😎

https://audioxpress.com/news/imersi...analog-converter-completes-32-bit-audio-chain

You?


PS: Practically this is of course the same as just shutting off the output signal at say -110 dBfs... if you have control of the current noise in the output stage...

//

When I decided last year to explore some Stax electrostatic headphones, I discovered that even their older-model headphone amps are jaw-droppingly expensive. So I got an SRD-7 Adaptor and converted it to power high- and normal-bias Stax 'phones. Unfortunately, the sound quality left much to be desired.

The good news is, it's most glaring problems are fairly easily addressed. I just completed these detailed mods for the SRD-7 adaptor:

Transforming the Stax SRD-7

Comments/questions welcome. (This is my first crack at creating web content of this ilk outside of a forum, so be gentle... 🙂 )

Edit July 28, 2023: here are the schematics, BOM, and info on the single rail SLB. https://www.diyaudio.com/community/...x-class-a-power-supply-gb.336479/post-5782376

Edit Jan 23, 2020: Connection diagram for single trafo and dual rail SLB with M2X amp
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit June 16, 2019: Error on Q5 orientation on Single Rail (SR) board. Please install Q5, BD139 with pin 1 to the square pad (as customary) but this will have front of part in contact with HS1. Ok to use smaller stamped aluminum finned heatsink here for back mounting. More info here:
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit June 12, 2019: in an effort to reduce my logistical overhead and efforts to pack and ship as track - I will be handling the GB2 via my Etsy shop. The SLB can be found here:
Smooth Like Buttah SLB Class A PSU | Etsy

I have been working on the development of a new power supply for Class A amps that really is quite a big leap forward from current designs used for so long. It utilizes an active bridge rectifier provided by the LT4320 and MOSFETs, followed by a precisely engineered CRC filter designed to match the load, and finally followed by a capacitance multiplier. The advantages that such a power supply will have include:

1. Almost no heat dissipation or loss through the rectifier
2. Improved voltage headroom since no 0.6v drop across the silicon rectifiers
3. Smoother inherent ripple from the rectifier since switching is active and time phased to occur at zero crossing
4. More compact since fewer and smaller bulk caps are needed
5. Lower overall cost since fewer large bulk caps are used (and we all know this is one of the most expensive parts of a Class A amp aside from the case)
6. Most importantly, improved performance relative to a traditional CRC supply with lower ripple and higher current capability.
7. The SLB provides a smooth and slower (1 second) ramp that may reduce speaker turn on thump. However, current in rush from the transformer being turned on is not prevented and a suitable soft start circuit such as the Soft as a Feather Pillow (SFP) SSR soft start can be used for a soft start.

You may say that the downside is that it’s more complicated - but for those of you going through the trouble of using 8 x MUR TO220 diodes with their requisite heatsink, insulator pad, bolt, screw, insulated bushing, snubber film cap, and tight spacing that makes assembly difficult - I am not so sure anymore.

Here is a photo of a single rail SLB portion of the amp (we integrated it as part of the amp for testing). You can see how small it is when using SMT variant of the active MOSFETs (mounted underside). Those are 15,000uF 50v bulk capacitors. Compare that to how usual Class A CRC or CRCRC supplies are using 22,000uF or 33,000uF caps. The large 3pin Molex connector allows us to place the cap Mx pass transistor anywhere we like and allows snappy assembly/disassembly from the chassis or heatsink:



Jhofland, Aksa, Vunce and myself have been working on a single rail prototype of this PSU which we are calling the SLB. The name says it all - Smooth Like Butter. Jhofland has been leading the layout and electrical design, Vunce and myself are doing the verification builds and testing of the performance and listening to the resulting music, and Aksa has been instrumental in providing insight and guidance, plus overal cap Mx topology design. It’s been a great collaboration and I feel that we have arrived at something really special and useful.

The design requirement was that it can flow 5 or more amps and have ripple in the single mV range (we are looking for about -60dB to -70dB ripple rejection) with a simple hookup of a secondaries from a power trafo. You then get clean mV ripple (sine like and not sawtooth) with a small adjustable output voltage range based on how much drop you want across the cap multiplier.

Regarding capacitance multipliers, we are testing 3 different topologies: Darlington, LTP differential (similar to the MrEvil design), and a new complementary feedback (CFP) pair with BJT’s. Work is on going but we are getting close to a downselect.

Here is the measured ripple (1.4mV rms) from the Darlington cap Mx with 4.35A load (37.5vdc output) with an 8ohm resistive load:


Under a real SE Class A amplifier load, the ripple is a bit higher at about 6mV rms with the Darlington topology, but still very respectable given a 4.35A current:


Our simulations show that the CFP topology should be even better. The LTP differential topology will be tested soon (tonight perhaps).

I thought it is now a good time to share the initial developments to get everyone ready for the SLB PSU. I hope that this compact little supply will be a useful new tool in your toolbox of Class A amps. It certainly provides some of the cleanest power Inhabe ever measured or heard.

Edit - here is layout:


Update May 5, 2019: Verification build test with 4.4A and 35.4v out and 3.1v drop gives about 1mVrms ripple with the SLB (with R17/18 replaced by jumper):


Here is the SLB vero build (v1):



Update May 6, 2019: Schematic and BOM of v2 (May 3, 2019) Production version of SLB here.. Pricing of SLB is $22.50ea (2mm thick FRP, 2oz Cu, ENIG finish, blue mask):


Edit May 6, 2019: Here is the SLB-SR (single rail version). BOM and Schematics here. Pricing on SLB-SR is $18ea (also 2mm thick FRP, 2oz Cu, ENIG finish, blue mask):


Edit May 9, 2019: Here is the pereformance of the SLB in single rail form as used on an actual SE Class A amp with 37.4v rail and 4A current. The top red trace is for a 10R value on R117 and bottom yellow one is 1.5R for R117:


Edit May 23. 2019: Production PCBs arrived.
Dual Rail


Single Rail


Edit June 5, 2019: Md_Stryker made a Mouser shopping vart/BOM for SLB v1.2 here. Please do not modify it - copy to your own project first!
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit Jan 23, 2020:
Connection Digram for a No-Hum M2X PSU with SLB and single trafo:


Connection Diagram for no-hum Alpha Nirvana:

* Disclaimer - Perform the following procedure at your own risk. Not responsible for damage to your own driver !!! *

I finally decided to take a chance at removing the mounting flange on one of my D7608-9200 dome mids. I'm documenting this so others can attempt the same. Again, please use caution doing this by yourself. This procedure is reversible if you're careful.

To start with, the flange is held onto the driver assembly with very tenacious contact adhesive. Do the following to pull the driver element away.

I started by grabbing the flange with the dome facing away from me, using two thumbs to push / bend the flang away from the magnet, little by little, opening the gap up. Once you start weakening the adhesive bond at the gap, working your way around the flange, you'll notice it starting to gradually separate, until the motor assembly can be completely pulled away by hand, holding onto it by the outer flange and motor / magnet assy edge. I dont recommend prying between the flange and inner edge, as this clamps the entire dome and motor together - you can damage the inner thin plastic ring which holds down and terminates the dome surround to the motor. Also watch the 3 clips on the side of the dome assy, which can break fairly easily when prying away the flange, especially at first as you start bending away the flange for the first time.

This whole process only took a few minutes to accomplish, but removing the left over adhesive was the hardest part, not having identified a suitable solvent to simply loosen and remove the glue. I ended up using some naphta (lighter fluid or BBQ charcoal starting fuel) to scrape away the bulk of the factory contact adhesive. This took about 30 minutes to do. DO NOT USE aromatic HC based solvents, as it will attack the plastic, which appears to be made from ABS.

If you're careful not to damage the flange upon removal, it can be reattached later on with some 3M weather strip adhesive or other contact cement.

Sorry for the lousy pictures.

- more D7608 info here to follow soon !

After reading about the AudioKinesis "Swarm" sub system and the Geddes paper on loudspeakers, I am fairly convinced that 3-4 randomly placed small subs are well worth trying in both 2-channel and HT rooms. Geddes specifically recommends multiple and different (not matching) subs to force more randomness (and I assume averaging) of room modes. The Swarms are matched drivers/cabinets.

My question is which small commercial subs would be appropriate for this theory? There are hundreds of small 8, 10, and 12 inch subs that are sealed, ported, etc. Has anyone tried this approach and can anyone recommend a combination of subs? I would like to use the smallest possible subs given the need for 3 or 4 or them in my room.

This amazing little amp has been discussed as part of the DB thread but I think it deserves its own thread given how it has quite different objectives from the Pocket Diamond Buffer (PDB) HPA.

This desktop variant uses TO-126 output BJTs with dedicated heatsinks and does not have the separate MOSFET rail switching needed for the pocket one. The setpoints have been optimized for a moderate 40mA nominal bias current that will let you run in full Class A operation for most headphone uses. It will leave Class A around 250mW into 32 ohms. Of course, you can adjust the emitter resistors to run higher bias currents. I have used it with +/-9v, +/-12v, +/-15v and +/-18v supplies and they all work great. It was designed for 15v rails but I don’t think performance suffers much from using lower voltage. For your particular use case you may want more voltage. High impedance 300ohm cans like more voltage, for example. There is lots of room for input cap rolling and I have used huge 4.7uF 400v MKPs and also smaller 0.47uF film to bypass 10uF Elna Silmic electrolytic caps.

Here’s a photo of a built up amp board in operation:

With larger MKP caps only:


I initially struggled with an oscillation but chased it down to a feedback compensation cap that was too large. That’s all fixed now rock solid. A stability analysis on LtSpice pointed me in the right direction. So the schematic shows a 470pF cap needing to be replaced with 47pF. It’s an easy swap and I’ll do this on the SMT pre populated boards that I will be offering in my shop. I will also have bare PCBs for those wanting to assemble it themselves.

Here is schematic for the overall amp, very simple. Power supply in, audio in, audio out and volume pot with MicroMatch IDC cable to an RK09 pot helper PCB (included).


Here is schematic of the Diamond output stage:


Here is a SMT prepopulated PCB so all you need to do is to install all the through hole parts:

Both sides:

Here is the board assembled with big 4.7uF MKP caps:


Standard BOM calls for ECB pinout TO-126 BJTs (Toshiba TTA004 and TTC004) but if you have some classic Toshiba 2SA1837 and 2SC4795 (BCE pinout) you can mount them in the bottom like I did here - leaves a cleaner look on top giving you lots of access to the parts:


Testing on the bench:

Nice low distortion but second harmonic dominant distortion profile for 1Vrms into 33ohms:

You will find that this headphone amp sounds very natural and clean, but has an incredible power reserve to deliver bass slam while maintaining great control authority of the driver transducer cone. It’s a wonderful headphone amp to listen to for hours. For normal headphone use (under 500mW power) basic AC/DC modules designed for delivering circa 350mA into 15v can be used with a 7812/7913 voltage regulator and it will work fine. You can also make really fancy PSU with linear trafos, cap multipliers, CLC, and low noise LDO’s etc. with a proper PSU capable of 750mA and +/-15v you can drive up to 1.5W into 32 ohms (for those fans of the HiFiMan HE-6).

I’ll be offering the SMT preassembled PCBs for $59. Bare PCBs for $22. Boards are all 1oz copper and ENIG finish.

https://xrkaudio.etsy.com/listing/1659118057

BOM is here. Note that BOM calls for OPA1642 but the pre-populated PCB has NE5532 installed. This was due to availability issues but I can assure you that the NE5532 sounds fantastic and measures well too. If you want to swap it out later, you are welcome to do so.

If you want to boost the output BJT bias current (80mA) for operation to a higher power under Class A, use this 2.2ohm metal thin film emitter resistor (R213/213/312/313):
https://www.mouser.com/ProductDetail/Vishay-Dale/TNPW12062R20DEEA?qs=vHuUswq2%2BswIE18TmZVkaQ==

Note that the heatsinks will get significantly hotter and the PSU also needs to provide more quiescent power.

For the 8pin Wurth IDC cable with matching connector for the potentiometer, get this cable (or its equivalent).

Hi,

I just bought two pieces of Aiyima 07 TPA3255 amplifiers and also bought 48V SMPS for them. But later learnt that the manufacturer advises not to use SMPS for it but use power adapter instead. Well, first of all, what's the difference between them, technically both are SMPS only?
Click this link for the actual listing

Thanks and Regards,
WonderfulAudio

I was just wondering if anyone knows what is going on with HifiEngine?
Since the past month I think, registrations are not possible anymore.
I've read some posts in this forum about HiFi-Engine being very paranoid.

My IP-Address was banned for no reason and I didn't even have a user account. I just tried to make one. (Maybe I tried it too often...)

Besides that, I was wondering if someone could help me with getting some documents from HiFi-Engine, as I cannot register nor can I download anything. I do however manage to view the site by using a VPN.
I just can't register and now registrations are closed.

Thanks in advance.

I have an OPA1656 story that may be interesting especially to whomever wants to build the RIAA preamp example in the apps section of the data sheet. I did build that and the slightly modified schemo is attached. I used the attached blank proto board. The Layout is attached. Of the three independent rails on each edge the outside L and R were used for -15V and +15V, resp. The inner two were 0V, center Gnd, branched at power entry at the top. The rails are heavily post-filtered and bypassed and the P/S is external. The DIP8 socket has 0.1uF X7Rs pin 8→gnd, pin 4→gnd and pin4↔pin 8. The enclosure is cast Al/Zn, at 0V and everything “grounded” only via the cable shields to the main preamp. I used polystyrene caps b/c they can be had surplus in 1% values. 000.0mV appears across the 47KΩ non-inverting input load resistors and at rest the finished unit is dead quite.

Now, my turntable is a full-auto linear tracker with internal mute switch used to short the ± moving magnet cartridge coil leads together while lowering onto and lifting off of the record surface. On the maiden voyage of my new external RIAA preamp I turned the system volume down; pressed Play on the TT and once the needle was down, slowly raised the volume to take a listen. Sounded GREAT. Turned-up the volume to let it “burn-in” while I did something else.

Once the side had finished I heard a tremendously loud POP-THUMP (tonearm lifting) and seconds later another very disturbing THUMP-POP (tonearm returned to rest). The mere action of the mute switch shorting and un-shorting the cartridge leads was causing a huge transient at the RIAA output. The 1656 just went berserk! “Somethings wrong and I have to use all my horsepower to fix it right now!”.

Of the op amps in my collection the massive misbehavers are the OPA1656, the LME49990 and the OPA1612. The completely docile op amps are the OPA2604, the OPA627, the OPA2107, the LM4562/LME49720 and the OPA2134. Those are fine.

Long-winded question for anybody is what’s the diff between these two groups of op amps that allows for such infinitely different behaviors in this very, very common circuit? In my case, my TT happens to have a mute function = I’m denied use of the 1656.

I have been playing around with designs for a small, thin kitchen system for a while now. I have a few drivers and layouts in mind and I would like everyone's opinion. If there is a large objective difference between these I would love if you'd point them out.

Here is the frequency range I would like to use the midbass units in. The green line.

Shotting for an F3 of 38-48hz. We like bass in our house.


Here is a mockup of the design in its location. This location and temporary until we get a new house. Then it will live in the new kitchen. In the new kitchen it will be far more separated. We will not get into the design details of the rest of the system here. Just focus on midbass drivers. I'll make a thread for this build once I get a more concrete idea of what I'm doing.

The narrow baffle is key since they cannot take up a ton of counter space and I want a nice spread of sound. Probably going to be 5-7" dual woofer, 3-4" mid, 3/4" tweeter. Nice spread of sound.



Box size will be between 24-50 liters. Quite a spread I know but I could easily make it taller in a MTMWW layout or not as deep to go lower in volume.


I really want to try out dual woofers here. Originally I wanted to use these Dayton 7" drivers and I still might. I feel these are more woofer than midbass though. They are cheap. They have some decent reviews. I can get them for $45 on amazon even though they are out of stock at PE. I would dual these. These are modeled in the mockup above. Aluminum, easy to clean

Next up are these currently unobtanium Peerless 5.25" SLS. I have the 8" SLS and I love them. These are 4 ohm so we are looking at series alignment. They are low sensitivity so definitely 2 of them. They would work very well ported and I could get away with a smaller and narrower enclosure. $35 a pop when PE has them, which should be soon. Poly, easy to clean.


Another unobtanium. I always wanted a set of these. Should be available soon. Are these more of large mids than they are woofers? I like the fancy motor design, they have incredible reviews. I could use one or two of them. Two would be best with a passive radiator. This, of course, is more expensive than the last two options. $90 each and another $50 for a PR. Paper, hard to clean, maybe not best for the kitchen.


I feel these are interesting driver. I know little about Wavecor. They look cheap, they seem overpriced, they apparently measure just as well as scanspeak drivers, they model well, and the distortion graphs have very low distortion right where I want to use these. Cannot validate but read multiple times that the balanced drive is the same technology used in the revelator lineup. Same price as the NE180W. Not as cool looking but if it has better dynamics I am all over it. Would need two. Could also use the 6.5". Paper, but looks super smooth so maybe easy to clean?


Definitely need two of these in series. Not sure if these can match the lower dynamics of the other choices. They sim out well enough for the bass I want. Are these more of mid range units? Aluminum, easy to clean. Pretty pricey for a 5" at $80 a pop


Pushing the limits of the baffle allotted baffle dimensions we have this Satori unit. The 6" is unavailable. Price point dictates I only use one. Defeats my purpose of trying out multiple woofers. By far the most expensive at nearly $200. Especially for a system that will not get listened to for hours like our other systems. I hear it is only slightly better than the aforementioned Peerless with the similar motor design. Which is a rip off of which?


There are a handful of Dayton drivers like the reference series I have also looked at but none of them stand out in any way as far as measurements, price, or reviews. I see no one ever mentioning them as notably special drivers like this collection I have assembled here. If nothing else, I surely do my research.

Let me know if I should be looking at some other driver. Again, midbass dynamic and an F3 of at least 48hz is the goal here. 25-50 liters.

If you have trouble understanding this test, or you have questions, please read:
TEST FAQ
Update July 3rd 2012:
Although the title of the thread contains the word "test" this is better thought of a s a survey or poll. The word "test" has caused a good bit of confusion and misunderstanding.
The test tone provided is not used to set you system levels, it is used to measure your system levels. You will set the levels by ear, or by pink noise if you wish.
What you will be doing is measuring your actual listening voltages and reporting them here. The test tone allows you to do that with very good accuracy using only digital playback and a voltmeter.

---

100Also have a look at Archimago's blog for a very clear explanation of this test, along with good photos and link to more info.

---

100
Here is a simple test to determine what voltage your speakers need to play their loudest. From that you can determine how much power you need.
Knowledge is good and this test will tell you just how much voltage (or power) you really need. Efficient speakers in a small room may need only a volt or two. Less efficient speakers in a big room may need a dozen volts or more.
I've included a poll so that we can see what's typical. If you want to also post your speaker details and room details, that would be nice.

For the moment, I'll leave this as a voltage test, we will talk about power later. Those of you who know Ohm's law can figure it out for yourselves. Amp power tends to be an emotional issue, so we'll post the results in volts for now. Since most amps are voltage devices anyway, it's not a bad way to measure. And a voltage measurement removes the speaker impedance from the equation.

All you need for this test is some sort of digital playback (CD, iPod, Squeezebox, computer, etc) and a volt meter with a low AC scale. Any scale 20V or lower should be OK. Meters with only 200V AC scale won't be accurate enough for this test.

Next post has the test tones and instructions.

Hello, I'm currently trying to repair a Luxman L-3 that I bought at a thrift store to make it mine and enjoy! For now I've read all the previous posts made on this forum and though I found the issue when I changed a resistor that was problematic for someone else (mine also was bad). Replaced the resistor with one that was good (Amazon) and tried to turn it back on... ohoh the dim light tester stays on.

That was my initial try at repairing it, since then, I tried to find the short, but I can't seem to find anything promising. I used a thermal camera to identify hot spots on the power board and found to spots, one around the D403 and D404 diodes and the Q408a area. Since then I pulled all the components to test them outside the circuit, but they all seem to be good from my understanding.

I'm kinda lost and don't know what I could check before starting to resolder all the components back on the board, do you guys have any wisdom to share that could help me with my project! Thanks. There seems to be a good amount of info on this site about the amplifier so if you want something specific let me know and I'll share it with you (schematic, components list, voltage drop of the components I pulled, etc.).

Is there any info about when BA3 front end boards will be available again? It´s been so long since those boards are out of stock, I hope they are back soon 🙁.

In the past years, the cost of CNTs has gone down radically while their purity has gone up. CNTs can be expected to far outstrip carbon fiber in their strength to weight ratio. Of course, making a speaker cone out of CNTs (only) directly is not practical because CNTs don't stick together well. However, CNTs are known for as much as doubling the strength of other materials. Common articles assert that only 2-3% CNTs by weight is required for drastic improvements. So I purchased some CNTs that I intend to include in a coating for speaker cones. It was like $75 for 100 grams whereas early on they were more like $50/gram ballparkish. .. clearly enough to do many cones. .. The challenge according to articles is that CNTs don't dissolve like solutes. They have to be disbursed using special solvents and usually stirring and ultrasonics. Otherwise, they clump up and cause more trouble than gain. So I haven't tried this yet, but I think it would be more fun to toss some ideas around. Articles have indicated that multi-wall tubes work better for strengthening other materials so that's what I got. I'm planning on sanding just a little paper off of some paper cones and then replacing with a thinned CNT based coating .. Polyurethane is on the list of possibilities as experiments have been done with it already. So let's see if anyone has any cool ideas about the best way to do this so I can make the best decisions before taking little risks. I intend to do trial runs on useless paper or cardboard.

Unless a two-way using system an Athos build of this horn offers measurably and audibly better performance, https://josephcrowe.com/products/3d-cad-plans-for-es-290-biradial-horn-horn-no-1670 , a tweeter will be required for use with one of these midrange drivers atop the same horn.

https://www.rcf.it/en/products/product-detail/nd950-2.0#specifications
https://bcspeakers.com/en/products/hf-driver/archive/2/8/DCM50
https://www.bmsspeakers.com/index.php-111.html?id=bms_4591

Troy Crowe typically offers these tweeter/horn combos with arguably improved performance over the stock tweeters,
https://josephcrowe.com/blogs/news/lens-no-1896-for-fostex-t96a?_pos=2&_sid=18decdf41&_ss=r

https://croweaudio.blogspot.com/2020/10/fostex-t925a.html

I can’t locate it now but in one of his midrange/horn combo reviews Troy said that some other tweeters (ribbons? AMTs?) couldn’t “keep up with” the power response, among other performance parameters, of one of these Fostex
“bullet” tweeters when paired with the above midrange drivers.

I couldn’t say either way, though others have discussed and/or may have found pleasing alternatives.

https://www.usspeaker.com/B&C-DE35-1.htm

https://www.diyaudio.com/community/threads/help-pick-a-1-4-compression-driver.391355/

I’m not saying that once a Fostex tweeter’s typically peaky HF response has been flattened without consequence
https://josephcrowe.com/blogs/news/...-for-fostex-t900a?_pos=3&_sid=43fb10bfe&_ss=r

and diffraction issues appropriately tamed with that waveguide, that the T96A or T925A won’t perform admirably.

But would other alternatives work much better?
https://faitalpro.com/en/products/HF_Horns/product_details/index.php?id=903010100

Click on Response Curves at that link. Am I wrong or aren’t these impressive looking horizontal polar charts that these Fostex tweeter can’t show to deliver wide and even HF response?

If so, what kind of driver should I be looking at for this or similar HF horn?

I have caught the Class D amp bug lately. I see many hybrid tube / TPX3xxx amps advertised (ex. Douk). Is the tube input stage just a gimmick?

My first radio in the 70's was an AM tube radio... it definitely had a warm sound that was great. My fathers stereo had a Scott integrated tube amp. I don't remember the tube colorations / too young to know a difference / don't think his speakers had the resolution to tell much of a difference.. I get tubes have their own unique sound. Do the tubes in the input stage just add tube coloring / warmth to the audio? I am pretty darned impressed with the "sterile" sound of the TPA3126 and TPA3255 boards I have been playing with. To me adding a tube input section will just alter the more pure sound to a warmer more colored sound?

"Back in the day" I had a Counterpoint SA100 class A/B amp with a triode tube input stage. I ditched it when I bought my used Threshold 400a Class A amp. There was a huge night and day difference between the two amps... but I doubt the difference was in the triode tube input stage. More just Class A (Nelson Pass) vs Class A/B amp. HiFi vs MidFi.

I am interesting in peoples thoughts on this?

I'm excited to join the DIYAudio community! I've been on an intense journey into high-end audio over the past year—diving deep into summit-fi gear like the Mola Mola Tambaqui, Feliks Audio Envy, and RAAL Immanis. I listen primarily through vinyl on a Pro-Ject Debut Carbon EVO, and my digital chain includes components like the WiiM Ultra and RME ADI-2 Pro. My musical tastes range from Pink Floyd and Fleetwood Mac to HVOB, and I'm always chasing that next level of sonic realism.


I joined DIYAudio to connect with others who are passionate about sound, learn more about tweaking gear for peak performance, and maybe even try some DIY builds down the road. Looking forward to exploring and exchanging ideas with all of you!


Cheers

Discussions about 6KV6 and/or 6KM6 pop up here and there from time to time.
What I haven't found yet is an example of this tube being used successfully in a SE triode amp.
So what's the (preliminary) consensus on how to best use them?
Appreciate your input.

AmyAlice is a simple DC filter which you install between a noisy Switch Mode Power Supply, and a piece of audio gear that expects relatively smooth, clean, high purity DC power input. It's intended to be used with line level audio equipment, such as DACs, active crossovers, NuTube boxes, preamps, headphone amps, H2 generators, DIYA front end boxes, and so on. The maximum voltage AmyAlice can support is 48V and the maximum current it can deliver is 3A, which is plenty for line level gear, and sometimes enough for a sub- 5 watt power amp (like for example the ACA mini).

There already exists a very nice DC filter for SMPS, as a project in the diyAudio store, which I encourage you to investigate. AmyAlice is similar to the Store filter, the differences being

• AmyAlice uses high performance, SMD-only, feedthrough capacitors. The thru-hole PCB in the store, does not
• AmyAlice includes a high performance ferrite bead to improve HF and VHF attenuation. The store PCB does not
• AmyAlice uses physically bigger inductors with 5x greater inductance than the inductors on the store PCB
• the Store PCB is smaller in size. See photo attached.
• the Store sells kits-of-all-parts. No such kits exist for AmyAlice, to my knowledge

There is a very detailed thread about the Store PCB here on the Forums (link), which contains many excellent contributions by Forum members. Clever ways to package an SMPS filter are shown, clever sources for cables and plugs and jacks are discussed, and many user testimonials proclaim the sonic benefits, before-versus-after installing a filter. Owners of the Store PCB are very enthusiastic about the sonic improvements they get.

THEN WHY BUILD AmyAlice AT ALL?

The DC filter kit in the store has always been implemented with thru-hole components only. A large number of builders are certain they cannot possibly succeed with surface mount parts, and quite a few more simply refuse to even try. For them, and everyone else, the all-thru-hole, zero-SMD store kit is available.

However, as Forum readers are well aware, there are lots of new electronic components which are offered ONLY in SMD packages. High volume electronics manufacturing is all-SMD in Y2023, therefore component suppliers meet their customers' needs with all-SMD parts. This is particularly true of new components, which, by the very definition of the word "new", do not exist in legacy thru-hole designs. The whole world has moved on to SMD assembly.

A couple of new, SMD-only components are now available, which enable much better performance (i.e. greater noise attenuation) in SMPS DC filters. These SMD parts cannot be used on the Store PCB, or any other must-be-thru-hole-only board. But they CAN be used on AmyAlice because AmyAlice allows SMD components.

One such SMD component is the 1.0 microfarad, 3-terminal Feedthru Capacitor sold by TDK. Its datasheet, and the attenuation plot from that datasheet, are attached below. AmyAlice uses the "2A105" model of Feedthru Capacitor; as you can see, it offers spectacular HF attenuation, even at 100 kHz. AmyAlice actually includes two of these, so its attenuation is spectacular-squared.

A second addition to AmyAlice is an SMD packaged ferrite bead from Wurth. The impedance curve of this bead is attached below; it rejects HF, RF, and VHF noise quite aggressively. The ferrite bead is the first series element in the AmyAlice cascade of filters.

As the schematic diagram (below) indicates, AmyAlice consists of the ferrite bead, followed by a series cascade of two identical R-FTC-L-C passive filters. "R" is resistor R1, "FTC" is feedthru capacitor C1, "L" is inductor L1, and "C" is electrolytic capacitor C2. Each L-C pair contributes two poles to the lowpass filter, so AmyAlice as a whole contains a four pole passive lowpass filter. A four pole lowpass has a total of 80 dB of attenuation per decade, which is quite steep. Of course Murphy's Law dictates that the parasitic elements (parasitic C of the inductors; ESR and ESL of the capacitors; etc) diminish the attenuation at frequency extremes. AmyAlice is certainly not 80 dB per decade all the way from 1 Hz to terahertz! Oh no.

But wait, we have underestimated the attenuation. The 80 dB/decade figure doesn't include the extra attenuation provided by each of the feedthrough capacitors. Which is about 23 dB of attenuation at 100 kHz, and in excess of 60 dB at all frequencies between 7 MHz and 200 MHz. Wow. AmyAlice gets this attenuation boost twice, from the two FTCs. Also note: the 80dB/decade figure doesn't include the extra attenuation provided by the ferrite bead at the input. The bead adds further attenuation beyond about 2 MHz, see plot attached below.

So, putting it all together, approximately how much better is AmyAlice than the store filter PO89ZB? My own conservative (under)estimate is: 18dB greater attenuation. {math: log10( 18dB / 20 ) = 8x}. I estimate that AmyAlice is at least 8x better than PO89ZB, removing SMPS noise. However AmyAlice IS a bigger board, with 3 additional parts, and it "cheats" by using modern, surface mount components. To choose one versus the other, you will need to do your own cost-versus-benefit analysis. Or in some cases, an annoyance-versus-benefit analysis.

HOW TO BUILD YOUR OWN AmyAlice BOARD(S)

This project is not suitable for beginners or people who are completely lost without a Build Guide, assembly video, or tutorial. It requires SMD soldering which is a skill you develop by repetition and lots of practice.

You will need to order AmyAlice PCBoards from a PCB fab shop. I have written a quick Walkthrough that shows how to do this at the fab called "JLCPCB" (link); however the same principles and same steps are used at all fabs. Study the Walkthrough and I'm sure you will conclude: ordering PCBs is not mysterious, it's not complicated, and it's not at all frightening. It's exactly like buying anything else on an e-commerce website.

If you're feeling generous, you can order a bunch of AmyAlice PCBs, so you'll have plenty of extra boards left over, after you've built the AmyAlice(s) for yourself. You can offer these extra boards to other diyAudio members for free, or at your cost, or for a net profit to you. Your decision! Simply post a message here saying "7 extra AmyAlice boards available in UK/EU at price XXX, send me a PM if you want any". Or whatever your convenient shipping zone happens to be.

As of today, all of the components needed by AmyAlice are available and on the shelf at both US-Mouser and US-DigiKey. At least they are on 2023-Nov-02. If and when a part goes out of stock, you will have to download its datasheet and find the important characteristics, such as physical size, lead spacing, wattage, voltage rating, current rating, resistance, inductance, capacitance, etc. Then you will need to search for an equivalent part which matches those important characteristics, and is in stock at a distrubutor you are willing to buy from. If you feel incapable of this task; if it sounds more advanced than your current abilities as a DIY hobbyist; then perhaps you should wait and learn and grow, building other less challenging projects, before trying to buy parts for AmyAlice.

Will AmyAlice ever appear in the diyAudio Store? I don't know the answer with any certainty. I . DO . NOT . KNOW . However my own personal opinion is: AmyAlice probably won't become a Store product, because (A) the kit in the Store right now is selling very well, why mess with a good thing? and also (B) AmyAlice requires SMD soldering and the existing kit in the store does not. Since so many people reject SMD soldering completely, why swim against the tide? Let those few people who really, really want AmyAlice, order their own boards and source their own parts. Meanwhile the store happily sells 100 thru hole kits every month (??) -- it's a smooth running, well oiled machine by now. 22INDEX22

This is just my own opinion; I have ZERO visibility into the operations or plans of the Store. 22INDEX22

News (13 Dec 2023): a Member has created new PCB layouts for AmyAlice, some of which also include a capacitance multiplier circuit. You can find them in this thread: A2CMx: AmyAlice DC filter and cap multiplier for SMPS .

News (27 Feb 2024): a Member has created a new "slim" PCB layout for AmyAlice, and added an LED pilot light. You can find the board+Gerbers in this thread: AmyAlice SLIM - SMPS filter .

News (14 July 2024): a Member has created a new PCB layout for AmyAlice, which fits perfectly within a plastic enclosure. You can find the board+Gerbers in this thread: Compact SMPS filter using AmyAlice circuit design .

ANSWERS TO FREQUENTLY ASKED QUESTIONS

FAQ_01: Is it possible to assemble a pair of AmyAlice PCBs to implement a bipolar supply filter? For example, a filter that receives noisy ±24V inputs and produces quiet ±24V outputs? ANSWER: yes. See post #31 of this Forum thread.

FAQ_02: Is it possible to assemble an AmyAlice PCB that filters a negative power supply voltage, i.e., a voltage below ground? ANSWER: yes, see FAQ_01.

FAQ_03: If I build two AmyAlice filter boards and connect them in parallel, can I safely run 6 amperes (2 x 3 amps per board) through the parallel combination? ANSWER: no. See post #37 of this Forum thread.

FAQ_04: Has anyone created a "shopping cart" at DigiKey and/or Mouser, containing all components needed to build one AmyAlice PCB? ANSWER: yes, see posts #16 and #56 respectively, in this Forum thread.

_

Hi everyone,
I'm a fairly new (second) owner of an MF nuVista m3 amp and was thinking of doing a service on it: a) replacing the old Jamicon electrolytics and, if at all possible, removing any electrolytic caps from coupling duties; b) checking/setting/re-setting the quiescent current on the channels.

With regard to a) there is one 10uF/63V cap that I just can't find a good-sized film cap to replace it C1 and C101 on the attached diagram (Nuvista_M3_Pre-amp_Line_OP[1].pdf). The other coupling caps in the chain (C32, C40, C41 on the right channel) are already some type of film cap, yellow-coloured with a circled L logo--not sure how their quality is honestly--although I'm going to replace them with WIMA MKP10s anyways. Not all that pricey and I'll have it all apart anyways...thank goodness for suppliers like mouser and digikey etc.

Second item, b), does anyone know how "far" I should set quiescent current, i.e. bias into Class A operation? The SAP15's datasheets indicate 40mA, (so 8.8mV across pin 4,5 or 1,2 depending on N or P type), but some manufacturers seem to like "giving it a bit more." Anyone have any thoughts/experience with MF quiescent currents?

Thanks!
verkion
P.S. Attached the whole bunch of M3 Amp diagrams for people's reference. I'll be replacing PSU caps too as those are the ones that are looking "slightly fatigued." i.e. plastic cover is puckering although the metal under it feels fine...for now.

Copyrighted materials removed by moderation.

Hello,

I am no expert in tubes at all and have an amplifier built from the kit purchased on Aliexpress:
https://nl.aliexpress.com/item/1005...3Lcnrian&utparam-url=scene:search|query_from:



I have a pair of 300B EH tubes which I would like to use so I am thinking to repurpose the chassis and power supply for new build.
The goal is decent amplifier, not crazy hi-end stuff, let's be realistic here. So my main question is what would be the way to go: can I reuse the output transformers? What to choose as the first stage?

Hey all,

I've started going down the DIY rabbit hole a little deeper and find myself in the need of additional testing equipment than I've been using for tube builds. Currently in my toolbox are a few cheap-o DMM's, a Fluke 117, Peak LCR45 and a Velleman DCA55 Semiconductor Analyzer. Last summer I saw an old Conar 255 oscilloscope for $20 at a garage sale but now I'm convinced I should just get something modern instead of doing a restoration and questioning everything it spits out. Maybe a fun future project but for now I'd just like to get up and going. Something modern-ish but am Ok with used if its a good bit of kit.

What do you guys recommend for a good testing / electronical / audio bench testing rig? I don't need to spend 10k but would like to start putting together a decent set up that will go for the long haul. Appreciate any recommendations!

If a crossover design calls for an 8mH / 0.790 Ohms and the two closest options are 8.2@0.800 ohms (Solen) or 8.0 @ 1.75 ohms (Janzen), which would be better or does it even matter? Actually I've already purchased the 8.0/1.75 Janzen which I suppose I could return. Any issues with either of these? If it matters, this is for a first order XO on the woofer with only a single inductor. Thanks

I’ll go first. Which one of you guys did this?

I can now provide the Gerbers and information to build an interface board that supports a compact connection between JLSounds I2SoverUSB vIII FIO and PCM2DSD with support circuitry hosting 2 x XOs, relays to switch in the correct frequency, re-clocking for the DSD signals and a clock doubler to provide ext_clk to the JLSounds if 22/24Mhz XOs are used.

The design relies heavily on that generously provided by Markw4 and was conceived not as an alternative to his design but to complement it where space was limited and requirements weren't as general.

This is the link to Mark's design: https://www.diyaudio.com/community/threads/general-purpose-dac-clock-board.413001/

Below is the re-clocker fitted to one of my two RTZ DACs:



The BOM & Schematic is also attached together with a document with some notes and details of the options.

Please let me know if clarification is required on anything. Or if anyone finds errors in the BOM. I've tried to keep it in step but as you can see there have been a number of iterations so mistakes might creep in.

The v15 board has been tested on 3 RTZ DACs and found to be working well on a number of different sample rates and sources. However, I cannot guarantee that there won't be unforeseen cases where timing issues might arise as I can only test with my limited scope of hardware.

BOM calls for Crystek CCHD-957 devices but since the 4 pin Aries XO sockets are used (part number has been added to the BOM) then any pin compatible XO can be used,, such as the Ian Canada scPure. The Crystek XOs also require a conversion pcb, as seen in my photo above. I bought mine from Ian Canada. The scPure XOs already use the correct format for the sockets.



For DIY use only!

Edits:
8th Feb 2025: BOM updated. R9 value/
9th Feb 2025: Updated BOM for XO socket part number, added photo with scPure

There are SMD parts, electronic relays, for audio signal. What kind of relays are these ?

Click this for the scientific paper.

This is the Abstract:
Quark movement is almost by the speed of light. Due to this speed their inertial mass-effect increases profoundly. That inertial effect is an accelerating force. Within the nucleon the force is the strong force. As quarks movements are back and forth movements, called zigzag or oscillating movements, there is movement in opposite directions. So the oppositely acting forces annihilate each other. However the force acting on objects receding from each other is a trifle stronger than that acting on objects approaching each other. This small difference between these forces is a “left over” force and “leaks” out of the nucleon. In previous manuscripts, formulae were presented to calculate these forces. In the present paper the “left over”, “leaking” force is estimated, and this force is gravity.