A thread for discussion on all purifi driver builds.

A place to brainstorm and speculate on drivers and potential speaker builds for arguably, objectively, the best no-nonsense engineering-first traditional speaker drivers' money can buy - If you have a complete project underway, please start your own thread and post a link to it in here. Otherwise posting occasional random progress pics and info here is fine but we will keep full build discussion elsewhere.

We are also pleased to have @lrisbo of purifi occasionally check in and post here of which is much appreciated.

A tweeter is on the way 🤓

Updated 26/01/23: Added more build links and intro - (I may stop updating commercial builds moving forward as they are now coming in thick and fast)
Updated 16/06/22: Added builds and review links, updates to builds
Update 17/03/22: below

Time for a bit of consolidation due to this thread getting some hits, and purifi has now released quite a few scrunchy woofers

Links to known projects & commercial speakers using the Purifi drivers (please PM me if I need to add any)

Of course - www.purifi-audio.com , and the team behind the drivers here


Full DIY:

DIYA user @spresto9 has come up with these beauties with the 8" purifi woofer like to details and more pics HERE




Check out this 4" pocket rocket proof of concept build from the Purifi team - all the info you need to DIY!

Spk8 appnote download (.pdf)



@lrisbo Proof of concept Purifi SPK4 (superseded) - Passive stand-mount



@lrisbo Proof of concept Purifi SPK5 - Passive stand-mount - I believe these were at some point being made and sold commercially but have since been discontinued - there may be some floating around second hand market see here Celuaris SPK5 review ASR



@xrk971 PTT6.5/RS28F Waveguide Harsch XO - Passive stand-mount later evolved into a nice Stand mount and Floor standing Transmission Line



@Joe Rasmussen Somewhat Legendary 'Elsinore' - Has been given an (expensive) purifi remodeling. Wow. Skip ahead to post #4,746 for the juicy bits.




Rick Sykora and team's Directiva - Active stand-mount with excellent (objective) reviews, requires external amplification for each driver and an external DSP crossover.





@xrk971 's Raal 70-20xr and PTT6.5 - this one the tweeter is not readily available to DIYers but there may be ways to get it if you're crafty.

(sorry X, couldnt find a finished pic, and I'm out of attachments for this post)


User tktran303's Collection of DIY designs here looking great




Some mindfood for the 8" - a concept by Purifi.



Paul Carmody's Virage - a full design, light on measurements but a fairly reputable designer.



.....and many more concepts within this thread, start reading. Most not fully documented or taken to finished stage though I suspect a few people are still perfecting their builds before showing them off. Remember you can drop people a friendly private message asking about how their progress is going.





DIY-Kits/Semi Commercial:


Yevgeniy’s PuriWave - 2-way stand mount with dual purifi passive radiators



Troels Gravesen Purifi 6661 - Semi-passive/Active plate amplified floor-stander



Troels Gravesen Purifi 6R - Passive bookshelf




Troels Gravesen Purifi Be - Looks like a revision to the above due to ribbon tweeter supply issues.




hificompass Puri Bliss BeWg - Passive bookshelf - I believe the plans are/were for sale.



Joseph Crowe's 1198 - I believe you have to get in touch via the webpage - floor-stand transmission line








Full Commercial:

March Audio Sointuva - arguably where "the bar has been set" for the Purifi 6.5 in a bookshelf chassis.



Jones Scanlon Baby Reds - self powered studio mixing monitors.



The Late Rick Craig's Selah Audio Purezza - A nice stand mount ribbon tweeter design, was available commercially but afaik discontinued, check SH market



Jachim Gerhard Surveyor's - stand-mounts , I believe there is/was a floor-stander made too



Dennis Murphy & Jim Salk's BePure2 - Floor stander - The legends behind the philharmonic BMR and BMR tower



and um, what ever this might be! https://www.audiocircle.com/index.php?topic=175599.0 - probably just a concept, I didn't read the thread. Likely Unobtanium tweeters and probably bottomless pockets required, if it is sold commercially.

Correction - the above was a concept which later evolved to the BePure2 - see this thread at AVSForums Post #10,174
https://www.avsforum.com/threads/th...rs-and-discussion-thread.939744/post-61186397


Further Build links:

Thrax Siren - a 2-way standmount

Jern 35 - 2 way standmount

Buchardt A500 Signature - Active 2 way standmount

WVL Serendipity - 2 way standmount

Taipuu Kero L active with FourAudio PPA-1000 dsp amps. - Not sure if available yet

Salk Sound BePure3 ... Holy **** I need to hear these.



Links to independent driver reviews:

https://www.erinsaudiocorner.com/driveunits/purifi_4/
https://www.erinsaudiocorner.com/driveunits/purifi_ptt65w04/
https://www.erinsaudiocorner.com/driveunits/purifi_ptt80x04-nab-02/ - the eight inch aluminum mid-woofer
https://www.erinsaudiocorner.com/driveunits/purifi_ptt6.5x04-naa-08/ - the 6.5 inch aluminum mid-woofer
https://www.erinsaudiocorner.com/driveunits/purifi_ptt6.5m-08-nfa-01a/ - the 6.5 inch dedicated midrange

Also - please consider visiting Erins Youtube Channel and subscribing! - a much needed light in the dark world of audio subjectivism.

https://audioxpress.com/article/tes...udio-6-5-midbass-transducer-from-purifi-audio

https://hificompass.com/en/reviews/purifi-audio-ptt65w04-01a-midwoofer
https://hificompass.com/en/reviews/purifi-audio-ptt40w04-01a-midwoofer
https://hificompass.com/en/reviews/purifi-ptt65w08-01b-ptt65x08-nfa-01
https://hificompass.com/en/reviews/purifi-ptt65m08-nfa-01a-65-true-midrange

http://www.troelsgravesen.dk/Purifi.htm


Original Post 02/04/2020:

With the group buys well underway the idea was bought up that a design thread be started to discuss build options.

Mine have arrived but I have no build materials and will not be able to get any until we come out of quarantine in (hopefully) three weeks time. I planned to start with a hybrid of purifi's SPK4/5 builds using the same AMT tweeter but maybe using a slot port with the 2.5khz crossover. That and I haven't done any AMT builds so it seemed like a good place to start.

I read of a guy in Aus planning on doing a line of passive and active speakers with the woofer so be interesting if he could chime in here.

So with no materials for the next at least 3 weeks, what better time to discuss build options! Fire away

Hi !
I'm looking for a person who is really up to speed with multi layer SMD boards and MHz SMPS designs to do a PCB design (drawing).
All technical specs. & schematic provided.
BR

Folks:

I'd like to replace the capacitors in my 17-year old Audio Electronic Supply AE-25 SuperAmp Signature. Selecting upgraded caps will be easy for the most part, but I'm unfamiliar with the five purple "Audio 1" 0.22uF, 600VDC capacitors shown in the photo. I have very limited experience with tube components and would be grateful for advice on a suitable replacement for those purple caps.

And before anyone points this out, yes, there's a 560uF 400V cap that's already been pulled from the lower left corner of the chassis.

Regards,
Scott

Hello All,

Cleaning out my garage to make room for a treadmill and a place to roll around on a swiss ball.

There are boxes of mostly JBL drivers that need to go. I may sell some along the way.

For entertainment I am planning a pair of 1 to 2 cubic foot speakers attached to the storage loft above.

There are more than a few options, the speakers likely will be 2-way with 12" woofers plus Compression Drivers / wave guides attached.

In the storage boxes there are 2204H, 2206H and 2217H (a 14 inch driver). I am leaning towards the 2204H's, they model a little lower in frequency response.

For the CD's there are several options, I am liking the 2453 SL mounted with the Progressive Transition 6-1/2" X 12" 90 X 50 wave guides.

Any thoughts or ideas?

Thanks DT

Inspired by the days of Zilch (RIP)

Edit April 5, 2019: Beautiful example of this amp in finished case by Avtech23 on post 425.




*****

This is a simple DC-coupled high performance SE Class A headphone amplifier design by member TimS who has approved this GB. The design uses four cascoded BF862 JFETs on the input stage. They provide compensation for DC drift and the amp has stable DC offset of less than 5mV. The design has a dynamic CCS, reminiscent of an Aleph to provide good efficiency and low distortion from two P-channel MOSFETs in the output stage. Simulations show very low THD in the sub 1 part per million (PPM) range for 5vpp into 55ohms for a 400mA bias current. At this bias, the heat output is about 14w per channel and allows it to be used as fleawatt speaker amp and able to drive 8ohm speakers to 1.5w with 0.004% THD. Increasing the main source/drain resistors to 2.7ohms sets the bias current at about 115mA and this has very good performance. I built a hand etched prototype and measurements and listening shows a very powerful, dynamic, and clean sounding amplifier. The GB boards will be high quality 1.6mm thick with 1oz copper and ENIG gold finish with blue solder mask.

Here is LTSpice schematic and DC setpoints for simulation:


Predicted FFT for 5vpp into 55ohms with 400mA bias:

Here is hand etched prototype:


Measured FFT for 115mA bias 1vpp into 42ohms - note that elevated H2 distortion peak is probably a component choice of the lwo cost prototype (cheap steel leads on resistor, etc). I am quite sure that a proper amp using a real PCB and all high quality resistors and MOSFETs will be superior:


Measured 1kHz sine wave at 17.6vpp for 115mA bias and +/-15v rails for almost 1wrms into 42ohm load


10kHz 2.5vpp square wave - nearly perfect performance with no overshoot, or ringing:


This is the schematic for production PCB:


Here is the layout by JPS64:


Here is 3d render of PCB with components (bottom side):


3d render of PCB with components (top side):


How does it sound? Very dynamic, transparent, open with deep deep bass. It is DC coupled in and out so there is no capacitor to color the sound. The distortion is very low and you have to be careful not to play your headphones too loud if you are used to judging loudness by distortion. It's a great little amp that is easy to build with relatively low cost parts, yet is very high performing. Compare the predicted distortion levels with amps using 5x as many transistors. The nice feature about this amp is the rather high output power it is capable of and a rather high gain close to 20dB that allows one to drive an inefficient set of planar magnetic headphones to loud+ levels with very low distortion.

If there is interest, please add your name to GB interest list. Cost will be about $28/set and shipping will be $5 in US, $10 in Canada, $15 everywhere else.

Update July 3, 2018;

The FFT of the wall mains powered 12v to the on-board ultra low noise DC-DC dual rail PSU has noise characteristics resembling a battery. Note total absence of 60Hz/120Hz/180Hz/240Hz mains peaks and how low the "grass" of the noise floor is:


Here is the final design for production, and it is an 8 panel board that contains:

• input and source switch board (only preamplifier version)
• crossfeed board (with defeat Xfeed ON/OFF switch)
• headphone jack output board (6.35mm stere TRS output jack)
• volume potentiometer board (with the possibility of three different types of pots)
• PSU (includes CLC, DC-DC dual rail step up, cap Mx, CRCRC filter to produce battery-like rails from simple 12v wall-wart)
• CLC filter board (in case you want to use your own PSU)
• ON/OFF switch board
• amplifier board

The above boards can be mixed and matched and connected for either an HPA or a preamp following this diagram:


Schematics and other data here:
Simple High Performance DC Coupled Class A HPA with sub PPM THD - Page 10 - diyAudio

Top side:


Other side:


Mounted in a popular all CNC'd $36 Aliexpress case as a HPA, it looks like this:


Here is rear view of HPA:


As a preamp with your own machined panels, it looks like this:


Rear view of preamp:


Edit July 21, 2018: final schematics and stuffing guide here:

Simple High Performance DC Coupled Class A HPA with sub PPM THD - Page 10 - diyAudio

Update Aug. 4, 2018: Schematic Update! Please use this schematic for the PSU as the original has a few typos.

Update Aug. 5, 2018: Silkscreen on PSU PCB has error: Diode V241 has cathode and anode flipped.. Mount diode with Anode towards Drain of P channel MOSFET on cap Mx.

Update Aug. 27, 2018: verification build of GB boards completed. Amp sounds superb and measures very well. Here is FFT for 1vpp into 51ohms - very similar to earlier measurement but much lower distortion.




Update Sept 2, 2018: BOM from verification build can be found here.
Simple High Performance DC Coupled Class A HPA with sub PPM THD - Page 24 - diyAudio

From time to time I stumbled across really nice OB / Dipole designs. Usually I just put them in my favorites, but it may be really nice if we have an exhaustive list of OB systems out there.

Post your systems too! Pics and short description.

===

Let me start with this really nice implementation by Perfect8. No spouse frowning here 😀






http://www.perfect8.com

basic information concerning the differences are described in detail here:
http://www.reallyreallyrandom.com/www/Zener_Theory_and_Design.pdf
and here:
https://www.onsemi.com/pub/collateral/hbd854-d.pdf

AI short form description as follow:
a TVS (Transient Voltage Suppressor) diode is used as an alternative to a Zener diode, particularly for dropping screen grid voltage in tube amplifiers. While Zener diodes clamp the voltage to a specific level, TVS diodes act more like a protector, absorbing over-voltage transients and shielding other components.

But I wonder, why such TVS diodes (TRANSZORB®) "SMAJ-5.0A" - for datasheet go to
https://www.vishay.com/docs/88390/smaj50a.pdf
very often causes a total failure of various components with 5V plug-in power supplies (because this TVS diode has an internal short circuit after a short time of use - i.e. works like a wire bridge between the plus rail and the minus rail).
In the moment I have 3 devices of this kind of electronic modules without any operating:
https://www.revitive.com
After looking for the most probably reason therefore I have found this video examples on youtube:
Revitive Circulation Booster | Won't turn on | Can I Fix It? (10:33)
Revitive Machine No Power Repair (5:35)
Faulty REVITIVE Circulation Booster | Can I FIX It? (3.15)
Always the shorting inside of the TRANSZORB® TVS diode "SMAJ-5.0A" was the reason - but the reason therefore again wasn't the 5V SMPS power supply.

I remember many previous repairs on other kind of assemblies that were operated with 5VDC, the total failure of which was also due to a short circuit of such TVS diodes. In these cases I always replaced it with a high power 5V1 Zener diode and additionally with a normal fast recovery diode BY299 to trim any transients in reverse polarity that may
occur - fortunately without any trouble with further use.

But what actually is the royal step to get on one hand optimal protection requirement and OTOH best reliability for the protection part itself (obviously TVS diodes like the SMAJ-5.0A isn't reliable)?

Thanks for an advice.

Hey all. Alex here. I live in New Orleans. I'm getting into HiFi and DIY HiFi.

My current setup is:
Fluance RT82 upgaded to OM20 stylus with acrylic platter
Schiit Mani 2 Phono Pre-amp
Schiit Freya+F Pre-Amp with 6SN7 Tung-Sol tubes
Schiit Vidar 2+F Power Amp
Cambridge Audio AXR100 (when not using the Freya+Vidar)
Eversolo DMP-A5 Gen 2 Streamer
Laiv Harmony uDAC
Cambridge Audio AXC35 CD Player
Wharfedale Evo 4.3 Speakers
Cambridge Audio Minx X201 subwoofer

Custom Cables: Various RCA cables with Deulund Silver 26ga wire and Gotham Cable with low mass connectors, speaker wires and XLR cables with mogami wire and neutrix connectors.

I've joined the forum for a few reasons. I've been building an IanCanada transport to hook up to the Laiv Harmony uDAC. I need some troubleshooting help getting the IsolationPi III working with the TransportPi Digi/II and RoPieee (I'll post details for that somewhere else), and I'm also looking for CNC custom enclosures, or putting together some people to find someone to make files where we can order one. I'm also interested in building the Amp Camp Amp Redux Kit. I've also been building all my own custom cables, so interested in speaker cable stuff. I'm also thinking long term building my own class A mono block amps.

Glad to be here. I've been reading the forums and lots of great stuff to see.

Hello friends,

Please help me understand what I am doing wrong. I have tried to learn the programs Hornresp and AKBAK by building simple models of horn speakers in both programs and then comparing the results. I have discussed the results with Mr. Chatgpt because I cannot get the comparison right. I do not really know what to expect in terms of similarity between the results. I am not very knowledgeable in electronics or theoretical audio technology but I still think I understand that the sound pressure curves and impedance curves should be quite similar for simple models with these two programs. Mr. Chatgpt has been very helpful I think but "he" has not managed to figure out what I am doing wrong.
I have placed an infinite baffle in the same plane as the horn mouth to get a 2 x pi radiation angle. The speaker element is this 15-inch element:
https://loudspeakerdatabase.com/BC/15DS115_8Ω

I think the impedance curves match quite well, at least the frequency of the first peak, but not quite the level (Hornresp: 4.4 Ohm@125Hz, AKABAK: 3.2 Ohm@128Hz). The second peak matches better in terms of level but worse in terms of frequency (Hornresp: 2.46 Ohm@284Hz, AKABAK: 2.2 Ohm@267Hz).

What bothers me the most is the difference in sound pressure for the two models. AKABAK has a first peak already at 54 Hz and sound pressure 74 dB. This peak does not exist in Hornresp which has its first peak at 125 Hz and 108 dB. The next peak in AKABAK is at 135 Hz and 68 dB. This does not match very well with Hornresp.

It is being developed by Mike Engelhardt (LTSpice creator). It seems to still be in very early development but already looks quite promising. I have tried it out for a few hours and have been quite impressed so far. I will definitely be keeping an eye on this to see how it develops, it would be nice to see some competition in this space as there hasn't really been any major developments made to free simulators in quite some time.

Things that I like are:
Modern interface
Fast
Can write Verilog code blocks that runs natively
You can type the location of where you want a cursor to appear in the waveform viewer

Few weeks ago I encountered a Sonab speaker (I think it was a OA5) fitted with a Philips M9710 driver, the back of the driver covered with a basked lined with damping material.



Photos from Troels Gravensen website here.

Troels descibes the purpose of this construction.

the 9710 driver placed in a metal mesh basket with some heavy glassfiber material between driver and mesh, making a low-pass filter that can be adjusted due to the basket being suspended on three screws that allows you to increase or decrease the acoustic resistance of the fiber material. An acoustic vent, sort of. Something similar can be found on some Lowther drivers.

Click to expand...

I remember having seen similar constructions in fifties and sixties radio's. Seeing it again made me curious, so I did a small experiment using a pair of mini 3 inch woofers (originally from a pair of Peaq PC speakers). I measured the TS parameters, shown right.



To keep it simple I just covered the back of the driver with gaffa tape.


And measured again the TS parameters and impedance. Red is driver impedance, White driver impedance with added mass (7 gram)





Effects:


I repeated the experiment with masking tape instead of gaffa tape. The result was essentially the same. To illustrate the effect of these changes I simulated a closed box with Basta:


Box 2ltr
GHP C=1200uF
Viso=80%
Qb=20

driver no tape Fs (-3dB) = 103Hz, Eff 81,2dB
driver with tape Fs (-3dB0 = 80Hz, Eff. 80,3dB

So for a loss in efficiency of about 1dB we can lower the Fc of the speaker from 103Hz --> 80Hz. The effect seems to be caused by the added mass due to the air enclosed between the cone and tape, and the added resistance to the air moving.

The method used by Sonab seems to be a way to control the effect.

Used in bass boxes some years ago, then stored.
Nice easy way to try aperiodic.

4 small holes I drilled to use screws to mount. Designed for press fit which I also did carefully cutting hole with router.

$40 shipped usps flat rate envelope to usa lower 48.

Thanks, Don

In good working condition. Shipped in dayton boxes, then in usps flat rate box.

$120 to usa lower 48.

Thanks, Don

Unfortunately one late night when tired I hooked one up without a crossover...man, I've only done that a couple times in 40 years of hobby at least. That one is marked with blue tape on the back.
No longer have original boxes so will use some for Dayton tweeters.

$85 shipped conus in USPS flat rate box.

Thanks, Don

All unused. Shipped usps flat rate to usa lower 48.

SOLD. SEOS-8. Pair. Black. $60 shipped. (= 20 each + 20 shipping).

WG-300. Two pairs. Black. $60 shipped per pair.
One is unwrapped, the others still in wrapping.

This is the best way I've learned to ship being on the west coast, otherwise prices climb quickly going east...unfortunately shipping has gone up a lot.
Will be cheaper if you buy multiples. For instance I can get all of them in a large flat rate for $26 shipping.

Thanks, Don

I am using this style of QCC3008 Bluetooth module in my car radio.


I've noticed when audio starts to play after silence, about the first second of it is cut off/not played. This behaviour is different from any wireless earphones I have used, which seem to wait a moment before starting to play.

Does anyone know of an option in ADK configuration tool which may change this? I recently bought a QCC5125 version of this too, which also has the same problem by default.

Just to explain why this is a problem, I have the chip in my car radio and use it for navigation.
Instead of -
"In five mile, turn left"
I get -
"...miles, turn left"

I have a problem with several of these modules for my BGW amplifiers. One module has this problem where -when I plug it in it will work fine for 20 or 30 seconds, then it will make a big "pop" noise and the music will come out distorted. Or, when I turn on the amp, it will make a (snap, crackel, pop) noise, and the music will come out distorted, then it will make another distinct pop noise, and the music will come back out clean again for another minute or two... and then it will make that pop noise again, and the music will come out distorted. Djk, do you have any ideas? It sounds like a cap or something on the module, but I don't know where. Also, I have three other of these modules that are toast. When I turn on the amp with these modules, it imediately cuts off and goes into protection. I have been trying to get some replacement transistors for the modules as well. Djk, I read a previous post to a question you answered about another guy who was trying to replace them too. I know that you said to use MJ15024 for earlier, and MJ15024/25 for later, but I cannot find these anywhere. Some of my modules have Motorola (SJ 7394 7852), or (SJ 7394A 7952/ 7939) or (SJ 7407A 7926) or (RCA 6803407, C, 7913). In the service manual it says to use SJ 7394 (part #1854-7394) for the upper rail of the module, and SJ 7407 (part #1853-7407) for the lower. Does anybody know where I can get some replacements comparable to these at a reasonable cost. Also, does anybody have any additional tips, tricks, comments, or suggestions for testing procedure of the transistiors, -or general maintenance of the modules. I am an amateur and NOT an experienced pro, so I would really appreciate any additional input. Thanks

Hi, this is my first post on this forum. I have however been here many times reading a lot about how to build my nCore mono amplifiers a few years back and also on how to build a stereo Purifi EVAL1 amplifier very recently.

However, I was not able to find a clear step-by-step instruction on how to build a stereo Purifi EVAL1 amp. So I created an instruction myself. I figured it would be nice to share it here as many like me would try to find such an instruction here.

I used the Ghent Audio stereo Purifi case kit, Ghent Audio harness, Hypex SMPS1200A400 and the Purifi EVAL1 module.

Hopefully you like my step-by-step guide. If you have suggestions or find errors, please let me know. Thanks!

Link: iCloud

BR,
Richard

Im new to the forum. Recently I retired from the Voice of America. I worked on high power shortwave transmitters. Ive been in broadcasting over 40 years. My audio interest are horn systems which I have just gotten into. I recently finished a set of EV eliminators modified to be a 4 way system great party speakers. I hope to learn n much here Hve a great summer everyone!

I want to buy or freely download JBL Paragon Impulse Responses to try on my Bose System .
Can you please help me to locate the sources ?

Thank you !
Umut
Istanbul

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.

I'm having trouble figuring out a replacement for a broken inductor for my Definitive Technology Demand D15 tower. It appears to be 20awg solid core, but the inductance on the crossover board says 40mH. Is that right? Thoughts on an adequate replacement?

Also, my local hardware store went out of business and I bought 150' of 18awg wire for 70c. Can I double the wire to get 12awg? Is that "bi-wiring"?

Thank you for the help!

Tubecad 12VAC ACF Rev.2. Built but never powered on. No tubes included. SOLD



Folded Cascode Cen IV - Bare boards - Includes build docs. PENDING



Wayne's BA2018 LS - Built and used. Just moved on to other linestages. SOLD



Salas Reflektor PCB's + Parts kit - $50/each including shipping within the CONUS and transfer fees

I just picked up a pair, also got the tops. Used to have the SP1 variant of these years ago.

I’ve seen some posts from people stating the Klipsch 33, 43 or the Emminence 15c is the way to go in these bins.

I’m using these in my workshop with the occasional yard parties with a pair of Dynaco Mark 3’s.

Does anyone have any experience with these and can recommend a driver for them as well as a complimenting horn driver(s) for a passive 2 or 3 way setup?

This is a long thread with many twists and dead ends. Before diving in, take a look a this first:

• The documentation files of the finished Open Source Monkey Coffin loudspeaker. I am (trying to) keep this up to date!
• The notes at the end of this post, which have some useful hints to navigate the thread.

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

Following up on the earlier Open Source Speaker thread (part I and part II) I am starting a new thread to discuss the develpment of the "Open Source Monkey Coffin".

Here's an update of my earlier Monkey Coffin ideas. Sorry it's so long.

POINTS OF DEPARTURE (as I see them):

• The first poll says it should be a three way, and it's okay to cost more than $500 per box.
• The second poll says that the Monkey Box should be "amplifier friendly" (work well with ACAs or small tube amps, etc.), and it should not be too big (not more than 60-80 L).
• The speaker should be straight forward to make for DIY novices (we don't want to scare them, we want them to run to the hardware shop and build stuff on their kitchen table). There is no point in designing for expert builders, because they will design their own speakers anyway.

MY IMPLEMENTATION IDEAS (I admit these are partially biased by my own preferences, because I need some motivation to actually put some work into this):

• The box shoud be easy enough to make on a kitchen table. Dimensions roughly 30 x 65 x 30 cm or so (will depend on the requirements of the drivers and box tuning).
• For "weak amp compatibility" I set the efficiency target to 92 dB/2.83V/1m, with bass extension to 45 Hz (-3 dB). Achieving this will not be very easy.
• The impedance curve should be flatish and qualify as "8 Ohm". This means we can't "cheat" with the efficiency target by using low-impedance drivers.
• Use high-quality drivers/parts with the right tech specs for the task. The look of the drivers has to be "right" for a HiFi system in a home environment, but is second priority after the tech specs (people may not want to build a speaker that does not look "right").
• Woofer: The woofer will likely be the limiting factor that determines the size/bass-extension/efficiency compromise. I guess a 10" unit would be the right choice here. The earlier threads already mentioned a few units that might be interesting for this design (Fane Sovereign Pro 10-300SC, Ciare FXE 10-2.5, Volt BM251.3, some Beymas, etc.). We'll have to look at this some more.
• Midrange: Needs to keep up with the SPL requirements, so many of the conventional "HiFi" midranges are out. I have some experience with the ATC SM75-150 dome, which is VERY good, expensive, and not available to DIYers anymore. When ATC stopped selling to the DIY market, Volt released the VM752 dome, which is a very good clone of the ATC driver. I really want to use the Volt VM752 dome. It can be used from its fs (400 Hz) up to about 3 kHz or so.
• Tweeter: There are many good tweeters out there. I am a big fan of Be dome tweeters (ScanSpeak D3004/6640, SB Acoustics Satori TW29BN). I also read a bit about waveguides, which do good things. They help with matching the dispersion of the tweeter to the midrange, they reduce the effects of baffle diffraction, they increase the on-axis efficiency, and they reduce non-linear distortion of the tweeter (by reducing the drive voltage for a given SPL). At the moment I can't think of a reason why we should not use a waveguide.
• Cross over filters: the x-over frequencies will depend quite a bit on the driver choices. However, if possible, I like to set the woofer/midrange x-over frequency such that it fits the baffle-step centre frequency. This makes it easier to compensate the baffle step by fiddling with the woofer SPL vs midrange SPL. If the drivers allow, I like using 6 dB/octave filters because it's easier to get the time-domain response of the loudspeaker right. In my experiments, my ears preferred 6 dB filters over 12 dB filters.
• I will openly admit that costs are not my first priority. If the right parts cost a lot of money and there are no alternatives, so be it. The earlier threads indicated that it's ok if the parts cost is more than $500 per speaker. Some said $1000. My priority is to make this a very good speaker, and suitable parts may cost a bit of money. In the end, there will always be substantial flexibility with costs related to x-over parts and enclosure materials + finishing.

NEXT STEPS AND QUESTIONS (everyone has his/her own approach to loudspeaker design, but here's my suggestion):

• In the first step we'll have to narrow down the driver choices. This will be a forward-and-backward process between driver suggestions and model runs using these drivers, always keeping the design targets in mind. I'd suggest choosing a woofer first, because that will define the box size, bass extension, and sensitivity. Let's say the midrange is set (yes, you are allowed to complain, but... ). The tweeter comes last.
  Question: What input data do we need for these model runs? Do we need actual measurements of the drivers in their baffle/box? I am not big with modelling tools, and I tend to replace detailed model runs by measurements from prototypes. Others might be more efficient than this by using their modelling tools.
• The second step is to build an actual prototype. Now we need money to buy parts. If the design is still attractive to me (i.e., it's something that I'd like to build and use myself), I'd be willing to put in some money and go for it. I could also do measurements.
  Question: How will the funding work? Anyone experienced with raising and managing money for open source projects? Anyone willing to put some cash on the table? Who will manage the money, and how?
• The third step is to tweak the prototype. Again, this will be another forward-and-backward process. And we may need more money.

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

Notes and updates:

Important note 31 Oct. 2019: DIYers may profit from this open-source project for their own private purposes, for example by building and enjoying a copy of the Open Source Monkey Coffin speaker. Please do not use the information developed in this open source project on a larger scale (for example by selling speakers based on the Open Source Monkey Coffin design or substantial parts of it) without written permission.

Note 4 Oct. 2018: This project has received financial support from LORDSANSUI, Paul Vancluysen, George Wright, KaffiMann, Charles Bueche, zimmer64, John Barbor, and others (anonymous) here. Thank you!

Note 10 Nov. 2019: This project has come a very long way, and the OSMC design is now completed. The design goals have been largely met, but some of the early implementation ideas have changed a bit along the way (x-over topology, woofer size, tweeter details). The full documentation of the OSMC design is here: https://github.com/mbrennwa/osmcdoc

Note 4 Oct. 2018 and 18 Nov. 2019: Final choice of drivers:

• Tweeter: ScanSpeak R2904/7000 ring radiator (post 295 and follow ups) with a custom waveguide as described in post 881 (available via group buy or by DIY 3D printing or CNC machining).
• Midrange: Volt VM752 3" textile dome
• Woofer: FaitalPRO 12PR320 12" paper cone (see post 162 and post 244).

Note 18 Nov. 2019: Final enclosure is in post 925 (drawings) and post 930 (photos, showing stuffing).

Note 18 Nov. 2019: Final x-over is in post 931.

Note 18 Nov. 2019: The polar response diagrams (horizontal and vertical) are in post 895.

Note 18 Nov. 2019: The power response is in post 901.

Note 18 Nov. 2019: The electrical impedance is in post 900.

Note 19 Feb. 2020: A bunch of graphs with test results as compiled from the documentation on GitHub (on-axis SPL response, step response, polar response, cumulative decay spectrum (CSD) are in post 917.

Note 9 May 2020: If you don't know where to look, here's a list with some shops and retailers for OSMC parts:

• diyAudio group buy for the OSMC tweeter waveguides
• Falcon (Europe): Scan 2904 tweeter, Volt VM752 midrange driver, x-over parts, etc.
• Solen (Canada, US): Scan 2904 tweeter, Volt VM752 midrange driver, x-over parts, etc.
• Audiohobby (free shipping everywhere!?): Scan 2904 tweeter, x-over parts, bass-reflex ports
• US Speaker (US): Faital 12PR320 woofer
• Blue Aran (Europe): Faital 12PR320 woofer
• Acoustical Surfaces (US): Melamine foam. Contact person: Tom Ewert +1 (952) 466-8229. They also sell in small quantities!
• Ebay: Melamine foam
• Buttinette (yes...): lambs wool
• Deer Creek Audio: Custom speaker stands

I am constructing a truncated line array with a single tweeter.

The 2 configurations that I am considering are

1. D'Appolito style
2. Uniform array with the tweeter offset

I am leaning toward 2. since the tweeter voice coil will be nearer to the listener in configuration 1.

Hi everyone,

My name is Friedrich, I’m from Germany, and I’ve been into DIY audio for quite a while now. Over the years, I’ve built a variety of speakers — sealed, ported, transmission lines — and a few amplifiers as well, including some SymAsyms. I’m currently working on my take on the Aleph P 1.7 preamp.

Now it’s time for something new: horn speakers. My first project in this area will be a clone of the Avantgarde Acoustic Zero XD, a speaker that’s inspired me for a long time. I'm really looking forward to the challenges ahead and learning from the collective wisdom of this community.

Glad to be here and excited to connect!

– Friedrich

I drove 8 hrs to pick up these three BEL 1001 Mk5 amplifiers a couple of days ago! From one private seller. I am ecstatic! This makes 11 of them. I wasn't planning on buying them, but the deal was way too good!

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

11/05/25 - Alternative P/N for the main heatsink. Details at post #368

My system lacks deep bass response—below approximately 65Hz—while the speakers have dual 10” woofers per cabinet; Braun LS200. The amplifier is an integrated amplifier Braun atelier A2. I normally don’t use Loudness button and tone controls (both bass and treble knobs).

In fact, the Braun LS200 were launched with their own amplifiers which would be attached to the recess at the back of the cabinets modeled Braun PA1. The PA1 literally has a deep bass adjustment knob which allows user to boost or cut deep bass output by +/-3dB. The deep bass is referred to 25Hz frequency according to the user manual. Nevertheless, there’s an alternative choice for amplifying these speakers. It’s a separated component launched for them as well which are Braun CC4 and PA4, preamplifier and power amplifier, respectively. The CC4 also has deep bass boost adjustment where deep bass is referred to 20Hz and level is 0-6dB range.

As you can see, it’s likely that the LS200 speakers were designed to have deep bass assistance by electronic. And, I couldn’t agree more with this idea. As mentioned earlier, I use an integrated amplifier, A2, with linear mode operation—never use Loudness and tone controls.

I’d like to ask how can I get deep bass assistance with the lowest cost, except using anything cosmetics the signal such as Loudness, EQ, and Tone Controls?

Actually, I also have the answer in my mind that is using a subwoofer. However, the question was initiated because my subwoofer is now being repaired, Lol. And I thought I already have four 10” bass drivers in my hands, so is there any way to maximize outcomes from them?

I would love to hear everyone’s thoughts.

I was looking around for quite some time trying to find a simple buffer to drive my high gain power amplifier and now I am really interested about this B1 project, so Mr. Pass are there any news about it?


Will it contain also volume control and selector as complete preamp unit?

Hello friends.


I have this zener follower regulator below and its input is 120 VAC; here in Canada that's the mains voltage. Although I do have a suitable transformer for it, for space and weight considerations it would be nice if I could dispense with it and hook up directly to the mains (ceramic fuse protected). I believe the correct term for such a connection is "in-line" ?.



Of course in that case the circuit ground above would not be tied to mains earth as that would shunt a diode at each half cycle, neutral and earth being tied at the distribution panel. This circuit feeds an ultrasonic vacuum tube heater supply that has an output transformer; so the business end will be isolated and grounded.

For safety and also EMI reduction, the whole contraption would be put in a grounded metallic case, which in turn would sit in the main amp enclosure, also earthed - Implementing class II double isolation. Not shown on schematic, discharge resistors across the caps both upstream and downstream of the pass mosfet would be placed for added safety.

So.............. What can go wrong right ?
As always, thanks in advance for any insights.

Joris

Nelson Pass testing procedure and instructions for DIY Sony Vfet amp -

Print this out!! 🙂

http://www.firstwatt.com/pdf/art_diy_sony_vfet.pdf

Pass DIY Sony Vfet amplifier illustrated build guide.


The Pass DIY Sony Vfet is a power amplifier from the brilliant mind of our technical, spiritual, and menu advisor, Nelson Pass. Quite possibly the most generous design yet, as Nelson released his private stash of the out of production 1970's Vfet to the DIY community so we can build an amp that nobody else can build nor buy. 🙂

How the circuit works


The Front End





The overall schematic of the VFET amp is somewhat complicated in spite of the simple gain path – this is due to the special DC regulation circuits to cater to the fussy VFET transistors in the output stage.

Fortunately the front end voltage gain stage of the amplifier is pretty simple.

The Vfet DIY Front-end is basically a mini-F5. It serves to give us enough voltage and current gain to drive the Vfets so we can wire the Vfet as followers (known as “Common Drain operation, where no voltage gain is acquired, only current).

The input signal starts at R1 (2,2K), which acts as a “gate-stopper” resistor for the input Jfets, as well as a current limiter in case the attached preamp has a big turn-on or -off thump. R2, (47K) is from the input of the Jfet to ground, this gives the Jfet gates a reference to ground, and also sets the input impedance, which is about 50K.

The signal goes through the Jfets (Q1,2) and the gain currents at their Drain outputs go through the cascode transistors (Q3,4) and then to drive the Gates of the voltage amplification (Vas) Mosfets (Q5,6). The cascode transistors, Q3 and Q4, act as a voltage umbrellas, protecting the Jfets from the voltages appearing at T11 and T13 so that their Drains experience a fraction of the DC and AC voltage T11 and T13 as determined by R7, R9 and R8, R10 driving Q3 and Q4.

To quote Mr. Pass, “Cascoding is a very useful technique where the gain transistor (in this case each of the Jfets) is coupled to another transistor operated in Common-Gate or Common-Base mode. This cascode transistor contributes very little of its own characteristic to the amplification, but it acts like a voltage umbrella, shielding the gain transistor from the high DC voltage and noise of the power supply rails.”

The Drain pins of Q5 and Q6 deliver the output voltage (but not enough current) to drive loudspeakers. This point is found at test node T18.

Mosfet Q5 and Q6 need some voltage applied to their gates in order to turn on (bias) and amplify signal, and this is provided by the voltage appearing across R35 + P3 and R34 +P4. P3 and P4 are there to adjust this voltage so as to set the right amount of current through Q4 and Q6. This right amount of current is defined by 1.5 V DC appearing across resistors R5 and R6 AND the output of the front end (T18) near 0 volts DC. So P3 and P4 not only adjust the idle current through the voltage gain transistors Q5 and Q6, but they also set the DC output that appears on their Drain pins.

Adjusting the Front End bias

Bias is set by measuring the DC voltage across R5, (test nodes T6-T7), and R6 (test nodes T8-T9). Proper bias is when you have 1.5V across each of these resistors, at the same time also having 0 volts DC offset, which is the voltage at T18 to GND.

Adjusting P3 and P4 will make changes in all three of those readings, so in my opinion, you must have three DC voltmeters to make this an easy job. Even the very inexpensive Chinese DMM will work fine for this, just make sure they have good, fresh batteries in them.

A single voltmeter will do that job, but it is more tedious. In any case you want to adjust each pot in small steps, going between the pots and voltage measurements in rotation.

You start with both potentiometers at full counterclockwise, which is the lowest bias setting. At first you are simply looking to get the voltages across R5 and R6 up to 1.5 in small steps. You turn P3 just a little bit, measuring a small change across R5, and then you do the same for P4 and R6. And then you go back to P3/R6 and repeat this process, raising the DC voltages slowly and in equal amounts.

You also want to check the DC voltage from T18 to ground as you do this – you want to keep it near 0V if possible.

I suggest you pause at around 1 V on R5 and R6 – as the Mosfets heat up, the current will rise on its own. Eventually you will find yourself with “warm” settings which give about 1.5V DC bias and close to 0 V DC output at T18.

How good is good enough? 1.3 V to 1.7V is OK for bias. +/-200 mV is good enough for offset at this point. We will tweak these values after the completed amplifier has run for a bit.

REMEMBER – BABY STEPS ON ALL ADJUSTMENTS.

If for some reason you can’t achieve full bias with zero offset, please troubleshoot in the build guide thread, and do tell us how much bias you can get with zero offset.




Please refer to the above schematic for component names

The output stage -





The Vfets themselves are wired as a complementary pair in source-follower mode. These add current gain to the signal sent to their Gate pins (to be able to drive speakers with a low output impedance) but have no voltage gain.

That’s it - the voltage gain has happened in the Front-End, and the Vfets just add current capability. 🙂

 But it’s not quite that simple… is it?

Well, it actually is, until you realize that the DC powering up the Vfets must be regulated for a stable DC voltage and low noise, the same with the bias voltage. Also, both the rail voltage and the bias voltage have to power-up and power-down in a specific order to keep the Vfets from trying to draw a ton of current when the circuit is powered up.



What’s the proof of Nelson’s genius in this circuit? In how simple (and quite effective) the regulator sections have been designed. Let’s talk about that now.



Regulators



Each rail of each channel has 2 regulators, for a total of 4. Each of the two rails has a bias regulator and an output stage regulator. For clarity’s sake, I’m now going to talk about the positive rail’s regs - the negative rails have the same thing, just in a mirror image.



Both regulators use a TL431, a nice little 3-pin shunt reg that can have it’s output voltage set by 2 resistors. 

Looking at the schematic around Q11, you can see the unregulated voltage coming from the rail through a simple RC filter (R29 and C7) then through R13 (2.21K) and then the set resistors R11 (10K) and P1 (5K pot).

Because one of the two set resistors is a potentiometer wired as a variable resistor, changing that pot value changes the set voltage which provides Vfet voltage bias. It is very important that the bias voltage is place when power is applied to the Drain of the VFET, so this regulator circuit (bias reg) is designed to charge up much faster than the regulated voltage powering the Drain. (The output stage regulator)



Remember how it was mentioned earlier that the Sony Vfets are “Depletion” mode? They are normally on, letting current flow, and require a negative voltage applied to the gate to turn them off (this for the N type – The P channel devices require a positive voltage), or to otherwise set the value of the current (bias) through the VFET.

Looking at the regulated voltage at T19, (+14V) you want to note that it crosses over and connects to the gate of the negative P-channel Vfet Q10. The positive N-channel Vfet Q9, is likewise biased from the opposite rail. This is the opposite of what you are normally going to see with complementary Mosfet followers.



Moving on to the output regulators, you can see the circuitry near Q13 looks similar to the other reg, the exception being the voltage setting resistors are both fixed resistors. (R15, R17) These resistors and the TL431 make a voltage of 24V, seen at T2. This fixed voltage is controls the gate of a power Mosfet, Q7. This Mosfet is slaved to the regulator and lets the tiny TO-92 package regulator control many amps of current. Wonderful! This is necessary because the regulator needs to regulate the power going to the output stage which drives your speakers.

However there is no free lunch, and the Mosfet eats up about 4.2V (the Mosfet’s Vgs) in payment for doing it’s job. This is why you see a regulated rail voltage presented to the drains of the*Vfets of 19.8V (or so). An important part of the rail regulators is C1 (220uF), there to delay the arrival of this 19.8V to give the bias regulator time to ramp up. More about this here;



Power-up and power-down sequencing.



Back to depletion mode devices - The Vfets are normally on, right? We need to apply a bias voltage to control them. If the bias voltage isn’t there controlling current flow when the rail regulators power up, the Vfets will conduct an excessive amount of current and the 40-year old, completely irreplaceable smoke made from vintage Japanese un-obtainium, ground unicorn horn and pixie dust will escape. A sad result which will also smell bad.


So we must have the bias regulator working before the rail voltage is turned on. 

How did Nelson do it? A simple application of the time constant to charge 2 differently sized capacitors in the regulator circuits. The regulator with the smaller capacitor will turn on before the one with the larger cap. These caps in the race are C3 (47uF) on the bias reg and C1 (220uF) on the output regulator. It’s a 4.7-to-1 ratio and C3 will be charged about 4.7 times sooner.



The TL431 are shunt regulators, so they do not conduct current until the voltage rises to the regulation value, and then they conduct so as to hold that value.


So what about power down? The rail voltage needs to be turned off before the bias voltage. (the opposite of power-up) BUT, the big cap/small cap ratio will NOT work in our favor when shutting down. It would work exactly how you’d expect, where the small cap will discharge before the big one.

So what? The VFETs will drain the supply quickly enough, but when the supply voltage drops down quickly we may find the Gate to Source voltage (Vgs) of the Mosfet at a high enough voltage to stress the transistor into failure. It's not that likely, but everyone knows that Pass wears both a belt and suspenders to hold up his pants, and this is reflected in his design.

The fix is a simple 2-cent diode. On power down, D1 will be a very attractive and very low-resistance discharge path for C1, discharging it rapidly and turning Q7 (and Q13) off, and therefore the rail voltage to the Vfets. Because there is no special path for C3 in the bias regulator to discharge, it will operate for a longer time, which is perfectly ok.



The stuff in the middle.

Ok, so far everything has been explained except for the wiggles in the center of the schematic near T16 and T17. Remember how the bias voltage regulator is set by the divider made from R11 and P1? This is a DC value but we also need to let the AC have it’s say in the circuit, as the AC is our music. 🙂 The Front-End output signal was all big and powerful the last time we left it at T18. Now this signal needs to get to the Gates of the Vfets to move our speakers, and that signal (even though it’s AC) can get pretty darn big. Big enough that it’s voltage could effect the current flowing through the regulator set resistors. The network of C5, C6 and R21 through R24 prevent the music signal from having much influence on the bias regulators. Stable bias makes for happy Vfets, so this is a good thing.



What’s left… Um… R25 R26 (221ohm) are gatestoppers for the Vfet, R33 (22.1K) adjusts the brightness of the LED (which must be blue, this is a Pass amp, after all…) and R32 (0.1ohm) gives a place to measure the output stage current. (Bias)



Global feedback is applied from the output stage from the Vfets to the Jfets through R3 (2.21K), and then R4 (332ohm) to ground.


Cool! That's the basic overview of how it works. Let's build!!

😀 😀 😀





.

Hello DIYAudio community,

Couple of years ago I’ve designed a DSP Class-D amplifier called Centure 21. It has got ADAU1452 DSP, TAS5548 as I2S->PWM modulator and 4 output channels, with 4 more available on the "PWM" header.

and photo of the prototype:



on the left there is Amanero header, which can be used for amanero module to have just USB 2 ch input, or my York interface. There was also header on the left side with S/PDIF and I2S which are connected to ADAU1452. The purpose is to connect daugter boards with different input interfaces: ADC, AES/EBU, TOSLINK etc. The module was used primarily for home audio.

After some discussion here on DIYaudio with @florentg (https://www.diyaudio.com/community/...-dsp-bluetooth-aux.376006/page-2#post-7719605) we meet in person played with the Centure 21 and discussed what we could do in the field of DSP amps, the specs and software and ways to build something better. Recently TI announced a new amplifier IC TAS6584 which basically combines I2S→PWM modulator and the output stage but also have some quite interesting features, like the H-Class power supply control.

So a new device was developed 🙂

Structure of Centure 24:



The structure of new version is quite similar to previous one: there is DC-DC for output stages, a DSP chip and MCU to control and monitor the system. The main difference is in more advanced diagnostic and monitoring of the sysem, thanks to TAS6584. Also since TAS6584 implement H-Class control together with the DC-DC, this fetature is also available and can be enabled/disabled via software. Here is demo from TI: https://www.ti.com/video/6287333584001



This time the module designed such that it can be also used as the plate amp: all the interfaces (S/PDIF, I2S, I2C) are routed to headers and supposed to be connected to interface board (which is not ready yet):



The amplifier has 4 channels which can be configured as 4xBTL, 2XBTL + PBTL or 2xPBTL. So it allows fleaxible configuration for multiway systems. The nominal output power would be around 200W for all channels combined, the peak power of course would be higher. Not all measurements are done, only up to 100W/channel.

There is also software development going on which is based on the York interface (thread on DIYaudio: https://www.diyaudio.com/community/...tichannel-input-output-interface-york.413504/)




Live monitor of Class-H operation:




Measurements, experiments with the H-Class control and config software features will be posted later.

I was wondering if someone has done a 1ET9040 build and could share some details? I only have the Micro audio Cobra S1 SMPS set, the 1ET9040 and a pair of the new Neurochrome buffers. That means I will need to source the cabling, switches and enclosures, anyone seen or has an idea where to look? Will be truly appreciated!

Hello. I'm about to build a speaker with Markaudio CHN110-Silver.
I see plans supplied by the manufacturer.
My question is if it is necessary to add a circuit for baffle step compensation, or does the bass compensation depend on the volume size of the box?

https://www.fane-international.com/view-product/FC-152F01TC

http://www.diyaudio.com/forums/full-range/308652-15-range-fane-6.html#post5219071

The DIY ACA mini (Amp Camp Amp mini) is in the process of shipping to
the Burning Amp Festival lottery winners and a few of the helpers and
associates.

I am pleased to present the DIY ACA mini article here (in two parts as it
exceeds the size limit of the forum).

There has been at least one addition to the design since BAF, and here's
your chance to look at it again and in more detail.

I am hoping that 6L6 will provide us with one of his usual exemplary build
guides, and I anticipate more general availability of this piece in the
future, as it was intended as a low cost, easily accessed project.



----
See Also:

• ACA Mini Bill of Materials V1.1 (currently used in the ACA Mini completion kit)
• Note about how to bend the trimpot leads in the current batch of completion kits

Hello,

here I want to describe how I do make a sandwich cone with aluminium foil.

This can be done with normal household aluminium foil and normal glue you can buy everywhere as "universal glue".

You need a scissor and the materials like aluminium foil, glue and the loudspeaker.

The foil can be applied easily to paper cones / diaphragms.

You can use thin aluminium foil from the gold smith and the glue they sell (in german "Anlegemilch") for making sandwich cones with polypropylene loudspeaker cones as here normal glue will not work. Also for delicate whizzer cones the thin aluminium foil from the goldsmith will be a better choice.

More information on this concerning loudspeaker history and theory in this thread and my post:
https://www.diyaudio.com/community/...cone-speaker-cone-profile.402470/post-7432593

I am considering this kit as an all-in-one solution to the problem of in-room bass response for a full range speaker (HiFi use only). I suspect it could give me Vandersteen-tier performance.

I like that you don't need to have two subs scattered around the room, or an in-line filter or DSP. Plus the 94dB sensitivity means I can use a cheaper amp.

Does anyone know of any pitfalls going down this path? GR Research's kits and speakers are highly rated and the designer seems to know what he is talking about.

https://gr-research.com/product/old..._subwoofer-jumper-set=Include+$75&zCountry=AU. (scroll for videos)

review:
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Guys

I have this transfomer ,, I want to use it with my transistor amplifier c5198 A1941 or c5200 a1943

My transfomer is 28 0 28 1.3A =72.8VA

My question is ..is that 72 watts or VA

If it's VA then we have to multiply it by 0.8 and then we get 57.6w which is usable power

Then class AB efficiency is only 50 to 70%

Let's assume 65% then we get 37w

Am I right with the calculation?

Then wat if I'll be using 24 0 24 5A transfoma how much power can I get with one channel (mono) or stereo or stereo and one extra channel for bass pls help

I have to remove a PCB from its heatsink in order to remove and replace a few components. Is it better to desolder the mosfets from the pcb and then remove the pcb (leaving the mosfets attached to the heatsink) or disconnect the mosfets from the heatsink and remove the pcb along with the mosfets?
Thanks for any help.

Hi,

There are many boards from Tinysine that use I2S input to ADAU1701 and then use the inbuilt DACs of the chip. It is comforting that the ADCs are not used and one can feed I2S from Toslink, Coaxial, bluetooth, and of course one could take HDMI ARC converter and feed Toslink to these amp boards from TV too.

The board I have in mind is this https://www.tinysineaudio.com/products/tsa1702c-spdif-coaxial-dsp-audio-receiver-board

Does the DAC quality matter on real speakers?
My speakers are https://jblpro.com/en/products/jbl-nano-k8
And I am building 12 inch stereo subs using TPA3255 for a 2.2 system.

The reason why I ask this question is I have a feeling that one could make out the deficiency of the ADAU170 DACs using headphone based listening but probably not speakers.

Warm Regards,
WonderfuAudio

I have designed adapter boards for replacing original relays found in APT Holman preamplifiers. These relays (IDEC and Aromat) are now about 40 years old; replacements are difficult to find at best, and are not optimal for low-signal usage - they were general purpose relays. Owners of these preamps know by now that one of the most common failures in these otherwise excellent units is the relay. Relays are a maintenance item, and when they are decades old, replacement/upgrade is a good idea. We're fortunate to have really high-quality relays available in small sizes like this Omron. I've installed and tested them in my 3 APT Holman preamps, and they look and function great. Total height is much lower, since the new Omron relays are really tiny compared to the original relays. Link to Omron relay datasheet: Omron G6S

My adapter boards are extremely compact - just barely larger than the original relay footprint. They utilize a top-quality, low-signal current production relay - Omron G6S-2-Y - that has very low current draw, very low contact resistance, and very high cyclic life. They are used in expensive, high-quality audio equipment by major manufacturers, and I've used dozens and dozens of them in my multi-relay input selector boards. Their performance is excellent, even with very low MC phono signals, as well as line-level output signals.

These are sold as completed and tested (on a jig with a flyback diode connected to my lab power supply) assemblies so you don't have to solder the pins or relay. The boards use header pins to connect to the original APT main preamp board. Just desolder your old relay, and pop in the new relay board assembly and resolder. I recommend you seat the pins only deep enough to solder properly so you don't have to trim the pins - there is no need to seat the adapter board against the PCB.

For the Aromat adapter board, I've revised the design to includes pads for the flyback diode closely across the power supply pads of the new Omron relay, rather than an inch or so away on the main PCB. If you want to keep your original layout, just ignore the new diode pads on the adapter board, but if you want the revised layout, let me know when you order and I'll solder in a 1N4148 for free - you will then remove the flyback diode on the Apt PCB when you replace your Aromat relay with the new board assembly.

Assemblies will be shipped by USPS in a padded envelope, with additional protection around each relay assembly. Postage costs me between $5.50 and $6.50 per envelope which costs more than $1 each, so total price is very reasonable - $34.00 for either version including shipping and PP fees (Continental US only) if using Good and Services, or $32.00 if using Friends and Family.

I've installed and tested them in my 3 APT Holman preamps, and they look and function great. Total height is much lower, since the new Omron relays are really tiny compared to the original relays.

Link to Omron relay datasheet:
Omron G6S




I've had a couple of questions about how to access the relay, and how to determine which factory relay is installed.
There is a bottom panel held on with Phillips head screws that are easily removed. The relay will be readily visible - you can take a photo of your relay and if you have either the Aromat or IDEC I'll let you know which one of my boards is correct.

Here are the Aromat (left) and IDEC (right) original relays. Pinouts are completely different, so the adapter boards are specific. Additionally, please read the voltage markings on your relay so we are sure your unit uses a 24VDC part.

Hi everyone,
I bought this Nemesis as is and the output Mosfets were annihilated. All 10 were destroyed. On the botton side there was 5 IRF3205'and naturally I assumed that the top would be the same. After further troubleshooting I noticed that they were not all the same. The top side had only two as pictured, PLUS a MUR2020CT and 2 goofy ones marked 01A. I feel like that is incorrect. Any inputs you guys are really appreciated.
Preview attachment IMG_2569.jpg
https://mail.google.com/mail/u/0?ui...attid=006C07E4-A75D-4FBE-9EAA-7B3B41B2B92F&zw
https://mail.google.com/mail/u/0?ui...attid=006C07E4-A75D-4FBE-9EAA-7B3B41B2B92F&zw


Preview attachment IMG_2570.jpg



Preview attachment IMG_2571.jpg




IMG_2571.jpg
4.7 MB


Preview attachment IMG_2573.jpg




IMG_2573.jpg
5.4 MB

Preview attachment IMG_2572.jpg




IMG_2572.jpg
4.8 MB

IMG_2570.jpg
4.5 MB

IMG_2569.jpg
3.6 MB

Some might call me a glutton for punishment, but I have taken on one of these that’s sickly and that has even had modification attempts! I’m nearly at the point of digging into the power supply. It’s great to have schematics available online, but I’m struggling with identifying ZD12. It‘s labelled as a ZD20, but I’m clueless at exactly what that specific Zener is. Would anyone know?

Over the next few months, I'll be building the DynakitParts ST-35 with their bias control upgrade and choke. I also will be doing some other simple and inexpensive upgrades, whether "necessary" or not. I have opted not to use "enhanced fixed bias" circuitry, choosing instead the bias kit from DynakitParts that allows adjusting each tube individually.

It's a very nice kit, complete with everything needed except tools, solder, and tubes. It even comes with a free Dynakit ball cap. https://www.dynakitparts.com/shop/st-35-kit-120-vac/



I did purchase the optional tube cage as shown above, but I doubt that I will ever use it. Some future owner might though. I might open up the solid sheet metal sides and install matching perforated metal if I can get a small quantity of it.

A discussion of tube lifespan and possible power supply mods is here: https://www.diyaudio.com/community/threads/dynakitparts-st-35-power-supply-mods.398189/

The first "upgrade" was to purchase a 14/3 power cord. The kit comes with an adequate 18/3 power cord with inline rocker switch, but I will be installing a switch on the chassis instead, ideally a rocker switch on the front panel if I can find one that will fit.

Today I mounted four larger rubber feet to the bottom of the chassis. The ones that come with it are very, very small, making it hard to lift or move the amplifier because you can't get your fingers under it. I just happened to have four new rubber feet from some other project in my parts box and some screws and washers that fit, so that worked out great.

The two power supply diodes look a bit skimpy by today's standards, so I'll order a couple of 3A diodes if I don't have any in my parts box.

The four coupling caps (C4 and C5) that came with the kit probably are fine, but I'll upgrade those with something a little nicer like the ones shown in the video at the bottom of this post. I'm not sure what those are though. What's a good cap to use without busting the budget and given the obvious space contraints? If Mouser sells something good, I'll be placing an order from them anyway so I could save on shipping charges.

I can't stand silver audio components, so everything is now satin black, including the choke and the quad cap. I have decided for a variety of reasons to stuff different capacitor values into a quad cap can that I emptied out, rather than use the included 60/40/20 uF 450VDC 100uF 25VDC quad cap. The 100uF section isn't used with the bias upgrade kit, so I only need three caps not four. I have retained the terminals and locking tabs unused and undamaged. I bought a cap that had a sticker on it instead of stamped values on the can so I can make a decal to show the values that I actually put inside along with the date.




I have completed the artwork for a new set of white decals to go on the satin black chassis. I haven't had them printed yet because I may use triple binding posts for the speakers instead of just the 8 ohm outputs, and I may be able to fit a power switch on the front.




My first technical question is, with modern equipment, C1 is no longer necessary, correct?




I'll be ordering some 6P14P-EV or 6P14P-ER tubes for it. The ST-35 runs the tubes quite hard, and those military ruggedized versions of the EL84 can handle it.

I'm not sure if there is any real need for the CL-90 inrush current limiter, but it seems to be a popular option.




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Update: here is the final schematic as-built. Parts in red indicate additions/changes vs. the kit.

I currently am running a pair of k402MEHs as a 3 way with a pair of f20 subs. I just picked up a Yamaha sp2060 and it offers a 2 way + sub configuration and a 3 way configuration. I like having the full range for my stereo setup (my MEHs will dom20hz to 20k, but I am pushing the M3H 15"Celestion woofers too hard..hence using as a 3 way now).
What is the difference, and what would the advantages and disadvantages be. I am using a Denafrips Athena 2 channel preamp for my stereo setup and feed my Marantz av8805a into one input on the Athena for movies.

I would like to introduce AST Conductors, a new company in the market, but with
a history of several years of advanced R&D. We have been passionate
audiophiles and DIYers forever and we also happen to include in our team accomplished
metallurgists with connections to the research community.
For several years we were discussing ways to develop the best possible silver
conductor, as there were products in the market which indicated that there is some
upside there,
Having rewired several amps and other equipment (both DIY or not) we knew very well
the importance of the hookup wire quality and, of course, the material used in cables.
So we embarked on this R&D journey and invested in some pretty high-tech equipment
for the production of silver wires.
We managed to achieve a purity of 6N+ measured by a very specialised independent lab in
France.
The sonic results were very positive from the beginning and, as we were improving our
processes and lab results, they were becoming really impressive.
Ultrapure silver, when correctly processed, sounds extremely detailed and balanced,
very harmonically rich and smooth sounding. Maybe its most important characteristic
is its naturalness. It does not have any of the typical silver \glare' and aggressiveness.
Even a short piece makes a clear difference in a system's sound quality.

We are getting excellent feedback from our customers, which include DIYers and
audio manufacturers.

Having sent some samples around we were pleasantly surprised to have our first
Youtube review by channel iiWi.
You can see it here:

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And you can read more at www.astconductors.com

SInce the start of this year our products are for sale and we are preparing a proper
webshop. Currently we receive our orders by email.

So, we are very happy to present ourselves to the community here (which in the past has included
members of our team) and answer any questions or enquiries.
Nick Mesimeris, General Manager AST Conductors

under
Schiit Audio: Audio Products Designed and Built in California
I read this:

Choose Magni 3+ for the ultimate expression of an affordable all-discrete current-feedback headphone amp. It’s now seriously like a mini speaker amp, right down to the driver stage and Vbe multiplier. Magni 3+ is in our traditional silver and gray chassis.

but in post #130 under
Review and Measurements of Topping A30 and Schiit Magni 3 Headphone Amps | Page 7 | Audio Science Review (ASR) Forum
and
Schiit Magni 3 abgefackelt - Verstarker, Lautsprecher, Zubehor - Analogue Audio Association
so as in the attachment (first both images) you will find versions with destroyed output stages.

A headphone friend I know well wanted to hear my opinion on this device because he is playing with the idea of getting this device.
But after checking the web I found the above mentioned (I was shocked), so that I strongly advise against buying it.

Nevertheless I want to know the reason for that or at least the schematic, which isn't online for download.

Hello All!

I just built two Elekit TU-8888 monoblock amps. One is working fine I have issues with the second. Look forward to discussing. I built a TU-8200 using Sophia Electric EL34 several years ago.

Full meaning the whole thing.....

I last listenend to my BEST OF MOUNTAIN record 🙂

Hi ! It is something about impedance matching or what else ? Capacitors value are so small that my multimeter shows 0.01nF that propably be an error, but it measures values about 5-10nF very well...

Hello Audio Enthusiasts! Some of you may know my work on www.audiocircuit.com, where for many years I have been helping to advise Acoustat owners. I was an engineer and manager with Acoustat, starting when the David Hafler Co bought Acoustat out of bankruptcy, right up to the very end of US production under Rockford Corp ownership (sad day that was!). So I thought I'd lend a hand here, too, because I LOVE Acoustats and want to help as many owners as possible to keep their Acoustats running for many years to come. I don't sell parts or do repairs, but my advice is FREE! So let me know how I can help YOU with your ACOUSTAT's! (And this being a DYI crowd, I don't mind discussing modifications to the speakers.)

Andy Szabo

stay safe my friends!

here are some projects i am working on at home

first i got some old vifa midranges back from a friend, and I got small dayton amt to mate them with
vifa 13wh-00-08 is somewhat special midrange, free of the breakup grunge, even the ones i got are old, they still measure nice

here are some pics from the build, work in progress

may go active!

I've used easyEDA to create an EF2 Blameless-style amp schematic and find it easy to use, but up to a point. After 14 months of reading Netflag breaks/errors and fixing these only to Save and Refresh and see rework dissapear or flags reappear, I've decided to swallow my pride ask for help.

My aim is to sell PCBs to raise money for a Social Enterprise [OneDollarGlasses] and local charity [SeeScape] - both support people with vision issues. Should anyone have an interest in assisting me please reply. Once the amp is soak tested, I'll make the Gerber available to those of a like mind who may wish to sell PCBs in their region and donate profits to a charity of their choice. Using easyEDA isn't imperative should someone wish use a different tool. The schematic attached has fuses and some protection diodes to get placed in.

There are plenty of cool pictures in the photo gallery threads posted in the other forums, so it only seems right that there be such a place to post your amp photos in the class d forum as well.

It doesn't matter whether you've got a prototype working on the breadboard, an amp jerry rigged on the table, or an electronic masterpiece in a case; post your stuff here for everyone to check out. It's a good way to share ideas and may even give someone a little bit of inspiration to tackle that project they've been wanting to do 🙂

Hey Guys

So the other day I picked up a used set of Martin Logan Aerius i ESL's in great shape and I have been really enjoying them. I was thinking it might be a good idea to think about replacing the 20+ year old electrolytic caps in the crossovers with something better such as Clarity caps. I'm fairly new to this but know this is popular with conventional style loudspeakers. I'm comfortable working through parts values but I'm not really 100% sure where my time and money would be best spent so I'm here to take in any info offered.

Martin Logan has proved to be extremely helpful and provided me with crossover schematics and a detailed electrical print on the whole speaker. I have not opened these up yet to take a look for myself but plan on doing so this week at some point. I've attached all the electrical info for everyone's viewing pleasure.

Hey everyone,

Hope you're all having a great day.

I've been locked into Troels Gravesen’s designs for the past 6 months, obsessing over which model to build. But recently, I decided it’s time to get out of my comfort zone and explore other options, and Lautsprechershop.de came up with some really interesting kits.

That said, I have a couple of concerns:

1. The website looks like something my grandmother used to browse on her dial-up modem, so I’m wondering, has anyone here actually ordered from them? How was the experience?
2. Some of the designs seem a bit under-documented, missing cabinet drawings and detailed build guides.

Would love to hear your experiences before I pull the trigger.

Thanks a lot!
Awni

Hi Forum

Warning: there is no such thing as "the beste (NOT, as in limited LF) full range Speaker in the world".
But the title sounds nice as a follow up of the previous thread. And like my previous design it is all about what compromises you want to make.

It has been over 6 years ago that I build that big 3 way speaker, together with my friend Joost who made the small two way that I also build as surrounds with Atmos upfiring section
"building the best 3-way full range speaker"
Earlier this year we did a big renovation of the living room with attached kitchen and when this was done, I found the speakers a big too massive.
Maybe it is my age and the testosterone is diminishing but the speakers always were big.

So I am starting a new design, with 20% smaller footprint and 30% less volume.
Still a large speaker but a bit better suited to the room and in this thread I would like to share this journey with you.

What did I do so far.

Wel in this design I want to be capable of simulating and measuring better to help tweak the end result with less trial and error.
For enclosure simulation and filter design I will use VituixCAD (with a well deserved donation when it all works as displayed)
For measurements most likely Arta

And to make sure that what we measure is accurate I bought an EarthWorks M23R and built a nice mic stand that should be close to the ideal setup.
The stand is described here:
The Ultimate Speaker Measurement Setup

A smaller speaker will be more limited in its LF performance, and that means a dual 8" instead of the original dual 10"
An 8" woofer will cross better to a 5" midrange then the previous 6" and also can live in a smaller enclosure.
The tweeter is to me still a beauty so it remains the same but might be crossed a bit higher
So the following units are selected and ordered:

• Dual Audio Technology Flex unit 8 H 77 20 06 SDKA
• Dual Audio Technology C-Quenze 15 H 52 06 13 SDKA-LR (so without the M surround as this one has a lower Fs)
• Scan Speak D29080714000

The smaller woofers allow for a smaller baffle and that will influence the way the speakers are perceived from a size point of view.
The underhung magnet construction should improve linearity and the smaller lighter cone will improve speed compared to the 18 H 52 17 06 SDKA that I used in the big speaker. the later was ordered with an Re of 7,5 ohm as was the 10" 10 C 77 25 10 KAP I used in the big design.

This selection comes with a few new design challenges.

• The midrange with its underhung motor cannot be ordered with a higher Re, so the two units in parallel will have an Re of around 2,7 Ohm
• These midranges have a higher efficiency and I want to use that to make the end result a >92dB @ 2.83V
• The tweeters low end will match that but the design will most likely have a slight roll off above 10k what in practice is also a normal design criteria
• The woofers will have a hard time catchup up with the MF/HF set so it will be powered by a Hypex module with DSP section

Using a (modified) class D plate-amp for the LF section has a few massive advantages:

• You can tweak the volume to keep up with the very efficient MF units
• You can add room correction without the risk to ruin your high end frontend (DAC/Phono/Pre/Power) as the important MF HF section does not need to pass a low cost ADC/DAC that is part of the plate-amp.
• The big impedance peak at 15Hz and and mainly the one at 60Hz (enclosure tuned at 30Hz) of about 20 Ohm would make a passive low pass filter complex and bulky. This all is not needed with the DSP filter section that is only used for the woofers
• The cost of serious LF filter parts is also substantial and I think the plate amp will be only mildly more expensive
• The Re of 2,7 ohm is fine for this nCore based amp with still 400 Watt @ 2 Ohm

The enclosure will have a similar construction and look and feel as that is what fits nice in our house.
multi layers of MDF and HDF, and for now a baffle milled out of a solid 40mm thick aluminum slab 🙂
10 pieces metal 8 mm rods that span the baffle with the rear to remove all fibrations by adding a tension on the total enclosure.
This is all copy and paste from something that worked very well.

The next challenge is to learn a 3D program (Fusion360) a I need a .step file so the CNC company can cut the front panel to the right size with the right diffraction preventing curves.
So I do not expect an update soon.

Cheers,
Peter

Hi guys,
Is it possible to change this buffer to have about 12db gain without sacrificing sonics.
One channel shown.

Hi everyone,

For years, I have been reading the various DIY turntable threads on this website, hoping to get some ideas for a design of my own. It seems that everything imaginable has been tried, and the only variations from turntable to turntable are visual rather than technical. The one area of interest to me is the design of the turntable main bearing.

No matter how precise the shaft and the sleeve bearings are made, there has to be even the smallest clearance and that clearance causes the shaft and platter assembly to wobble in a counter-clockwise direction. I have learned that quite recently. So, I set out to design my own “Zero clearance” main bearing.

My bearing design is based on a principle that was discovered hundreds of years ago, but to my knowledge, has never been used in the design of a turntable main bearing.

I am not ready to disclose how the bearing is going to function, for fear that I’ll fall flat on my face if it doesn’t.

Because of that uncertainty, and because I don’t have the money to build “iffy” turntables, I am going to build a no-cost test model, just to test the bearing principle.

So, I looked around my shed and discovered a discarded disk brake rotor, left over from a brake job I did on my pick-up truck some time ago. The rotor weighs 24 LBS. and is about 12” in diameter. I machined a spindle for it from aluminum pieces lying around my shop, and I made a base from ¾” hardwood plywood also lying around my shop. And then my CAD computer crashed. That was in December 2021.

I used to do all of my design work on a drawing board many years ago, and around 1994 I switched to CAD, and there is no going back! Luckily, I paid off my mortgage in January of 2022 and I was able to build a new computer. Three weeks ago I finally got it set up and running.

So, in this first post I’ll show you the beginning of my test model, and in subsequent posts I’ll show you the proposed design of my turntable that I will build, if my initial tests work out.

The build might take the rest of 2022 because I have yet to establish sources for the various components of my turntable.

Sincerely,

Ralf

�-��m�

Hi, I'm new to the forum and a real amateur at the technical end looking for help, advice on a PMC TB2-a that has developed a mains hum. I've tried swapping over with its "twin" (which is working perfectly), changed cables etc. but the hum persists. The speaker does work and once music is coming through I can drown out the hum . . . though it'd be nice to try and sort it. Thanks for any thoughts.

Hi all, extremely keen on building a tiny tiny listening bar. I’m a visual artist and intend to transform a tiny self built pavilion into a listening bar.
The purpose: set up the bar in exhibition spaces, collaborate with artists, dj’s to concoct weird drinks menus and musical explorations.

The place is already built: 18mm plywood room (floor and walls) with a paper/wood cassette ceiling, dimensions 220x330x230 cm LWH.

It will feature a bar and 4 fixed stools, and a booth for 2. (See plan sketch)

What isn’t there: the bar, sound system, drinks&vinyl shelves etc.

My skills: sculpting, wood.
My interest: building speakers (I like large speakers in a tiny room!), to set up a weird but also nice experience for visitors. Afterwards also building some more if it turns out well.

The speakers could be built into the wall, since there is space around the pavilion, like backpacks hanging from the wall exteriors.
Almost no budget, so looking for diy or assembled parts to build with.

Curious!

Having build the very capable F6 I was left wondering (more like fantasizing) about how I could improve this magnificent amplifier.
Fortunately I'm not the first one here having this crazy ambition, so I soon gathered a list of improvement candidates.
This is where my problems started. I am educated in the field of software so i quickly realized that I am in over my head when it comes to electronics.
However, this has never stopped me when creating software so I quickly decided that I'm not going to let it stop me this time either.
Having considered the options I have chosen to start with the power supply.
After gathering tips and suggestions from this forum I have settled on a dual mono power supply in a separate box.

So far I have gathered:
Two sets of Nelson's Bipolar Power Supply
Two Toroidy transformers
A soft start board from the DIY Audio Store
A Pesante 2U from Modushop

I have attached a picture of the layout I'm considering.
I welcome suggestions to this setup and anything that might make it better will be considered.
Thanks in advance.

Oh, by the way, I could use a suggestion for a nice power button for the front.

At long last, I have completed the LX-mini Analog Crossover and posted
in in the Article section of FIRST WATT

It will serve as the documentation and assembly manual for the kit which
will soon be available in the diyAudio store.

Enjoy.

Hi,

I'm about to add a subwoofer output to a 6SN7 driver stage (Williamson style). U1a is the amplifier; U2b is the phase inverter.
Too keep things simple I added a STP8NM60 MOSFET (or similar) as source follower. My idea is that the MOSFET will lot add a lot of load to the first triode (U1a),

According to LTSpice this seems to work OK. With only 1.1 mA and approx. 300 VDC across the MOSFET the dissipation is only 0.33 Watt.



Note: The original 100K plate resistor for U1a was split into 2 resistors of 85K and 15K. Adding C5 creates a short for AC. The reason for this change is to lower the gain without changing the DC settings.

Any additional suggestions will be welcome.

Regards, Gerrit

DCX is taken.

I have a dcx2496 that was damaged with a power surge when we recently had an outage.
The unit is cosmetically perfect and can pass for new. It’s free plus actual shipping if you want to try to repair it.

US lower 48 only please.

Hello, i m andrea and i m from italy.
I just joined the forum to get some help with my projects.
I build tube amplifiers, guitars and cabinets.

Why is there such a big price difference between the two TDAs?
TDA7294V 2.9$
TDA7294HV 12.8$

Hi everyone!

This is my first post, so I hope everything abides by the rules and you get something out of it! This project was a long time coming for me and I would like to share it here.
I want to make a headphone amplifier, as I think it is a perfect "beginner project". Not too much power, not many unnecessary features, just a simple but performant amp. Going back to the basics if you will 😉
In this first post I will go over the background, some decisions I made for now and share the schematic I came up with.

Thank you all a lot in advance! I am really looking forward to your comments 🙂

Background and Goal
This amp is meant to deliver the best possible performance with the least amount of complexity and cost. Power efficiency is not a primary concern, as it is "just" a headphone amplifier, so naturally I chose a class A topology. The amplifier is meant to be built up entirely of through-hole components. While this makes it a lot nicer to build up for me as a hobbyist, it will also make the amp last a lot longer, as it will be easily repairable - especially as I am using only main-stream components (standard BJTs, standard values and packaging for resistors and capacitors). Furthermore, it is intended to feel premium and make a statement design-wise - audio gear has to look and feel premium as well imo. While the design is still a work in progress, I have some features in mind that I really want to implement. I want to show off certain parts of the electronics as a design-feature; more specifically, the power transistors in a TO-3 package. Therefore, the output-stage is designed in a way that there is only one high-power transistor - a MJ2955 BJT. That transistor was specifically chosen for its good availability and the TO-3 case available in a configuration with the collector connected to the case. The emitter-follower configuration of the output stage in combination with the grounded collector allows the case of the power-transistor to be grounded, which makes it possible to safely display it on the outside of the amp's case. I have always found old TO-3 packages to be really cool to look at and wanted a way to display them safely. I think this will be a really cool design-feature in the later amp!

Schematic
Following the philosophy of simplicity and fully discrete design, the preamp-stage of the amplifier is kept relatively simple as well. The input stage consists of a long-tailed pair. The constant current source is set to a current of approx. 620 uA for a high input impedance (roughly 100 kOhm) of the two input transistors. This stage is followed by a common-emitter voltage amplification stage biased to roughly 2.6 mA. Finally, the power-stage is made up of a PNP-darlington pair in a common collector configuration. The amp is designed for a single voltage rail of roughly 20 V, so a bias-current of roughly 500 mA will flow through the output stage (with the DC-component of the output signal at half the supply voltage). The output is coupled with a large bipolar capacitor (how large exactly will be determined as well by some factors of the final design, but it will be somewhere between 3.3 and 10 mF; the simulations are done with the "best case" of 10 mF). This makes it possible to use a simple power-brick as a supply and therefore circumvent a lot of the headaches with regulation and safety when it comes to the higher grid-voltages. I plan on using a 24 V power-supply with a barrel connector (easy to get, cheap and safe) and filter the supply heavily to get a smooth 20V supply for the amplifier.

Projected Performance
The simulations done for now show a power output of >500 mW into 32 Ohms. The distortion is low (simulations show <0.0001% THD at 1 Vrms into 32 Ohms and <0.0005% THD at 0.5 W into 32 Ohms - both at 1 kHz). The simulated bode-plot shows plenty of phase margin and a flat gain curve (to within 1 dB) from 1.5 Hz to >200 kHz. The clipping behavior and power dissipation of the components seem decent. I am really happy with the schematic so far. To be clear: I know that simulations are just the first step and I fully expect the real-world performance to be worse, but the results encourage me to go further at least. I am curious to see what the real circuit can do!

Outlook
The next steps now are to build up a prototype and - if that works - design and order PCBs to populate. In parallel I am designing a suitable case. This will be a long project, so bear with me; I really want to push this amp to the best possible outcome. To this end, I would love feedback if you have some! I know some parts of this project may seem weird, but I really want to keep the single-PNP-output stage and just keep the whole thing simple and easy to build. I guess the spirit of this forum is to try new stuff after all 🙂

What do you guys think?

I did some measurements of this circuit with some changes. The VAS stage is loaded by 1k to just show how it works together with the current mirror and the input stage.




The table over the measurements.
Measurement 1: No current mirror just 1,92k instead to get the same current in T1 and T5.
2: Now we have a current mirror and it raises the gain of the circuit 44,4dB.
3: The VAS has now 2x BC548B. 1 mA In the driver and 6 mA in the VAS output as usual. 5 dB more gain
4: With the resistors in the current mirror increased to 470 ohm the current mirror shows its potential.
5: 2N7002 as VAS and back to 47 ohm mirror resistors.
6: We are back at 470 ohm. No difference at 100kHz but at 1.
7; Increased current in the input transistors. Max gain of the test at 1kHz.
8: BC 558B as input transistors and no current mirror. We lost 58dB gain.
9: Current mirror shines.
10: Now lower current in the input transistor but no great change.
11: 2N5401 is a popular input transistor especially at high voltages. No gain change.
12: 2N5551 as current mirror is a tick give as a tick less gain.
13: 0,5 mA for the input transistors doesn´t change much.

Input noise: BC557B and the BSS84 has both good noice figures but with the 2N5401 care in the planning is needed especially if you use the amp with a volume control at the input.

The BSS84 and the BC 557B has different strong sides so the actual amplifier topology decides wich one will fit the best.
The MOSfet might give lower RFI with higher current and the gate not rectifying. Maybe a tick lower distortion. Maybe higher ripple rejection.
The BC gives lower offset voltage and price + you find it everywhere.

Hello. I built this serial fx loop as drawing below. It work very well with two small issues: First it raise a bit of noise - very extremely slight but still here when 5ft. patch cables connects.(I can pass that). Second it slightly pops when I engage any pedals I have ( not any external noise, just popping when engage the foot switch). All my pedals are supplied from mains from 9V independent smps adapter supplies. Please help how I can cure the popping noise when pedals engage please ? Thanks.


The level of noise is dependent by 100k pot position. More loud as the pot is more open. Should I isolate the recovery stage input with a cap please ?

Late: oh no, a cap at input recovery stage did not do a difference...more, it seems it pops a bit louder than before...A capacitor from the whiper output to pedal input did not helps either...
There are not ground loops, supplies are galvanic isolated by separation transformer...just a comute regime I cannot get rid of...

Boost channel worked fine for 32 years then provided reduced output, I put in a new valve but to no effect, something on the PCB such as an opamp or diode may be culprit

Any ideas folks?

This is a very simple Bingham tilt tone control which I found here: https://www.angelfire.com/sd/paulkemble/sound4e.html

I have recalculated components values for lower impedance (= lower noise) and smaller adjustment range (+/-5dB). The original circuit gives up to 40dB variation over the audible frequency range which is a bit excessive to say the least.

Schematic:



Frequency response:



Turnover frequency is 935Hz which is close enough to 1kHz.

Worst case input impedance is ~3kOhm which can be easily driven by any modern audio opamp:

I thought why not try the 3 pole compensated blameless amplifier clone. It worked out pretty well in simulation.
All important information is on the pictures.

Hello, a bit ago the amp suddenly died when sitting at idle and not playing anything, after that when trying to power it up just pops the speakers and goes into protect.

I only have some basic knowledge of amp repair. The tools I have are a scope, multimeter, thermal probe and soldering iron.

In the amp I was able to identify 1 dead output fet (B31N20D), but I also wanna check the overall health of the amp and if everything is working like it should, as it has been repaired before by someone else.

Currently I've removed all of the output FETs for testing, it seems to power up fine, but I found that a KSP92 transistor on a card gets very hot (over 70c). Along with some other transistors on the card being about 50c.

The card:



What would be the next steps? The KSP92 isn't shorted according to the multimeter.

Some observations:
One side of the output side:
Gate: 0v (has some sort of pulses)
Drain: +64v
Source: 0v (has some sort of pulses)

The other side:
Gate: -78v
Drain: 0v (has some sort of pulses)
Source: -74v


EDIT: measuring output section without and with signal (37hz sine wave) applied
One side gate:

One side source:


Other side gate:

Other side drain:

Speaker outputs:


Edit 2:
Removed the hot KSP92, but seems there are 2 of them in parallel, so now the other one gets hot.
Measured what's going to the removed transistor:
Base and emitter: about 84v
collector: pulses

why would they be getting so hot?

offer an original Audio Buffer pcb from PMA as well as a completed power supply from PMA,
the audio buffer can also be set up as a headphone amplifier, details on Pavel Macura's website,
there are also three BUF634 which are currently available for around 20 euros per piece at Mouser are available,
ask for 70 Euros for all

Has anyone had experience with this Oldchen EL34 Valve Tube Amplifier. Thanks.

Hi, after re-igniting a decades ago interest in electronics, when I recently re-capped an old Meridian 577 power amp, I was looking for another project and came across the Wolverine amplifier. I've registered my interest and I'm looking to build a 557 replacement and learn along the way.

I expect this forum to be a mine of information of the build. 🙂

Regards
Steve