Who can remember listening with friends to Mortal combat song, and the unintelligible words:

Test your might, Mortal combat, sounded like : whowwoodtlungtodwwoooo (mortal combat) tksssssss yuourrrrr migshhhhht (test your might).

I cannot seem to set the center voltage on my Quad 303, started with replacing R130 as was open, I've changed the adjustment pot but to no avail I still cannot get the voltage to go under 40vdc ( should be 33.5vdc)

Any ideas on where to look next?

Hi All,
Have this next build in the works that clones Andres' upgrades to the Eico ST70 - http://www.tronola.com/html/st-70_hotrod.html
It was discussed on this forum - https://www.diyaudio.com/community/threads/eico-st-70-supermods.196790/

This will be clean sheet build using schematic from Andres, not a modified original ST70. I'll be using 6gm5's in place of 7591's.
I feel pretty confident that substitution.
I plan to evaluate performance similar to steps outlined in article to verify substitutions, once biases and balance settings are achieved.

Design question- Can I use single 6U10 ( 2 low mu, one hi mu triodes) to replace (2) 6sn7 and (1) 12ax7? https://tube-data.com/sheets/123/6/6U10.pdf
Related question- Are interelectrode capacitances important factors to compare when substituting tubes in design? If not, are there other chart characteristics besides Typical, Maximum Voltages and Gain that I should compare?

Thanks,
Jim

Hi,

I have a Sony TTS 4000 with a failed CX032 chip (verified failed).
Can anyone help?
Any one got a spare?
Bango?

Thenks Kosta

Anyone know when the single ended iron pre kits will be restocked?

Look at these two circuits. They do the same.
The difference is the single and the dual supply.
Another difference is the capacitor C1 and C3.
Because the negative voltage at input pin C3 should be put 'upside down'.
This goes for all bipolar opamps with NPN input transistors.
And when using dual voltage supply.
If a bipolar opamp has PNP transistors input the C3 should be turned the other way.

Friday evening chez Weldon:

Start with a warm winter evening and a bit of a sunset
Add a glass of red, a shot of hooch
and a couple Dungeness

Good day mates!

I had tried my best to read all posts regarding this amplifier I could find here, I might be overlook though, I didn't see much discussion on how to route the input signal away from source direct switch and it's PCB. Hence I am seeking advise and like to learn from you guys here.

Firstly I done a very simple routing last night by removing the ribbon cable between input PCB to switch direct PCB then use 4 wires to tap signal directly from input PCB to volume control PCB. I like the cleaner/clearer sound but wonder why only right ch get the signal but left is no sound. I attached a rough picture here. I keep looking at the service diagram still doesn't get it why like that. Any other way to do it?

Secondly, even the signal tap directly from input PCB, still need to engage the source direct switch to activate the relay to let signal pass thru the relay. Any other possible way to totally route out the source direct switch?

Hi everyone,

I'm designing a 3-way passive crossover for my home audio speaker setup and could use some help optimizing the design. My goal is high-fidelity sound with good bass response and smooth integration between drivers.

Driver Selection​

• Woofer: Dayton Audio DC300-8 (12", 8Ω)
• Midrange: Dayton Audio MB620-8 (6", 8Ω)
• Tweeter: Eminence ASD1001B compression driver on B-52 PHRN-N01 waveguide (8Ω)

Crossover Goals​

• Woofer to Midrange: 500Hz
• Midrange to Tweeter: 2.5kHz
• Crossover Type: 2nd-order Linkwitz-Riley (12dB/octave)
• Flat frequency response with smooth phase transitions

Any advice on impedance compensation or phase alignment?
I've attached my XSim schematic and response graphs for reference. Any suggestions or improvements are greatly appreciated!

Thanks in advance!

Hello Dear friends i am building crossover for the first time

i have watched all videos on youtube and did some calculations but i still need your help

Woofer = GRS 12SFPC-B 12" Square Frame Paper Cone

Horn Driver: Eminence ASD1001B​

Crossover design:



Frequency response graph:



Impedance graph :


i like frequency response but when i look at impedance graph i think i should do better what you think?

Also i have attached Xsim file.

Parts list:

Dayton Audio DMPC-1.5 1.5uF 250V Polypropylene Capacitor
Dayton Audio DMPC-7.5 7.5uF 250V Polypropylene Capacitor
Dayton Audio DMPC-0.33 0.33uF 250V Polypropylene Capacitor
Dayton Audio DMPC-3.3 3.3uF 250V Polypropylene Capacitor
Dayton Audio DMPC-10 10uF 250V Polypropylene Capacitor

Dayton Audio IC181-5 1.5mH 18 AWG Laminated Steel I-Core Speaker Crossover Inductor Coil
Dayton Audio 0.33mH 18 AWG Perfect Layer Air Core Speaker Crossover Inductor Coil
Dayton Audio 0.10mH 18 AWG Perfect Layer Air Core Speaker Crossover Inductor Coil
Dayton Audio 1.5mH 18 AWG Perfect Layer Inductor Crossover Coil

Dayton Audio DNR-3.3 3.3 Ohm 10W Precision Audio Grade Resistor
Dayton Audio DNR-8.0 8 Ohm 10W Precision Audio Grade Resistor

Thanks

Hello dear friend this is my first post and Greetings from Sakartvelo i think you are doing great job helping each other also shearing helpful information so I also need your help.

I saw oswaldsmillaudio/monarch series speaker and i fall in love Login to view embedded media so i don`t have 300 000 $ but i must have this speakers at home.
i am good at woodworking and i can build exact same cabinet by myself with custom dimensions, but i could not decide what drivers to use in this build so please help. also my budget is pretty limited max 400$ per speaker (plus minus 50$) also room dimensions for this peace of art is 26 feet X 26 feet X 19 feet (ceiling high ) i know that for 400$ i cant do much to fill this room with crystal clear sound but this design need some good sound, ( also i thought to build World's Second Best Speakers! with pair of full rage tang band w8-1772 speakers and attach wings and design to his built cabinet ) but horn on OMA Monarch speakers should be 3 way horn driver sorry for my English

Would this work as CLD glue https://www.homedepot.com/p/Loctite...ion-Adhesive-Blue-Cartridge-1421941/202020476

I did. For years in fact, but put it off thinking there was no way my skill level was up to the task. That is, until our good friend xrk971 opened the door to something that is easy for the layman and very rewarding. See this thread:

http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html

There is a lot of info in there but it is a good read. The project I did starts at post #101 but I urge you to read it all as there is some good info throughout and lots of learning as you go along.

Here is a post from member palmiepaul, summarizing the project before even starting to build. It is recommended reading.

http://www.diyaudio.com/forums/full...u-spiral-horn-now-you-can-49.html#post4153092

It's been a long time since a speaker project has been this fun, rewarding and quick. I admit my hopes were not that high to start, but my mind has changed completely regarding the materials used and the overall effectiveness of the project.

They have been coined the 'Cornucopya' Here is a site with the drawing. It is also in the next post.
seb:diy:audio: Cornu Spiral Copy Horn

Enjoy.

Deeply moving news this afternoon about the cutting down of a timeless and completely defenseless ancient icon.
Thousands have stood here and admired the beauty of this landscape.

If any of you have photos or tangible memories of this place, post them here in memory of this unique tree.

Please, no condemnation of the alleged perpetrator, it has not yet been proven who did it.
https://www.theguardian.com/uk-news...amous-sycamore-gap-tree-hadrians-wall-england


Picture: Wikipedia

Hugo

Good morning my friends
I am confuse with a pioneer vsx605s power transformer as the voltage selector switch is distroyed i wanted to bypass and connect just the 120 volts but i do not understand the setup

Preceding thread here : https://www.diyaudio.com/community/threads/zms-2sk2087c-musings-phase-one-sissysit-as-cradle.386654/

What was logical precursor/reason to dust off schematic I'm having for some time and to implement it in form of new pcbs, arranged so both Tokin Pucks and Tokin 2SK2087 can be used

Novelty - reason enough for playing with, is full DC connection from input to output, and also current-mirrors based biasing circuit

Nota Bene that DC connection between FE and OS is typical Cheating Papaway - anyway, see it by yourself, draw your own conclusions

Changes vs. SissySIT R.3 - none regarding sound (had my time with farting elephants, life is simpler after that), even steadier output DC Offset and Iq stability, vs. time, temperature, mains fluctuation

As I can see, there is some better drive (shown in clipping level for Big One) but these differences are strictly academic ones, sorta pity that this amp is never going to be considered by Audiophools, having all pizzas for great Drek-selling Story

as always, basic pics first


EDIT on 02.02.2023. Last bling, precision CCS moved to separate Daughterboard - post #109 https://www.diyaudio.com/community/...o-sissysit-42-as-a-cradle.387767/post-7256125

Life has been rather hectic lately, but it looks like the chances are good that I will be returning to the Dayton Hamvention again this year. This will be my third trip to Dayton, and every year I have met at least two diyAudio forum members there just by chance. People tend to recognize me. I imagine that there were other members that I didn't see. If anyone is going, and there is interest in a bull session or a guided tour of the swap meet junk (oops I mean goodies) we could arange to meet, or at least swap cell phone #'s.

The Dayton hamfest is the largest in the world. Last year attendance for the 3 day event was 22,000 people. The swap meet area holds over 2500 swap spaces. The theme is ham radio, but there are very few restrictions on what can't be sold there, so it is an excellent place to find tubes, transformers, components, complete tube amps, not so complete amps, test equipment, and who knows what else. Sometimes people purchase space just to show off their latest creation, like last years Prius that was covered in solar cells, 11 miles a day without any gas at all.

The swap area is entirely outdoors and is subject to Dayton's finicky weather. It can be cold (35F), warm (75F), sunny or raining, or as with last year all 4 over the 3 days. NOTE! Rain makes the prices drop, a LOT! Last year the weather was cool but nice on Friday. A seller wanted $50 each for some MRI RF amplifiers. Saturday the rain started, and then the rain came down hard. I bought all 6 amplifiers for $100! I got a 0 to 2KV 100 mA Kepco power supply for $20 and an RF spectrum analyzer for free (known to be broken). Both times that I went to Dayton I left with a small SUV full! This year, I have a bigger vehicle.

There are 3 buildings (a hockey arena and support buildings) that house convention style booths that are mostly ham radio related equipment. It's cool to look at all of the ways that you could spend some serious money in ham radio if you are into it. I do have an extra class ham license and a working radio, but not much interest. Being a radio designer, at work for 35+ years, is enough.

I plan to be there when it opens Friday morning, staying until closing, and returning Saturday, staying until I have to set out on the 1100 mile drive home. It really does take more than one day just to cover the swap meet area. The first time I went, I spent two days in the swap area and never did see the ham radio stuff. Last year I was a bit more orgainzed and I covered the swap area in one long day. Saturday I hit the swaps in the morning, and went inside after I got soaked in the rain for the third time (mid afternoon).

Dayton Hamvention 2010 - Amateur Radio Clubs Worldwide: The Lifeline

WTB: Please reply either here or by DM with details, condition, and asking price.



Greg in Mississippi

Hello, Tim here I am into rebuilding crossovers and upgrading capacitors in speakers. I have also built a bunch of powered subwoofer’s. I have an Aleph JZM that sounds amazing.

no signal, bridge.


5hz.


100hz.


2khz.

10khz.



20klhz.


50khz.


100khz.

300khz.

senoidal 20khz.


the preamplifier.

1.177 / 5.000


Hello, first of all I want to make it clear that, as almost everyone knows, Chinese advertisements and clones often do not even look like what they advertise. In this case, I want to make known what I consider a bargain. Leaving aside the title we have a preamplifier that I consider excellent, at a ridiculous price of 10$ with shipping (at least to Spain), small size (easy to connect if you want an integrated amplifier), you only need a 15-0-15 v. transformer, or a switched source for example of equal value for another 7$, it has its regulators, with its capacitors that really work very well, at the input it has an OP JRC-5532D, then BC550 and BC560, everything quite normal, I ordered 2 units, assembled it and passed it through the oscilloscope, the result is excellent (in my opinion and the price) I put captures of up to 400khz in square wave, the sine wave logically better, it responds from 5hz without problems, I have tried other clones and other originals that I have, and this one on paper gives better measurements, something that measures well can't sound bad. The sound, the little I have tried so far, is quite good, better than the Denon 1500pra that I have.
and other clones except the PASS 1.7, for me it is better for more detail, dynamics and width, but for the price it is gold, now here come the more technical forum members (I am not) who could suggest improvements, for the already excellent preamp, I attach captures from the oscilloscope, greetings.

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

Hello,
I don't have as much free time as some years ago so I'm selling my Transistor stock of 609 transistors in total.

I'm asking 75€ for all of them

Here is the list of whats included:

Hi Guys,

Please register your details for the Wolverine 5th Group Buy - Pre Order.​

After the success of the past four group buys and increasing demand for Wolverine boards, we are thrilled to announce another group buy for the DiyAudio community.


This time, we are offering the new and improved Wolverine V5 boards, along with supporting parts and boards:

The IPS, EF3-3, EF3-4 and EF3-5 boards will now include mirrored versions for Left and Right channels! These allow inputs at the rear of your chassis and outputs on the lower heatsink half, all while fitting the current UMS (with just 3 new holes for EF3-4, courtesy of Gianluca’s updated drill pattern). Huge thanks to Mainframe and DanielJW for prototyping, Harry for BOM review, and Jeremy for schematic checks.

1. IPS, Pre-Driver & Driver Heatsinks with Mill-Max pins installed:
   • EF3-3 (IPS, Pre-Driver & Driver)(Amp Board,Parallel or Perpendicular Mount to Main Heatsink): $27.50 USD (6 Heatsinks Total)
   • EF3-4 or EF3-5 (IPS & Pre-Driver)(Amp Board, Parallel Mount to Main Heatsink): $22.50 USD (4 Heatsinks Total)
   • EF3-4 (IPS, Pre-Driver & Driver)(Amp Board, Perpendicular Mount to Main Heatsink): $27.50 USD (6 Heatsinks Total)
   • IPS: $10.00 USD (2 Heatsinks Total)

1. 2SA1381E / 2SC3503E Transistors:
   • $6.00 USD per pair.

We are also offering the following supporting boards:







Thank you all for your support of the Wolverine project over the past 3 years. It’s incredible to think our first group buy was back in March 2022.

Registration Instructions:
We will follow the same process as the 3rd & 4th group buys to streamline processing. Board color will be determined based on order numbers; if insufficient, only one color will be ordered.

Pricing for Boards:
Wolverine V5 Special Edition IPS Board (2 boards) (Right and Left channel):


EF3-3 Boards: (270mm x 77mm)


EF3-4 Boards: (347mm x 77mm)

EF3-5 Boards: (354mm x 77mm)
I’m excited to share a fresh development for the Wolverine family: the EF3-5 output stage board! As you know, our current lineup includes the EF3-3 (3 current gain stages, 3 output transistor pairs) and the EF3-4 (3 current gain stages, 4 output pairs).

Now, we’re taking it up a notch with the EF3-5, featuring 3 current gain stages and 5 output transistor pairs for even greater power and stability.

To top it off, I’ve mirrored the EF3-5 design—just like the EF3-3 and EF3-4 in the 5th Group Buy—offering dedicated Left and Right channel versions. This keeps the inputs at the rear and outputs low on the heatsink, maintaining that clean, symmetrical layout you’ve come to love.

The EF3-5 boards are 7 mm longer and 10 mm wider than the current EF3-4 boards. All the holes still follow the UMS, except for the two at the top where the output transistors mount—they’ve moved up 10 mm. The output transistor mounting holes have also shifted up 10 mm, so some drilling and tapping will be required if you’d like to use the EF3-5.

The EF3-5 is perfect for those pushing higher currents or lower impedance's (think 2-ohm loads or beyond) with the same Wolverine Class AB finesse.

Please note.
The discount will only be applied for those members who order boards before they are ordered from the PCB Manufacturer.
If you wish to order more than 2 sets or adjust quantity, please contact us for pricing details.

Shipping: Prices exclude shipping costs. Shipping is at cost price plus $3.00 for packaging. No added handling fees. A copy of the shipping receipt will be emailed upon payment.

Each Order Includes:

1. Your ordered PCBs.
2. A3 Schematic copies for 57V and 64V versions. (Dropbox Link)
3. The Build Guide (~74-page illustrated A4 document). (Dropbox Link)
4. BOM in Excel with Mouser part numbers. (Dropbox Link)
5. Heatsink Hole Pattern DXF & PDF files. (Dropbox Link)
6. "How to Wire an Audio Amplifier" by Bonsai. (Dropbox Link)
7. Future updates will be available via Dropbox. Please provide an email for this purpose.

Payment: Through PayPal. Requests will be sent upon ready-to-ship boards.

How to Register:

1. Open the attached Excel order sheet, fill it out, and email it to: Stuartmp@internode.on.net
   • Subject: "Wolverine Project – Your DiyAudio Username"
2. If unable to open the file, please reply with:
   • Total number/type of EF3-3, EF3-4 & EF3-5 boards.
   • Name and total number of any of the supporting parts / boards on offer.
   • Full name, address (including country and postcode).
   • Phone number for tracking.
   • Your PayPal email address.
   • You Email address for Dropbox updates.

We will order boards once a sufficient number of pre-orders are reached and keep you updated throughout the process. Once received, we will calculate shipping and send payment requests. You will receive a tracking number once your order ships.

Please refrain from using my email for other inquiries; post questions on the main Wolverine Build thread or contact me via DiyAudio PM for order-related questions.

Wolverine Development Thread
For ongoing project updates and technical discussions, visit the Wolverine Development Thread on the DiyAudio forum. Engage with fellow audio enthusiasts and share your build experiences.

Wolverine Build Thread
The Wolverine Build Thread is your go-to resource for assistance with assembly tips and troubleshooting advice. Feel free to ask questions and contribute your insights.

YouTube Build Series
Explore our YouTube Build Series for visual guidance on assembling your Wolverine amplifier. Our instructional videos cover each step-in detail, ensuring a smooth build process. Thank you to @danieljw for putting this series together.

Support Contacts
Feel free to reach out to me directly through the forum's messaging system or my e-mail if you have any question related to the ordering process.

We truly value your involvement in the Wolverine project. By working together, we continue to make high-quality audio amplifiers accessible to enthusiasts worldwide. Thank you for your enthusiasm and support.

Best regards,
Stuart & the Wolverine Team

Hi,I have a stripped Spectral DMA 100 amplifier,need help finding power supply specs for both driver and output.
I have a need to build power supplies as the chassis is missing both transformers……maybe use the chassis,I do have a Diyaudio 5U chassis new in the packing…I have been saving it for a new project,or,if the transformers needed can fit the original chassis,maybe use the Spectral case.
all outputs verified ok.
The boards appear to be prototypes,there is no serial number sticker on the back of the case….found at the Alameda Antique Fair,SanFrancisco in 2017…..
thanks,Dave Grady

Han anyone else thought about building a La Scala type enclosure with different dimensions? I have a Joseph Crowe ES600 horn equipped with a SB Audience 65CDN-T compression driver and was planning to build a La Scala type bin but feel the ES600 would out of place with the 24.5 inch (62cm) wide box. So I thought I could maybe build a narrower and taller box keeping the same area for the throat an mouth. What do you think? Stupid idea? 🙂

I have a set of Half-Chili cabinets that need new drivers. Is the Fostex FF165WK a good substitute for the FE167e in this case?

So I'm working out the final details of my chassis for my Tubelab Simple SE and I figured there are enough Tubelab owners on this board that it might be nice to have some pics of everyone's finished products all in one place. I draw a lot of inspiration from you guys!

So, please post some pics of your Tubelab projects. Finished amps, internal shots, construction pics, etc would all be nice to see.

Hi All

I have an MF 3.5 amplifier and it it has a serious crackling on the right channel. It bled over to the left a bit but this was fixed by replacing the NE5532 chip on the motorised volume control.

Now it only faults on the right channel. It is a high dc voltage that jumps up and down as I rotate the volume pot. goes from the usual 20 -30mv to 190 + difficult to get it to stay put.

Measuring across the Pre amplifier O/P phonos it is about a 1.3volts.

The caps on the Volume PCB were replaced, and the ceramics tested all OK.

The fault disappears if I disconnect SK5 from the main PCB.

then I can get a 1K tone out of both channels Ok albeit a reduced volume.

So the fault appears to be around the PIC chip perhaps?

All the DC voltages from the regulators are OK and no noise on the rails.

On IC8 Pins 13/14 no noise at all.

Any suggestions would be welcome.

thanks
Phil

Jhofland and I are pleased to introduce the long-awaited Soft as a Feather Pillow (SFP) solid state relay (SSR) soft start circuit for use with power amplifiers. The development for this circuit has actually been going on for a long time, you will notice that the board design is at v2.1.

The goals of this circuit were to provide a gentle in-rush current limiter using a bank of power resistors during initial turn on, and then having a low Rdson MOSFET bypass the resitors after a set amount of time. By using a SSR vs a mechanical realy, we eliminate a source of arcing and wear, and the switchover is silent - no clacking of relays. Another goal of this circuit was to provide an added benefit of providing an open collector logic signal that can be used in conjunction with a speaker protection SSR that will tell it to instantly shut the speakers off if the voltage rail of the small on-board 5v SMPS turns off.

A special SSR ultra-low Rdson MOSFET was chosen that is rated for 600v, 23A, and has an Rdson of 22mOhms. This SFP can basically soft start almost any power amplifier in DIYA. With a low Rdson value of 44mOhm for two in series, we will have very low dissipation for even higher bias current Class A amplifers. The MOSFET is controlled with the usual opto-coupler and the start on time delay is controlled by a selectable RC circuit and comparator. Variable turn on time delays ranging from 0.5 sec, 1 sec, and 2 seconds is available via a jumper setting.

Here is the schematic:


Edit Mar 3, 2020 revised v2.3 schematic with NTCs instead of resistors:


BOM for v2.3 here:
https://www.diyaudio.com/forums/attachment.php?attachmentid=821923&d=1583218278

Here is the verification unit undergoing testing with the Omega amplifier:
https://www.diyaudio.com/forums/att...soft-start-circuit-gb-sfp-v2-1-test-setup-jpg

Here is a closeup of the board in action:


At turn-on, about 52Vac is registered across the four 100ohm (5w ea) wirewound resistors:


2 seconds later, the SSR kicks in and the voltage drops to about 92mVac:


A clamp on current meter showed that the amp was drawing 1.62Arms at the wall plug. So the dissipation across the MOSFETs is only about 150mW. An earlier

I will continue testing out over the next few days to ensure tha everything works out well.

Edit Dec 17, 2023: including the schematic and BOM to the latest variant called the SFPP (SFP Plus) which includes remote turn on/off with a momentary SPDT switch with LED indicator. Great for low voltage front panel power switches with ring LED.

https://www.diyaudio.com/community/...ssr-soft-start-circuit-gb.350441/post-7538507

Introduction:
Hey guys, been a long time lurker here. I've been pretty busy lately working on a dirt cheap unity horn project for my desktop setup. The entire horn is going to be 3D printed for ease of assembly. A lot of effort has been put into making this build as cheap as possible. I actually think this might be one of the cheapest unity horns out there. I have two goals I want to achieve for this project.

1. Wide phantom image and constant directivity. I have lots of pc-monitors in-between my current speakers. The problem with this is it forces my speakers to be very far out from the listening spot (around 150 degrees). Unless you are seated perfectly between the speakers, the sound-stage collapses. It is my belief that a wide CD horn will fix this.
2. Provide an affordable MEH so that more audio geeks can hear these awesome speakers. I really love unity type speakers, the linear phase, constant directivity, and acoustic filtering provide a lot of benefits that are hard to achieve otherwise. My dream is to eventually make this into a diy kit, but I'm not sure if I have the resources to make this a reality.

Woofers:
This all started when I discovered these little Dayton TCP115 woofers. I was working around in hornresp and pasted the driver profile by mistake. Low and behold, the simulation had an extremely wide bandwidth for such a cheap driver. The high xmax is also nice for going low so I was able to make this design a 2 way and still get decent bass.

Tweeter:
Most, unity horns seem to use compression drivers. Since I don't need high output and need a cheaper option I decided to go with something different. The XT25 is what I am using for now and it seems to work quiet well. By using a really large horn I was actually able to push the crossover frequency quiet low (around 1.2khz). I know, I know, that crossover is insanely low for this tweeter. I have more data on why this works; will post more later. Right now I am having trouble getting accurate distortion measurements to confirm my theories.

Measurements:



Around 15 degrees off axis after some quick EQ. The dips at 6k and 10k appear to be from a problem at the throat which are being fixed in the next version. The next box is also going to have a flush mounted horn and 18mm round overs on the baffle. I am hoping this will improve those ripples. You can't just EQ those ripples at any one angle. As you can see the dips move around depending on your angle off axis.



1/3 smoothing of the same graph. I don't know what the exact angles are, it's really just a proof of concept to show the directivity is being controlled. The light green line is around 60 degrees, which is why it is so low in level.

Things I still need to do:
Throat optimizations, active xover tweaking, passive xover development, take more accurate polars outside, measure below 200hz, port it (maybe?), make it pretty.

Hello everyone,

and I would like to discuss a topic that is often mistakenly associated with the dynamic range of loudspeakers in my opinion. It is about the subjectively perceived by the listener decay time of instruments. In some loudspeakers, for example, a hi-hat decays for a very long time, and in others, although the strike itself is not less loud, the reverberation disappears very quickly and a clean, empty background appears. I thought that these loudspeakers might differ in the SPL characteristic as a function of the supplied electrical power - a loudspeaker that produces a long reverberation would have this characteristic more linear, and the one that produces less reverberation, falling more abruptly towards the muting of the sound level.

Since I could not find such graphs on the Internet, only a typical SPL graph in the frequency domain, I decided to make simple measurements myself. I connected the amplifier to a computer that played white and then pink noise, and I measured the sound intensity from the near field to eliminate the influence of the room. I increased the volume from zero to a specific level, then repeated one of the measurements with reduced amplifier gain, i.e. the volume intervals were smaller. And what?

These graphs show that the faster decay of instrument reverberation in some loudspeakers and slower in others does not result from the slope of their measured SPL characteristics vs. the supplied electrical power. So it is not any dynamic range of the loudspeakers or their SPL given in catalogs that decides the phase of the instruments' decay, because even if some loudspeakers play louder overall, the reverberation is received relatively to the impact and also decays relatively to the level of the impact (attack phase).

And my question: what, in your opinion, can decide that some loudspeakers beautifully convey the nuances of sound with a long phase of instrument decay, while others leave this information "to themselves"? PS. I used the Revox BX-350 and Wega Direct 200 speakers for the measurements. Both have dome tweeters, with the Wega being 3-way and the Revox being 2-way. The midrange measurement in the Revox speakers concerned one of the 4 parallel mid-woofers, while in the Wega - one midrange dome. The Revox BX-350 have 4 paper speakers and one tweeter, and the crossover frequency is 3200 Hz. As you can see in the graphs, the course of the SPL curves is almost identical, apart from the difference in levels for the midrange, resulting from the measurement of only one of the four speakers in the Revox speakers.

The question returns: what does the length of the instrument decay phase depend on? Is it about, for example, the damping of the speaker membrane? I almost forgot: out of the tested speakers, the Revox are the ones that "eat" the details of the sound. In addition, they have their own character, which is always audible, and the Wega speakers "disappear", they are almost transparent to the sound, they do not add a strong signature to it. Both play very pleasantly, but the difference in sound detail is huge in Wega's favor. And this despite the fact that the Revox-s have undergone recapping to MKP capacitors, and the Wega still have factory-fitted Wego electrolytic capacitors in the entire crossover. Any hint will be valuable - besides, this is a topic for an interesting discussion 🙂 And now I will try to paste photos 😉

For tweeters (X axis - PC volume sent to DAC and amp):



For the midrange:



And now midrange with reduced volume increments and reduced room noise floor.



...and well, above graph says that Revox is a speaker that should transmit more silent details to the listener as the difference between quiet and very quiet sounds is lower than in Wega. The reality shows the other way 😉 And what could I do to encourage Revox four tiny cones to show more silent nuances of the sound - no idea as this is not about sensitivity of a speaker. That must be something else - more sensitive speaker of course would play the decay phase louder but that is all relative to the attack phase which would be also louder played.

Regards,
Mike

How many amplifiers is too many? For me, one too many. This is highly regarded and great sounding Nelson Pass First Watt F5m amplifier. It's a really nice build done by an electrical engineer. Specs are as follows:

Italian made chassis.
Antek 200VA toroidal transformer
All Cardas Solder
Swedish Gotham internal wiring
CMC Speaker Binding Posts
Neutrik RCA input jack
Gold plated AC terminal and fuse.

If you'd really like to own one of these great amplifiers, but don't have the solder slinging skills that some do - this is your easy pathway to do just that.

It's big. It's heavy. I really don't want to ship it. It would be very expensive. If you're in the Illinois or Wisconsin (heck, even Iowa) we can work out some type of transfer in person. Bonus points if you're in the Chicagoland area. $800 OBO.

TLDR; amp is picking up interference from cellular equipment

Last week I picked up a Yaqin MC-10T for a great price and couldn't wait to get my first tube amp into my system. At first listen I was really happy with the way it sounded and settled in to spend some quality time. After about 10 minutes, the right speaker emitted a fairly loud BZT-BZT BZZZZZZZZZT sound, familiar though I haven't heard it in probably 15 years: that noise that GSM phones used to make if they were close to your car radio and about to receive a message. The noise appears like clockwork, every ten minutes. It's not dependent on volume level, or which input is selected. It's in both speakers but one quite a bit louder than the other. I've never heard this before in this room, even with other electronics. I listened to the amp in the previous owner's home for a good 30 minutes with no noise.

I have the schematic; there is nothing in this amp that could possibly be making that noise, nor anything else in the room that I could think of: I unplugged all the electronics in the room, including the DAC and streamer. I unscrewed all the LED smart bulbs. Still the noise continues.

Yesterday the entire country lost power for a day and while waiting for the lights to come back on I decided to move a big ecoflow power station into the room and see, now that NOTHING could possibly be generating RFI, if the amp continued with the noise. It did. What the hell? And then it finally occurred to me: my home has an alarm, and the control panel has a several-day battery backup, and I know there is a SIM card inside because I watched them put it in when they installed the alarm. Clearly it's using the old GSM/GPRS network to communicate with the alarm company, and is phoning home every 10 minutes. This alarm panel is not in my listening room; it's on the other side of a wall about 3M away.

I've tried moving cables around, switched interconnects, put a fancy "hifi" power cable on the amp, oriented the amp a different direction; nothing seems to make a difference. Can anyone offer advice for taming the interference problem? It isn't going to be practical to move the alarm. None of the other gear I've had in the room has had the slightest interference, so I'm guessing I need to look to the amp to solve the problem - is it normal for these amps to be so sensitive to RFI? Or is it possible it's got a fault of some kind?

System: Wiim Pro, Music Hall DAC2.5, Yaquin MC-10T, Dahlquist DQ-28s. AQ Ruby interconnects (tried Evergreens) and Indigo speaker cables.

Well, I somehow managed to build my first solid state amp, based on the TPA3116D2 chip. I used the schematic from the data sheet and it works and sounds great. The power supply is a 130 watt Dell laptop power brick putting out 19.5V. The chip barely gets hot driving 8 ohm speakers. Thanks to everyone who posts here for their ideas and inspiration, especially xrk971 and his great amp, that thread is what pushed me from building a chip amp to a cheaper, high efficiency class D. I scoped the output and the wave is smooth, into a resistive load you can barely see the switching on top of the sine wave. The purpose of the amp is to have something portable to take with me to the garage, basement, etc and it fits the bill quite nicely.

The only problem I ran into was with the output capacitors, I originally had cheap 50V caps in and they quickly smoked without a speaker load. I replaced them with the square 100V caps and all is well. I don't plan on running it without a load but it has to survive at least for a little while if a speaker wire pulls out or isn't connected.

I have an original ST-35 from the 1960s and a Dynakit version I built in 2012. All was going well. The old one is in storage and the Dynakit is the daily use. Upon power up the Dynakit one went quiet. I could see one tube was out. I decided to check out the reason (besides 13 year old tubes). Upon opening it up I see a burnt resistor. I was an early adopter of the EFB modification. I made my own board for it, but I no longer have those plans. The 100 Ohm resistor used across the tube pins 8 and 9 was fried for the dead tube. By the way, I have the 2012 version of the Audio Regenesis PC-13 boards in the amp. This is basically my issue - I can't find the original plans covering the EFB mod, the resistor was fried. I don't remember how to check this thing out or how to set the EFB bias pot.

I bought some new 100 Ohm 0.5W 1% resistors to replace the four used in the original EFB mod at each tube. I turned it back on and the tube is still toast (dimly lit and no heat generation). No sound comes out of either side. I also have a matched set of replacement tubes, but I do not want to put them in if I have another issue. Everything else looks fine visually.

A couple of observations:

I see on the one schematic I found of the old EFB mod that there is a 5 Ohm resistor between pins 3 of the tubes on each side. I see TP on either side of those resistors. I suspect that the bias is to be measured there and then adjusted. I do not have 5 Ohm resistors there, just a wire connecting the two pin 3s. Were the 5 Ohm resistors a temporary install to set bias or were they to remain?

Where else should I troubleshoot? Any help is greatly appreciated - I miss the sound. I am using the 1960s one now, but am a little concerned by its age and lack of use.

Any help would be appreciated!

Hi,

I have a couple of questions about my Croft super micro. I tried to create a schematic:



It looks similar to the schematics by @Alex M (see here) and also to this one. Please point me to errors in the schematic. There are differences in values (as always with Croft). For example I have 1K8 at R2 and 2K7 at R8 in both channels: the other schematics have 2K7 everywhere. This schematic shows the voltages on top of those resistors: I guess it has to do with the different voltages that sink current through the resistors?

EDIT: schematic updated

WTB

Prefer without batteries, OK with as long as you can ship them safely.


Please reply either here or by DM with details, condition, and asking price.



Greg in Mississippi

Finally, Plethora of Pinjatas, origin of P series of amps

These (P) being more or less derivatives of my recent M2 derivatives ........and you know them , so no need to go in detail

So, active FE instead of buffer+autoformer FE; biasing mech. being more or less same (current sense in rails), only - with help of current mirrors, being sorta flipped upside down, vs. previous optocoupler based one

even if optocoupler based biasing is more than good, believe me, this one is even better ...... in anything you can remember to ask about

Iq and Offset stability is bespoke, in any domain I can think of - time, temperature, rails change ( mains fluctuation), no even slightest pops during Power On and Power Off

everything to embrace Square Law OS

(aha, this one being origin, even if its bigger brother - Babelfish XA252 been made first)

OK, straight MOS being real Plethora of Pinjatas ....... (is it Mini Babelfish XA252?)

SET P being then same pcb with twist - upper mosfet in Schade arrangement (is it Mini Babelfish XA252 SET ?)

pretty close to point where I can't even follow my self, go figure

'nuff babbling, some usual pics

schm is cumulative; down will post separate ones

Looky Here... Original article by Nelson Pass:
Amp Camp Amp #1
😀
______________________________________________________

Info for Amp Camp Kit (updated by Moderators)

Here's the ORIGINAL step by step photo build guide: ACA illustrated build guide

A new Build Guide for the V1.6 Two channel Chassis in the diyAudio Store.
Amp Camp Amp V1.6 Build Guide - diyAudio Guides

The small changes of the 1.8 version.All ACA’s that have 2 channels in one chassis can be converted to Version 1.8 which only requires buying a different rear panel switch and some re-wiring of the rear panel. Amp Camp Amp V1.8 Change Information - diyAudio Guides


The link below is to a Step by step build video by Patrick Norton on his TekThing website. He makes an error in cutting out the thermal insulator and leaving the backing on. Thebacking just peels off, no cutting required:
February 2016 Patreon Build Video: Amp Camp Amp Dual Monoblocks! - YouTube

See post #1453 for a tweak to the original V1.0 circuit boards. It’s not essential but should improve the sound. This tweak has been incorporated in subsequent versions (1b & 1.5, 1.6,1.8). if you have those circuit boards or kits it's already added to the board, and the part (R15) included in the kits

An ACA thread with lots of great ideas which may or may not improve the amp to your desires:
ACA amp with premium parts

Here’s a thread discussing the kits from the DiyAudio store for V1.6 and V1.8
Amp Camp Amp Kit 1.6/1.8

And here’s the link to the kits:
https://diyaudiostore.com/collections/kits/products/amp-camp-amp-kit?variant=7072933085218

http://www.hostboard.com/cgi-bin/ultimatebb.cgi/ubb/get_topic/f/3729/t/3273

Greets!

Averaged specs used:

Fs' 28.84
Qts' 0.307
Qms' 4.614
Qes' 0.329
Vas' (L) 473.024
Re' 6.442
Le' 1.295
Sd' 856.336
BL' 15.383
Sens' 97.24
Znom' 8

Being fond of the 800 series cab's baffle proportions, an 81" long folded pipe looks good with internal dims of 40.5" H x 28.5" W x 18.75" D including 3/4" divider, so just a hair over the 12 ft^3 limit with external dims of 42" W x 30" W x 20.25" D. Driver down from top front 8.5" and 6" dia. (or other shape = 28.274"^2) x 2" vent on the rear up 17.56" from the bottom for a ~27 Hz Fb.

GM

I bought a 1000A. Just replaced ALL the electrolytics, oil caps and a few others. New diodes. Works and sounds great except when playing it will make random popping noises every minute or so. I tried wiggling all the switches and the control pots are cleaned but can't seem to find out whats doing it. Any suggestions?

Up for sale:
10,000uF/63V Vishay - MAL225658103E3 - 4pc, $10.00ea
4,700uF/63V Vishay - MAL205018472E3 - 4pc, $10.00ea
10,000uF Panasonic - ECO-S1HA103EA - 4pc, $6.00ea
Condition - Brand new

I am looking for an owner of Sibelius speakers who is also able to perform sound measurements. I am building a Sibelius clone (see other thread) with the Markaudio Alpair 10.2 or 10.3 and would like to have measurement data to be able to tune the speaker similarly. I would like to see a measurement from 20Hz to 20Khz with the microphone at 1 meter from the driver and a 2nd measurement with the microphone just in front of the bass opening. I am very curious how well the Sibelius cabinet supports the driver.

A new thread to discuss DIY guitar pickups.

I recently built one using six electret microphones. Every other one is wired out of phase with the adjacent mic. The set of six therefore cancel, for far field sounds. Each is arranged to be below the corresponding string, which is near field to the mic. It works pretty well - I've had it out on stage at an open mic more than half a dozen times. Other players say it sounds good. Different sound than you'd get from a piezo bridge pickup or stick-on puck.

Why microphones? I normally play classical nylon, which of course doesnt work with the magnet based embodiment shown below. I melted the hot glue and ripped out the coil, to use the plastic shell as a pre-made holder for the electret mics to start. The three low strings on this guitar are from a nylon set.

Hi everyone!

It's been almost two years since I last built a speaker, and I'm getting the urge again.

[TLDR:
A more compact floorstander using an SB Acoustics SB15SFCR39 for bass in a vented enclosure, extending further down to the early 20hz with boundary/room loading. The B&C 5CXN44 in a sealed enclosure for mid and high.]

My current setup is really good (here), but a few aspects have me considering a change:

Size: The speakers are quite large.
Low-end Limitation: They only reach down to 35hz with boundary loading.
Horizontal Coverage: It's not as wide as I'd like.
Practicality: The horn on top is a bit of a concern, especially with baby GG² about to start walking.



As you can see below the measured 'anechoic' response yields quite a bit more low-end extension when in the listening position. I thought this would be fine but there has been the odd movie or song that lacks a little in the rumble department. Boundary loading really is my friend here (more on that later).




Shortly after building these I added Dirac and that improved things a lot over my manual room correction (manual not shown).



When I made my workshop speakers (here) I really enjoyed the sound of the B&C 5CXN44 coaxial drivers and found that they gave quite a nice wide image even when I am at the end of the sofa. I think this is because of the diffraction and tuning the response to work best slightly off axis due to the choppy response a 0 degrees.



SO...

An idea I have been chucking around in my head for a couple of weeks is this:

A more compact floorstander using an SB Acoustics SB15SFCR39 for bass in a vented enclosure, extending further down to the early 20hz with boundary/room loading. For mid and high, the B&C 5CXN44 in a sealed enclosure. Both drivers would share the floorstanding unit, reducing both physical and perceived space.

SB15SFCR39 ≈ 26L / 35hz vented
5CXN44 ≈ 4L sealed

I am totally up for other drivers but I don't want to go beyond 200mm wide baffle and I'm not too keen on a side mounted woofer owing to little fingers.

As you may know I am in the final stages of my first ever build (measuring and tuning). In the meantime, I am thinking through the concept for my next project and I am thinking a small 3-way monitor with horizontal orientation, i.e. this layout:





The conceptual requirements are:

• self contained (i.e. electronics i.e. amps, crossovers built in) stereo pair
• as compact as possible: dimensions as small as possible while still fitting the plate amp and drivers
• very good LF extension (this is in conflict with the above)
• SPL low to medium (no high SPL should help the above)
• simple (to make) cabinet. Sealed box.
• cost low to medium (i.e. low to mid tier drivers, MDF as main box material, cheaper electronics if available

Questions:

• what are the options for plate amp and crossovers module? I am only familiar with Hypex FA series and from those it would be either the 123 or 253. They are both 360mm long, which would dictate the minimum size (width). I would like to find similarly featured options cheaper and smaller, if available
• what would be a few driver options for each channel?

For example, if the overall width is 36cm, then a abt 20cm woofer can be (tightly) accommodated, together with a abt 12cm midrange and abt 5-6cm tweeter (typical tweeters with 10-13cm plate would not fit). Woofer chamber will need to be small, which would limit the range of suitable woofers, I suppose.

Hello,

I joined hoping to find a solution to my problem, seen some threads from guys that are very knowledgeable about the circuits and components, figure to give it a shot here and maybe learn a thing or 2.

My B4-X recently stopped working and I've been trying to fix, but I am very new to this kinda thing. The tubes no longer light up or heat up but I'm not sure which part would need replacing or fixing (DC-DC Converter or tube or something else?)
I've done what I can with a multi-meter and seen that the battery is fine, sitting at ~12.5 V. Where would I probe to check the DC-DC converter and the tubes and what should I expect to see? What else might have failed to cause this?

Thankful for any information

Cheers!

I'm a new member here
ヾ(´︶`*)ﾉ♬
(^y^)

Hi Folks!

I would like to turn an AES/EBU Input which I don't need/use



into a Toslink Input. But neither Neutrik nor anyone else seems to have a mechanically compatible product. The electronics after the socket with sensor are less of an issue.

This product would do the job, but does not fit mechanically:


Thanks for your solution suggestions!
Regards,
Winfried

Hi. My name is Ian. I like to work on and build tube amps. I've come to this site many times for help but haven't joined until now. Look forward to chatting with you all.

pls delete post

Hi,
I am a new DIYer and am trying to build Salas Ubib. I have done some soldering on practice PCB board and this my first real project. So far I have soldered the resistors (pics below). My question is how do I verify before turning on the power that the solder joints are good? The resistors are firmly in place. When i put a multi-meter on the solid solder on the PCB i'm getting the correct resistance. I have also checked there is no shorting, with continuity test. Are there other tests?

Nice to meet you all! Been working on some 3d printed speakers which eventually led me here.

Balanced audio technology VK500/1000: "Single-Ended Bridge" Topology, 450W into 4 Ohm

About
http://www.balanced.com/resources/brochures/1998/VK500desc.pdf
I read:
A typical solid-state amplifier
will have four or five gain stages, with a feedback loop traversing these same
stages to correct the signal. The VK-500 uses only two gain stages—without
global feedback. Unusually direct for any amplifier, this purist signal path is even
more surprising in a design of such high power. The ingenuity of the signal
path is complemented by a unique single-ended bridge topology that allows the
use of superior N-channel MOSFETs in both driver and output stages. The
result is a clear, open sound that breathes life into music.
This sounds like a design from Mr. Nelson Pass.
Also the review about
Balanced Audio Technology VK-500 Reviews
and
Product Review
Perhaps a transition from a "ZEN"-topology to a "CSPP" (Circlotron)??
Who knows more about BAT's topology?

Hello all....

Here's my Sunday night fire sale... All prices reasonably negotiable. Will ship anywhere in the US for FREE! If outside of the US we'll work something out. Zelle is preferred, Paypal, and Venmo also ok.

I've had some medical bills that I didn't expect and need to raise some funds. Thanks everyone for looking!

Arrow Video 4K lot 9 titles: SOLD
The Last Startfighter
Conan The Destroyer
Conan the Barbarian
An American Werewolf In London
12 Monkeys
Witness
Silent Running
Weird Science
Narc




Beagle Bone Black Rev B unopened, and Twisted Pear Hermes-BBB Cape with extras: $75




2 TDA1540P chips with SAA7010 and SAA7030 included on CDP mainboard with 2 of Miro's TDA1540 NOS PCB's: Sold



2 AD USB isolator Eval Boards. EVAL-ADUM4160EBZ (sealed) and EVAL-ADUM4165EBZ : $70



Chord Electronics Mojo DAC Complete with box, cover and cable: SOLD




The Beatles CD box set in Mono ! This real and was purchased at Tower Records in San Francisco. As you can see from the photos, the box, the rear paper, the inner and outer plastic sleeves are all correct. I opened this bran new still in the shrink wrap and played each disc once. : Sold

I'm trying to gather details on all available stepped attenuators. Anything and everything that's available, off the shelf premade, kits, diy, parts to make one
The obvious choices like DACT, Goldpoint and some others are I'm certain very good, but considering the cost and that I'll need several units over time I'm hoping for a less expensive solution. I was ready to purchase 2 Goldpoint blank units but stopped. Maybe something for under $80USD is possible? Thanks!

1) 24 Steps or more
2) 2 decks
3) If premade 20-25K ohms, 5K Linear, 100K linear for one design
4) I'll accommodate any size

Hello everyone, after 30+ years of my equipment in storage my son has decided to revive it and begin becoming a car audio enthusiest. Hoping to find some information here to help in that journey. Thanks Justin

Where can you find nice attractive backlit meters for our projects. Not Simpson White background black lettering. Not finding a source.

Been into audio for a long time, but haven't diy'd much yet. Closest thing I've done is build a lyra 8 synth. Looking into doing a headphone amplifier next to power some HE1000se headphones. Also have a pair of rotel rb 1070 amps I'd like to refresh running some vandersteen 2c. Computer programming / math is my background.

Hi all, I am installing some more powerful sub amps in my home set up and I have an interesting 'problem'
To cut a long story short when I earth the chassis I have a GND loop sound the signal GND is NOT connected to the chassis earth and I have double checked. So the chassis each is only a safety earth and not related to 0V signal in any way directly as far as I can measure. The chassis has no connection to the board. Apart from the heat sink and this houses the output transistors in the normal way, no short as far as I can see or any leakeage

Any ideas, it has a relay for soft start but this is only on the Signal out. The transformer has L, N only connections and I have rewired the unit for mains as I have added a 12V fan with power supply (thermally operated) so very clear on all of the mains connections. It works its just the 'GND loop' sound that I want to remove but still want to keep it safe and have the chassis earth

Any ideas ?

CFP really shines at low bias current. My last MOSFET output DIY amp runs too hot as my like. This might be my next one.
The THD in simulation is about -100dB with 10KHz.

mosfets are used in the input stage and the VAS. I find they are just better than BJT in this context.

Hi,

I just joined diyAudio.com. I have spend my entire life designing, repairing and buildingjavascript:smilie('') electronic equipment, electronics is my passion. I have designed a lot of High-End audio equipment over the last decades. The following projects are the "newest":

-Fully symmetrical cascode MOSFET amplifier with high resolution microcontroller based VU meters.
-Modular 6 channel control amplifier with remote control
-Modular input switchbox
-Twin TDA1541A DAC in differential mode with 8th order active hybrid filter
-Sonic resonators (passive semi 4-way 360 degree omnidirectional radiators
with real-time error correction). How do they sound? hearing is believing!
-Non inductive copper wire resistors for High-End passive filters, using stranded wire and a spiderweb winding technique. These resestors have extremely low noise and improve sound clarity.

javascript:smilie(':att\'n:')I am now developing a NON oversampling DAC using 4 X TDA1541A. The 44.1 kHz problem (ultrasonic interference in the audio band) is solved by using a trick I named Direct Interpolation (well this system had to have a namejavascript:smilie('😀')). This results in a virtual sample-rate of 176.4 KHz, 18 bits resolution, quadruple output voltage, improved signal to noise ratio and lower distortionjavascript:smilie('🙂'). I used a second order bessel filter at 40KHz for linear group delay just in case. The sound and dynamics are breathtakingjavascript:smilie('') since both phase-shift and ultrasonic interference are greatly reduced. Now finally I could hear music the way it was originally recorded. At the moment I am optimizing the Direct Interpolation system. Tips or suggestions from you all are highly appreciated


- Why the TDA1541A? it uses current sources based on dynamic element matching instead of resistor networks. The current sources are externally decoupled so they produce clean signals. Furthermore a smart design elliminates signal transients all together. In my humble opinion this is the purest form of D/A conversion, and the sound quality of these DAC's prove this. It is really a shame this state of the art DAC is discontinued, but I guess that is called "progress". Modern DAC's have the digital brickwall filter and decimation noise generators built in. I cannot follow the logic of spoiling a fine signal by decimating and then try to filter it out the mess you've createdjavascript:smilie(''). The high oversampling frequencies will make sure there is lots of addittional noise and interference to listen tojavascript:smilie('🙁'), it's as if you put your High-End amplifier inside a PCjavascript:smilie('😱').

- Why more than 1 DAC? With 2 ore more DAC's linearity errors are reduced, and normal lower cost TDA1541A's can be used. Signal to noise ratio improves, differential output can be used, elliminating residual interference and... the DC component can be cancelled out, enabeling a fully DC coupled DAC. In the new design Multiple DAC's are a fundamental part of Direct Interpolation. Many listening sessions confirm that a well designed multiple DAC system can sound significantly better than a single one.

- Jitter, I solved this by designing a custom made differential interface for the SPDIF signal, so no coax and no TOSlink. My opinion is to avoid jitter at the source. (asynchronous reclocking just seems to add jitter instead of removing it caused by the coincidental D-flipflop trigger). The higher the reclock frequency, the lower the jitter.

- I/V conversion, I used the classical OP-AMP approach, an OPA627, 470 Ohm and 220pF for this (shame on mejavascript:smilie('')). Passive I/V conversion using 33 OHms already creates a voltage drop at 4mA full scale of 132mV. Philips datasheets indicate that more than 25mV already causes distortion. Of course I also tried a tube output stage, it sounded nicejavascript:smilie('🙂') but it doesn't solve the distortion problem caused by the I/V resistor and/or inductors (inductors seem to produce addittional noise). It also requires capacitors or transformers in the signal path. Personally I don't like non-linear components in the signal pathjavascript:smilie('').

- Clock syncing, I used separate 1% polystyrene 470pF capacitors on all TDA1541 (the close tolerance is important). It is used for internal timing of the current source switching. If you want to sync them use a 100pF between both pin's 16 instead of a direct connection, the oscillators run in phase but oscillator output amplitude may vary.

- Decoupling, The decoupling capacitors are just used for that, decoupling, not sampling. However, leakage currents cause massive distortion. High quality polyesterfilm or polypropylene will do fine. Keep wiring as short as possible.

- Differential mode, I inverted the data signal on one DAC. The first dac outputs L and R, the second one L- and R-. So basically I used 4 I/V converters that feed into a differential amplifier. Interference is significantly reduced this way and the output is DC-coupled since the offset voltage of both TDA1541A's is cancelled out.

- Filtering, I experimented for over a year with the most exotic filter setups. I finally used 2 closely tuned Allen key 3rd order butterworth-isch filters followed by a 2nd order MBF butterworth-isch stage. Filter was optimized for both flatness and linear group delay that's why I stated butterworth-isch. The sound is about the best you can expect from a 8th order filter. By the way, there is a nice filter calculation program available from TI.

- Printed circuit board, Over the many years I designed hundred's of circuit boards (without autorouter), so this is a piece of cake. The twin DAC was placed on a single circuit board, but the new quad Direct Interpolation DAC will be a modularar design to achieve optimal results and future updates.

Well as you can see I can get quite enthousiastic about electronics.....Well that was it for now, I am pleased to join diyAudio. If you want more information about my D.I.Y. projects, please feel free to ask, your comments, tips and reactions are very welcome.

Hello everyone,
So I'm finally getting round to repairing my tweeters. Will it be a good idea to change the voice coils aswell? If so from whom do you recommend I buy them.

Folks,

Over in the other meta thread we have been discussing the TDA1541.

https://www.diyaudio.com/community/threads/building-the-ultimate-nos-dac-using-tda1541a.79452/

Based on my experiences, various articles and application notes and practical work by a number of peeps we now have a pretty decent understanding of the TDA1541 and what makes it really tick. Much of it is in line with my previous understanding, but where before I had many black boxes I now have a better feel for the internal circuits and the various implications.

---

In short:

1) The TDA1541 needs a syncronised DEM system with correctly sized DEM filter capacitors and a way of feeding the DEM Oscillator pin's that do not cause DEM switching feed trough into the substrate. Empirically 8 X DEM Clocks (352.6/384kHz) offer the best objective performance.

Very low frequency DEM oscillators with big value electrolytic capacitors are an alternative but a bit questionable insofar as it takes hours of the DAC running to get to correct operation and long term stability is highly questionable. In the end both achieve the same fundamental result in different ways.

2) The TDA1541 has significant capacitive feedthrough from the digital inputs into the substrate and from there into the outputs. It is best imagined as a coupling capacitor of ~ 12pF between each digital input and the analogue outputs. 12pF does not sound like much but with MHz bit clock frequencies there is a lot of feedthrough.

Slowing down the edges of the input signals will reduce this. By using "Simultaneous Mode" we can lower the Bit Clock frequency maximally. At 192kHz Sample Rate we only have 3.072MHz Bit clock in this case. It means the edges can be slowed down much more without ill effects on the digital side, compared to I2S mode which typically has 12.288MHz Bit clock at 192kHz.

Existing "SIM" converters unfortunately (almost) all use the fallacious "stopped clock" system, which maximises the clock speed so a lot of clock feedthrough happens for a short duration and then nothing for the rest. This means we cannot slow down BCK edges too much, nor any others. So I will not consider such systems desirable.

There are debates around analogue stages and other TDA1541 related circuitry, but they are not (yet?) part of this project.

---

So, what is the project?

Make a PCB design (open sauce, free as in Free Speech and Free Beer) for a TDA1541(A) frontend that accepts an Amanero standard USB Module, incorporates an SPDIF receiver (optical, Coax and XLR) and includes an IIS to Simultaneous converter that outputs a continuous BCK at 16 X FS and the necessary LE Signal and Data and slew rate and voltage swing limiter circuitry.

Just add a TDA1541 (we might bring the IC position onto the PCB with other bits, this remains to be seen), power and analogue stage (where nobody seems to agree on anything).

As this is DIY Audio, we want to do this in discrete logic, not using CPLD or FPGA or bought in CPLD/FPGA Modules. Why no complex logic? Typically we find a few 100pS P-P additive Jitter from CPLD, FPGA or CPU's (e.g. XMOS). Ground bounce and other problems are significant. The IC cases are distinctly DIY unfriendly, a tool chain and programmer is also needed. It adds up. We can reclock to block a lot of this, but still, why?

---

With an Amanero Footprint (we can add more) the USB input is taken care of. For SPDIF the WM8804/05 series is EOL and others re unclear. So adding a CS8412(14) footprint is probably easiest, we can add suitable adapter PCB's for WM8804, CS8416/DP7416, AK4118 etc. on the PCB.

The main challenge is that we need to take a BCK of 64 X FS and a 2 X 32 Bit Data steam on one data line and output a BCK that is divided by 4 and two Data lines that have 16 Bit Per sample.

There are a number of possible approaches using shift registers, but as we need an input register to hold data from the I2S input (say 8 X 74HC595) and then an output register (say 4 X 74HC165) to hold 16 Bit that go to the TDA1541, this rapidly becomes a logic IC grave. We can find some 16 Bit Shift registers but these still account for a lot of circuitry.

On the plus side, the logic in this case becomes very transparent, obvious and easy to design and debug. Still 16 IC's or so seem a lot to me. It does remain an option.

An alternative would be to use the 74HC(T)40105 FIFO. As we have separate input and output clocks and the "elastic" FIFI we can stuff our 16 Bit into the Input side at the 64 X BCK speed and clock our data out steadily at 16 X BCK and the FIFO takes care of everything.

This would use one 40105 FIFO configured as 64 Bit Delay line with data taps at 16/32/48 and 64 Bit's so we can have the input bit's for our FIFO arrive simultaneously.

Two more 40105 FIFO handle data build as a 32 Bit X 4 FIFO. We stuff bit's into the first FIFO from where the ripple immediately to the output. We then clock out using our 16 X FS BCK. On the input side we invert MSB and only pass actual 16 Data bits, stopped input clock to block off the rest.

I think the FIFO solution is by far more elegant. An option for a secondary PLL with VCXO (or a VCLCXO) can be designed in as well.

A discussion start is here:

https://www.diyaudio.com/community/...ac-using-tda1541a.79452/page-517#post-7939329

So, if anyone wants to join into the discussion and project, feel free.

Thor

Looking for a Bliesma T34B-4 tweeters (pair).

Hi everyone!

I'm planning two (maybe three) fun speaker projects and would love input from experienced DIY speaker builders – especially if you’ve worked with FaitalPRO, Beyma, Fostex or Morel drivers (those are the only ones I have access to order..).
Passive radiators from other brands are fine. DSP, REW and measurement mic are available for all setups.

---

Project 1: Mini 2-way + Mini Subwoofer for my boy’s room (16 m²)

Small Satellites: max 150 mm (W) × 250 mm (D) × 300 mm (H) – smaller is okay.

Mini subwoofer: Can fit either 600×500×230 mm under the bed, or 540×400×230 mm under a shelf.

I want something fun, with real bass, but not necessarily high SPL. Think “mini system that feels like a big one.” (Electric music)

Full DSP control – so EQ, crossover, limiter etc. are available.

Fun factor is key. :-D

---

Project 2: Subwoofer for high-end home theater (35 m² room)

Enclosure limit: 500 × 300 × 500 mm (~75 liters gross).

I already have a Velodyne DD-10 (Gen 1) and want to complement it – more depth, punch or both. (and front ELAC FS-249 (gel1) )

DSP + 700–1500 W Class D amp available.

Passive radiator or sealed design preferred (ported is tight on space).

Priority: Deep extension, musicality, cinematic power, and clean performance down to 15–20 Hz.

I might be able to increase the box volume a bit if needed.
---

General questions:

Which drivers from FaitalPRO, Beyma, Fostex, or Morel should I take a closer look at?

Are there any particular models you’d avoid?

I feel like I'm stuck 😕

John I was wondering if you came to any conclusion about the pink noise from the da-capo DAC from the post on the forum middle of last year.

I also have a Da-Capo which creates the same pink/white noise sound, with a hint of the music behind it, after a period of being powered up (doesn't seem to make a difference if it is in standby or not, just the power being plugged in).

The DAC has the HDCD filter fitted (so isn't the 1307 filter issue that you mentioned).

I have tried re-seating the filter module and moving the Input card to a different slot. Neither have made any difference.

Funnily enough about 4 – 5 months ago a Da-Capo came up for sale that must have been one of your development ones. The serial was no 1 and it had a dedication to your wife actully on the circuit board. If I had seen your name on these forums before now I would have let you know as it sold for silly low money…

Lastly I wondered if by any chance anyone might have a copy of the original Da-Capo instruction manual at all? I would really appreciate a photocopy of it (been trying to get one for ages), I am also looking for a Cardinal instruction manual as well…

Does anyone know the dip switch settings for the HDCD filter (or will I only get intelligible sound if I have used the correct setting)

What transport was the Cardinal based on… Yes I know the drawer etc is some bespoke low vibration material etc… but I guess the laser and motors etc. were taken from a commercially available Transport… It would be of immense help as I could then track down some s/h really cheap units that used the same laser and motors etc for future spares.

John can you remember if the cardinal produced performance figures (jitter etc.) better than most other transports produced, or is it just good figures for it's era?

Lastly is there any other transports that use a compatible clock lock to the Da-Capo DAC? Just wondered because at some point if the cardinal broke and it can’t repaired it would be good to know of any other transports that would work with the clock lock connection on the DAC.

Thanks for any info that can be offered.

John H

PS my Cardinal accepts CD-R’s without any drama (including the cheapest of the cheap CD-R’s), I haven’t tried RW’s but will later tonight.

Fourteen days ago, on October 1st, Wayne Colburn presented his Pearl 3 phonostage design at the 2023 Burning Amp Festival. Today I'd like to unveil "UDP3", a PCB which makes it relatively straightforward to build an external power supply for Pearl 3, in a separate chassis, connected by an umbilical cord. A few reasons why builders might wish to put Pearl 3's DC supply in its own box, include:

• This lets you move the mains transformer far away from the sensitive Pearl 3 PCBs. Greater separation gives greater isolation.
• The external PSU chassis provides an electrostatic and electromagnetic shielding box, surrounding the mains transformer. This dramatically reduces noise radiated from the mains transformer and wiring.
• If desired, you can build an additional box-within-a-box, thereby double shielding the mains transformer. You don't have to worry whether the extra size and volume of the second box will intrude upon the Pearl 3 phonostage PCBs.

The UDP3 board (Umbilical Cable Driver for Pearl 3) is shown below. It requires a dual secondary power transformer (2 x 22VAC RMS) which is not mounted on the UDP3 board. Many builders will probably choose a blue encapsulated Toroid from Tamura or Amgis, 15 VA, mounted on a blank piece of experimenter's perfboard.

The UDP3 circuit is a cascade of several lowpass filters connected in series; it is NOT a voltage regulator and there are no negative feedback loops. This is intentional and deliberate; NFB loop gain generally falls as frequency rises, often at a slope of -20dB per decade of frequency. But we want lots of attenuation (a/k/a "PSRR") at high frequencies, exactly where NFB regulators poop out.

Instead, UDP3 uses ferrite beads and several cascaded filters (one of which is a two-pole LRC filter), to achieve excellent noise reduction even at radio frequencies. The big idea is: provide Pearl 3 with a pair of low-ripple, low-noise, RF-free raw DC voltages, and let Pearl 3's onboard voltage regulators do their job, when given pristine inputs.

The UDP3 outputs plus and minus nineteen volts (approximately! remember, UDP3 is not a regulator), which the 7815 and 7915 voltage regulator IC on the Pearl 3 boards, then reduce to smooth and regulated plus and minus 15 volts.

CIRCUIT DESCRIPTION

(You may want to open the schematic image in another window, or print it on paper, to follow the discussion in this section and quickly see which component is "C5", etc.)

C1, C3, R1, BR1, and C5 form an unremarkable, ordinary AC-to-DC rectifier and filter, plus Quasimodo snubbing. You'll notice I have used C3 = 1000 nanofarads, and 1000 != 150. I spoke to the Quasimodo inventor about this, explained my reasoning, and got his approval. So use 1000 nF in your build (see Detailed Parts List) and be happy.

Then ferrite bead FB1 converts high frequency noise on C5, into heat. The ripple waveform (now on C7) has far less high frequency noise.

NPN Darlington Q1 and its supporting components, forms a capacitance multiplier that is protected against overvoltage (ZD1) and turn on/off shocks (D1). Resistor R3 ensures that the collector-base voltage of Q1 never goes negative ... which could allow input ripple voltage to shoot straight through to the output.

Then L1 + C13 + (the DC resistance of L1) form a two pole LCR lowpass filter, attenuating high frequency noise quite effectively. The relatively pure, low noise DC signal on C13 is presented to Q3 and its supporting components.

The Q3 circuit can be considered a "clamped capacitance multiplier" because its output voltage is clamped and cannot exceed (approx!!) 19 volts, even as the input voltages rises far above 19V, thanks to U1 and ZD3. The relatively weird and unknown (but extremely CHEAP) adjustable shunt reference part called AZ431AZ is used, because it offers plus minus 0.4 percent accuracy for less than USD 0.50. Much better bang for the buck than the T.I. "TL431" which is pin compatible but less accurate.

Finally, there is an output rail fuse F1 and a ferrite bead FB3 to remove the last vestiges of high frequency noise. The fuse, a small thru-hole packaged device, blows if/when you mistakenly short UDP3's output. It is available on DigiKey and Mouser for about 40 cents per fuse. Because they cost so little, I recommend you buy at least six fuses of each of three different fusing currents. Or more. Now when you get a surprise fuse-blow event during testing, you will have plenty of spares, and they don't cost an arm and a leg.

To test the first UDP3 prototype, I connected a pair of 100 ohm, 30 watt resistors to the UDP3 outputs (see photo below). These are cheap to buy and build, I suggest you get some too and test your UDP3 carefully before hooking it up to your precious Pearl 3. At plus and minus 19 volts output, these load resistors consume 190 milliamperes per supply, comfortably more than Pearl 3 draws. During testing with 190 mA load current, fuses rated 250 mA never blew.

HOWEVER, it's all but inevitable that some "hot rodder" types of builders, will add high current discrete opamps to Pearl 3. And increase the bias current in the BJT output stage. And possibly other stunts or gymnastic shenanigans which are unimaginable at the moment. Therefore UDP3 is deliberately over-designed, to provide 350 mA from +19V and 350 mA from -19V (with higher current fuses fitted of course!!) Heatsinking the pass transistors lets them operate comfortably even at these high current levels.

Schottky diodes D5 and D6 are panic protection components, whose only job is to set the rails to not-stupid voltages after a fuse blows.

WHO SHOULD COMPLETELY IGNORE UDP3?

A quick glance at the UDP3 schematic reveals that there are a LOT of components. Including four Euroblox connectors, four extruded aluminum heatsinks, eight super-low-ESR electrolytic capacitors, oh and by the way, a second chassis (!!). If you're hoping to build a cheap, cheap PSU for your Pearl 3 phonostage, this isn't it. Too many parts.

Similarly, if you're hoping to build a teeny tiny PSU that occupies very little chassis volume, UDP3 isn't for you. PCB size is 112mm X 132mm (mounting holes 100 x 120) and the heatsinks are an inch tall (25.4 mm). That doesn't even include the power transformer. See the photo of UDP3 atop a 170x230 Modushop "Galaxy" below.

Finally, if you're hoping for a "paint by numbers" audio project that doesn't require you to reason about electronics, not even once: UDP3 may not be a good project for you. There's no wiring diagram, there's no suggested part numbers for the AC mains IEC inlet or fuse holder or on/off switch, there's no transformer mounting recommendation, the list goes on and on. Avoid misery; don't attempt UDP3 if it is beyond your current builder-training-and-skill level.

ATTACHMENTS

The schematic, detailed Parts List, and PCB manufacturing Gerbers (.zip archive) are attached to this post, below. It is "Rev.A" -- the first official release of UDP3.

I've also got a few extra PCBs of the experimental prototype (rev.0) which are built on extra sturdy 2.0mm thick fiberglass, and are 50% stiffer than standard PCBs. {remember, stiffness is proportional to thickness squared}. Send me a selfie photo of yourself holding up your two chassis for Pearl 3 and UDP3, also holding the two bare Pearl 3 boards, and I'll send you a rev.0 UDP3 circuit board for $5.00. That's the cost of a mailer envelope and shipping via USPS.

Hello, I repaired by XPS2 as it no longer had enough output to power the turntable motor. As per earlier thread the XPS2 service manual is here:

https://www.vinylengine.com/library/roksan/xps2.shtml

Firstly here are some notes on the circuit diagram as it is a bit sparse. IC 706 is an M706 counter, pin 8 is Vcc (+15V) and pin 5 is GND (0V). IC 324 is an LM324 op-amp, pin 4 is +Vcc (+15V), in 11 is GND (-15V). OP1 and 2 are LM1875T power amp ICs,pin 5 is V+ (+28V) and pin 3 is V- (-28V).

I added some further labels to the circuit diagram as follows. Outputs A (shown as AA by mistake) and C are 90 degree phase, one of these is connected to E and hence OP1. Outputs B and D are 0 degree phase, one of these is connected to F and hence OP2.

The capacitor and resistor on the - input to OP1 are C26 and R7, and that on the - input to OP2 are C25 and R5.

A few years ago I replaced most of the mini electrolytic caps, these are annoyingly small and fail due to overheating. This year a few of them needed replacing again, PSU was still not working. I found that the 33/45 and the Operate/Standby switches were high resistance, Fortunately pressing them many times restored the contacts.

I found that C25 and C26 had both failed being close to the hot LM1875 chips. When replacing them I lifted the opposite end of the corresponding resistors (R5 and R7) and soldered the new caps between the resistor lead and ground, then shorted the old C25 and C26. This left the new caps further away from the hot ICs. I now had outputs from both OP1 and OP2, but the OP1 (90 degree phase) AC output voltage was half that of OP2 (0 degree phase). It was only when I connected a scope that I saw that OP1 output was not a continuous sine wave but rather a series of bursts of sine followed by no signal. Replacing the LM1875T for OP1 restored normal output and the turntable was back in use.

Also note that the 22k ohm resistors between OP1 / OP2 output and - input are SMD parts on the track side of the PCB. I lost one so replaced with a resistor with leads.

Regards,
John

Hello there and thank you for giving me access and any guidance you can provide. I came across a line array design that caught my attention and I would like to make a couple of them to see how it is. It has 1 x 6.5" and 1 x 8" and a driver. It does not say the size and the design does not explain if it is 2 way or 3 way, although I personally understand that the 3 way is more complete.

First off let’s make sure everyone understands I know very little about the subject I’m bringing up and my total amp repair experience is the changing of a faulty protection circuit in a h/k avr500....so please dumb it down as much as possible!

I want to figure out if it’s possible to easily upgrade any components of the sonamp 260.....I own one of these (bought new around 2000’ish) and it’s hardly ‘audiophile’ but seems to me a well built and simple platform that might benefit from some ‘upgrades’.

I understand it’s not as simple as it may look and hope to find someone local to maybe mentor me through it.

Anyhow am I safe in assuming this amp is worthy to upgrade?
It’s currently seeing duty as a sub amp driving dual 10’s
The 260 is supposedly stable to 2ohm and I’ve never been able to make it break a sweat.
As a full range amp the top end is a bit too grainy and harsh (since new) for me anyway.
Is there simple change outs to make it smoother on top?

I think this amps simplicity and low worth (can be had on eBay -$100)
lends itself as a good ‘training’ piece if nothing else?

Anyone have experience with this amp?

Thanks bob

Hi, friends!
I'm trying to make a simple preamplifier for a dynamic microphone. The microphone has an impedance of 600 Ohms and a frequency range of 50-15000 Hz. The power supply will be single-polar, 5 V, from a regular smartphone charger. The gain will be fixed, 100 times.
The microphone and preamplifier will be used with a simple mixer in a karaoke system.
My questions:
1) Will the input impedance of the amplifier be too low with R1 = 4.7k?
2) Are capacitors C1 and C3 necessary?
3) Is it worth adding inductance to the power supply filtering circuit (and what is its optimal value)?
4) What else can be improved/changed?

Does anyone have a source for an assortment of SBM belts?. Just one kit with a bunch of sizes.
"That sight" seems to only have SBS. I need better.

Any ideas?

Thanks

Working on a Kicker KXA2400.1, there doesn't seem to be much info out there on these. Found schematics of the KX (not "A") series, radically different. Powers on, everything looks reasonable, protect light comes on then goes off, draws about an amp once it's stable, no output.

Opening it, found a nice flash mark where a little lockwasher came from somewhere and wandered over to short the positive rail busbar (near the green LED & USB port) to the grounded pressure plate for the rectifiers. The washer was mostly vaporized and the rail is no longer shorted -- the positive rail comes up to voltage fine, but the negative rail is dead.

Also found a blown capacitor in between the two output coils, replaced that, still doesn't work. No other obviously failed components or flash marks from said washer shorting other things before meeting its demise.

Weird power supply architecture, using two non-isolating boost converters instead of the usual transformer. Seems to be asymmetric as well, the positive rail having more transistors and higher voltage rated caps than the negative. And here I thought Rockford was the king of trying to find new ways to patent a switching power supply.

Anyone worked on one of these yet and have any pointers, or perhaps a schematic of it?

Thanks!

Here is a 1990 circa Citronic PPX300 Lateral MOSFET amplifier, made in the UK!. As some will know these PPX amps are very well built and reliable. (The bigger versions have drain fuses on each MOSFETS)

100 watts @ 8 ohms per channel, 500VA transformer, three pairs of lateral MOSFETS per channel, 2x10,000uF filter caps, headphone output via dropping 68ohm large resistors and caps (big ceramic resistors in pic) No relays. DC protection via TRIAC crowbar. Also includes some sort of VI limiting circuit to protect the gates? Looks like there is drain resistors for each MOSFET? Help limit current instead of fuses like the bigger models? Dead silent main outputs and headphone outputs

All seems original. Just going through a little refurbishment. Nearly all capacitors are still in tolerance except for the DC blocking input caps around the level pots. Changed them from 10uf to 100uf for a lower high pass frequency. Changed the feedback DC blocking cap to 470uf. There is a few tantalum caps but they measure spot on.

Bias was a bit hit and miss. The bias pots have an unknown value. On the case of both pots there is melted part, I guess to prevent movement? Little sticker on top to prevent dust ingress. Both pots fell to pieces when I removed them. I tried a 470 ohm pots as a replacement but got very little movement in bias so I tried a much high resistance 5k pots for now. Bias quite sensitive to these high resistance pots. Higher resistance increases bias, lower resistance lowers bias. Set bias at 150ma. The bias transistor gets rather hot though on both sides no matter the bias current. Too hot to touch, approx 50c, TR7/TR17 2n5416 in pic .

There also seems to be a Thermistor (TH1) connected between P and N gate resistors. Anyone know why?

The dropping resistors for the opamp 15v supplies will need replacing, Heat cracking 1.8K I think.

Subjective sound qualities... Bass very good, top end best I have ever heard. Very smooth.

Does anyone have a schematic for the PPX300? I have a schematics for the PPX900 but there is differences and board printed component numbers are different on this 300. Thanks.

Lads, I thought this issue is better suited to be looked into by the technically well-exposed people here.

I have a streamer preamp(Primare i15) that is connected to the power amp(NAD 208) using an RCA connection. There is no 12v trigger running from the Pre to the Power. Therefore, when I switch on the system, it will be the Pre first and just a few seconds later, the Power. I did the same today and when I switched on the Power amp after the Pre, there was a loud pitched sound from both the speakers- the sort that is often encountered when the pre is switched off before the power. I have no idea what caused this but I immediately switched off the Power amp and the mains.

I waited and switched ON again in sequence and started playing some music. Felt something was not playing as it should and when inspected closely, I heard the mid-woofer producing a distorted sound. Strangely the vocals were clear but when a track that had a double bass was played, I heard distortion. I listened to the tweeter and the lower woofer and found nothing unusual sonically.

I did a quick check with the multimeter for the DC offset numbers. I took the readings an hour after the power amplifier was powered ON. The next day, measurements were taken immediately(2-3 minutes) after it was powered ON to see if there was any difference and/or whether there were any DC fluctuations. They were the same though. Also, the readings on the multimeter took a few seconds to stabilise. But when they did, they remained solid.

The measurements taken at the amplifier's terminals are as follows:

Speaker A's terminals:

Left channel - -1.4 mv
Right channel - -2.8mv

Speaker B's terminals:

Left channel - -1.4 mv
Right channel - -2.8mv

The heatsinks on both sides felt equally warm. However, I made another observation. When the amplifier was switched ON(after a week), it took about 4 minutes for the relay to click in and emit the green light for usage. The last time this happened was when I got it serviced(after 2 years of storage) and put it to use. The next day, it took 10 secs to get ready. I am wondering if this is normal. In the last 3 weeks, I have been using it, it is ready for use almost immediately upon power ON; sometimes within a few seconds.

I hope I have given enough information for you good people to look into and help me out. Do let me know if you need further information of any sort.

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?

Hello,
I'm looking for the spec of this 3 ways project but I cannot find any info, please help. (I already have the box and drivers ready ;-))
Thanks
ADZ

Looking for two B&C Speakers DCX50 for a loudspeaker construction project in our non-profit cultural association.

Willing to pick it up in germany or uk.

AI, for or against?
I'm one of those who thinks AI should be reserved for important things, like research, basic research, medicine, etc.
Any other use, often futile and out of laziness, drives me crazy!
And what about "images" generated by AI? It's unbearable. For me, who loves photography in general (as someone who looks at things, not takes them), everything in an AI photo is disgusting and disgusting.

I see more and more people using AI to try to troubleshoot or modify one of their devices. I think it's even worse than anything. It's literally separating the head and the hands, and generally, when you separate these two, it doesn't go very well (referring to the headless chicken running around).

This is a DIY forum, I mean, the answer is in the title... and also a place for mutual support and LEARNING, and I'd rather not see this AI thing here. Even for fun, it's an insult to human intelligence and its hundreds of thousands of years of evolution.

I also think that human beings are lazy by nature and will always take the easy way out rather than the hard work, even if the latter allows us to grow and learn.
As proof, relatively speaking, I have people who no longer know how to park their car without assistance, and worse, those who don't know how to park it with assistance.

The "Method" and the "gesture" are things that have been lost for years. AI is accelerating this phenomenon, and I would like it to be banned from this place.
I would like to know what you think.