There are a few people actively working on it, including myself. I've been slow to post updates here, although I will soon after I've made additional progress.
I plan to use the ClassA^3 board as a guitar amp.
I was thinking using it as guitar power amp too!
So, will you incorporate mixed-mode feedback to lower damping factor? And will you also use soft-clipping feature?
So, will you incorporate mixed-mode feedback to lower damping factor? And will you also use soft-clipping feature?
Cool. I plan to use current feedback, soft-clipping, and a variation of "power scaling (TM)." Ian sent me a bunch of stuff on how to accomplish this, although I have to sort through all of my files to piece it together.
Presently I'm designing a custom PSU, as I plan to use a high-voltage solid state pre-amp.
I can recommend you JFET preamps by AMT, which sounds absolutely amazing! Or if you want custom good sounding solid state preamp look for inspiration here: Main page
Why do you need power scaling? To be able to soft-clip power amp at lower volumes?
Great minds think alike: KMG sent me two of his LND150 JCM800 PCBs. I plan to use this as the pre-amp. I would like to use the ClassA^3 for the power section, as I don't want to custom wind my own transformers...
The AMT solid-state tube devices are a neat idea, although I'm not sure if I want to use proprietary technology in my design.
Yes, exactly. I would like to have Power section distortion (vs. Pre-amp) at lower volumes.
How far along are you in your project?
I didn´t meant AMT warm-stone tubes, but their Legend amp series (P1, S1, R2 etc.) They are 9V-12V JFET preamps.
I have not started building amp yet, because I am in stage of gathering data, options and thinking.
Ah, do you have any schematics for the Legend series? I have the AMT Tube Cake TC-3, although this is a high feedback design.
KMG's LND150 triode emulator is appealing to me, as they closely resemble the topology and overdrive characteristics of a real tubes.
Please PM me if you want to compare notes. I think it might be off-topic to dive too deep into the specifics of a guitar amp; I originally started this thread with the intent of building a ClassA^3 stereo power amp, which I plan to tackle after my SS guitar amp.
You can also check out my guitar pedal (Tribus Drive): Greenchild - Greenchild Home
There are some schematics of Legend amps series on net, but they are not too much expensive to buy.
I had AMT TC-3 too, but I didn´t like it at all. I have better sounding design. I will PM you...
I had AMT TC-3 too, but I didn´t like it at all. I have better sounding design. I will PM you...
No, not with this amp, I meant in general term slow. Now I do other project, but soon who knows.
If I could give up sleeping every day, then I would have time to build everything I want.... Unfortunately my body does not agree! 😀
Unity gain?
Could be this design run at unity-gain? Change outputs to common drain to lower open loop gain?
Could be this design run at unity-gain? Change outputs to common drain to lower open loop gain?
I am happy to see some continued interest in this project.
I thoroughly enjoyed reading Ian's articles in Linear Audio and the supplemental information provided for in the links.
As my budget allows, I am collecting materials for a two channel amplifier. So far I have two boards (one donated by a member here), my heat sinks, transformer, Universal PSU board from the DiyAudio Store, and my Lateral MosFets from Profusion. Next month I will finish the power supply then start putting together the amplifier.
This is a ambitious project for my skill level so I am taking the slow and steady road to completion.
I thoroughly enjoyed reading Ian's articles in Linear Audio and the supplemental information provided for in the links.
As my budget allows, I am collecting materials for a two channel amplifier. So far I have two boards (one donated by a member here), my heat sinks, transformer, Universal PSU board from the DiyAudio Store, and my Lateral MosFets from Profusion. Next month I will finish the power supply then start putting together the amplifier.
This is a ambitious project for my skill level so I am taking the slow and steady road to completion.
Last edited:
Class A^3 Update
For those who are interested, Ian's Linear Audio, Volume 8, article supplement and addendum are ready for public consumption.
Addendum v1.7 address oscillation, DC offset, and problems with U1 high p-channel to n-channel threshold voltage mismatch.
Modifications may be made to existing Linear Audio PCBs to fix the aforementioned issues. We plan to make revised PCBs available in the not too distant future.
Supplement v0.2 provides additional information in regard to the cube amp topology and design.
Here's a link to the public folder.
I have the amp up and running, and it sounds fantastic. The soft clipping really makes a significant difference. Have fun.
Regards,
Mason
For those who are interested, Ian's Linear Audio, Volume 8, article supplement and addendum are ready for public consumption.
Addendum v1.7 address oscillation, DC offset, and problems with U1 high p-channel to n-channel threshold voltage mismatch.
Modifications may be made to existing Linear Audio PCBs to fix the aforementioned issues. We plan to make revised PCBs available in the not too distant future.
Supplement v0.2 provides additional information in regard to the cube amp topology and design.
Here's a link to the public folder.
I have the amp up and running, and it sounds fantastic. The soft clipping really makes a significant difference. Have fun.
Regards,
Mason
Mason, many thanks for putting this up.
And many many thanks of course to Ian for such a long-standing effort to get all the details right and documenting it.
I am planning to upgrade my own cubeLaw amp of course, as soon as I get a free day.
Is there also some information on using the Toshiba FET arrays or did I miss that?
Jan
And many many thanks of course to Ian for such a long-standing effort to get all the details right and documenting it.
I am planning to upgrade my own cubeLaw amp of course, as soon as I get a free day.
Is there also some information on using the Toshiba FET arrays or did I miss that?
Jan
No explicit info in regard to the TC7WU04FU in the addendum, although folks can use this unbuffered array as an alternative for U1. Ian's own measurements indicated that the WU04 is very well matched.
Thanks for sending me the adapter boards, Jan. I have several on hand if anyone wants to try one.
FYI, for the v2.0 PCB we plan to make provision for the WU04 directly on the board.