A Directory of Apex Audio Amplifiers - Chapter 2

[xrk971]

This thread is an extension of the main Directory located here:

http://www.diyaudio.com/forums/solid-state/292226-directory-apex-audio-amplifiers.html

Another thread was needed since a post is limited to a max of 50 images. Since I felt that it is important to visually be able to see the schematic of an amplifier design in the index, and Apex Audio is so prolific with his designs, we ran out of room on the main thread. I will try to alphabetize/categorize to the extent possible, but may have to resort to serial ordering of when I discover it if I don't have time to maintain.

We will start this thread off with the

Retro Amp 50W Single Supply - added Aug. 14, 2016:

http://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply.html

Build by Olafk:
http://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-18.html

Listening impression by Olafk:

Very nice little amplifier .
Built and work. Nice warm sound.

PCB pdf's by Olafk:
http://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-18.html#post3986254

Video of this amp in action (speakers sound a bit tinny so probably not fault of amp):
https://www.youtube.com/watch?v=gFbivge6oVY

*****

F8 (diamond buffer front end latFET outputs) - added Aug 14, 2016:

PCB layout:
http://www.diyaudio.com/forums/soli...ate-fidelity-amplifier-841.html#post4801156tt

No confirmed builds as of 8/14/2016.

*****

FR100 - added Aug 16, 2016, new design not tested as of this date:

http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-207.html

Nice layout by Prasi:

http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-219.html#post4833070

*****

A3 - added Aug. 19, 2016:

http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-796.html#post4772109

PCB:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-836.html#post4799564

First build here:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-849.html#post4806080

Preamp - added Sept 4 2016:

DC crowbar speaker protect (powered by speaker cable so can be placed in speaker itself) - Sept 22, 2016:

P30ZF Zero negative feedback preamp - added Oct 7, 2016:
http://www.diyaudio.com/forums/soli...imate-fidelity-amplifier-875.html#post4850095

AX11F (FET input, no need for preamp) - added Dec 15, 2016:

 

[Karl vd Berg]

Making "place holders" on #11, #21 posts...

Hi xrk971,

Maybe you can also make post #11 (first post on 2nd page) as a "place holder" for another 50 images on 2nd page in this same thread if it works.
Should be good/enough for a while, but as Apex goes on highly productive, then post #21 (first post on 3rd page) as another "place holder" for another 50 images, and so on... 🙂

 

[xrk971]

Added FR100 from here:
http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-207.html

 

[xrk971]

SR PP12 preamp added. Can be headphone amp too.

 

[xrk971]

DC Crowbar Speaker Protect (passive)

Circuit will be activated with DC over +/-10V - then will blow fuse at amp to protect speaker which is shorted at terminals.

http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-215.html#post4823438

 

[xrk971]

Just added Zero Negative Feedback preamp:

 

[xrk971]

Added AX11F - FET input

 

[kandimba]

FH14 PCB Not Tested

 

[2pist]

Many thanks to all that contributed! I just get to walk in here like a kid in a candy store.

Anyone actively working on a apex project right now?

 

[alain98]

Which Apex amplifier can work well at + - 25v DC?
Thanks in advance for your suggestions and advices.
Regards.

 

[xrk971]

Almost all +/-35v amps will work at +/-25v. You just need to adjust some of the resistors that control the bias current into the input stage and VAS as they will be lower than optimal. However, they will sound pretty good. I would say, pick an amp and play with it in LTSpice to get the new setpoints. Or ask Apex Audio to reconfigure it for you.

 

[Hiten]

Since there are many versions, which would be a go to Apex amplifier of more or less than 100w, which is built, tested (may be refined later on) and well documented ?
Regards

 

[xrk971]

The FH9 has been pretty well liked by all who built it. I have made a version of it with better spec’d parts and superior layout called the FH9HVX. It achieves 100w with only a single output pair of Fairchild MOSFETs. Sound is beautiful and powerful.

 

[Hiten]

Thanks xrk971.