Aleph-X builder's thread.

Official Court Jester
Joined 2003
Paid Member
I have a question for the 9610 differential
is it possible to change by an equivalent like the FQP3P20
because the threshold voltage is 5 v.
I have a hard time finding 9610 pairs in mini 4.2v VGS.

here lien:
Products - ON Semiconductor

specific value of Ugs of input LTP mosfets is pretty much irrelevant, simply because they are biased with CCS

just match them and that's it
problem Aleph X

hello everyone
I need your lights, on the Aleph X of the pcb KKpcb
I sent 3 emails there but he does not answer
I have an absolute offset of 4v that I can't get down
despite the 33 ohm out to ground nothing helps with the VR2 fully
I put a trimmer in place of the 360ohm resistance which for Gray's pcb is R24 and even that I can not go down more.
but my main concern, i connected an xlr preamp and a cd player and i have no sounds.
does the absolute offset prevent me from this
knowing that I have 80mv between out + and -
I do not understand !!!!!!!!!!!!!!

thank you
Jean Claude
An externally hosted image should be here but it was not working when we last tested it.
thank you for telling me about the differential
in fact I put tulip plugs to change the pair of 9610 and I just noticed that the pair was badly inserted and suddenly
even the absolute offset is immediately adjusted
thank you for your help.
I took for the finalization to go well

leg 9610 in the two 3.7v
resistor 390 or 392 5v
thank you
Jean Claude
Hello diyaudio, my first post here. I'm sorry if I've double-posted, I haven't used a forum in a long time

I've chosen the Aleph-X design for my learning entry into the field of DIY amplifiers since Nelson Pass has written so many of the articles I've learned the most from. Plus, it looks like the Aleph-X is a great practical design with a number of positives, including relatively elegant simplicity and symmetry of the circuit, and excellent linearity and noise cancellation, and in a non-mathematical way I think I grasp how the whole circuit functions.

With that said, numerically I'm hitting roadblocks understanding how this circuit works. I'm in over my head but I'm determined to study this circuit, and learn how it and Class-A works and why 'this' way was chosen to build it. In the linked image I labelled groups to help clarify the meaning of my questions/observations. I hope that's considered an acceptable design of the Aleph-X on diyaudio. I know I'm asking a ton of questions, I'm grateful for any help offered. Please feel free to correct any mistakes or assumptions I made. I have a lot to learn and I have made a LOT of assumptions while trying to teach myself, and it helps me here to take a shot in the dark and put my 'understandings' of all this into my own words.


1. Group D: Looks like it is meant to be a 9V, approximately ~1A voltage regulator for the E-group, which would place the E-group MOSFETs at -27V drain-to-source? I think I understand this one well enough.

2. Group E: My confusion starts. An IRF 9610 P-type MOSFET for each phase-side of the circuit, source at +9V, drain at -18V, gate at 0V, Vgs is about -9V due to resistors. This is the first stage, the 'preamp' for the power MOSFETs, the IRFP240s. When audio input voltage Vi is received, it swings the Vgs on the 9610s up or down by about 0.5 * Vi due to the 10K resistors. The wide open circuit path resistance for each 9610 is about 60-Ohms, meaning with zero audio input, Vgs resting at -9V, the current through each 9610 is about 0.3A/27V. Just looking at the datasheet, at -9Vgs each 9610 is able to flow more than 3A of current. With 0.3A well below the 3A limit imposed by -9Vgs, how is the small gate voltage change from the audio input supposed to change our output?

3. Groups A and B: I can see that there are pairs of IRFP240 power MOSFETs here which are connected by gate to BC-550-C transistors. I assume, first, that these pairs are simply parallel for more power and you could take one out if you wanted. I assume the idea is that both groups of IRFP240s are meant to idle at an intermediate current in keeping with Class-A design, passing directly from the 18V rail to the -18V rail, except when a left-to-right voltage differential in group B forces current to travel through the output load to the other phase-side of the circuit. However I want to make sure I understand this whole interaction. Section A is intended to operate at a constant throughput, and section B is meant to fluctuate based on the input signal from section E. Then the left and right phases of section B symmetrically increase/decrease current to force power through the outputs. Somewhere in all that, the BC550s are there to limit some type of feedback or voltage transient from affecting the gates?

4. Group C: This is simply a parallel resistor group equal to one resistor worth about 0.12-Ohm correct? Is it split up in order to improve power handling/heat dissipation?

Thank you to anyone who sat through this novella of a post, and thanks for any help.
that's actually the board I designed, it's based on the original circuit whose author I forget (besides NP of course).
I still have quite a few of these boards. I have been away from here for almost 12 years.

'Master' Grey Rollins was the 'father" of the Aleph-X design... and
PS: I have moved and now retired am going to revive the build of my Aleph-X... got all the components, hope to find some time to start the build!

Nice to have you back !
mufasa - have a look at the Aleph-X link in my signature. There is a good description of the circuit and some of the primary functionality that was offered by Grey Rollins when this circuit first appeared in this forum.


Oh, wow... great site, Eric! Thanks so much for your help preserving the early history & documentation of this project.

I just poked my nose in at random and see this thread is still quite active. It's very gratifying to see people are still reading about it, and building their own... learning and having fun along the way.

As with many of the other early contributors, life got busy and I haven't been able to participate here much in recent years, so it's wonderful to see folks like you have picked up the torch in our absence and carried on.

Hey Chad - welcome back, it's great to hear from you! The Aleph-x amp doesn't quite have as much activity around it as it is did years ago, but there is still some interest. I think the variety of newer designs have made it easier for new builders to get started. Thanks for all of the help that you provided to me over the years, I am still enjoying my big Aleph-X mono blocks, they still sound great!
mufasa - have a look at the Aleph-X link in my signature. There is a good description of the circuit and some of the primary functionality that was offered by Grey Rollins when this circuit first appeared in this forum.


Eric, that is an insanely awesome write-up. I haven't had a chance to absorb nearly a tenth of it, but just scrolling through it is breathtaking. Also, that's a nice looking Agilent stack you've got there. :D
Thanks, guys! It was quite a bit of work to gather, sift, and sort all of that information. It started off as a Word doc of gathered notes from the enormous build thread while I was waiting to build my amps. Then I figured it would be worth making it available to others as a reference. I don't think I completed my amps until about 7 years after the boards were made available ;-)