Aleph J-X Amp Project

Just out of curiousity, since this seems to be a popular project: Did anyone plan to build a proto? The X'ed homebrew amps are notoriously tweakers amps, so the newb to intermed DIY'er will have their hands full with something like this😉 Especially when adding more output-devices!
If a hundred boards are being shipped, its just as well to ensure that implementation is pretty easy. Never saw that yet with an x'ed homebrew, though. J-fet input is even more trouble. It can be done, but its not a beginners job to make the amp balance out to zero DC's at the output.
The exception is CheffDeGaars UGS amps. They just work!

🙂
 
Peter,
Aside from having fewer output devices what other major differences will there be between the XJ and the AlephX besides the jfet frontend.
If my memory serves me correctly the J is a hot running little amp.

The shipping charges overseas for a priority package approach 10.00 U.S. The domestic U.S price is 4.50 approx. I would be willing to distribute here if you would like to keep prices down.

Tad
 
Do not see Nelson using 2 or 3 2SJ109's in Aleph J ?

IMHO it is not necessarily. Especially if you are only using 4 output devices per channel for AJX. In that case you do want a high-ish resistor at the diff pair drain. And 1k is just fine.

If you do want higher open-loop bandwidth at the 2nd stage, you can use low-C MOSFETs like Toshiba's or Fairchild's (as in F5).

Just my 2 cents.


Patrick
 
parallel input fets

Hi,

Since i'd want these boards for the AJ alone and no X, i'd rather not have parallel input fet's. However, maybe that is also something one could transfer to the daughter board so one can still have it both ways.

Just a quick line of thought and reaction.

regards,
Joris
 
Peter Daniel said:
Any comments on previous suggestion of using 2 or 3 pairs of parallel input jfets?


EUVL said:
Do not see Nelson using 2 or 3 2SJ109's in Aleph J ?

Patrick

Nope, and excactly right! For a stock Aleph J, thats just fine. 20 watt's or something.....PPL here are getting the impression that this amp is easily scalable, which it is not, by any standard. One pair of the treasured dual fets are ok, as long as the CCS's are calculated accordingly to the current/voltage demands!!. Again, check out LeCheff's masterpiece! You need a real UGS with a TO220 in each corner:smash:

🙂
 
All i can say with my inexperienced hat on is please keep all circuit requirements close as possible to nelsons original design. Tonight i have just completed within 2 hours the B1 buffer preamp. Another masterpiece. It is clear to me tonight, in my short adventure with his diy projects, he is not just another engineer. He obviously understands the components of the harmonic structures involved in mimicking real sound so he must have a really well trained audiophile ear. In his typical style of just using a few choice sentences to describe his babies on PASSDIY, the sound i hear from the B1 is precisely as he describes it in his overview but oh so much much more.

apologies to those of you who already appreciated this.
 
steenoe said:





Nope, and excactly right! For a stock Aleph J, thats just fine. 20 watt's or something.....PPL here are getting the impression that this amp is easily scalable, which it is not, by any standard. One pair of the treasured dual fets are ok, as long as the CCS's are calculated accordingly to the current/voltage demands!!. Again, check out LeCheff's masterpiece! You need a real UGS with a TO220 in each corner:smash:

🙂

There's also the issue I've read about regarding driving the Aleph-X single-ended......and the DC offset going a bit nutty. I would assume the same applies with AJX.(?)