convert aleph 2 to aleph j

[slr 5000]

hi guys
can i convert my aleph 2 into an aleph j if i change the traffos to 2x 18v
and modify the front end for jfet input without changing anything else ?

this means i will have an aleph j but it will use 12x irfp240 per channel

will it work or will the jfets not be able to handle the bias current to run the 12 output devices per mono block

cheers

[juma]

Originally Posted by classafanatic

...can i convert my aleph 2 into an aleph j if i change the traffos to 2x 18v...

Yes

Originally Posted by classafanatic

...without changing anything else?

No

[Nelson Pass]

The Aleph 2 has rails which are too high for many Jfets that
you might put in the input stage, such as the 2SK74 types.
You would need to consider other parts or cascoding of the
input differential pair.

[slr 5000]

hi
so if i lower the rails buy using a 18/18v traffo will all be ok ?

will a aleph j work well with 12 output devices per mono block or should i convert the a2 mono blocks to alj stereo amps in which case each aleph j would have 12 output devices per stereo amp

i hope this is not too confusing

[Nelson Pass]

The word should probably doesn't apply. What do you
want to do?

[slr 5000]

hi nelson

ok my passion is for esl speakers so id like to be able to drive them.
at the moment i am using aleph 2 diy mono blocks , idealy id like to convert each of the mono blocks to a aleph j stereo amp and still use the output boards from the a2 and just modify the driver boards to aleph j

i would of course use 18v/18v toroids instead of the 40v/40v in use at the moment which takes care of the rail voltage but not the amount of output devices so my question is i suppose can a aleph j be run with 12 irfp240 per stereo amp using the 18v/18v toroids and single 2sj109 per amp

cheers and thanks for any help you can give

oh also if it helps i have 4x2sj109 for this project so i could parralel 2 per stereo amp if this hlps with the extra power required to drive the 12 output devices per stereo amp (if they can be paralleled) oops another edit my aim from this is to have an aleph j that will double its power in to 4 ohms

[Nelson Pass]

What are you esl's like? If they are like most (Sound Labs,
Martin Logan) then I think you need a different design. If
they are like Quads, then there are some possibilities.

[slr 5000]

hi nelson
they are ml quest z but i will be changeing to some er audio acorns in the near future which are a much easy,er load for the amp and would be similar to the quads

i would like to change the current mono blocks to stereo amps so the speakers will be biamped as well which will help in driving the esl

i have plenty of 2sj109 to so i could maybe parralell 2 per amp if this would help to drive the extra output devices (wishfull thinking on my behalf that it would be that easy )

so what i am proposing would be the same as your production aleph j but with 12 irfp240 per stereo amp instead of 8 and whatever mods i need to do to acomplish this , i have already ordered 2x 1kva 18v/18v toroids for the power suplies and i have 8 2sj109 sitting there doing nothing

i hope the above is achievable ,alternatively i have a stereo set of pd ajx boards that i could use

cheers