Aleph 2 questions

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ive been wanting to make a Aleph 2 since some times now, now that i found the free time to do it, before i start i got some inquiries

first of all, how does the Aleph 2 sound? ive never heard any of the pass labs series.

then, about the irf244, the only available replacement ive found is the NTE 2921,
and this for the IRF9610

you guys think they would work whitout altering the sound too much?

and what about matching em? how do i proceed in doing that?
Peter Daniel said:
Why are you looking for replacements if you can get original parts next day from ? Or better yet, contact Dale and get everything matched from him. You can even get the boards. As to the sound, you don't have to look any further.;)

hum, well how important is it to match em?
yhea, i just checked off digikey, and its 5$ each, id need 13, hum, i know its not alot for a good amp, but i can get NTE parts cheaper cuz of the suppliers in here.. what do u think of those replacements?
They have to share the same work load, that's why we match them. You could probably not do it and the amp would work, but who knows how good?;)

Here's my quote from another thread regarding the sound:

" from Stereophile's Muse Kastanovich comparing Aleph3 and ML 333:

Levison imparted a slight but persistent quality to everything played through it. It was a little metallic, changing instruments timbres and hardening the texture of the whole ensemble. The woodwinds sounded less woody and the solo violins sounded too wispy. In adition to that, the Levinson soundstage was not as large, and the hall reverberation was less audible. Nor was its microdynamics as fast or as natural.
If the No.333 had to be characterized with one phrase, it would be synthesizerlike. It gave a somewhat Technicolor presentation of music, superficially dramatic but missing some of the juicy harmonic body that can be enjoyed from the recording. This is of course, in comparison to the sound of Aleph3. In comparison to other amplifiers, the Levinson may very well sound natural and open; but after becoming accustomed to what the Pass amp could do, I just didn't want to keep listening to the Levinson for very long.
Perhaps the most telling indicator of good overall sound for an experienced listener is their whole emotional response to a familiar recording. Though music was very enjoyable through both the Mark Levinson No.333 and the Quicksilver M-135s, it did not create quite the excitement and happiness that it did when played through the Pass Aleph3. The Aleph3 is juuuuuuuuuuust right!"
The Pass Labs Aleph3 is, by a good margin, the finest power amplifier I have ever had in my system."

If you need more info, try the search engine. You can practically find the answer for any imaginable question.;)
As Mr. Pass said in an A75 article:

"Other devices will also work well, as long they have similar characteristics. You should not be afraid to use them. Because of the audio circuit simplicity, it's design is very forgiving to substitutions. The primary criteria are adequate voltage, current, and dissipation ratings".

And also consider input capacitance.;)
I've had pretty good luck with NTE semiconductors in general service work but have never used them for the purpose of building an amplifier like the Aleph 2. The output devices MUST be matched to at least .1 volt, preferably tighter. You'd still have to buy a bunch of those NTE's(probably 50 or more) to be able to properly match them. I used IRFP240's for my Aleph 2's and bought 100 of them from Digi-Key at a reduced price cause of the quaitity. In addition they also were very kind and supplied me with the same date code, or batch number(what ever they go by) on these semi's. On the 9610's its imperative to match them to .01 volts. If you can't, be prepared to balance things by adding, or changing resistors in that circuit. Both 9610's MUST share the current equally. I had no problem matching my 9610's from a batch of 25 transistors, and the 240's from a batch of 50. That leaves me a batch of 50 IRFP240's, and 19 IRFP9610's for building another Pass project! Yee-Ha! (Yes, I live in the wild west!)
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