There are diyAudio members who report that their M2x "Ishikawa" input stage (using obsolete Toshiba JFETs) is outperformed sonically by one or more of the other daughter boards. Listeners report that the various boards sound different from one another, and the number one ranked + favorite board is not always Ishikawa.
I know that 6L6 loves his Tucson_604 M2x boards, but he'll be the first to admit, he hasn't yet done any long term serious listening with his Norwood boards. No final conclusion from him, yet.
I know that 6L6 loves his Tucson_604 M2x boards, but he'll be the first to admit, he hasn't yet done any long term serious listening with his Norwood boards. No final conclusion from him, yet.
The Aleph Jango never got built, I was having a heck of a time getting PCB that would work, and then I was going to make a Jfet F6, but that project stalled, and basically I just listen to the my M2x all the time now anyway... 🙂
I use the chassis from store with the UMS spacing, and Fastons for electrical connections...that makes it fast and easy to just swap boards to try different circuits. I do replace keratherm isolators though, I just don’t trust reusing them
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I suppose I already have an ACS in my F3, and I don't have anything with those funky opto-couplers, so that would argue for building the J2. 😉
If it's optocouplers you want, build a Whammy headphone amp. It has the distinction of being the only Pass DIY amp project designed to use optocoupler bias and bipolar output transistors in the same amplifier. M2 and many others use optocoupler and MOSFETs.
As far as bias stability goes I find the Aleph J to be rock steady in terms of bias and offset. I don’t see the need to use more exotic options for bias in any given circuit if the conventional approach works so well.
I have built a number of Aleph J channels....using the latest diyaudio store boards...
Of the last pair that I built...one channel runs real hot and measuring the voltage across the gate stoppers of q5 q6 q7 and q8 I get .77 volts...
Every other channel I have built, the meaurement is around .55s volts, which is the correct voltage.
Everything else about this hot channel seems ok...
Any Thoughts anyone on where to look???
Of the last pair that I built...one channel runs real hot and measuring the voltage across the gate stoppers of q5 q6 q7 and q8 I get .77 volts...
Every other channel I have built, the meaurement is around .55s volts, which is the correct voltage.
Everything else about this hot channel seems ok...
Any Thoughts anyone on where to look???
Thanks...
I meant the Source Resistors...good channels measure around .55v and the hot channel measures .77v or so...
Thanks for responding...
I meant the Source Resistors...good channels measure around .55v and the hot channel measures .77v or so...
Thanks for responding...
That's 40% more current with the hot channel.
Referring to post #3 on the first page
https://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide.html#post3615479
have you tried very gradually adjusting R27 while monitoring the
voltage across the source resistors to see if you can lower it? You'll
want to make very small changes and wait a bit after each change
for the bias to settle down.
You'll probably need to readjust R8 to null the DC offset.
Cheers,
Dennis
Referring to post #3 on the first page
https://www.diyaudio.com/forums/pass-labs/241729-aleph-illustrated-build-guide.html#post3615479
have you tried very gradually adjusting R27 while monitoring the
voltage across the source resistors to see if you can lower it? You'll
want to make very small changes and wait a bit after each change
for the bias to settle down.
You'll probably need to readjust R8 to null the DC offset.
Cheers,
Dennis
Got the Aleph J bug.
Of course, the hitch is sourcing the Grade B LSJ74's.
Only ones I can find are in the diyaudio store matched LSJ74/LSK170 pairs.
Could the LSJ74's out of two matched pairs be used in the Aleph J boards without further matching or other ado?
Expensive, and wasteful of the 170's (so far as I know) obviously, but this is the only option I see available to me, other than giving up on the AJ.
Of course, the hitch is sourcing the Grade B LSJ74's.
Only ones I can find are in the diyaudio store matched LSJ74/LSK170 pairs.
Could the LSJ74's out of two matched pairs be used in the Aleph J boards without further matching or other ado?
Expensive, and wasteful of the 170's (so far as I know) obviously, but this is the only option I see available to me, other than giving up on the AJ.
Missed the edit cutoff by a minute.
Please disregard LSJ74's question in previous post.
Just doesn't seem right to try and use up the diyaudiostore JFETS that way.
Please disregard LSJ74's question in previous post.
Just doesn't seem right to try and use up the diyaudiostore JFETS that way.
My searches were fruitless, thank you for the lead.
Mouser Toshiba 2SJ74 data sheet shows BL suffix Idss of -6.0 to -12mA, so that makes the bdent Toshiba 2SJ74BL a grade B part, right?
Now on to educate myself as to how to determine what it takes ensure usability in the Aleph J circuit, matching requirements and how to accomplish them, etc, etc.
Thanks again for the tip, my Aleph J hopes are revived.
BTW: My amp building resume consists of being an electrician that can solder with two ACA's completed.
Interesting...They're selling 2sj74/2sk170 pairs also, but it doesn't say anything about being matched.
are 26.5v rails allright
Just finished two channels of Aleph J...Basically, have been replacing old Aleph 30 channels
On this Aleph J amp, rails are 26.5v. The circuits are correct, power supply is a little too high voltage.
Can I run the Aleph J at 26.5v rails, or should I work on the power supply to reduce voltage a bit...
Thanks
Just finished two channels of Aleph J...Basically, have been replacing old Aleph 30 channels
On this Aleph J amp, rails are 26.5v. The circuits are correct, power supply is a little too high voltage.
Can I run the Aleph J at 26.5v rails, or should I work on the power supply to reduce voltage a bit...
Thanks