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Old 28th October 2013, 09:13 PM   #1
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Default Aleph H Schematic - Revealed at Last

Many ... many ... many moons ago, I adapted the Nelson Pass` Aleph circuit topology to build a nifty, but ridiculously overbuild headphone amplifier that I named the Aleph H. I thought it was pretty cool, and circumstances came about that presented the opportunity to have my DIY project reviewed by Srajan Ebaen of 6Moons. Turns out Srajan liked it too and gave it a very positive review.

Somehow, I just never got around to publishing the schematic here for others to use. Periodically through the years I have had pokes from diyAudio members who have read the review and want to build my version, given its reviewed and 6Moons approved status. I have always shared with those that asked, but stupidly never taken the extra few moments to post it here.

That laziness ends here!

I have finally attached the schematic for the ciruit I built.

A couple of important notes:

1) The component numbers in my schematic DO NOT MATCH with the component numbers for the Aleph-Mini group buy boards. Be careful to ensure the right components end up in the right circuit locations.

2) All resistors are 0.25W rated except for the ones labelled in my schematic as R22, R23, R29 and R35, which are 3W rated.

Please forgive my excessive tardiness, and hopefully those who buikld this circuit will enjoy it as much as I do.
Attached Images
File Type: gif Aleph H Schematic.GIF (31.6 KB, 1913 views)
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Old 28th October 2013, 09:31 PM   #2
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Did you ever try JFETs for Q1 and Q2? Got any distortion numbers or graphs?
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Old 28th October 2013, 10:54 PM   #3
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If you search for thread by jwb with headphone in the thread title you can find a variant with JFET inputs. I was trying to keep more in line with Nelson's original designs, and also was avoiding using "unobtainium" parts. That being said, now that the LSJ74's are for sale here I am certainly tempted.

Unfortunately I don't have much in the way of measurement equipment, so no distortion graphs or numbers.
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Old 29th October 2013, 12:06 AM   #4
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I remember that article ; so , for our amusement , here it is :

6moons audio reviews: Reality Check with Terry Aben

howeer , I was always puzzled - why you didn't change name of the article to , say , Mini H Aleph with Maxi Screw

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Old 29th October 2013, 12:11 AM   #5
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another question - in article , amp was rated as unity gain ;

so , please , clarify - what's more preferred by you - unity gain , or 10V/V , as in sch enclosed in your opening post ?
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Old 29th October 2013, 01:33 AM   #6
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Very cool! Thanks a bazillion for posting it!!
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Old 29th October 2013, 02:04 AM   #7
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All Hail Metalman!

(I've said it before...)

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Old 29th October 2013, 07:37 AM   #8
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Thanks metalman
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Old 1st November 2013, 01:25 AM   #9
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Metalman, great work!

It seems that you run the Aleph H at a "high" (subjectively) biased current.
Have you experimented with other biased current values?
Why do you choose the present value?
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Old 13th November 2013, 06:43 PM   #10
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Is there a reason why R4,R5 have such low values? Other mini-Aleph circuits show these as 100k or 221k.

Last edited by needtubes; 13th November 2013 at 06:46 PM.
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