Aleph J for Universal Mounting Spec

Official Court Jester
Joined 2003
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Taking it further would mean matching for Yfs, Ciss, and leakage. He was simply trying to reiterate the practical use of pot at R7.

we were talking strictly about DC condition ........where only leakage maybeeee can take some influence

anything else is story for Back to the Future part II , III and IV - armed with AP or any surrogate
Buzzford and Zen Mod,

Thank you for your feedback. As I mentioned in a previous post, since I still have to test the second board, I'll add the R7 cermet before mounting it to the heat sink. This way I can make the adjustments to see how low I can get the DC offset and also determine if anything else is needed. I am not disputing any of the advice given.
I have added C7. Since it is a standard bypass capacitor I assume that it is the same as C6. Please correct me if I am wrong. I might have to give an exact value for each here for those with not much experience. Suggestions for the values of C6 and C7 please.

Please verify the values of the pots that I suggested, especially R27 and the resistors around it.

BOM now at revision C already due to late changes/updates.


  • BOM-Aleph-J-UMS.pdf
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Joined 2010
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JFETs are graded by IDSS and grouped in 3 ranges identified as Green, Blue and Violet.

So that's what G, BL and V mean! It always seemed arbitrary, and I never thought it was a color code!!! :cool:

In the channel on the photo the JFETs have IDSS 9.31mV and 9.36mV. In my view, "tightly" matched.

That is more than good enough.

I made a commitment to build the boards quickly and had the parts in hand for a "standard" build, as the boards I intended to use do not have room for trimpots. I made good on my commitment to 6L6. Now, with the help of Mighty ZM and other members, I'll try to make the amplifier as close to "perfect" as possible. :)

Your (very) fast construction and testing is greatly appreciated. The PCB dimension issues and pad sizing is exactly what needed to be found by this process. Thanks!

Your photos look great, BTW. :)

I never meant for the 'standard' build to be without the pot on R7... That one seems to be necessary, while the rest of the pots are there to adjust it to the last degree of perfection or just to play around.

Please do whatever adjustments you wish to get the amp all tuned up and measuring the way you expect -- I am quite eager to see what it takes to get it perfect.

I see Mouser currently has no stock of that capacitor, and are only getting stock in during April. I have updated my BOM to use your version as I made a mistake in the one I listed. I see that the one I listed has a lead spacing of 10mm and not 5mm.


These will all fit and are currently in stock. Their values range between 100nF and 150nF, and they differ mostly in voltage and tolerance. Any of these can be used in C6 and C7 positions.

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Please do whatever adjustments you wish to get the amp all tuned up and measuring the way you expect -- I am quite eager to see what it takes to get it perfect.

I am planning to continue working on it this coming weekend. I only have 20K and 100K trimmers on hand, the 2K ones are on their way.

One more issue about the board, and this one is purely cosmetic, the designators for R7 and R8 are superimposed by their respective alternates R7' and R8'. That results in a blurry print on the PCB. Didiet can easily correct that on the silk screen layer.


Joined 2010
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I haven't gotten to the AJ yet, the F4 guide is 90% done (and posted) and the F5T is about 60%.

buzzforb is currently very busy with group buys.

Once those are complete, then I will focus the attentions to the AJ. I have the parts, it should go together very easily.

I don't know if Grimberg has completed his stereo amplifier, perhaps he can comment?