Schade Common Gate (SCG) Preamp

Thanks for all the feedback! Yeah, a small heatsink could be used. I am currently using this one on the test bench:
1662127802256.png
 
Yup, sorry about that.

Use this sheet to enter your handle and # of boards. One board makes two channels.

Will leave that open for two weeks at least. And I'll contact everyone who reached out over PM over the next week or so.

I got five boards for about $65 from JLPCB. 2 oz. boards. So, more boards will likely come in under that and I would add shipping and Paypal to the board cost. I would estimate about $20 per board shipped to your door (USA). As I've said before, I don't want to turn this into a money-making exercise. So, I'm just looking to recoup my costs. What would make happy is to see this design get built and DIYers enjoying the sound!
 
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Hi there,
I just read the whole thread, and I think I have most of the parts (with some differences) to build this preamp. The reason: I use two Mofo monoblocks, and I realized that I need a good preamp. Plenty of options, but this one got my attention.
Last week I got a broken amp, so I figured out that I can use a transformer, though the secondary voltage will be somewhat lower (2x27V ac), do 54V AC. Mosfets:
Irf 9620, Irf620. The CSS will be made with a small bjt one as well (something like in original Pass Zen amp). Current, around 30-40 mA.
Maybe I should leave the lower P mosfet like in the original schematic (post nr. 1), to leave more headroom for the upper mosfet (due to a lower power supply voltage)...
Later, if I am happy, I can upgrade with other mosfets, higher ps voltage...
 
Hi there,
I just read the whole thread, and I think I have most of the parts (with some differences) to build this preamp. The reason: I use two Mofo monoblocks, and I realized that I need a good preamp. Plenty of options, but this one got my attention.
Last week I got a broken amp, so I figured out that I can use a transformer, though the secondary voltage will be somewhat lower (2x27V ac), do 54V AC. Mosfets:
Irf 9620, Irf620. The CSS will be made with a small bjt one as well (something like in original Pass Zen amp). Current, around 30-40 mA.
Maybe I should leave the lower P mosfet like in the original schematic (post nr. 1), to leave more headroom for the upper mosfet (due to a lower power supply voltage)...
Later, if I am happy, I can upgrade with other mosfets, higher ps voltage...

I would first build the preamp with the parts Ra7 has designed for it. Order up what is needed, nothing is expensive here.

Get that up and running (and debugged) first. Then use that as a baseline for any mods/operating points/part changes proposed.

That’s what I would do, to not eat up Ra7s time chasing ghosts instead of progressing on PCBs.
 
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