Hello.
Recently built Chunk. Everything seems to be fine exept two problems.
First is that changing position of Bass and Mid pots doesn't affect on sound at all. I've triple checked wiring. My treb pot is 20k but it works ok. Wired Bass pot shows 50k. Could this be a cause? ???
Second problem is lack of gain. This is my second Chunkchunk build, but first had much more gain. It's aprox 5v on drains.
Lack of gain...I would start there. 5v bias is a bit off spec. but the fets should still run good at that voltage.
I have a CRAZY :o amount of gain with 201's at 4.25v.
Two things I would check.
Apperently...there is a batch of counterfeit j201's out there that are waaay off spec. Swap them out with a known good set if you can (found a thread just this weekend on the diy forum about this).
Also check that the pots are actually working ok. I had bought some cheap ones off the bay that did not react well when I got them a bit too hot with the iron. ;). I had a muff I was working on for two weeks that came down to-two faulty pot's.
Honestly sounds like a missed value or a cold joint to me.