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So when I fired her up last night she was dead silent and I was sooo happy. But then I realized I had all the knobs turned down When I turned up either volume and/or the gain it hums really bad and gets louder with the increase in volume/gain. Seems like a grounding issue because when I touch the chassis or the knob stems (didn't install the knobs yet) it decreases slightly. It's a low 60 cycle hum like my Strat sometimes. I didn't get to investigate it though because my daughter called about that time and it was too late afterwards. I will probably get back to it Sunday because I have a gig tomorrow night and we have to get set up tonight and go through sound checks, etc tomorrow.

If you note which control does or does not reduce the hum, it helps pinpoint which section of the circuit is causing the hum.
Stew

Also, pull out V1 see if hum is there, then v2 etc until hum goes away. Problem is probaly afterthat tube somewhere.

Check all your grounds and input jack grounding.

_________________
Stephen
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In both the 18-watts I've built I had hum issues with V2. It was actually tube related, not the build itself. Swapped another tube into V2 and it was fine. Might just have been fluke that it happened to V2 in both amps, but you never know.

Thanks for the tips! I will swap the tubes first to see what happens. I am using old vintage tubes in all sockets. RCA in V1 and old stock Tung Sols in V2 and V3, Sylvania blackplates in V4 and V5 and an RCA EZ81 . I have some newer 12ax7 Groove Tubes laying around that I will try when I get home in a couple of hours but I probably won't have time to really dig into it

Swapped tubes around and it did help but only a little. I gave a quick once over as I didn't have much time and nothing really stood out until I looked down at the floor to think. The table I was using to build this on was too far away from the wall to plug it directly into the wall outlet and I had it plugged into a multi-plug extension that had a couple of lights plugged into it as well. I unplugged the amp and relocated it to another wall outlet and presto, the hum dropped off about 80 to 90%. Now it was very usable but still not perfect. I will need to track that down.

I blew my back out on the 25th so I hadn't been able to work on the amp until today for a little while so I have an update on the humming issue. I re-soldered the mains ground wire and touched up the input connections. Now the TMB inputs are very quiet and the chassis isn't affected when I touch it. However the other inputs (both high and low) are still pretty noisy. I will probably totally remove the connections from those two inputs and re-install when I feel a little better.