humming issue, and grounding schemes...help..

[swt]

Hi!!. I've been wondering if someone could help me with this issue.
I have a dumble hybrid style amp clone. It works and sound good to my tastes. but i have a noise issue that's killing me. Here's the detail story...
If i ground input of power amp (driver) the amp's dead quiet, so no problem here. If i turn down drive pot, it's also quiet. The problem lies at output of stage 2. if i ground that, it's quiet. So i have isolated the problem to stages 1 and 2. If i turn down the gain, the HISS goes down, but still have some bad humming. The ground is a bus, it goes: ot, first filter, bias, and screens filter, to same point, then the string is wired as tut books, with distributed capacitance, so it's driver filter and 390 res, od filter to od's cathodes, and clean stages to last filter. At first i had the input jack isolated from ground, and everything connected to the same filter point, cathodes, stack, pot, etc. It didn't work. Now i have tried grounding jack through chassis, and cutting the bus from the chain, so only first filter and clean stages hung from that point at input jack...it's not working also.
Don't know what else to try...and the amp simply smokes...so i need to solve this. Any ideas??. Thanks a lot for your help or advice.

[swt]

wow...anyone?.

[mlp-mx6]

You've swapped known good tubes?

[Dai H.]

there is a thread in the trainwreck section where I translated an article on tube amp grounding, plus put in a bunch of links dealing with the subject if you'd like to do some reading