Star Ground, preamp / tremelo confusion

[ampcamp]

This is my fourth amp build, and my first class AB. Schematic from a Fender aa964 (princeton). No bias pot. Went through Paul Ruby's startup , checked voltages (a little low all around - all polarity correct) . Powered up, it works -even the tremelo. The bass and treble pots seem to do the same thing, with the action of the bass perceptively backward. HUM. More than I can live with. The tremelo is as smooth and airy as I've ever heard. Installed artificial CT with a pair of 100 ohm resistors near the PT. Ran all the grounds to local nodes, and then to a central (star) ground. At first power up , the amp was clean and quiet,slightly reduced output. The tremelo worked, but at the peak of each oscillation cycle would distort. Now the volume will not turn all the way down, and the tone controls are quacky - vox twin t oscillator phase cancellation sort of thing. I can do the intro to voodoo chile with the bass control. Now the tremelo has gone away and the gain has dropped to a mere plink. Obviously a miswire. Considering starting over from the power section back - or forward depending on how you read it. I am posting this just in case someone has done the same thing and knows where to find it. I've checked values - and yellow lined it-twice.

[tubeswell]

Re: the tone stack, you probably have the bass pot wire jumpered on the wrong side - it needs to be jumpered to the pot's 'input' lug. If its jumpered to the 'ground' lug, then the bass cap and the mid cap will be in parallel with the bass pot at maximum c/w rotation (not giving the effect of increased bass, but the 'opposite').

Re: the grounding hum - you'll just have to work at it.

[ampcamp]

It had not occurred to me that the 250k pot might be internally grounded. Didn't show up all the way until I attached the star ground. I'll bet you're right. THANK YOU!