Dear all, I have a problem with my pro reverb that I can't solve. It's a '73 silverface that I had blackfaced a year ago, it got full service; - New filter and cathode caps - New tubes (tried alot), now V1 pulled, 5751 in V2, NOS mullard 12AX7 in reverb driver, tung sol 12AX7 in reverb recovery and a NOS RFT 12AT7 in the PI. Power tubes are Shuguang 6L6WGS - New power tube sockets - New orange drop coupling caps - New plate resistors - Solid state rectifier (like it more than with the 5U4G rect) - New 1k5 power tube grid resistors and 470ohm screen resistors - Blackface bias circuit - New Jensen neo tornado speakers But since they the day I got the amp there was always a kind of fizz and buzz on top of the notes when the amp is pushed into distortion. I like the overall tone a lot with all the mods, but it is just that fizz that really annoys me. I can hear it too with on the normal ch. It seems that higher bias improves it a bit, but then the idle current is too high. I recently tried to re- route the grid wires of the power tubes because I suspected oscillation but that did not made any improvement. Tomorrow I'll add some pictures of the inside of the amp. Has anyone other ideas?