Preamp suggestion for Quicksilver M120 amps

agranttz,
Update: today I swapped back and forth between my very best vintage 1960s Mullard 12AU7s and latest version PSVANE MKIIs in the QS Mono 120s. My buddy did the same in his Linestage last week, replaced the stock low grade JJs you have now. They do sound lean in our rigs too. Both of us gave the lower version JJs away. There are much better JJs up the line into the high $ Black Sable JJ versions but those are more costly than several vintage and 40% more cost than the new MKII PSVANEs which are decent for the $ if you don’t wanna mess with vintage.

Personally, I’ve tried the best from vintage 1960s Mullard, Tungsram, RCA, Sylvania, CIFT, Brimar, Amperex and more in my QS amps. Tried 17 different vintage pairs (some on loan) and 3 different new-reissues pairs in total. Same with my friend with the QS Linestage and QS Mid Monos. Both of us agreed, all so much better than the new low version JJs that came with your QS Linestage new-stock from Quicksilver. And, gotta say the new PSVANE MKII 12A?7 tubes are pretty nice too. Maybe a little fuller upper and lower midrange, maybe a tad more forward than my best Mullard "Blackburn" small signal tubes, but not bad ad all. With more burn-in they are settling back a tad more now. I like both, a lot. The Mullard vintage and the newer PSVANE are my #1a and #1b for different reasons. Have some of the latest "12AT7" PSVANE MKIIs coming this week to re-test those again too.

The QS Linestage and Mono amps are VERY responsive to replacement of quality small signal/driver tube changes, fwiw. And, with really great interconnects we noticed an even bigger difference with changes in the small signal and driver tubes. Hope this helps.

The pre responded to tube rolling, I like how it sounds. Still a question if it's better than Simaudio.

Need to address an issue with the power amps. Both produce a vary audible hum (big trannie on the left), can hear 60Hz from the speakers.

How do I clean up AC power? Balanced transformers? Isolated?

Thanks.  

1 Did you invert polarity?2 Did you try lifting the AC cord grounds FYI its the round ones with cheaters on the amps?

The amps hum with the rest of the gear off.
I did try lifting the ground with no success.

@argranttz

1) Are your preamplifier and amplifier plugged into the same plug/circuit? If not, try plugging both into the same circuit too.

2) Does it change removing and replacing all small tubes back to originals?

3) Disconnect the RCA cables between amp/preamp and see if it still occurs. A buddy had same issues with a different pair of amps. His new/vintage replacement tubes were bad, but not the entire issue. Turned out to be his preamp causing the hum, had to send it back. He confirmed this trying different preamps

4) Can you plug the amp(s) into a completely different location somewhere else (away from your neighborhood) to isolate if it’s some kind of local electrical induction from power lines that are too close to audio lines. Often referred to as “60-cycle hum.”