VAC Signature 2a Preamp Question


Before you say, "Dude, there's already a thread posted about this question!" Well, forgive me, I could not find it. This is an inquiry for Signature 2a owners who have the built-in MC/MM phono stage: When the selector is on #6, which is the turntable, I get a background hum and some of what is probably tube rush, and it's especially audible with no music playing with the volume up. When I switch to the DAC setting, with the same volume setting, everything is dead quiet. Do I have a problem or is this normal?

Your feedback is welcome and appreciated,
Alón
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Showing 4 responses by alonski

Thanks for responding. Yes, it's grounded and I checked the connection. It's good.

Any other potential culprits you can think of?
Thanks everyone, your advice is appreciated. I would normally call Kevin or Brent, but it seems like in my audiophile life, the hum-chasing episodes only happen on the Weekends.

I know you're right, Maril555. With my components in a rack, it's difficult to find much physical separation of the Sig2a from its own power supply, which is one shelf below.

Today, in addition to the hum, I heard crackle and pops, so I went all Sherlock Holmes on my amps and found the bad tube in the right channel mono block that wouldn't take a bias adjustment. Replaced it, rebiased all the tubes, and now the pop and crackle is gone, but the hum is still there, so it's not the Phi 200 mono blocks. Everything is grounded well. It could be tube rush from the phono section tubes (the line stage is quiet). I'll probably call Brent for some advice and buy some really quiet tubes from VAC if necessary.

Almarg, I've been wanting to try shorting caps, so your advice seems well-timed to help find the source of the problem. I'll report back if I encounter some big audio life lesson that I can share!

Thanks again,
Alón
Gentlemen,
Two issues with moving the power supply out of the rack: first, it looks so darn cool to have all four VAC logos lit up at night while tubes are glowing... (See rack photo on my system page). So, now that I've outed myself as one who cares about the esthetics of my system, not just the sound... Here's the real issue: I have nowhere to hide the PS, unless I stand it on its side between the rack and the couch, something I don't want to do to this beautiful component. No other place is available, and the amps are too heavy to go to higher shelves, so I think for now, if it's indeed a proximity issue, I'll just have hum along with the hum... Thanks everyone for trying to help!

Alón
Hey All – your suggestions are good and appreciated. I agree with the ideas and warnings about where things "should" go... I've been looking at this set-up for a long time trying to find a way to give my gear more breathing room... but it's not realistic in my living room. A new (wider) rack won't fit unless I sell the armoire, which would not earn me any WAF points. And putting the amps near the speakers, which I would love to do, would require spending about a thousand bucks on my electrician, buying two amp stands, buying a third AC Power Regenerator and acquiring two reference quality interconnects of 32ft in length!
That original hum in question is sounding like a very minor issue about now. Maybe one day I'll build a dedicated listening room with lots of room to play with and no WAF considerations. If you all have your own space, I'm envious.