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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
Ag insider logo xs@2xalonski
maril555
619 posts
 
Zd542
You are right saying, that switching to MM will likely alleviate the hum. But for a different reason.
It has to do with the SUT in the MC section picking up EMI from the PS, and not with the higher gain of the MC input.
zd542
5,339 posts
 
"Zd542
You are right saying, that switching to MM will likely alleviate the hum. But for a different reason.
It has to do with the SUT in the MC section picking up EMI from the PS, and not with the higher gain of the MC input."

I agree. But its just too simple not to try. Also, it can't be ruled out either because we don't know what the OP has, or how its set up. You're probably right, though, given this is a common problem with this model preamp.
knghifi
1,668 posts
 
07-27-15: Maril555
Alonski,
I can save your time and effort- I've had that EXACT same problem, called Kevin, and that's what he advised me to do- move PS away from the control unit. By doing so, you will get rid of 90% of the hum. And that is THE ONLY solution. I even played with some additional shielding with m- metal, no difference.
Maril555, Just curious did you try covering all unused input and output connectors with Cardas or AQ caps?
maril555
619 posts
 
Knghifi,
No, I didn't, but I used shorting plugs, that I feel is a more effective options, than Cardas- made no difference anyhow.
I tried mu-metal sheets to shield PS and control unit- no difference.
Actually, the advice of moving PS and control units farther apart comes from Kevin Hayes himself.
I'm pretty sure he knows what he's talking about giving that advice.
wrm57
1,045 posts
 
I had this problem with my Phi Beta preamp, which is much like the 2a Sig. As others have said, you simply have to move the power supply as far away as possible, at least 3 feet.
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