2. cables
  3. 1437856439

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
alonski

Showing 6 responses by maril555

maril555
619 posts
 
I've had Signature 2a before, and can tell you with confidence, that the problem you are experiencing, is the EMI induced. And its generated by the power supply. EMI affects SUT in the MC section of the phono stage. If you switch to MM, or any other input, the hum disappears.

The only cure is the physical proximity from the control unit.
Keep it as far away, as the umbilical will allow.
This is "normal" for that design.
maril555
619 posts
 
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
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.
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.
maril555
619 posts
 
Just take the amps the hell out from the rack and pur PS on the lowest shelf.
You have a beautiful system, but I'm sorry to say, but it is a rack update time for you
maril555
619 posts
 
I think he's right, Alon
In the end, rack is an essential part of the system, so it's quality should be commensurate with the quality of your components.
Plus, I would try to avoid placing hot tube amps right under your other components.
They (amps) belong on a separate stands, next to the speakers
More to discover