VAC Signature 2a Preamp Question

Adding to Dweller's comment, is the control section of the preamp sitting on top of or close to the power supply?

The phono stage uses additional tubes plus the line stage tubes. So you could have more tube noise. That said, did you buy new, or a used unit? How many hours on the 6 12AX7 phono tubes?

I would contact VAC, Kevin and Brent have always been very helpful and responsive to my queries.

Alón, a couple of experiments that may shed some light on what is causing the issue:

1)Disconnect the turntable from the preamp and insert shorting plugs into the preamp's phono inputs, and assess the hum and noise levels under that condition. (Have everything turned off, of course, while you make the change). Googling "RCA shorting plug" should turn up a number of such plugs you can buy, or else you could simply buy a couple of RCA plugs at Radio Shack or wherever and solder a wire between the center pin connection point and the ground sleeve connection point.

2)Temporarily, as an experiment, put a cheater plug (a 3-prong to 2-prong adapter) on the preamp's AC power plug, without connecting its safety ground (what would normally be connected to the wall plate screw) to anything. That will break any ground loops between the preamp and the other components it is connected to. Ground loops, of course, can sometimes contribute to hum and noise.

Those two experiments should help to determine if the problem is due to something internal to the preamp, or to some external influence.

Also, as I recall you purchased the Signature 2a a couple of years ago. Has this issue been present all along, or did it just arise recently?

Best regards,
-- Al

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.

I think you have told us. I hear what I think is tube rush! There may be a bad tube in the phono circuit, which BTW can also make humming or other baseline noise. Check your tone arm wires and check the tubes. You can get very quiet tubes from Jim McShane at his website McShane Design over at audio asylum. I have no connection to him other than being a customer.