Bah Hum Bug


I am having an issue with hum.Hum is only apparent in very quiet passages while listening to lps or when unit is in idle mode.Unit is Dead quiet..no hum in cd mode of operation.

I am running a Fosgate Signature Phono amp,Thorens Td124 with Ortofon Silver Meister Cart,Wright AU-1000 linestage, 2A3 SET power amp into Klipsch Heresy speakers.

When ground is is attached from TT to Phono amp the hum is intolerable so I run the TT with no ground to Phono amp.

I have tried cheater plugs and that has made no difference.

When volume is turned up say past 1 oclock in either the Wright or the power amp the hum is very noticable. Is this indicative of the high efficiency of the Heresys and 2A3 tubes? or is there some other thing going on here?

Please help.Thanks.
fromunda
Yes you know the sound does change when I move the phono cables. These are brand new Shielded Tributaries A6's. The hum would change upon moving them around with the old cables as well so I replaced them thinking that was the culprit.
02-26-13: Fromunda
Fosgate sig was the last addition. But I believe the hum was there before as well.

Was your previous phono preamp a tube unit too? Hum is not uncommon using tubes in high efficiency systems. Try a SS phono stage and see if the hum goes away. It doesn't have to be an expensive one, you can find a SS phono preamp for under $100, it should at least let you know whether or not the Fosgate is the problem.

I have something like this as a back up to test for issues like this. In my experiences, I prefer solid state for very low level signals like vinyl. Tube line stages and amps are great, but you have to be careful with tube phono stages. The more efficient your speakers are, the more likely you are to hear tube artifacts in low level amplification.
Yes previous phono stage was Pro Ject Tube box MK11.
02-28-13: Fromunda
Yes previous phono stage was Pro Ject Tube box MK11

Well there, we seem to have narrowed down the problem area. Try a SS phono stage.
Yes but that phono stage did not have the hum-rush problem. Could it be my cart? the Ortofon SPU Silver Meister?