advice required - speaker buzz following change of amp.

Archived from groups: rec.audio.tech (More info?)

I'm using a set up with a CD player, DVD player, and Surround sound
processor and 2 channel Amp.
I use the surround processor to drive the sub, centre and rears with an
output to the 2 channel amp to drive the front speakers when using the
surround system.
I just replaced my existing amp with the Arcam and now I have interference
which manifests itself as a low buzzing in the speakers unless the the
'direct'
switch on the amp is pressed. This reduces the noise but does not eliminate
it totally.

I notice that with the direct switch off (such that the controls are not
bypassed) adjusting the treble control on the amp has an effect on the
interference.
also
I notice that with everything switched off at the front panel power
switches - if I touch the interconnects from the DSP-E800 to the Arcam amp
with one hand and the case of the Arcam amp at the same time I can feel a
mild tingling in my hand....(not sure if this is normal - does not seem
right.)

looking for advice....

System is, should it be important...
Arcam Alpha 7 CD, Arcam Alpha 7 Amp, Yamaha DSPE-800 and Tosh DVD.
Mordaunt short Front and centre speakers (bi-wired) and an Eltax active sub
& Eltax bipolar rears.