lm3875 and tube pre loud buzzing

[evozero]

Hi all,
Can you guys help me out?
I have two chipamps and two ASL wave 8 monoblocks, running bi amped with a passive pre no problems. But when i try and use my Tube pre with the chipamps i get a very load buzzing through the speakers, the kind that makes you jump and hit the kill switch! This is the same if i just use the tube pre and chipamps, no bi amping.
My aim was to run the tube pre + lm3875 for woofers + wave 8's for the tweeters.
Is this possible and what should i check?
All the tube kit is branded AV Reavox but its the same as asl i believe?

Many Thanks

Ian

[russell allen]

sounds like an earth loop,

regards

russell allen

[evozero]

Hi Again,
Could you explain how you resolve a ground loop please?
The chipamps are two little hammond alu boxes with wires running back to another box with the transformer in it, this is where they are earthed.
Thanks
Ian

[Les Reed]

Is your tube pre-amp fully warmed up before you switch on the chip-amps?
What is the configuration of the output circuit of the pre-amp and is there a DC blocking capacitor?