[roscoeiii]

Yes.  Hum was through speakers.  If your hum is coming from the amp itself (transformer) then there's not much you can do about it other than make sure all the fasteners are tight - including bolts securing the laminations and the bolts securing the tranny to the chassis.

Actually, in addition to tightening the transformer, hum from the amp itself can often be easily fixed by a DC blocker (if DC is the culprit). AVA's Humdinger may be the best bet being sold to address that issue at the moment. Appears to be more robust and effective than other DC blocker options currently sold (like one from Emotiva).

[Bigfishhk]

an electrician friend came over to help me isolate hum issue. we had limited time but we tested the amp on 3 different circuits and we tried taking upstream components off one by one to detect stray EMF.

Results indicated a probable mix of causes, though by no means conclusive.

1. noisy circuit. on another circuit the hum was reduced (not totally)
2. transformer hum
3. light tube rushing sound when pre amp connected.

Am considering both a power line conditioner since the circuit it's using is noisy, and the Humdinger or some such thing to help with the trasnformer noise.  I anyone has a good suggestion for power line conditioner pls let me know. I have seen a couple of Furman products at around $100. I do not have a rack, so rack mounted piece not so helpful for me as a power strip shaped product.

If I can get rid of the hum or 70% of it, I think I will be satisfied. Then I'll see if the tube rush is loud enough to bother me .

thanks

Tom

[Bigfishhk]

just ordered humdinger with 30 day retrun if doesn't help.
tom