Please advise - volume-variable buzz in spkrs

Introduced a new (used) tubed preamp into the system yesterday. Having had tubes before, I was prepared for a tube hiss, but what I got was a buzz that increases with volume. It is in both speakers and seems to be about the same level in each. It definitely gets in the way of the music and during a late-nite session could be heard even farther away than the listening position.
Nothing else in the system has changed. I use Chris VH power cords on the cdp, amp and preamp. I tried lifting the ground on the pre and amp (separately); tried a cheap 2-prong cable; no change. The HT comes through this system, so I disconnected that including the cable tv. No change. The only thing I haven't tried, I think, is changing tubes, and that's because I don't have replacements on hand.
Any ideas? I've been thru the forums here and on AA (but not fully; my DSL chose this morning to crap out as well!).
I have the same problem but I don't have tubes. I have tried many ways to get rid of this noise even a b-p-t power cleaner and no success. So I'm still working on it.
Well, you can start from scratch. Disconnect everything from your preamp (except amp) and see if you have a buzz. If you don't add each source, one at a time, when the buzz appears you have your culprit.
Swap the right and left channel tubes. If the buzz moves with them then you have your answer.

Did a lot of experimenting, and found that I could eliminate 75% of the buzz by rerouting cables. There was a set of ICs touching and partly intersecting the path of a power cable. Lifting it in my hand reduced it quite a bit. As the rat's nest did not allow for too much tweaking there, I just moved components around.
There is still that 25% or so left. I will try more fiddling tonight.
Try that, Clydemetz!
I doubt this is your situation, but I was using my amp and DAC with a SS pre and it was dead silent. Switched to a tube pre and a similar noise appeared. Tried everything to no avail. Eventually found out that a connection inside of my amp was bad. It was fixed and the noise went away. For some reason, the problem only manifested itself with the tube pre and not the SS pre.
Phild, that is interesting. I have the exact same symptoms, and in fact I did have an SS pre that had no hiss. What was the guilty item and how did you find it? Of course my amp would be different from yours but it is worth a try.
I actually didn't find it myself. I unhooked everything and slowly put pieces back together and narrowed it down to my DAC and/or amp. I sent my DAC in for a check-up first. It checked out fine, so I sent my amp in for a check-up and that's when the loose (or broken?) connection was found.

I'm not sure if the SS pre actually blocked the interaction between the DAC and amp (it seems to have done so), or maybe the amp's connection coincidentally got worse when I hooked up the tube pre?? Either way, I never had the hum problem until I hooked up the tube pre...eventhough the tube pre had nothing to do with the problem at all. It was incredibly frustrating and it went on for months. Listening at night was almost impossible. I was very happy when it was all over and I had beautiful silence again.

This all happened about 18 months ago. I can't remember if the symptoms changed when I fiddled with power cords and interconnects like yours do, so I can't say if the problem is really the same or not. Good luck!