3 preamps with transformer hum, DC on the line?

DC on an AC power line is highly unlikely unless you live in the third world. You can easily check this with a DVM. Just set it to DC volts and put it across the line.

The AC frequency is set at the generating power station and cannot be "adjusted". It's usually very accurate and variation will not cause hum problems.

DC is also unlikely to cause "hum", if you are speaking about electrical noise. Are you speaking of an audible noise coming directly from the equipment (and not through speakers/headphones)? Are the transformers overheating?

Have you checked the grounds in your house wiring? Bad grounds could account for hum problems.

DC on an AC power line is highly unlikely unless you live in the third world.
04-04-12: Dhl93449

Not true.

You can easily check this with a DVM. Just set it to DC volts and put it across the line.
04-04-12: Dhl93449

Not true.

Are the transformers overheating?
04-04-12: Dhl93449

DC offset on the mains will cause an xfmr to run hotter than normal.

Have you checked the grounds in your house wiring? Bad grounds could account for hum problems.
04-04-12: Dhl93449

Not xfmr mechanical vibrating noise.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1209767274&openflup&6&4

http://www.altavistaaudio.com/hum.html#trafo

http://sound.westhost.com/articles/xfmr-dc.htm

http://sound.westhost.com/articles/xfmr-dc.htm#dc1
.

one other thing you can try (which costs money, of course!) is to use a AC power regenerator (like one of thos PS Audio units P300, P600, P1200 or Power Plant Premier) or from PurePower.
The AC power from your wall will be used to power the electronics inside the AC regenerator but the AC power regenerated should be clean.

Looks like you might have a mechanical hum in the xformers. Does putting a brick or some heavy weight on top of the xformer stop the humming? Of course, put the heavy weight on the xformer when your preamp is off to avoid any personal harm.

So, I took the case off the preamp today and tightened all power supply screws (none really budged). Powered it up with every breaker turned off except my dedicated 20 amp AV line and only the preamp plugged into the dedicated outlet. Still hums - grrrr.

It looks like I have very few options, some which I cannot afford and 1 I really am not sure I want to do:

1. Send back to Audio Plus Services (Seattle to NY). Anyone had any experience with this shop and their service dept? I can see a $250 diagnosis bill plus shipping both ways and them coming back saying there is either nothing wrong with it or they are unable to fix it. Really not sure about this route. Probably a No.

2. A custom or 3rd party power supply is probably out of the question after looking at various wires coming off the factory power supply. No.

3. Trying a PS Audio or similar power regenerator. Too expesive. No.

4. Going to an integrated amp if I can find an Audio Refinement Alpha Complete in black that does not hum in 8/10 shape I just might do it. I've heard it is a good unit but not as good as my Audio Refinement separates, especially the Pre 5. A Maybe.

5. Trying my best to get the power company come out and test the line. Hopefully something that is easily addressable and I can actually get the power company to show up and test the line and do it for free (I do pay them for a resource with hopefully some kind of service level agreement backing it.

6. Going to try a Environmental Potentials DigiPlug Stationary in series before my Porter Port on my dedicated 20 amp line. They will do a 30 day refund trial and I can do the wiring myself. A Yes and hope it fixes things.

What I really don't get is that all 3 preamps I've tried do hum and got better with using the PS Audio Humbuster, but again, I lost the high frequencies so the PS Audio Humbuster is out. If it is that common of a problem, why is there not more of an industrial standard that avoids this problem. On top of that, the Linn Classik K music (integrated amp with tuner and CD player) just cranks away with no hum but does not sound as good as my current Audio Refinement gear and probably loses out to the Audio Refinement Complete Alpha integrated also.

Things that annoy you with their hum...

BTW, the Linn Classik is part of my bedroom system with some Tukans and is not on a dedicated line and I have quite a few dimmers in the house.