Transformer hum with AC fluctuations


I was about to buy an isolation transformer (Tripp Lite) in hopes of cleaning up my inexpensive CDP's sound a bit (Tobias's rec on the cables forum), and now I've run into another AC-related problem.

I live in an old, small rural town in PA, and this time of year power demands start overwhelming our grid: our lights dim for brief moments (a second or so) and then come back to normal all evening long. Coinciding with that--and only at high-usage times on the grid--the transformer of my NAD C325BEE has started making a hum that's audible from across the room. The trannie has always hummed faintly (had to put my ear above the amp to hear), but now it's hard being in the room with it. It doesn't come through the speakers or headphones.

I have two questions: is an isolation transformer likely to hum just as much as my NAD's transformer? and is there a better route to cleaning up my AC (the kicker: within a $200 budget)? I appreciate any other suggestions/solutions. Thanks in advance.
ablang
Channel Islands Audio XDC-2 is designed to eliminate (or reduce) transformer hum. Available with a 30 day trial.

The Tripp Lite will likely buzz as loudly, if not louder than your NAD.
Unlike Tvad, your problem isn't DC offset. Sola/Hevi-Duty offers regulators, or what they call conditioners, in many configuations and sizes. These are more than just transformers. They also have an interesting FAQ page.

There are a couple used ones on Ebay. For sizing, find the maximum amp draw of your amp and double it. Do not undersize to fit your budget.
APC S15 conditioner will address brown outs.
Thanks for the responses. Shadorne--your APC tip turned me on to them, and I've just ordered an APC H10blk (cheaper line, still true 120V AC conditioning) that fit my price range: $218 shipped from B&H Photo/Video. I'll post again if it's the screaming bargain it seems.
Get a PS Audio Premier Power Plant immediately and this problem will be gone.
Tvad,

Have you used that Channel Islands product? How did you configure it in your system? I've had transformer hum no matter what conditioner I've used.
Have you used that Channel Islands product? How did you configure it in your system? I've had transformer hum no matter what conditioner I've used.
Johnmcalpin (System | Threads | Answers)
Yes, I have used it. I plugged it into the wall, and I plugged my amp into the XDC-2. No other AC products on the line.

Transformer hum was reduced by about 2/3.
Well, I said I'd post again if the thing worked--and it does. Even the usual quiet transformer hum is reduced to practically nothing, my TT strobes at the steadiest speed I've seen, and sound has improved subtly but noticeably--better resolution of low-level detail, a slightly tighter bottom end, and improved soundstaging, especially front to back. The EMI/RFI filtration has a good bit to do with all that, I'm guessing. It's the only AC cond I've tried, but I'm pleased--it works, it's cheap, and it's a tank. Thanks for the leads, one and all.
Hi,
I have also a problem with my 2nd system.
Noise/hum in both spks. but a specialy in left.
Disconnected everythig but amps and spks, still there.
Used power stabilizer, quantum 800, PS ult. outlet and
Granit Audio Ground Zero. Nothing helps.
It is a real pain in the neck. By adj. gain on Supratek preamp I get it down somewhat but not 100%.
I am giving up now.
Was thinking about running new line from the basement but not sure if it is going to help.
I am not sure if any of you guy have any ideas how to fix it.
Thanks

P.S
Sorry for coming in without knucking.

Mariusz
Thanks, Tvad.

My amp's massive transformers hum from time to time. I've got the amp powered through an Equi-Tech balanced power unit which runs off a dedicated 20 amp line. The hum is definitely audible and varies. It was there in my old place and here in a new house. Plugged into the wall directly or through all sorts of power boxes. But the sound of the amp is still amazing.

A friend who designs and builds large scale manufacturing machines told horror stories of transformer hum, with some folks resorting to hand wiring and other techniques. He said old timers believed some times there was a harmonic built into the transformer through the wiring and nothing would rid it.
John, it's interesting to me that your Rogue Zeus' transformer hums. I have never owned a tube amp that had a problem with a humming transformer. Also informative to me that the Equitech has not solved the hum problem, as I was considering a balanced isolation transformer to address my problem.
It certainly is odd. I figured the Equitech would take care of it, but it's still there. But, and more frustratingly odd, is that it is intermittent. It's a head scratcher.

I also have the amp -- and every other component -- sitting on a Sistrum platform. I wonder if setting it on something else might do the trick.

Don't get me wrong, this amp is amazing and in the grand scheme of my system the hum is a very minor flaw. And while I go through all sorts of system do-over fantasies -- like the one I'm in now -- I know the Zeus is a keeper.
12-19-07: Johnmcalpin
But, and more frustratingly odd, is that it is intermittent.
As is mine. It varies from day to day and time of day.

I have an appointment with my local Dept. of Water and Power to have my power line monitored for two weeks. Apparently, if there is a certain amount of voltage fluctuation, they have a fix that can be applied.

I also have the amp -- and every other component -- sitting on a Sistrum platform. I wonder if setting it on something else might do the trick.
I once had a DVD player on a Sistrum platform. The DVD player is a model known to have a fairly pronounced vibration issue. The Sistrum exacerbated the vibration two-fold (at least). FWIW...
Since it varies in time and intensity, I would have to guess that it is something coming in on the AC, but using an isolation transformer would seem to rule that out. Some units seem to be prone to transformer hum, like my old Moscode. If the hum is exacerbated, I would guess that the transformer hum, which I am pretty sure is a mechanical issue/resonance is exciting a resonance in the platform it is sitting on, if that makes it worse. I would try a diff platform to see if that helps. I also think that it is possible that a stick on vibration damper (is it dynamat?) might help. Also tightening the xformer hold downs. Or maybe loosening them and putting a elastic washer btwn fastner and xformer.
When I first got the amp it sat on a Polycrystal stand for a month or so. I might go back to something like that, or a maple block. Sistrum has been awesome for the speakers and other components. Time to experiment.

Swampwalker, you've got some very sound tips. I kicked around the idea of losening the nuts the other night while I was biasing the tubes.
So I spent part of yesterday thinking I needed a new amp stand and searched out the Symposium and others and decided to make a switch after Christmas.

And then last night not a peep out of those transformers whatsoever.

Talk about audio nervosa!
And then last night not a peep out of those transformers whatsoever.

Talk about audio nervosa!
Johnmcalpin (System | Threads | Answers)
You and I have the same gremlin. Whatever solution you discover will likely solve my problem and vice versa. If I find a fix, I'll let you know.
I'm guessing that you both have a power issue, whether from inside or outside the house, who knows? I have also been told that sometimes some blue-tac can help dissipate the resonance.
Same here!