SP-12/PH-12 Buzzing on Shelf

My SP-12/PH-12 was emitting a buzzing sound this morning when I leaned toward it to turn it on. I shut off the outlet that supplies power to it and the buzz stopped. The pre was not powered up. I turned the pre on and it continued to buzz but operates normally and sounds great as usual. Whether on or off the buzz remains about the same and seems to come from the area of the power switch or Antek toroid. It's not especially loud but can be heard from about a foot away. Anybody have any thoughts here? As I say, it's operating properly and sounds fine.

Have you double checked to make sure that your power switch is on the hot leg and not the netural. The fact that it can buzz when turned off makes me think that you switched the netural side. Then something failed in your amp that caused the buzz and it happens all the time because your amp always has power that now leaks to the ground.

Have you tried tightening the bolt that secures the toroid transformer just a bit?

Well, the plot has thickened a bit today...This morning no buzz, none. Ruffian's suggestion that the neutral wire was switched is not the case. That the buzz has ceased on it's own has led me to consider something else. As we all know, electronics issues seldom, if ever "fix" themselves. But I have had ongoing issues with the horn tweeters of my 99db./meter Klipsch Forte II's buzzing as well. They do it especially in cold, dry weather, regardless of whether or not they are plugged into an amp. There never seemed to be a rhyme or reason to when they'd do it, but almost always in dry weather. Sometimes the buzz is so loud that it can be heard six feet away. It generally is louder from the left speaker but they both do it. I brought this up over at the Klipsch forum a couple of years ago and general consensus was that stray RF was causing it. I suspect my next door neighbor's burglar alarm but have never been 100% sure. I'm going to hold off on tightening the toroid down until when or if this happens again. I sense that a loose toroid could cause the buzz while the pre is powered up, but just doesn't make sense while the unit is off. Theoretically it shouldn't be seeing power with the switch off, right? I'm thinking that based on my known RF issue, the toroid and perhaps some of the wiring may be acting like an antenna, causing the buzz. Any thoughts welcomed.

Hi guys,

Let me tell you what happened to me last winter. Might not be related at all, but you never know.

I have a Hagerman preamp that was emitting a buzzing sound, more of a sizzling sound than a hum actually.
Kind of a high pitch thin buzz. Weird.
I opened the preamp to have a look inside, and noticed that the buzz was in the power supply area.
Would be there sometime, and some other time gone.
I would turn the preamp on and off, still there. But the preamp would have to be on to hear it.
And what's even weirder, is that if I pinch the small ceramic capacitor in the power supply circuit,
it would muffled the sound a bit. Like a mechanical vibration. No kidding.

And then, once in a while, I would turn on the preamp and it would be gone. No pattern to it.

Then I noticed the same thing happening to my brand new computer. Even when it was not running.
I would have to get close to it to hear it. And again, in the vicinity of the power supply.
But in the case of a computer, the motherboard still has some power applied to it even though
you shut down the operating system. I would have to unplugged it from the wall to make it stop.

Not knowing what to think about it, I mentioned it to my wife and she told me that her brand new McIntosh
monitor (Apple Thunderbolt Display) does the same!!??!! (I have a PC, and she has a MAC. No fighting over computer access)

The same type of sound, and near the power supply too. Wow.
After a few tests, we noticed that, when she turned off her monitor, the sound would
stop on my preamp and computer.

Obviously. the power supply on her new Monitor had a problem of some kind.

I suppose it introduced some noise on the main in our apartment.
And it was on the whole main circuit, no matter on which breaker I would connect the preamp.
Cause I tried everywhere in the house.

She got her display fixed and there is no more buzz... they replaced the power supply circuit and the fan.

If you suspect the next door neighbor's burglar alarm, and if you're in good term with them, maybe ask them to
turn off their alarm system and see if it stop?

Anyway, sorry for the long post, but even though it might not be the same, it does look like some parasite
interferences...

Took me a while to figure that one out.

there were a few similar posts about a year ago, it turned out the problem was a florescent lamp fixture somewhere in the house
putting RFI on the AC line!! I suspect the computer power supplies do the same type of thing.
I've got my stereo system on a well filtered power strip. Can't really go wrong buying a power conditioner either.