Sounds like magnetic hysteresis causing something metal vibrate.

I'm making things up.

Have you thought about getting an electronics geek to have a poke around inside for the cost of a cheap lunch? Could be worth it.

Well, the first thing I'd do is waste a couple dollars on a phone call to Furball. And especially if you are dealing with a high-voltage item such as a power conditioner. Power conditioner can mean any number of things. It can have a simple "MOV" device so as to prevent surges (beyond 300 volts). It could have a tapping toroidial transformer to automatically vary voltages. It could have batteries with a full-time sinewave generated inverter (not modified sinewave)?

If it's making a big acoustical buzzing sound, IT'S READY TO BLOW UP! So what kind of conditioner is that? The kind that blows your equipment up! Throw it out. It's not a necessity. That kind of mistake can make you pregnant! You're talking about a desktop bedroom set up. If you want a real power conditioner go to the SIGNAL TRANSFORMER COMPANY who can sell you a "Power Isolation Transformer". That's what I use. It will handle 75 amps. Over 7000 Watts. Weighs 85 pounds in a 8 inch cubic square. Costs over $1000. Now that's power conditioning. What you have is a fan. Go to the hardware store and get yourself a surge suppressor to replace you're broken surge suppressor "power conditioner". What you might be hearing is like the break wear indicator on your car that causes your brakes to squeak. So as to let you know THEY ARE WORN OUT. That might in fact be your problem? It's letting you know, it gave its life protecting your cherished ones. It's a Dead horse. Shoot it to put it out of our misery.

Or you could ask the company for a schematic, take out the old old volt meter & find out what failed? This should be a quiet running device. It should produce no noise. It's out of warranty? So is my Neve. Now what do I do?? I fix it. So should you. No....., I don't think I want you fixing my Neve?

What's that button to ?
Ms. Remy Ann David

can you post a clip?

I am going through somewhat the same problem with an amplifier. I called the company and they told me that I may have some harmonic distortion in my AC power lines that is causing an asymmetrical wave form which is causing my toroidal transformer to react and cause the buzz.

I too have power conditioner that is on my computers and hard drives which makes some buzzing noises especially when it is overloaded. When overloaded it sounds like what you may be experiencing. Best to contact the company and see if others have reported the same problem and what they would suggest to cure the problem.

In the old days (and still true today) sometimes transformer laminations would come loose and buzz and you could sometimes cure that by retightening the screws that hold the transformer together or by potting the transformer in an asphalt type product to keep the laminations quiet.

Best of luck!