Never heard an amp do this before, ideas?


I have a primaluna 100 unplugged from any inputs. It has this awful high pitched sound coming from the speakers when it's turned on. It happens on both channels, and through headphones.

I have turned off all electricity in the apartment, turned all breakers off except the one it's on, moved the amp around the apartment, tried a humx, and different power cables. I even replaced the unit with another primaluna and they both do it.

I'm running out of ideas, anyone ever seen this before?

 

hobbes101

When you say "apartment", it makes me think of multiple households and things that are beyond your control in those dwellings. Though you probably have separate meters, some god-awful faulty appliance or wiring flaw could be generating interference. 

Can you take it to a friend's home, Along with a pair of headphones and see if the problem exists away from your environment?

"I tested two primaluna amplifiers, both did it. I also tried a cheater plug."

This tells me not to waste time on the tubes or components in your amp, unless it does the same thing in a totally different environment. Heck, take it to work and try it there.

What's a cheater plug?

 

@mwinkc it's a (not very safe) bypass on ground, so you can rule out ground loop issues. I think you're right, it's environmental. Unfortunately I don't think it's related to electricity, it's probably radio interference. Because the only thing that made the sound almost go away was wrapping the thing in a faraday blanket.

 

The disappointing part is that I can't fix that-- it's probably coming from outside. So I'm wondering if SS will be as sensitive to RFI, or if I can get away with hybrid.

Take the amps to your local stereo shop to check out some speakers with it.  Gives you a reason to go listen to some speakers.  Maybe even to work with a pair of headphones.  Eliminate the environment.

You would not be using expensive speaker cables, would you?   I'm recalling back in the day, there were speaker cables that certain "tube" amplifiers did not like. Would set the amp into oscillation.  My idea was that the circuit were seeing a resonant tank circuits of their tubes, transformer and speaker cable. Try going back to zip wire or other cable.