BHK preamp emits high-pitched whine when warm


#1

I have a BHK signature preamp, about four months old. Recently I have noticed a high pitched whine from the unit that is annoyingly audible from my listening position (about six feet away). I’m pretty sure it was not making this noise when I first received it. Just to be clear this is not a noise through the speakers; it is a noise generated by something in the preamp. It stays at the same level regardless of where the volume is set, but it disappears immediately when I put the unit into standby by pressing the button on the front. If the unit is warm, the noise comes back right away when I turn it back on. It is there while the preamp goes through its 45 second warm-up cycle and gets a bit louder when the warm-up cycle is over and the unit clicks on. If I turn it off using the switch on the back, the noise disappears and does not return until after the 90 second warm-up cycle is over.

Any ideas what could be causing this? Is it normal behavior and I just didn’t notice it until recently? Could it be tube-related?


#2

Yes more than likely tube related.


#3

Might be a noisy tube and/or a bad connection.

I experienced your situation with a Quad preamp and I tracked it down to a tube. No noise coming through the speakers just from within the amp… Bad connection on one of the pins. By moving the tube slightly I could alter the frequency of the whine.
I changed the tubes and I also made sure all the socket connections were tighter…
The tube was also causing the transformer to make a noise.


#4

Hi Tcatch,

Sorry to hear this!
Please reach out to us at service@psaudio.com with your serial number.
We’d like top take a look at the unit to make sure that it is not malfunctioning.
Thanks,

  • Jeremy

#5

Thanks for the advice and info, all. I think I’ll try messing about with the tubes a bit before I think about sending the preamp to Boulder. It’s been a busy week but I should have time in the next few days to open it up, try different tubes, etc. (I’ve got the Tungsram tubes that came with the preamp from Upscale Audio still waiting to go in.) The sound coming out of the speakers is still wonderful, so its hard to get motivated to part with it, even temporarily.


#6

Hi tcatch,

That sounds like a plan.
We will be here so let us know how we can assist.
Best wishes,

  • Jeremy