BHK preamp emits high-pitched whine when warm

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?

Yes more than likely tube related.

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.

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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

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.

Hi tcatch,

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

  • Jeremy

Just thought I should close the loop on this. I changed tubes, tried a tube damper, nothing worked, so I finally sent it back to Boulder. The PS Audio techs did not succeed in replicating the problem, but they did replace most of the innards of the preamp. I’ve had it back for a couple of months now and it has been much quieter and trouble free. I did have to break it in all over again.

The level of customer service I have experienced from PS Audio is truly outstanding. They paid for shipping both ways and basically gave me a new pre-amp, even though they could not find a problem. Wow.

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A bad capacitor can do that and it likely wouldn’t manifest itself until it warmed up. Maybe a cold solder joint?

I’d like to resurrect this topic as weather has become warmer and I’m experiencing this same issue, except now the high pitch sound now is audible both from the machine and the speakers (gone from speakers once I muted the volume). I had this issue soon after I bought the bhk preamp just over a year ago, it then actually went ok after I took out and reinsert the tubes. Also was quite sure it wasn’t audible through speakers before. Anyone experienced the same? My local 1 year warranty had expired less than 2 months ago.

I would source some different tubes and try those first.

Thanks. I tried pointing a fan to the bhk preamp. As long as the temperature gets lower, that noise is gone. Have tried it eiyh the stock tubes and a set of Mullard and results were the same. Something inside must be very sensitive to heat.

This is absolutely a wild ass guess suggestion, but I remember someone from my audio club once mentioning this pertaining to one of his components (non PS Audio).
He found the toroidal transformer to be not even finger tight. Gentle snugging of the nut was the fix for him.

Thanks! I tried lifting up the bhk pre and couldn’t find any screws for the transformer. Guess will need to open up the case but that’s not something I’m gonna do. What I do now is to point a fan to it for 10-15 mins before turning it on.

Is this the noise that you are hearing?

Yes exactly this! Did you manage to get it fixed?

No, never bothered to send it in as I’m a believer that the fix could be worse than the problem that you can live with. Also, the noise would go away once I reset using the rocker switch on the back. Lastly, I notice the noise would come when I plug in or take out cables while in standby mode so I learned to avoid doing that.

Thanks @Excelgam. Good that you know how to avoid it consistently. Does it happen also when it’s hot in standby? For me it’s become a usability issue and I hope PS Audio has a fix for it.

I’ve only had this problem so far when swapping cables so it hasn’t happened yet unprovoked…knock on wood.