Just bought used BHK preamp and 300 mono blocks

Right now I have an Audience AR 6 power conditioner plugged into a dedicated 20amp plug. I have everything plugged into it. When I turn on just the mono blocks, there is a quiet, but very noticeable 60 cycle hum. When I turn on the preamp, I get higher pitched hum that’s even louder. To be clear, it’s not a squeal, it’s a hum. I was told that the tubes in amps were almost new and the clock on the preamp shows @300 hours. The only source is an Aurender streamer, that’s dead quiet.

Any ideas on what I should do to quiet my system?

Thanks in advance.

As a start, check all connections to make sure everything is seated properly, including the tubes.

Second, research DC hum and make sure you are not experience that. I don’t recall the specifics, but the cure for DC hum may require a different tack to get sorted.

Third, make sure your signal cables and power cables are sufficiently separated and/or crossing each other at 90 degree angles/are perpendicular to each other.

Also, play with the gain on the preamp and any sources that have adjustable gain to see if you can lower the noise.

Final thought, please confirm where the hum is coming from (e.g., one speaker our the other - or both; or the kit itself).

Hopefully others will chime in here, and any additional information you can provide will help with the trouble shooting.

Good luck.

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Hi Scotte,

Thanks for your reply,

I wasn’t aware that I could turn down the gain on the BHK preamp, but with my system being screaming loud when the preamp is @40, I’d love to learn how.

And I did try to do some cable management, but haven’t completed it yet, the tubes have been giggled, and I swapped power cords between the streamer and the preamp and there was no difference.

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Re: “turn down the gain”

Bad choice of term on my part maybe. I meant to have you make sure you don’t have more than one volume or gain setting working in tandem with each other. If you have the possibility of combining two different “noise floors” in your set up, then setting those levels in a way that best compliments their interaction MIGHT provide some relief.

Good luck.

I assume you tried the system without the power conditioner? And is the noise in 1 speaker or multiple speakers?

Yes. And the sound is coming from both speakers.

First, plug everything into the wall. See what happens.

SE or Balanced IC’s?

Sad to say no change.


Depending on the efficiency of your speakers and with the tubes in the input stages of the amps you are going to get some faint level of hum if you get close enough to the tweeters. I had the same with the BHK 250 and in your situation you are times two. The higher pitched noise when the preamp comes out of mute is likely tubes or an input board. If you haven’t remove the tubes and re-seat them in case they got bounced around in shipping. Even though your gear is plugged into a dedicated line if you haven’t check to see if you have a ground differential on the line with a multi-meter.

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