BHK Preamp Transformer Noise?

Recently acquired a new to me BHK pre and it produces great sound coming out of my speakers but is a little noisy during use and very noisy while in standby, when rear switch is in the off position it’s completely quiet. Is this normal/should I be concerned? The unit is still under warranty so would like to get this taken care of before the warranty runs out if it’s a matter of concern.
Video available to help with clarity. Warning: audio is very low so device volume needs to be maxed out or use headphones.

I should also add, I did try some old 12au7’s I had laying around and it was the same.

Probably worth the shipping to have PSA check it out and repair if needed.

When you say noise, do you mean the unit or the speakers? Depending on the efficiency of your speakers and also amp impedance, you may have slightly different result, but BHK does produce faint tube buzz more than a typical SS preamp. For headphone use, you need headphones with 300Ohms and higher impedance to eliminate the tube buzz. Any low ohm/high sensitivity headphones don’t match well with tube pre. Some of that noise also comes from the display of the BHK pre, so dimming it helps.

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Sorry I should have been more clear, the noise comes from the unit itself. Audio from the speakers is perfect.

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I have two BHK pre’s and neither has any transformer noise. There is no change whether in standby or full on with output muted or not; also no noise no matter the volume.

Because it is mechanical noise, do yourself a favor before going through the hassle of returning it by checking whether the mount came loose in shipment. Not at all uncommon. I haven’t looked at the transformer of mine, so I’m assuming a mount bolt is accessible under the chassis. If it is, GENTLY try tightening it. If it is loose, tightening it down again naturally damps it through contact with the chassis. My two cents …


You can also bed it in silicone caulk if it continues to vibrate

or play-doh or silly putty :wink:

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