Tube amp buzz (amp, not speakers)

Tube amp buzz (amp, not speakers)

Hello -

Almarro a318b makes buzzing sound at random: sometimes it does, sometimes it doesn’t, completely unpredictable. The buzz comes out of the amp itself, like a transformer buzz; the sound out of speakers is completely clean.

I’ll appreciate any ideas - what causes it, what to do? boriso

I also would say DC offset on the mains power if the amplifier uses a toroidal power transformer in its’ power supply.

Here are some pictures of the bottom side of the amp.
https://www.audiocircle.com/index.php?topic=138713.0


I have no idea what kind of power transformer that is in the picture. You might want to check the supporting bolts and nuts for tightness. Do not over tighten. Unplug the unit from the wall outlet the night before you stick your fingers inside to assure the DC high voltage has completely discharged.
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Descent sized toroidal power transformers are usually the ones that buzz, vibrate, from DC offset on the AC mains. As a rule EI transformers do not buzz, vibrate, because of DC on the mains.

I think the power transformer in the OP’s amp is a bobbin transformer. I couldn’t find any info on how they react to DC offset on the mains.

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