small hum coming from the BHK250: normal?


From the beginning when I used my BHK250 amp, a small hum can be heard from the amp itself (not the speakers), even in standby mode.

This is easily covered by the music when played, but I am just wondering whether it is normal and if other owners have the same noise?

My previous tube amp was dead silent.

Most amp transformers hum a little. How loud is it?

My BHK 250 has hummed off and on since I got it. At one point it was doing a cyclical thing that had me concerned. I could hear it with the music off at my seat, but once the music started it was masked completely. Since then I’ve come to the conclusion that the humming was caused by noise and/or a small amount of DC on the power line. At the moment it is nice and quiet. A regenerator such as the P10 would certainly help if it is a power line induced issue, but for me the P500 I use is inadequate to power the amp so I haven’t tried that yet.

In my case it is not very loud, and it is constant. Also it it the same whatever the input tubes I tried.

I am quite sure it is a transformer noise.

My previous amp had transfomers too but was very quiet. Thus I don’t think I have DC on my power line.

It is not a problem for music reproduction, the only annoying thing is that have it in mind. At the beginning I was a little worried that there could be a failure somewhere. But it seems normal in the end so I am not concerned too much.

I have a pair of the 300 mono’s that both have some slight mechanical hum, and they are powered by a P10. It is so slight that I cannot hear it at my listening seat 8 feet away with not music on. One amp is clearly louder than the other, so I am attributing it to variation in the transformers, but since it doesn’t ever intrude on music, no problem.

Same here S300s - both hum. One slightly louder than the other too. Can be heard as very low hum 3m away but not when music playing.

I don’t have any DC on mains. The amplifiers are powered through a P10.