tube pre-amp

[Matthewong]

I've built a tube pre-amp using 2 6sn7gts. I'm facing a very big problem now and hope that someone out there can help me. My pre-amp will come out humming aound, and have tried a lot of methods, but still there the humming. Can anyone tell me how to solve it?

 

[Simpleton]

Do you have it's schematic, together with the PSU? it would help a lot.
Could be a faulty ground connection, filaments(?), ....

 

[SY]

There's a 99% chance that you've got a ground loop.

 

[kmtang]

Do you use DC for the filament? Also, you need to raise the potential filament supply to approximately 80-100V in case the last stage is a cathode follower.

Of course, the ripple level of the B+ could induce in lot of hum as well.

Please post your schematic and picture of your amp so that we could find whether there are anything we could see.


Johnny

 

[Matthewong]

Humming

Thanks all of you. I've tried everything I could to reduce the hum, but the hum still there. From voltages to ground looping, everything I've tried. First I thought It was bacause the heater voltage. But after some modification, the hum only reduce a little bit, the hum is still there. I've attached the schematic, hope you all can help me. Thank you.

 

[sklimek]

Re: Humming

Thanks all of you. I've tried everything I could to reduce the hum, but the hum still there. From voltages to ground looping, everything I've tried. First I thought It was bacause the heater voltage. But after some modification, the hum only reduce a little bit, the hum is still there. I've attached the schematic, hope you all can help me. Thank you.

Schematic? Sometimes when you attach a file and 'preview' before sending you need to re-attach the file before sending.

if that's what happened.

Stan