• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

tube pre-amp

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

Member
2005-06-09 5:10 pm
KL
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.
 

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Re: Humming

Matthewong said:
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