The ShadowMusic Web Community

Does anyone know where one can purchase a Hum Cancelling Pot (Preset) for an Ac30.

Thanks

SJB

Two 100 ohm resistors should do it

http://www.valvewizard.co.uk/heater.html

Thank you Roger.

The Web page will be very useful.

I will resort to the resistors if I can't fine a pot. You know that owners of AC30's like to keep them original.

Cheers

Yes, of course, Stuart! Though I didn't think AC30s had a hum balance pot originally but is this what you're looking for?

http://www.angela.com/100ohm3wwirewound ... eamps.aspx

thanks roger.

I note from one of the pictures of a Vox AC30 that a small pot was used. So I fitted one obtained from RS. It's a half watt with the actual running wattage less than 0.1 watt.
The original pot was well over to one side to balance - the new one sets up bang in the middle.
Seems the original pot was log one. This is what led me to believe two resistors of the same value would be no good - thinking I would have to use differing values to match the setting on the original pot.
This is not the case.

Its now up to the owner - but I would think that resistors will stand up to a valve Anode - Cathode into the heater flashover - better than a pot.
Probably one of the reasons later amps used resistors.

Stu

The pot circuit is (or was) called termed a humdinger.
I have always used a skeleton preset control 100R to 500R. I currently have a 500 Ohm in my guitar amp.

Search the web for "valve circuit humdinger".

Regards

Tony