Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hylaphone on June 11, 2025, 11:41:06 am

Title: A humdinger question
Post by: hylaphone on June 11, 2025, 11:41:06 am

Hi, I'm working on an amp with completely separate filament supplies for preamp and power amp.One will have 100R CT resistors, the other will have a humdinger.Would you use the resistors for the power tubes and the humdinger for preamp? Or vice versa?Thanks --

Title: Re: A humdinger question
Post by: Merlin on June 12, 2025, 03:43:01 am

Humdinger on the preamp makes the sense

Title: Re: A humdinger question
Post by: scstill on June 12, 2025, 02:49:48 pm

if you are adding humdinger on one, why not do both?
have you considered elevating the filament?
https://www.valvewizard.co.uk/heater.html

Title: Re: A humdinger question
Post by: hylaphone on June 17, 2025, 04:36:36 am

Quote from: scstill on June 12, 2025, 02:49:48 pm

if you are adding humdinger on one, why not do both?
have you considered elevating the filament?
https://www.valvewizard.co.uk/heater.html (https://www.valvewizard.co.uk/heater.html)

Yes, but I was curious if hum from filament imbalance is more of an issue with preamp tubes..I would think it gets cancelled out in a push pull stage..

Title: Re: A humdinger question
Post by: pdf64 on June 17, 2025, 06:52:16 am

I suggest to DC elevate both circuits to the output valve cathode voltage.