Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: navdave on April 30, 2015, 03:59:50 pm

Title: Bias circuit addition
Post by: navdave on April 30, 2015, 03:59:50 pm
Hi all I need to add a stable bias supply to a tube amp build. Which transformer would yield more voltage when hooking it to the tube heater voltage supply a 6.3/120 or 12.5/120?
Title: Re: Bias circuit addition
Post by: sluckey on April 30, 2015, 04:06:29 pm
Hi all I need to add a stable bias supply to a tube amp build. Which transformer would yield more voltage when hooking it to the tube heater voltage supply a 6.3/120 or 12.5/120?
The 6.3v transformer would produce 120vac. The 12.5v transformer would produce 60VAC.
Title: Re: Bias circuit addition
Post by: tubeswell on April 30, 2015, 04:07:50 pm
I'd go with the 12V one myself
Title: Re: Bias circuit addition
Post by: navdave on April 30, 2015, 04:23:07 pm

Alright thank you very much I thought the 6.3v would yield 120v I'm a go with the 6.3 my b+ is very high over 500vdc thanks again!


Hi all I need to add a stable bias supply to a tube amp build. Which transformer would yield more voltage when hooking it to the tube heater voltage supply a 6.3/120 or 12.5/120?
The 6.3v transformer would produce 120vac. The 12.5v transformer would produce 60VAC.
Title: Re: Bias circuit addition
Post by: ernie_jr on May 02, 2015, 10:22:59 am
the 12.6 tranny will give you 84volts dc (60 x 1.4). i have used this in many sunn builds that have over 500 volts on the plates. 84 volts is plenty. if you use the 6.3 volt tranny to get 120 volts it may be harder to get the voltage down. All sunn amps had a 60 volt tap on there power tranny.
good luck.
Ernie