Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Doc58 on January 31, 2013, 05:06:36 pm

Title: Do I need to Bias?
Post by: Doc58 on January 31, 2013, 05:06:36 pm

I took out my Mullard NOS 5ar4 and installed a JJ GZ34...
BOTH TUBES ARE 5AR4/GZ34'S...
DO I NEED TO RESET THE BIAS?
I think at most I might have changed the Bias by a 1/2 a Milliamp either + or -
I need some opinions...
Tubes were set at 35 ma with the Mullard
Lets hear it?????
I DON'T REALLY WANT TO PULL THE CHASSIS AGAIN!

Title: Re: Do I need to Bias?
Post by: eleventeen on January 31, 2013, 05:29:03 pm

You shouldn't have to. The DC bias voltage is rectified elsewhere, typically by a diode or diodes.

1/2 ma variance? Pfffft. That's nothing.

Title: Re: Do I need to Bias?
Post by: HotBluePlates on January 31, 2013, 09:56:17 pm

If it were my amp, I wouldn't rebias just with swapping a rectifier for another of the same type.