Re-biasing...

SinnerBoy61 · May 10th, 2005, 05:08 PM

Does it have to be performed should a 12AX7 wears out? I know if a 6L6 goes I have to, but what about my 5U4 rectifiers (2 of 'em)

Also, I have an "internal bias pot"...what the heck does that mean and how does it work?

Thanks!

SB

Daddy Elmis · May 10th, 2005, 05:38 PM

replacing preamp tubes (12ax7) does not require rebiasing.

Replacing power tubes can mean rebiasing. If you replace with substantially similar tubes of similar rating (either in the GT scale or by testing), then you can get by without a rebias.

For recty tubes, I guess the answer is "it depends." If you replace a 5AR4 with another 5AR4, then you "shouldn't" need rebiasing. Changing the recty value will change the voltage to the power tubes, and then you might want to rebias.

At the end of the day, except for extreme cases, "wrong" bias will either negatively affect tone or shorten power tube life, or both. Hard to damage the amp with "wrong" bias.

SinnerBoy61 · May 10th, 2005, 07:41 PM

yeah...these are all GT

I'd like to put some JJ 6V6's in and see how it'd sound. I've also read my amp will run better and more efficiently if the 2 5U4's were replaced with a single 5AR4...

Daddy Elmis · May 10th, 2005, 08:29 PM

Quote:

Originally Posted by SinnerBoy61

yeah...these are all GT

I'd like to put some JJ 6V6's in and see how it'd sound. I've also read my amp will run better and more efficiently if the 2 5U4's were replaced with a single 5AR4...

Don't know what amp you've got, but switching from 6L6 to 6v6, or going from 2 5U4's to one 5AR4 would cause me to go to a tech. That's a lot of changes to the basic voltage requirements.

May 10th, 2005, 05:08 PM	#1 (permalink)
SinnerBoy61 Tele-Holic Join Date: Feb 2005 Location: Johnson City, TN - Morgantown, WV Age: 21 Posts: 629 77 Photos	Re-biasing... Does it have to be performed should a 12AX7 wears out? I know if a 6L6 goes I have to, but what about my 5U4 rectifiers (2 of 'em) Also, I have an "internal bias pot"...what the heck does that mean and how does it work? Thanks! SB

May 10th, 2005, 05:38 PM	#2 (permalink)
Daddy Elmis Tele-Holic Join Date: Jun 2004 Location: USA Posts: 961	replacing preamp tubes (12ax7) does not require rebiasing. Replacing power tubes can mean rebiasing. If you replace with substantially similar tubes of similar rating (either in the GT scale or by testing), then you can get by without a rebias. For recty tubes, I guess the answer is "it depends." If you replace a 5AR4 with another 5AR4, then you "shouldn't" need rebiasing. Changing the recty value will change the voltage to the power tubes, and then you might want to rebias. At the end of the day, except for extreme cases, "wrong" bias will either negatively affect tone or shorten power tube life, or both. Hard to damage the amp with "wrong" bias.

May 10th, 2005, 07:41 PM	#3 (permalink)
SinnerBoy61 Tele-Holic Join Date: Feb 2005 Location: Johnson City, TN - Morgantown, WV Age: 21 Posts: 629 77 Photos	yeah...these are all GT I'd like to put some JJ 6V6's in and see how it'd sound. I've also read my amp will run better and more efficiently if the 2 5U4's were replaced with a single 5AR4...