Bias methods?

[flyinglemur]

Hi,

Just wondering, what most use for the adjustable bias function - potentiometer on the cathode or what?

L

 

[mississippi]

No, when using a potmeter then control the negative bias voltage on G1.
The cathode is then connected to the GND with or without a low ohmic resistor.

 

[flyinglemur]

Hmm, might just leave with cathode resistor and let it self-bias

 

[Shoog]

CCS have worked well for me in output stages, simple LM317's are adequate. Baby Huey bias blocks are a bit better.
Garter bias works remarkably well.
http://www.tubecad.com/2005/May/blog0046.htm
BOTH ARE ADJUSTMENT FREE !! Both can keep the output transformer from saturating with standing current in PP.

LED bias on single ended preamp duties perform very well.

Shoog

 

[hotbottle]

Hmm, might just leave with cathode resistor and let it self-bias

That's what I'd do. I like everything as simple as possible, and there's nothing shabby about self-biased SET amp sound.

 

[flyinglemur]

Can always go experimenting later 🙂

L

 

[Brett]

Hi,

Just wondering, what most use for the adjustable bias function - potentiometer on the cathode or what?

L

Class A: prefer fixed bias from a seperate low noise reg supply, with pots for each grid. Next one will probably implement bias regulators. Even better for 'A' I suspect is differential with bias regs.
AB: also prefer fixed, but have briefly experimented with mixed cathode and fixed.

 

[TubeHead Johnny]

For fixed bias, I get good regulation using a Rat Shack 25.2V filament trannie wired up to a voltage doubler (2 X 1000 uf caps). This gives me around -66V to work with. You may laugh but it works great!

 

[flyinglemur]

I'm going to go with the resistor, just to learn the basics first and then go with differential supply at a later date (and hey! Make this adjustable!!)

L