Bias methods?

Psychobiker · 30th March 2008, 10:22 AM

Hi,

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

L

mississippi · 30th March 2008, 10:31 AM

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.

Psychobiker · 30th March 2008, 05:56 PM

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

Shoog · 30th March 2008, 08:29 PM

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 · 30th March 2008, 11:55 PM

Quote:

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.

Psychobiker · 31st March 2008, 12:03 AM

Can always go experimenting later

L

Brett · 31st March 2008, 05:53 AM

Quote:

Originally posted by Psychobiker
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 · 2nd April 2008, 10:09 PM

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!

Psychobiker · 3rd April 2008, 09:07 PM

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

30th March 2008, 10:22 AM	#1
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Oireland, bejappers	Bias methods? Hi, Just wondering, what most use for the adjustable bias function - potentiometer on the cathode or what? L

2nd April 2008, 10:09 PM	#8
TubeHead Johnny diyAudio Member Join Date: Jan 2005 Location: The Electric City, Schenectady, NY.	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! __________________ "No man really becomes a fool until he stops asking questions" - Charles Proteus Steinmetz

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
on the job teaching methods....	unclejed613	Everything Else	1	12th April 2009 09:39 PM
Veneering methods	KennyBradley	Multi-Way	55	11th December 2006 11:46 AM
Best methods for I/V conversion?	ezkcdude	Digital Source	7	20th April 2006 01:14 PM
Favorite bias measuring and metering methods?	audiobot	Tubes / Valves	14	15th March 2004 11:13 PM
Balanced amp methods	PWatts	Solid State	6	26th June 2003 04:17 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

30th March 2008, 10:31 AM	#2
mississippi diyAudio Member Join Date: Apr 2006 Location: holland	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.

30th March 2008, 05:56 PM	#3
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Oireland, bejappers	Hmm, might just leave with cathode resistor and let it self-bias

30th March 2008, 08:29 PM	#4
Shoog diyAudio Member Join Date: Aug 2002 Location: Eire	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

31st March 2008, 12:03 AM	#6
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Oireland, bejappers	Can always go experimenting later L

3rd April 2008, 09:07 PM	#9
Psychobiker diyAudio Member Join Date: Jul 2005 Location: Oireland, bejappers	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

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)