Choosing plate voltage

SamiBami · 2nd May 2011, 08:41 PM

I'm newbie to tube circuits and interested in building tube distortion/overdrive
based on 12AX7 (due to the high amplification factor)
it is easier to choose low voltage (9,12,18v filament will get 6.3/12.6v)

what are the criteria for plate voltage that I should consider?

Thanx,
Sami

DF96 · 2nd May 2011, 08:53 PM

To a first approximation, the lower the voltage the more distortion you will get.

SamiBami · 2nd May 2011, 09:56 PM

The lower voltage the more distortion, is that due to clipping of lower voltage?
But also the higher voltage the more amplification

DF96 · 3rd May 2011, 10:42 AM

Both clipping and non-linearity. The 12AX7 is very linear when driven into a high impedance load with adequate anode voltage.

Two options: study the data sheet, or try it and see.

SamiBami · 3rd May 2011, 08:00 PM

What plate voltage would you suggest for this application?

DF96 · 3rd May 2011, 09:27 PM

Sorry, I design for low distortion so I haven't a clue. I'm sure someone will be able to help.

mario13 · 3rd May 2011, 10:56 PM

it depends on the circuit. I built a similar OD with a 12ax7 in cascode. My plate voltage was about 125v. It was a litle clean for my liking so i addaed some clipping doides as well. Experiment with low voltages first and see how it sounds.
Best of luck!
Mario.

mastodon · 4th May 2011, 09:54 AM

Try running the first half of the ax7 on a high plate voltage (150V or more) for lots of gain, then couple the signal into the second half which you run at a low voltage (50V or less) to drive it deep into distortion.

SamiBami · 4th May 2011, 04:57 PM

Thanx guys for your answers

if any body has something to add..

Merlinb · 4th May 2011, 08:50 PM

You may like to look at one of the many DIY valve overdrive pedals:
The Real McTube Article: How It Works

http://www.diystompboxes.com/pedals/.../shakatube.gif

Beavis Audio Research

2nd May 2011, 08:41 PM	#1
SamiBami diyAudio Member Join Date: May 2011	Choosing plate voltage I'm newbie to tube circuits and interested in building tube distortion/overdrive based on 12AX7 (due to the high amplification factor) it is easier to choose low voltage (9,12,18v filament will get 6.3/12.6v) what are the criteria for plate voltage that I should consider? Thanx, Sami

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2nd May 2011, 08:53 PM	#2
DF96 diyAudio Member Join Date: May 2007	To a first approximation, the lower the voltage the more distortion you will get.

2nd May 2011, 09:56 PM	#3
SamiBami diyAudio Member Join Date: May 2011	The lower voltage the more distortion, is that due to clipping of lower voltage? But also the higher voltage the more amplification

3rd May 2011, 10:42 AM	#4
DF96 diyAudio Member Join Date: May 2007	Both clipping and non-linearity. The 12AX7 is very linear when driven into a high impedance load with adequate anode voltage. Two options: study the data sheet, or try it and see.

3rd May 2011, 08:00 PM	#5
SamiBami diyAudio Member Join Date: May 2011	What plate voltage would you suggest for this application?

3rd May 2011, 09:27 PM	#6
DF96 diyAudio Member Join Date: May 2007	Sorry, I design for low distortion so I haven't a clue. I'm sure someone will be able to help.

3rd May 2011, 10:56 PM	#7
mario13 diyAudio Member Join Date: Jul 2010	it depends on the circuit. I built a similar OD with a 12ax7 in cascode. My plate voltage was about 125v. It was a litle clean for my liking so i addaed some clipping doides as well. Experiment with low voltages first and see how it sounds. Best of luck! Mario.

4th May 2011, 09:54 AM	#8
mastodon diyAudio Member Join Date: Jan 2011	Try running the first half of the ax7 on a high plate voltage (150V or more) for lots of gain, then couple the signal into the second half which you run at a low voltage (50V or less) to drive it deep into distortion.

4th May 2011, 04:57 PM	#9
SamiBami diyAudio Member Join Date: May 2011	Thanx guys for your answers if any body has something to add..

4th May 2011, 08:50 PM	#10
Merlinb diyAudio Member Join Date: May 2006 Location: York	You may like to look at one of the many DIY valve overdrive pedals: The Real McTube Article: How It Works http://www.diystompboxes.com/pedals/.../shakatube.gif Beavis Audio Research