Tubes Asylum

Heater Voltage For 12au7's

74.44.74.164

rosendds@frontiernet.net

My Clarinet preamp heater voltage for the 12au7's is 6.7 volts.It works fine,but the tubes have a dim glow.Is that enough heater voltage?

Follow Ups:

It's unusual that 12AU7s in preamps are run as paralleled filaments. - Michael Samra 16:15:35 03/19/14 (4)
If the preamp is running with the filaments at pins 4,5,and 9 at 6.3vdc,that would be fine..If the 12AU7s are using pins 4 and 5 and only,you need 10.8vdc to 12vdc.Do you have a schematic?

Honest amplification is better than excessive 2nd order distortion anytime.
- RE: It's unusual that 12AU7s in preamps are run as paralleled filaments. - rosendds@frontiernet.net 06:36:57 03/20/14 (3)
  The schematic is posted on Hagerman's web site.I will look at which pins are used.
  - RE: It's unusual that 12AU7s in preamps are run as paralleled filaments. - rosendds@frontiernet.net 06:44:17 03/20/14 (2)
    The schematic posted doesn't show how the heater supply is wired.I saw a post on the web forum advising checking heater voltage between pins 4,9.
    - RE: It's unusual that 12AU7s in preamps are run as paralleled filaments. - Michael Samra 13:09:20 03/21/14 (1)
      The filaments are in parallel just by the fact you are checking between pins 4 and 9.. You are ok with 6.7vdc and it wouldn't hurt to drop it s tad.
      
      Honest amplification is better than excessive 2nd order distortion anytime.
      - RE: It's unusual that 12AU7s in preamps are run as paralleled filaments. - rosendds@frontiernet.net 13:28:00 03/21/14 (0)
        
        In Reply to: RE: It's unusual that 12AU7s in preamps are run as paralleled filaments. posted by Michael Samra on March 21, 2014 at 13:09:20
        
        Thanks!
RE: Heater Voltage For 12au7's - TubeAcolyte 14:54:05 03/19/14 (2)
Nah nah, everything should be fine. Heaters run 6.3v typically. So at 6.7 you're over. Max is 6.9v. Is this an older piece of tube equipment?

Just because it doesnt glow hard, it doesnt mean its not working hard :) I have had similar experiences. Shouldn't be a worry.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively and long-lasting. Holy be thy heater.
- RE: Heater Voltage For 12au7's - rosendds@frontiernet.net 15:26:20 03/19/14 (1)
  Thanks for the information.It is a kit built Hagerman Clarinet linestage.
  - ASk - unclestu 15:31:31 03/19/14 (0)
    Jim Hagerman: he is quick to respond and will offer a solution.

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

The Cable Cooker