Bias mods - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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
Thread Tools Search this Thread
Old 12th January 2013, 06:39 PM   #1
diyAudio Member
Join Date: Nov 2006
Default Bias mods

I will build soon my vavle preamp. Before begining my construct i would like to add an adjustable bias. Indeed, in order to change voltage i have to change two resistors : one of 660R/20W(It's expensive) and one of 4K7/11w... the process is not very convenient...
I try to discover how i can add 2 pots bias instead of the two resistors ?

Thank you in advance for your help.

ps: i have found this schematic on the web, do you think it is possible to adapt it to resolve my problem ?
Attached Images
File Type: jpg alim - Copie.jpg (63.3 KB, 104 views)
  Reply With Quote
Old 12th January 2013, 08:42 PM   #2
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
Why do you want to adjust the bias on your preamp? Do you mean the DC power supply voltage B+/HT?

What problem are you trying to solve?
  Reply With Quote
Old 12th January 2013, 09:10 PM   #3
diyAudio Member
cogsncogs's Avatar
Join Date: Jul 2003
Location: Wayne, West Virginia
Looks to me that the power supply you posted is intended for a power amplifier, rather than a preamp.
  Reply With Quote
Old 13th January 2013, 02:03 AM   #4
diyAudio Member
Robert Kesh's Avatar
Join Date: Oct 2012
A pre amp will not need 20W resistors.

Bias is not done at the power supply, it's typically done at the cathodes.
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Soundstream Picaso - Bias and mods question JZatopa Solid State 26 8th April 2013 06:53 PM
Dynamic Bias - Active Bias - Automatic/Self biased - Overview wanted tiefbassuebertr Pass Labs 16 29th July 2012 04:03 PM
Stray hum pickup *preamp* cathode R-bias vs. battery bias & 12AU7vs.5687 awedio Tubes / Valves 2 19th April 2008 01:30 AM
hafler 9180 BIAS+Mods bluesmoke Solid State 25 12th April 2006 04:14 AM
Supressed bias amplifier, automatic variable bias system. destroyer X Solid State 2 20th September 2004 10:24 AM

New To Site? Need Help?

All times are GMT. The time now is 09:56 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2