Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

How to test bias
How to test bias
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
Reply
 
Thread Tools Search this Thread
Old 20th March 2006, 09:52 PM   #1
adlaic is offline adlaic  United States
diyAudio Member
 
Join Date: Feb 2006
Location: united states
Default How to test bias

What is the bias and how do you test it on a transistor amp?

Thank You,

Adlai
  Reply With Quote
Old 20th March 2006, 10:36 PM   #2
darkfenriz is offline darkfenriz  Poland
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
You can measure idle current of output devices by measuring voltage drop on emitter/source resistors (>95% of amps have them) when no signal is applied to input. Every digital voltmeter can do this.
  Reply With Quote
Old 20th March 2006, 10:40 PM   #3
lgreen is offline lgreen  United States
diyAudio Member
 
lgreen's Avatar
 
Join Date: May 2003
Location: San Diego, USA
Quote:
Originally posted by darkfenriz
You can measure idle current of output devices by measuring voltage drop on emitter/source resistors (>95% of amps have them) when no signal is applied to input. Every digital voltmeter can do this.
we are not as smart as you, does this relate to bias? how so?

If I measure 1V drop across 0.5 ohm resistor, do you simply say V=IR and I = V/R so bias = 1/0.5= 2 amps per device. Then multiply by the # of devices to get bias/channel? Then multiply by # channels to get bias/ amp?
__________________
Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.
  Reply With Quote
Old 20th March 2006, 11:16 PM   #4
darkfenriz is offline darkfenriz  Poland
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
Quote:
Originally posted by lgreen

If I measure 1V drop across 0.5 ohm resistor, do you simply say V=IR and I = V/R so bias = 1/0.5= 2 amps per device. Then multiply by the # of devices to get bias/channel? Then multiply by # channels to get bias/ amp?
Yes, that's how I understand it, except idle current is the same through a pair of output devices.
  Reply With Quote
Old 20th March 2006, 11:38 PM   #5
cpemma is offline cpemma  United Kingdom
diyAudio Member
 
Join Date: Jul 2003
Location: S Yorkshire OK
Default Re: How to test bias

Quote:
Originally posted by adlaic
What is the bias and how do you test it on a transistor amp?
For what bias is/does, see this guide.

On the actual setting procedure, I found it slightly misleading in places, "Then, turn the amp off if you have only one set of speaker binding posts, or turn on Speakers B, and measure the DC offset." I'd just turn the volume right down, switching the amp power off seems a bit counter-productive.

If you can find a Service Manual for your amp it will advise on the manufacturer's recommended setting (and the test points to use).
  Reply With Quote
Old 21st March 2006, 12:19 AM   #6
anatech is online now anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
How to test bias
Quote:
If you can find a Service Manual for your amp it will advise on the manufacturer's recommended setting (and the test points to use).
Yes. There are some general rules that experience will teach you. Also, when you have multiple output pairs, make sure the current is shared relatively evenly. That's an indicator of transistor matching.

-Chris
  Reply With Quote
Old 21st March 2006, 12:30 AM   #7
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
How to test bias
Default Re: Re: How to test bias

Quote:
Originally posted by cpemma


For what bias is/does, see this guide.

On the actual setting procedure, I found it slightly misleading in places, "Then, turn the amp off if you have only one set of speaker binding posts, or turn on Speakers B, and measure the DC offset." I'd just turn the volume right down, switching the amp power off seems a bit counter-productive.


snake oil....

just another "expert" article,from series of "how to make that sheeety amp little less sheeety".......

I agree with you about manual- in any case manual is good for knowing exact procedure
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote

Reply


How to test biasHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Changing grid leak bias preamp to cathode bias bereanbill Tubes / Valves 8 28th March 2009 06:26 PM
Bias problem- 1 Socket shows extremely low bias! otokomae Tubes / Valves 12 31st December 2008 11:01 PM
Stray hum pickup *preamp* cathode R-bias vs. battery bias & 12AU7vs.5687 awedio Tubes / Valves 2 19th April 2008 02:30 AM
Battery grid bias to fixed bias in Toccato? w00t Tubes / Valves 3 2nd December 2007 01:34 AM
Supressed bias amplifier, automatic variable bias system. destroyer X Solid State 2 20th September 2004 11:24 AM


New To Site? Need Help?

All times are GMT. The time now is 05:38 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki