Burning Amplifier BA-2 - Page 100 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 23rd January 2012, 11:22 AM   #991
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
be careful.
Higher bias in the output stage also pulls higher bias in the preceding stages.

Changing the bias of these transistors can/will move them to a different operating point where their parameters are different.

I think these changes can change the stability margins of the standard amplifier.
One that shows no oscillation during any testing, may now show damped oscillation on a part of a signal waveform.
__________________
regards Andrew T.
  Reply With Quote
Old 23rd January 2012, 11:30 AM   #992
oiphy is offline oiphy  Norway
diy newbie
diyAudio Member
 
oiphy's Avatar
 
Join Date: Sep 2011
Location: norway
so for now its probably better to leave bias at 250mA and finnish the BA3 merge them and listen?
When you say osilate what exactly do you mean? is this what I'm seeing on output as it moves a little round +- some mV? this normal?
as I've said earlier I'm a newbee....so please have patience with me.
__________________
" If you're going throu hell, keep going"
  Reply With Quote
Old 23rd January 2012, 11:31 AM   #993
diyAudio Member
 
Join Date: Sep 2008
I have the bias set at 400mV. At this bias the heatsinks stay within the temp suggested by Mr. Pass. Nelson has written that the mosfets do benefit from running at a higher bias if the heatsinks are up to it and all I can say is that the amp sounds very good at 400mV.
What is your DC offset?

Last edited by Backbones; 23rd January 2012 at 11:33 AM.
  Reply With Quote
Old 23rd January 2012, 11:39 AM   #994
diyAudio Member
 
Join Date: Sep 2008
Zobel networks.
I have been using a Zobel across the loudspeaker wires for some years. If values and components are chosen properly one can get tighter bass, less brittle and hard upper frequencies. Since I took out the RC components of the BA-2 board for the Salas reg I have noted an immense clarity to the sound but also some hardness creeping in to the upper mid frequencies and perhaps a little too much upper frequency energy. After scratching my head a little I reversed the Zobel so that the cap made contact with ground and the resistor on the +ve terminal. This has abolished the hardness and over bright upper fequencies whilst retaining the overall clarity.
  Reply With Quote
Old 23rd January 2012, 11:42 AM   #995
oiphy is offline oiphy  Norway
diy newbie
diyAudio Member
 
oiphy's Avatar
 
Join Date: Sep 2011
Location: norway
dc offset 0v to -0.5mV moves a little around. meassured from +- binding post.
__________________
" If you're going throu hell, keep going"
  Reply With Quote
Old 23rd January 2012, 11:47 AM   #996
diyAudio Member
 
Join Date: Sep 2008
Quote:
Originally Posted by oiphy View Post
dc offset 0v to -0.5mV moves a little around. meassured from +- binding post.
That's good. Why don't you listen to the amps at this bias and then if you want to at a later date turn up the bias and let us know what differences you can hear.
  Reply With Quote
Old 23rd January 2012, 11:54 AM   #997
oiphy is offline oiphy  Norway
diy newbie
diyAudio Member
 
oiphy's Avatar
 
Join Date: Sep 2011
Location: norway
ok. will then finish both amps,(2x mono) listen and report back later. will take some time.... home with sick kid today so... later.

anyhow. all help is mutch appriciated.
wish you all an exelent week
__________________
" If you're going throu hell, keep going"
  Reply With Quote
Old 23rd January 2012, 02:12 PM   #998
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally Posted by Backbones View Post
......After scratching my head a little I reversed the Zobel so that the cap made contact with ground and the resistor on the +ve terminal. This has abolished the hardness and over bright upper fequencies whilst retaining the overall clarity.
can you imagine amount of head-scratching if someone , during the night , again rotate position of cap and resistor in Boucherot , and you don't spot any difference ..........

block cap and resistor pretty much don't care where their head is , only ppl take too much care of it

__________________
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
Old 24th January 2012, 12:02 PM   #999
diyAudio Member
 
Join Date: Sep 2008
Quote:
Originally Posted by Zen Mod View Post
...someone , during the night , again rotate position of cap and resistor in Boucherot , and you don't spot any difference ..........

:
But who would do a thing like that?
  Reply With Quote
Old 24th January 2012, 12:13 PM   #1000
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally Posted by Backbones View Post
But who would do a thing like that?
RC chain is R and C series connected - between two nodes ;

it's irrelevant is it RC or CR

__________________
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


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
Burning Amplifier BA-2 Nelson Pass diyAudio.com Articles 5 14th September 2011 07:11 PM
The Burning Amp Festival-Burning Gadgets Preview Zen Mod Everything Else 115 27th October 2007 06:50 PM


New To Site? Need Help?

All times are GMT. The time now is 08:19 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2