Burning Amplifier BA-2 - Page 92 - 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 16th December 2011, 10:15 AM   #911
diyAudio Member
 
Join Date: Sep 2008
Quote:
Originally Posted by Zen Mod View Post
do your homework - read all Papa's papers , if not for your own pleasure - then from respect for his sharing ; papers are written to be read .

adjust DC offset on output with P2 on output stage
He's absolutely right.
  Reply With Quote
Old 16th December 2011, 08:52 PM   #912
diyAudio Member
 
Join Date: Nov 2010
Location: Athens Greece
Quote:
Originally Posted by Zen Mod View Post
I told you about possible differences between source resistors (in value )

those 150 ohms resistors aren't "bias resistors" in any meaning ; they're gate stoppers , intended for preventing oscillations and somewhat for shaping frequency response of mosfets

do your homework - read all Papa's papers , if not for your own pleasure - then from respect for his sharing ; papers are written to be read .

adjust DC offset on output with P2 on output stage
Dear Zen Mod,
Appreciating your "refer to "on fundamental references.
I myself have studied the manual very thoroughly.
If you have the time to read with more attention you will see that i have pointed out on post 901 on this thread that I do not have any other turns to trim on P102.
Additionally
When you suggested to check the source resistors for possible variances i thought that measuring also the 150 ohm resistors is a good idea in terms of providing a more complete picture.
If this measurement is irrelevant to the problem i do apologize.
Finally please do not make any assumptions that lead to falls conclusions.
In any case thanks for all your help and support.
  Reply With Quote
Old 16th December 2011, 09:05 PM   #913
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Measure the source resistors to see if the fets are sharing current equally or close. If you followed the schematic exactly, they should be the 1R 3W resistors.
  Reply With Quote
Old 16th December 2011, 09:38 PM   #914
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 nikosgrgr View Post
.....
Finally please do not make any assumptions that lead to falls conclusions.
........
nobody is perfect , except me ....... and (just ) maybe Papa .....

anyway - fact is that you mention gate resistors as possible culprit in individual biasing of mosfets ; that can lead to confusion any other greenhorn reading these posts in future ....



turn off amplifier ;

turn pot P2 approx. to middle position ;

if offset is positive - solder 220K resistor across R25
if offset is negative - solder 220K resistor across R26

turn on , set offset with P2

setting offset - referring to this attached schematic :

(FE doesn't have anything with output offset )
Attached Images
File Type: jpg BA2-output.jpg (75.3 KB, 243 views)
__________________
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

Last edited by Zen Mod; 16th December 2011 at 09:51 PM.
  Reply With Quote
Old 16th December 2011, 10:31 PM   #915
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Quote:
Originally Posted by Zen Mod View Post
nobody is perfect , except me ....... and (just ) maybe Papa .....

anyway - fact is that you mention gate resistors as possible culprit in individual biasing of mosfets ; that can lead to confusion any other greenhorn reading these posts in future ....



turn off amplifier ;

turn pot P2 approx. to middle position ;

if offset is positive - solder 220K resistor across R25
if offset is negative - solder 220K resistor across R26

turn on , set offset with P2

setting offset - referring to this attached schematic :

(FE doesn't have anything with output offset )
Is this to compensate for possibly unusual difference in N vs P parts? Reason for checking offset polarity is to identify which side is in need of compensation.
  Reply With Quote
Old 16th December 2011, 10:36 PM   #916
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
sort of
nothing to write home about
__________________
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 17th December 2011, 02:01 PM   #917
diyAudio Member
 
Join Date: Sep 2008
Nelson mentions using some large capacitors between the BA-2 front end and any voltage regulator. Any idea how large?
I'm using Salas SSLV1.1.
  Reply With Quote
Old 17th December 2011, 02:28 PM   #918
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by Backbones View Post
Any idea how large?
high impedance load = smaller cap
lower load impedance = bigger cap
  Reply With Quote
Old 17th December 2011, 02:30 PM   #919
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
if reg is situated near BA FE , you don't need additional decoupling , especially with shunt regs , where too much of capacitance on output is counter-productive

if reg is situated at more than , say ,10cm from BA FE , you'll need some local decoupling , just in case
__________________
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 17th December 2011, 02:36 PM   #920
diyAudio Member
 
Join Date: Nov 2010
Location: Athens Greece
Quote:
Originally Posted by buzzforb View Post
Measure the source resistors to see if the fets are sharing current equally or close. If you followed the schematic exactly, they should be the 1R 3W resistors.
Dear Buzzforb hi,
Olready did that
Post #907
I do not see significant value differences on the source resistors .
Left channel
IRFP9240 (40mV bracket)
1ohm
1ohm
1,1ohm
1,1ohm
1.1ohm
Right channel (10mV bracket)
IRFP9240
1,1ohm
1,1ohm
1,1ohm
1,1ohm
1,1ohm


Thanks
  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 06:11 PM
The Burning Amp Festival-Burning Gadgets Preview Zen Mod Everything Else 115 27th October 2007 05:50 PM


New To Site? Need Help?

All times are GMT. The time now is 11:50 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