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 13th March 2013, 10:10 PM   #2071
diyAudio Member
 
bnorrish's Avatar
 
Join Date: Oct 2012
Location: Boston
Quote:
Originally Posted by wayne View Post
When I layed out the Pearl Two allowance was made for a lag capacitor around the ZVP3310. After building more of them I find it is not needed. I suggest you just leave it out. Your mileage may vary if you roll your own boards or change parts. Saves finding a good 10 PF cap.
Quote:
Originally Posted by wayne View Post
As an experiment try R16 at 100K. Also on one version I built, C7 caused oscillation. Remember it isn't fixed until you can break it and fix it at will.
The DC flip flop can be oscillation caused.
Sounds like I should pull C7.

I read this before building it - need to carve a half a day and re-read the entire thread.
  Reply With Quote
Old 13th March 2013, 11:26 PM   #2072
milosz is offline milosz  United States
diyAudio Member
 
Join Date: Oct 2006
Pearl (first version, not Pearl II)

LINK TO TESTS OF PEARL MK I

Click the image to open in full size.
  Reply With Quote
Old 14th March 2013, 02:38 AM   #2073
diyAudio Member
 
bnorrish's Avatar
 
Join Date: Oct 2012
Location: Boston
Pulling C7 seems to have fixed my issue. DC offset very stable on both channels > +/- 20 mv. No oscillation.
  Reply With Quote
Old 14th March 2013, 02:39 AM   #2074
diyAudio Member
 
bnorrish's Avatar
 
Join Date: Oct 2012
Location: Boston
Milosz. Nice tests, data. Ready to build a Pearl 2?
  Reply With Quote
Old 14th March 2013, 04:29 AM   #2075
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally Posted by bnorrish View Post
Pulling C7 seems to have fixed my issue. DC offset very stable on both channels > +/- 20 mv. No oscillation.
Those trannsistors in the vendors must be different enough inside by now than what Wayne compensated in the original design then...
  Reply With Quote
Old 14th March 2013, 04:52 AM   #2076
rsavas is offline rsavas  Canada
diyAudio Member
 
Join Date: Aug 2012
Location: Ontario
Suggest to read Bob Cordell's Audio PAmp book p226, this may better explain whats going on. One way or the other you have managed to figure out how to make the circuit oscillate.
  Reply With Quote
Old 14th March 2013, 05:00 AM   #2077
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
He had it before manipulating stage 1 though.
  Reply With Quote
Old 14th March 2013, 07:45 AM   #2078
milosz is offline milosz  United States
diyAudio Member
 
Join Date: Oct 2006
Quote:
Originally Posted by bnorrish View Post
Milosz. Nice tests, data. Ready to build a Pearl 2?
Don't need the extra gain.
  Reply With Quote
Old 14th March 2013, 09:52 AM   #2079
diyAudio Member
 
bnorrish's Avatar
 
Join Date: Oct 2012
Location: Boston
Quote:
Originally Posted by rsavas View Post
Suggest to read Bob Cordell's Audio PAmp book p226, this may better explain whats going on. One way or the other you have managed to figure out how to make the circuit oscillate.
I just read, Mosfets are fast and prone to oscilliation. Discusses topologies to combat (Gate Zobel network). Does not discuss effect of lag cap around MOSFET and oscillation like the Pearl 2. Wayne has experienced as well and recommends eliminating cap around Mosfet. Not going to worry how I (and others including Wayne) managed to make the circuit oscillate.
  Reply With Quote
Old 14th March 2013, 11:56 AM   #2080
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
Quote:
Originally Posted by bnorrish View Post
Not going to worry how I (and others including Wayne) managed to make the circuit oscillate.
What's the saying...

"If you want to build an amplifier, you will likely get an oscillator.

If you want an oscillator, you will likely get an amp. "
__________________
Illustrated Build Guides - Pass F4 - Pass B1 - Pass F5 - Pearl 2 - O2 HPA - Hagerman Bugle 2 - Pass Aleph J - Me at BA '13
  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
Another diy-pearl... lykkedk Pass Labs 18 15th June 2007 04:44 PM
ono or pearl PCB's mantisory Pass Labs 1 28th September 2006 11:12 PM
Pearl need help dzkh63 Pass Labs 1 26th September 2006 03:16 PM
WTB: Pearl PCB aire Pass Labs 1 26th February 2006 10:51 AM


New To Site? Need Help?

All times are GMT. The time now is 02:05 PM.


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