The purpose of R0 in Aleph 30 circuit - 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 28th March 2005, 06:07 AM   #1
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Default The purpose of R0 in Aleph 30 circuit

I have a question with regards to the actual purpose of R0 in Aleph 30 circuit. It's been said that this resistor breaks ground loops, but I can't quite figure out how it does that. I mean, would it make any difference if R4/R5 were connected directly to signal ground, as it seems like signal ground connects to those resistors through R0?
http://www.passlabs.com/downloads/ol...t/a30manr0.pdf
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 28th March 2005, 08:19 AM   #2
Account Disabled
 
Join Date: Aug 2002
Location: Near to the Pacific Ocean
It seems to be for the zeners not directly to see the ground.
  Reply With Quote
Old 28th March 2005, 08:53 AM   #3
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
R0 is not strictly necessary, but I think of it as a resistor in the ground loop, reducing the amount of hum-current. Call it some sort of ground lift.

/Hugo
  Reply With Quote
Old 28th March 2005, 10:02 AM   #4
diyAudio Member
 
Join Date: Dec 2002
Location: Poland
I think, that it is here to prevent zener diodes from blowing when they get the voltage more than expected.
__________________
Jarek
  Reply With Quote
Old 28th March 2005, 10:30 AM   #5
diyAudio Member
 
Join Date: Dec 2002
Location: Poland
Or better, to keep a low voltage at gates of the differential pair when diodes had blown.
__________________
Jarek
  Reply With Quote
Old 28th March 2005, 12:57 PM   #6
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
I thought initially that this is a resistor separating signal ground from output ground, but it does not seem to be a case (you can notice such resistor on National's LM4780 evaluation board). So in most cases it's probably not needed anyway ( as I'm also not using the input diodes).

I'm still considering improving the ground scheme on the A30 board. I recall Zigybait commenting that running separate ground paths from current source circuit and the signal ground to main star ground point improved performance.
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 28th March 2005, 03:25 PM   #7
diyAudio Member
 
Join Date: Dec 2002
Location: Poland
Quote:
I recall Zigybait commenting that running separate ground paths from current source circuit and the signal ground to main star ground point improved performance.
You can try to put an about 24V Zener diode between R13 and supply (-). Than you don’t need a connection R13 to the ground.
__________________
Jarek
  Reply With Quote
Old 28th March 2005, 08:54 PM   #8
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
As I recall, R0 simply helped to break the RCA connection
loop going back to the source equipment. There was a
little less noise this way, and both the input and feedback
referenced to it, so it didn't compromise performance. If you
don't need it, there's no requirement to use it.

  Reply With Quote
Old 28th March 2005, 09:47 PM   #9
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Now I understand it, thanks for that info.
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  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
Aleph P Attenuation Circuit amo Pass Labs 13 6th October 2011 07:20 PM
What is the purpose of TL431 in this circuit? Sunsun22 Digital Source 16 30th October 2006 09:36 AM
The HotRod Aleph Circuit Board Blues Pass Labs 148 9th September 2006 04:37 PM
Purpose of Parallel Capacitor with AD811 I/V circuit? fastcat95 Digital Source 3 9th February 2005 05:09 PM
Aleph P1.7 circuit question Peter Daniel Pass Labs 6 22nd May 2002 03:43 AM


New To Site? Need Help?

All times are GMT. The time now is 07:11 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