Buffer pre-amp - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 31st August 2010, 07:56 AM   #11
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Great ! I think this is the first time somebody does that in public. I always try to avoid common mode distortion in my designs but actually i measure and did not do listening tests other then checking the finished circuit.
  Reply With Quote
Old 31st August 2010, 10:32 AM   #12
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default opamp follower

is the cancellation resistor a resistance in the normally seen shorting link of the opamp as (non-inverting) unity gain follower?

Normally we see Output connected to -IN as a direct short.

This has come up in a couple of other threads recently.
__________________
regards Andrew T.
  Reply With Quote
Old 31st August 2010, 11:12 AM   #13
sandyK is offline sandyK  Australia
diyAudio Member
 
Join Date: Apr 2007
Location: Sydney
Quote:
Originally Posted by AndrewT View Post
is the cancellation resistor a resistance in the normally seen shorting link of the opamp as (non-inverting) unity gain follower?

Normally we see Output connected to -IN as a direct short.

This has come up in a couple of other threads recently.
Andrew


This was done by Silicon Chip magazine in their Studio Series Preamplifier of October 2005 with an OPA2134.(P.29)

SandyK
  Reply With Quote
Old 31st August 2010, 12:43 PM   #14
diyAudio Member
 
panson_hk's Avatar
 
Join Date: Aug 2005
Blog Entries: 10
Quote:
Originally Posted by AndrewT View Post
is the cancellation resistor a resistance in the normally seen shorting link of the opamp as (non-inverting) unity gain follower?

Normally we see Output connected to -IN as a direct short.

This has come up in a couple of other threads recently.
Yes, this is a resistor between output and -IN.
  Reply With Quote
Old 1st September 2010, 03:34 AM   #15
diyAudio Member
 
panson_hk's Avatar
 
Join Date: Aug 2005
Blog Entries: 10
Quote:
Originally Posted by Joachim Gerhard View Post
Great ! I think this is the first time somebody does that in public.
Do you ware of the Samuel Groner opamp distortion report? http://www.sg-acoustics.ch/analogue_...distortion.pdf
  Reply With Quote
Old 1st September 2010, 03:36 AM   #16
diyAudio Member
 
panson_hk's Avatar
 
Join Date: Aug 2005
Blog Entries: 10
One more test data for CM distortion in voltage follower. The opamp under test is AD8620. Again, 12 k cancellation resistor seems to be a good choice.
Attached Images
File Type: jpg AD8620 THD vs freq vs Rs 1.JPG (127.9 KB, 437 views)
File Type: jpg AD8620 THD vs freq vs Rs 2.JPG (133.9 KB, 414 views)
File Type: jpg AD8620 THD vs freq vs Rs 3.JPG (137.3 KB, 396 views)
  Reply With Quote
Old 1st September 2010, 10:57 AM   #17
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Yes. I know Groners work and of cause i know what Dougas Self has to say about it. Sofar i have only seen and done measurement and a listening test whould be really interesting.
  Reply With Quote
Old 9th September 2010, 02:05 AM   #18
diyAudio Member
 
panson_hk's Avatar
 
Join Date: Aug 2005
Blog Entries: 10
Listening test is tough this comparison ... taking much longer time. I am still working on it.
  Reply With Quote
Old 22nd September 2010, 06:07 AM   #19
rabbitz is offline rabbitz  Australia
diyAudio Member
 
rabbitz's Avatar
 
Join Date: Jul 2003
Location: Newcastle, Australia
Silicon Chip mentioned in their article to use a resistor that's the same value as the wiper to ground resistance on the pot at your normal listening level. On my buffers I just tend to use 10% of the pot value.
__________________
No longer DIY active
  Reply With Quote
Old 12th February 2013, 12:39 PM   #20
diyAudio Member
 
Join Date: Dec 2001
Location: South Sweden
To necrobump this a bit :
How is the distortion affected by signal level, i e CM voltage, fex if you have a volume pot before the buffer? Here and in Selfs book the testing is done at quite high voltage.

I rarely feed 3Vrms into my power amps, as the distortion from the speakers probably outshine the buffer distortion by a couple of magnitudes then
__________________
listen! Can you hear that ...
  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
Arjen's tube buffer for pre-amp Josephjcole Class D 22 8th February 2010 01:18 PM
My pre-amp / buffer SimontY Solid State 12 15th November 2008 05:48 PM
Pre-Amp / Buffer on Ebay poynton Solid State 1 22nd June 2008 12:40 PM
Pre amp or Buffer for Inverted GC? 5150ed Chip Amps 9 11th July 2006 06:27 PM
Building a pre-amp output isolation buffer? rruss Solid State 4 18th October 2004 03:52 PM


New To Site? Need Help?

All times are GMT. The time now is 01:47 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