John Curl's Blowtorch preamplifier part II - Page 3733 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

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 26th March 2013, 11:42 AM   #37321
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Regardless low supply voltage, OPA836 has VERY high noise and VERY low quiescent current. No good for audio, would be source of troubles only.
Attached Images
File Type: png 16.PNG (24.8 KB, 180 views)
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 26th March 2013, 12:03 PM   #37322
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Hmmm, just looked at the AD797 sheet, the OPA836 has 4 times the noise voltage amplitude - does that take it from a winner to a loser?

Frank
  Reply With Quote
Old 26th March 2013, 12:33 PM   #37323
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
High 1/f corners.
  Reply With Quote
Old 26th March 2013, 12:46 PM   #37324
fas42 is offline fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 11
Got it ...

Frank
  Reply With Quote
Old 26th March 2013, 01:06 PM   #37325
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
John and Scott (and everyone else). If you had a design brief that said you had to use one of todays dual opamps as a unity gain buffer, what devices might you consider, if the goal was putting sonics above all else. Just one or two examples you might consider worthy to work with from all todays countless offerings.

Also I read that Nelson (probably not alone in this) advocates "throwing away" some open loop gain, either by increasing the noise gain for inverting configurations or (presumably) attenuating and then amplifing for non inverting unity gain. Any thoughts on that ? I think the argument is that many devices run with 100% feedback are right on the ragged edge stability wise.

(I know there are more opamp rolling threads than you can shake a stick at but I'd really value your opinion)
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 26th March 2013, 01:10 PM   #37326
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I wouldn't use an op amp for that use. I got 'burned' the last time I tried. Nelson is probably right.
  Reply With Quote
Old 26th March 2013, 01:17 PM   #37327
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Quote:
Originally Posted by john curl View Post
I wouldn't use an op amp for that use. I got 'burned' the last time I tried. Nelson is probably right.
Fair enough... but if push came to shove and you had to go down the opamp route (lets say no discrete alternative due to board space) what might you use ?
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 26th March 2013, 01:33 PM   #37328
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Please ask someone else, Mooly. I don't have a convenient answer.
  Reply With Quote
Old 26th March 2013, 02:57 PM   #37329
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by Mooly View Post
Fair enough... but if push came to shove and you had to go down the opamp route (lets say no discrete alternative due to board space) what might you use ?
No need to shove and I'm not the one for listening tests but a modern JFET dual like AD8066 would do. I don't see the noise as an issue at G = 1. Those are free for me there are more choices out there.
__________________
"Greetings from The Humungus! The Lord Humungus! The Warrior of the Wasteland! The Ayatollah of Rock and Rolla!" aka the Wizard of Wrestling.
  Reply With Quote
Old 26th March 2013, 03:33 PM   #37330
godfrey is online now godfrey  South Africa
diyAudio Member
 
Join Date: Nov 2009
Location: Cape Town
Quote:
Originally Posted by Mooly View Post
Also I read that Nelson (probably not alone in this) advocates "throwing away" some open loop gain, either by increasing the noise gain for inverting configurations or (presumably) attenuating and then amplifing for non inverting unity gain. Any thoughts on that ?
You can do it like this. For unity gain, just leave out R3.
Attached Images
File Type: gif throw away.GIF (2.1 KB, 153 views)
  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



New To Site? Need Help?

All times are GMT. The time now is 04:14 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