Dual opamps - best PSRR - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 11th April 2010, 10:01 AM   #1
diyAudio Member
 
Join Date: Jun 2007
Default Dual opamps - best PSRR

Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.

Additionally, the headphone amp this is for uses a circuit which biases the output heavily into class A - any chips out there which would benefit from this?
  Reply With Quote
Old 11th April 2010, 05:51 PM   #2
Minion is offline Minion  Canada
diyAudio Member
 
Join Date: May 2006
Location: Cowican Bay , vancouver island
Just add some Bypass caps close to the IC Pins , It will filter out some of the PSU noise ...... Or built a well filtered Regulated supply and drop the wall mart ....

The OPA2134 doesn"t have Bad PSSR and getting an opamp with better PSSR still doesn"t get rid of the problem of a Noisy PSU .....


Cheers
  Reply With Quote
Old 11th April 2010, 07:29 PM   #3
diyAudio Member
 
Join Date: Jun 2009
Best PSRR I know of is National's LME49990, though I suspect it'll be some time before a dual version's available. The LME49720/49860 offer a slight gain over the 2134 (but their main advantage is they sound a bit more precise, probably due to the higher GBP). If you want more rejection you'd be better off throwing together a basic 7815/7915 type supply; that'll give you 60-80dB versus the 10-30dB from an op amp upgrade. Chips are cheaper too. Seeing as the 2134s are ~110dB I'd be surprised if PSRR is really an issue; have you measured the ripple or checked for bad bypass caps?

In other words, what Minion said.
  Reply With Quote
Old 12th April 2010, 02:41 AM   #4
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by lordearl View Post
Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.
With typical decoupling arrangements, your performance is probably not going to be PSRR limited. Rather it will most likely be limited by power supply hash coming down onto the signal ground through the decoupling capacitors. Better to regulate the wall wart (relatively easy) or rejig the grounding (more difficult).

Quote:
Just add some Bypass caps close to the IC Pins , It will filter out some of the PSU noise ...... Or built a well filtered Regulated supply and drop the wall mart ....
So long as those caps are between the rails, it could be a good idea. If you tie them to the signal ground, all that happens is you dump power supply rubbish on your ground. The second option is sounder.
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.

Last edited by abraxalito; 12th April 2010 at 02:46 AM.
  Reply With Quote
Old 13th April 2010, 02:48 AM   #5
diyAudio Member
 
Join Date: Jun 2007
Thanks people - that's a great start. I'm going to build a better PSU. My headamp pcb already has 470uF caps on it, so you are probably correct simply swapping the opamp may not make too much differece. I notice that OPA2134 gives a nice, well defined bass, but the top end is a little shrill and not as tightly defined as the bass - how would the LME49990 compare with this?
  Reply With Quote
Old 13th April 2010, 12:21 PM   #6
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Quote:
Originally Posted by lordearl View Post
Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.
So measure the output off and on load to see what the regulation is.
Scope the output under load to see what the ripple/noise is.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 13th April 2010, 12:24 PM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by lordearl View Post
........ I notice that OPA2134 gives a nice, well defined bass, but the top end is a little shrill
is the decoupling as recommended by the opamp manufacturer? Have you seen any reliable references to alternative decoupling that improves on the manufacturer's recommendation.
__________________
regards Andrew T.
  Reply With Quote
Old 13th April 2010, 12:35 PM   #8
diyAudio Member
 
Join Date: Jun 2007
Thanks Mooly & AndrewT -
(1) How to I measure the regulation with a multimeter (bear in mind I'm a newbie).
(2) I've attached the circuit for one channel - C3 is 470uF because I'm using a wall wart - does this clarify anything (unsure whether this cap is 'decoupling' anything).
Attached Images
File Type: jpg headamp.jpg (32.9 KB, 147 views)

Last edited by lordearl; 13th April 2010 at 12:43 PM.
  Reply With Quote
Old 13th April 2010, 12:37 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
do you have the datasheet to hand?
It will explain in detail the decoupling required.
__________________
regards Andrew T.
  Reply With Quote
Old 13th April 2010, 12:56 PM   #10
diyAudio Member
 
Join Date: Jun 2007
you mean this;
"Power supply pins should be bypassed with 10nF ceramic capacitors or larger to
minimize power supply noise."

If that's the case, sounds quite possible - how do I wire it in?
  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
The Best Sounding DUAL opamps mudihan Chip Amps 251 28th August 2014 08:05 AM
Burson Dual Opamps (EU) Slash47 Swap Meet 6 19th April 2010 12:09 AM
DIP14 adapters for dual SO8 opamps pmkap Parts 1 3rd December 2009 12:45 PM
Which dual opamps should I try for I/V conversion? homemade Digital Source 11 6th October 2006 09:26 PM
FS: Power Chip OpAmps and other OpAmps & D to A Converter dtm1962 Swap Meet 4 12th January 2006 11:07 PM


New To Site? Need Help?

All times are GMT. The time now is 11:35 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