Recommendation for a good CMOS op-amp? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 19th October 2004, 02:51 PM   #1
rruss is offline rruss  United States
diyAudio Member
 
Join Date: Oct 2004
Default Recommendation for a good CMOS op-amp?

I'm trying to add pre-amp outputs to my Denon receiver. The intent is to add a buffer in parallel with the final amplifier stage in the receiver to effectively "port-out" the pre-amp signals without loading them.

I've gotten great recommendations on building an op-amp buffering stage, but the recommendation was to use a 5532 op-amp. This BJT op-amp may have an input impedance that loads the pre-amp stage more than desired.

Can anyone recommend a CMOS op-amp with excellent audio characteristics? Again, my goal is to buffer out the pre-amp signal without loading it internally...

Thanks,
-Russ
  Reply With Quote
Old 19th October 2004, 04:02 PM   #2
Mr Evil is offline Mr Evil  United Kingdom
diyAudio Member
 
Join Date: Aug 2004
Location: Behind you
I think a CMOS op-amp would be overkill. A normal FET-input op-amp would give a high enough input impedance. Of those, OPA604 is alright, or OPA627 if you have cash to spare.
__________________
https://mrevil.asvachin.eu/
  Reply With Quote
Old 19th October 2004, 10:32 PM   #3
diyAudio Member
 
Join Date: Oct 2004
The load of ANY op amp is more than 1Mohm|| a few pf and is at high frequencies less than a few inches of cable.
Use any OP that sounds good.
  Reply With Quote
Old 20th October 2004, 09:36 AM   #4
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
"The load of ANY op amp is more than 1Mohm"

Read the data sheet for a 5532, they say 300K typical but only guarantee 40K.
  Reply With Quote
Old 20th October 2004, 09:39 AM   #5
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Default Re: Recommendation for a good CMOS op-amp?

Quote:
Originally posted by rruss
Can anyone recommend a CMOS op-amp with excellent audio characteristics?
I'm afraid but there aren't any good CMOS opamps good enough for high quality audio (correct me if I'm wrong). Why don't you choose any JFET opamp? You have tons of them.

In fact almost any audio opamp bipolar and JFET will do.

What are you demands for "loading"?
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 20th October 2004, 09:42 AM   #6
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
Originally posted by djk
"The load of ANY op amp is more than 1Mohm"

Read the data sheet for a 5532, they say 300K typical but only guarantee 40K.
Note this is _without_ feedback. With feedback it is higher and you can't use the opamp without feedback, not for audio at least.
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 20th October 2004, 09:47 AM   #7
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Default Re: Recommendation for a good CMOS op-amp?

Quote:
Originally posted by rruss
Can anyone recommend a CMOS op-amp with excellent audio characteristics? Again, my goal is to buffer out the pre-amp signal without loading it internally...
You need

input impedance > 10 kohms, 100 kohms is good

output impedance < 1 kohms, 100 ohms is good

Speed, 5-50 V/us is normal

Noise <10 nV/sqrHz

Many opamps will fit this description
__________________
/Per-Anders (my first name) or P-A as my friends call me
  Reply With Quote
Old 20th October 2004, 05:51 PM   #8
diyAudio Member
 
Join Date: Oct 2004
Load impedance of NE5532 is 30 - 300kohm alright, but referred to what. Of course from pos input to neg input, elemetary electronics gives that this resistance is multiplied with the
open loop gain. This means that the Real input impedance is enormous. It is one thing to read specs, yet another to understand them ; )
  Reply With Quote
Old 20th October 2004, 09:39 PM   #9
diyAudio Member
 
EchoWars's Avatar
 
Join Date: Dec 2002
Location: Left of the Dial
He knows better...he's just nit-picking.

I happen to like the 5532, and it would work fine for what you intend. There are other options though.....
  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
need recommendation good sounding transistor tomat Solid State 6 8th July 2009 11:48 AM
Recommendation on good USB-SPDIF interface? kop89 Digital Source 13 2nd August 2008 08:51 AM
does someone have a good cmos overdrive schematic ??? prorms Instruments and Amps 7 3rd March 2008 11:33 AM
3.3v to 5v CMOS interfacing Zodiac Digital Source 9 15th May 2006 11:11 PM


New To Site? Need Help?

All times are GMT. The time now is 01:52 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