Thoughts on the sound quality of one op amp full feedback phono stages. - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, 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 4th July 2014, 07:42 AM   #1
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
Default Thoughts on the sound quality of one op amp full feedback phono stages.

G'day all, over the years I have built or bought quite a few solid state/op amp based MM phono stages that all work well although they all sound a little different.

This might be due to slight differences in the RIAA eq and there may be other reasons too. The popular one op amp full feedback design is potentially a good one however some designs of this type that I've built have sounded great, and others a bit 'ordinary'.

Recently I built a stripped down (moving magnet cartridges only) version of this design Op-amp Based RIAA Phono Preamp for MM and MC Phono Cartridges and it sounds tremendous, much better than its circuit suggests and I wonder why?

Looking at the components in the feedback loop there are many possibilities that will provide accurate RIAA eq but the one used in this circuit sounds great, for some reason. In fact my Shure M97xE (with its OEM stylus) sounds particularly nice with this phono stage which hasn't always been the case with other similarly designed phono stages, even with optimum capacitance loading of that cartridge.

Again, looking at the circuit, nothing really stands out, but for whatever reason it does sound great! Any thoughts or comments? Regards, Felix.
  Reply With Quote
Old 4th July 2014, 07:58 AM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I doubt deviations from the RIAA response account for any major sonic differences tbh, at least not in the sense that you mean.

I suspect its more a classic case of "the whole being more than the sum of its parts", possibly the FET opamp (which is highly regarded for audio) sounds particularly pleasing used at such high gain and where its distortion profile may change somewhat.

Only detailed measurement with the right gear would show if that was a possible reason though.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 4th July 2014, 08:03 AM   #3
vulejov is offline vulejov  Serbia
Sin Bin
 
Join Date: Aug 2010
Few days ago I made this single-opamp MC phono..

First try was with LT1028, sounds good.. than change for AD797, now is excellent..
Attached Images
File Type: jpg PHONO.JPG (67.7 KB, 233 views)
File Type: jpg PHONO (2).JPG (188.7 KB, 232 views)
  Reply With Quote
Old 4th July 2014, 08:18 AM   #4
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
G'day all. Mooly: thanks for that. I suspect that 'interesting' and possibly unexpected things happen in the feedback loop of the op amp!

The OPA2134 'sound' is something that I've often umed and ared about. I personally can hear and like the sound of the OPA2134, yet I've read so much on the 'net that considers the whole subject of op amp sound a myth.

I honestly suspect that op amp sound is real, but cannot be 'measured' accurately easily, and possibly is dependent on other factors as you inferred.

For what it's worth I've used many different dual op amps like the TL072, LM833, NE5532 and other dual op amps with good results, however I 'think' that I hear the OPA2134 as the nicest sounding. Even the manufacturer implies this, but offers absolutely no evidence to support it. Regards, Felix.

Last edited by fap; 4th July 2014 at 08:21 AM. Reason: Addition.
  Reply With Quote
Old 4th July 2014, 08:24 AM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Its no myth, opamps do sound different, even when used correctly.

Sometimes those difference are subtle and you have to listen for extended periods, days rather than hours. Its then that you start thinking, yes I really like this, or you are constantly aware that "something" isn't right for your ears. You have to trust what you hear, not what others tell you is correct or better.

I agree the 2134 is good, although for line stages I've come to consistently prefer the LM4562 over everything else. The OPA2604 is worth a listen too.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 4th July 2014, 08:26 AM   #6
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
This might interest you,
A Different Opamp Compensation Technique.
__________________
-------------------------------------------------------
A simulation free zone. Design it, build it, test it.
  Reply With Quote
Old 4th July 2014, 08:37 AM   #7
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
G'day mate, very interesting and yes I'm now using LM4562's in my DIY phono stage (ESP P06), and yes it is very low noise. Previously I used OPA2134's in my P06 and found them to be noticeably noisy (hissy), yet in the one op amp phono stage I linked to and built, one op amp is delivering around 40 db of voltage yet is surprisingly quiet.

The 'impedance' of the feedback loop must be important and probably depends on the op amp used in the circuit. Regards, Felix.
  Reply With Quote
Old 4th July 2014, 10:40 AM   #8
diyAudio Member
 
Join Date: Apr 2008
Blog Entries: 1
Default low noise Op Amp

Hi I have read in other forums that the AD823AN is an incredably good Op Amp for a phono circuit of this kind. If cost means (yes I know it does not always mean this) better quality then at around US$10, it should be. But it would still be a great buy as a good phono design using a AD823AN can better most US$600 commercially available units. You should try one
__________________
tabarddn
  Reply With Quote
Old 4th July 2014, 10:44 AM   #9
fap is offline fap  Australia
diyAudio Member
 
Join Date: Sep 2010
Location: North Queensland.
G'day mate, I have used the AD823AN and didn't think that they were anything special.

I'm not sure that they are designed for audio. 'Instrumentation op amp' comes to mind. Regards, Felix.
  Reply With Quote
Old 4th July 2014, 10:50 AM   #10
vulejov is offline vulejov  Serbia
Sin Bin
 
Join Date: Aug 2010
Quote:
Originally Posted by fap View Post
I'm not sure that they are designed for audio. .
So what!
Opamps designed for audio are nonsense..
  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
Feedback in amplifier is ultimately the driver of sound quality ? ash_dac Solid State 175 4th February 2011 11:41 AM
Please help with sound quality- op-Amps Nora Solid State 32 5th February 2006 10:55 PM


New To Site? Need Help?

All times are GMT. The time now is 04:50 AM.


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