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Old 20th January 2014, 02:18 PM   #11
Mooly is online now Mooly  United Kingdom
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Well, very little interest in this thread (and many thanks to those that did participate) so I think I may as well show what the set up was.

The test set up was a Sony CDP790 THIS ONE

Here is the circuitry of the output stages.
Click the image to open in full size.

The 5532 was a JRC5532 of single in line style. That made trying modifications difficult but I made a couple of little adapter PCB's to allow DIP devices to be fitted. Notice the supplies to the opamp, just -/+5 volts. That's low.

Now I wanted to try FET opamps in this location and chose the TLE2072 as a suitable candidate. The data sheet says "fully specified for operation at -/+5 volts". The results however were slightly unexpected with a huge increase in distortion as levels approached 0db level. What was surprising was the distribution of this "level dependent" distortion which you can see here.

So here we have the distortion as level increases. Ignore the HF artifacts at 18 to 20kHz as they are generated by the sound card.

-10db
Click the image to open in full size.

-6db
Click the image to open in full size.

-3db
Click the image to open in full size.

-1db
Click the image to open in full size.

0db
Click the image to open in full size.

So as you can see, we have a "classic" distribution of distortion with very high second harmonic as level tops out toward 0db.

I was intrigued whether anyone preferred this particular "sound". The two results I received were very interesting.

fas42 never even blinked

Beta
Kappa
Pi

were the preferred choices. The comments included. Quote "Smoother, less "hifi", less edge, the usual thing - the other version just started to bug me more the longer I listened ...".

So fas42 preferred the totally original set up of the 5532.

The other result (thanks BYRTT) preferred Beta, Kappa and Omicron but with special mention of the acoustic guitar on Pi coming across particularly well.


I think the Omicron and Pi tracks might have a higher overall level then the others (the masters on the CD... I left all settings the same between tracks) and that would push the distortion ever higher.

Many thanks guys. I'll leave the files available for a little while in case anyone wants to try these.
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Old 20th January 2014, 05:46 PM   #12
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What is your 0dB referring to in terms of actual voltage? Was the signal created by burning test tones to an audio CD? I guess there was no such harmonics when the 5532 was in place?
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Last edited by richie00boy; 20th January 2014 at 05:51 PM.
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Old 20th January 2014, 05:59 PM   #13
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by richie00boy View Post
What is your 0dB referring to in terms of actual voltage? Was the signal created by burning test tones to an audio CD? I guess there was no such harmonics when the 5532 was in place?
Its bang on the CD standard, 5.6 volts pk/pk (2volts rms). The test disc is the Philips "audio signals disc 1" pictured in the link to the player. The original 5532 is totally clean.
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Old 20th January 2014, 10:38 PM   #14
BYRTT is offline BYRTT  Denmark
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Thanks Karl
Still thinks file Omicron follows sound stage from Beta and Kappa, but must eat the fact.
About your config, do you think it's your layout in form of the Opamp adapter or just a matter of feeding 12-15V instead that makes the distortion ?
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Old 20th January 2014, 10:48 PM   #15
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Ah-haa! This is telling me a lot about the PM bunch of files - I was wondering whether you had made a "mistake" when creating the files ...
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Old 21st January 2014, 07:23 AM   #16
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Karl, the TLE's are clipping. You have not only tried 0dBFS level, but also -1dB, -3dB, -6dB ... etc. Music is usually well below 0dB so the near-to-clipping distortion might not been audible.

These TLE's are nothing special, anyway.
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Old 21st January 2014, 07:49 AM   #17
Mooly is online now Mooly  United Kingdom
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Quote:
Originally Posted by BYRTT View Post
Thanks Karl
Still thinks file Omicron follows sound stage from Beta and Kappa, but must eat the fact.
About your config, do you think it's your layout in form of the Opamp adapter or just a matter of feeding 12-15V instead that makes the distortion ?
It seems to be just the low supply causing this, I was very surprised. The layout of the adapter is straightforward but I might run some parallel test with the TLE2072 in a circuit on low rails just to see.


Quote:
Originally Posted by PMA View Post
Karl, the TLE's are clipping. You have not only tried 0dBFS level, but also -1dB, -3dB, -6dB ... etc. Music is usually well below 0dB so the near-to-clipping distortion might not been audible.

These TLE's are nothing special, anyway.
Hi Pavel. An interesting observation. Even at -6db some distortion residual is still observable. As previous tests have shown, some can discern minute differences between circuits, differences that almost defy measurement even with the best of set ups. I'd bet there is much going on even below these levels if only I had the means to measure it. At the higher output levels the distortion could be observed on a scope as (to me) classic asymmetric 2nd harmonic. There was no visible suggestion of it approaching a hard clip limit.
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Old 21st January 2014, 07:54 AM   #18
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Quote:
Originally Posted by fas42 View Post
Ah-haa! This is telling me a lot about the PM bunch of files - I was wondering whether you had made a "mistake" when creating the files ...
Is it There is a genuine change of circuit between the pm files. Rails are the same and its not using a TLE2072 either
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Old 21st January 2014, 08:51 AM   #19
PMA is offline PMA  Europe
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You might like to try Arta

ARTA Software

It is for free, very well designed, with much higher resolution than Audacity. Audacity is nice for music file handling, but close to useless for spectral analysis and distortion measurement. With Arta, you will know much more about opamps and soundcards.
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Old 21st January 2014, 09:11 AM   #20
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Quote:
Originally Posted by PMA View Post
You might like to try Arta

ARTA Software

It is for free, very well designed, with much higher resolution than Audacity. Audacity is nice for music file handling, but close to useless for spectral analysis and distortion measurement. With Arta, you will know much more about opamps and soundcards.
Thanks Pavel, I'll be sure to check that out.
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