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Old 17th May 2012, 04:24 AM   #51
EUVL is offline EUVL  Europe
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Out of curiosity, I did some measurements.
In my setup, the PCM5102 uses a 45.15MHz XO, 3.3V power supplies (3x), and has I2S input at 16 bit 44.1kHz.
The measured signal is taken directly at the IC output pin, without the datasheet 470R-2.2nF low pass filter.

Indeed there is clipping at the negative rail at full 0dB output.
The charge pump does not generate the full -3.3V, and hence the output opamps run out of voltage.
The clipping is gone for -1dB signals. And this can be solved without too much effort even for 0dB.
A similar problem exists also for the ES9022, which is why they brought out the 9023 to run on +3.6V supplies.

In real music material, this (0dB signals) hardly occurs.
Or at least in my own CD collection, I don't have anything that goes the full output amplitude.

We shall certainly continue to play around with this.
I particularly like the low latency filter.




Patrick
Attached Images
File Type: png 120517 PCM5102 1kHz 0dB.png (23.4 KB, 995 views)
File Type: png 120517 PCM5102 1kHz -1dB.png (22.6 KB, 966 views)
File Type: png 120517 PCM5102 1kHz Magnified.png (14.6 KB, 963 views)
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Last edited by EUVL; 17th May 2012 at 04:29 AM.
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Old 17th May 2012, 01:43 PM   #52
EUVL is offline EUVL  Europe
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Very quick & dirty, but problem solved.

I forgot to mention that the output was loaded with a 600R load in my setup (headphone with series resistor).
The charge pump generated -3.16V with a +3.3V supply, and is somewhat load dependent.
So loading it less (say RL 0 10k) will probably also remove the "problem".

Back to some more listening .....


Patrick
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File Type: png 120517 PCM5102 1kHz 0dB mod.png (19.9 KB, 953 views)
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Last edited by EUVL; 17th May 2012 at 01:50 PM.
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Old 17th May 2012, 01:50 PM   #53
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the clipping I refer to is NOT analog based.

it happens when you run too hot a DIGITAL signal to the chip. that's what gibbs is all about.

this was never a PSU or buffer issue, at least in the problem I was having.
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Old 17th May 2012, 01:51 PM   #54
EUVL is offline EUVL  Europe
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I do not consider e.g. a 0dB square wave to be a realistic music signal, if that is what you were referring to.


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Old 17th May 2012, 09:01 PM   #55
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It seems a flawed product when digital and analog clipping can occur (but a 0 dB square wave is indeed unrealistic).


Quote:
Originally Posted by EUVL View Post
So loading it less (say RL 0 10k) will probably also remove the "problem".
Probably is not enough.
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Last edited by jean-paul; 17th May 2012 at 09:10 PM.
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Old 17th May 2012, 09:10 PM   #56
EUVL is offline EUVL  Europe
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The "analogue" clipping was gone when I removed the headphone and changed back to 10k load.
I have not seen any evidence of digital clipping, and there are no other similar reports on the inet.
No test conditions, no oscilloscope plot, .....

I just spent 5 hours listening to it.
It is going to take the place of my ES9022 for a while.




Patrick
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Old 17th May 2012, 09:15 PM   #57
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Have fun with it ! That's what it is about. I will go on with ES9023 on 3.6V for a while. I still have to compare with FN1242a.

BTW data sheet of PCM5102 says it can be loaded till 1 kOhm so there is something not right here...
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Last edited by jean-paul; 17th May 2012 at 09:21 PM.
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Old 17th May 2012, 11:13 PM   #58
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Quote:
Originally Posted by EUVL View Post
I do not consider e.g. a 0dB square wave to be a realistic music signal, if that is what you were referring to.
the cd (flac) I was listening to was not a function generator output, lol. maybe I should cut a sample and post it so that others can try. artist was loreena mckennit and there were some very low bass notes that, along with the music, just seemed to sum up to a very high near-zero level. hey, its how they are mixing and releasing music these days; expect more and more of this problem, not less and less ;(

at first I thought I had a bad rip. it was that bad. was it my phones or phones amp? the dac? the player? man, it sounded bad. I had to verify it all and it sure looked like the badness went away when I kept everything BUT the dac.

so, maybe a sample/clip would help. I'll try to do that. what's the legal limit on how much I can clip and post for demo use? is 10 secs of music enough? that might be enough to show the bug.

(for those that have LM's cd's; its the ancient muse cd, 2nd song).
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Old 18th May 2012, 03:49 AM   #59
EUVL is offline EUVL  Europe
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Send me a email, and I'll give you a email address to send the clip to.
I will then repeat your test and report back.
I have as much an interest as you to find out the facts.
And if it can be proven, we could file a complain to TI and let them sort it out.

It is a good product otherwise.


Patrick

PS Please send me in WAV and not FLAC.
I cannot play FLAC.
Or try playing WAV and see if you still has the problem first.
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Last edited by EUVL; 18th May 2012 at 03:53 AM.
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Old 18th May 2012, 03:52 AM   #60
EUVL is offline EUVL  Europe
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> data sheet of PCM5102 says it can be loaded till 1 kOhm

My phone is 200R, and it has a 240R series resistor.
So a bit less than 1k.

In normal line level use, it is no issue at all.
So I consider this academic.
You can also use a 3.6V supply and the "problem" is gone.


Patrick
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