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Old 7th July 2011, 10:17 PM   #11
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Why do you think it's from that PS connection?
Its the one that powers the fast digital circuits, the datasheet says there's 40mA of current going in. The bigger the current, the bigger the noise current potentially.

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You think it's digital noise or analog?
Noise is noise. Can't understand how 'digital' noise could differ from the 'analog' variety.

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I could just add a ferrite bead with some wire thru instead of the inductor for the test.
Let you know what the outcome is when I have the time to mod.
In your subsequent post you refer to 'a choke' - is this a slip or did you really fit a choke as opposed to a ferrite bead? Assuming you did use a ferrite then the next noise source to explore would be the other digital chip, the 7310.
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Old 8th July 2011, 07:37 AM   #12
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Hi,

I wrote choke but mentioned ferrite bead. Just a bead with some teflon wirewrap wire thru.

How come the non modded cd player is quiet and the modded is not? It might have something to do with my mod right?

I lifted p10 an p44 earlier and they are still lifted, maybe that is the problem?
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Old 8th July 2011, 08:43 AM   #13
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No p10 and 44 are not the problem.

With digital noise I mean noise wich is born in digital circuitry, same with analog.
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Old 8th July 2011, 09:11 AM   #14
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How come the non modded cd player is quiet and the modded is not? It might have something to do with my mod right?
That would be my best guess yeah. What other mods have you done and not mentioned so far?

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I lifted p10 an p44 earlier and they are still lifted, maybe that is the problem?
They seem to be just analog outputs. Not likely to be noise sources.

OK then if digital noise is noise born of digital circuits, then yeah it seems you have a digital noise problem here.
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Old 8th July 2011, 09:42 AM   #15
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I cut traces from WSI CLI and DAI from I2S bus just after the PCF3523 that would go to the 7321 so the inputs from the 7321 are floating.........eeehhh what else, cut traces from p40 and 14 and one cap came off 2656 100p near p40.
Fast shottky type diodes in power supply BYV26's that's about it I guess...........

The opamp stage after my tda1543 has just one feedback resistor of 2k7, no cap used parallel, can't be the prob. cause I lifted the opamp out already, same noise.

I discovered the excessive noise whilst listening to a noisy recording. After listening to a silent recording or no recording at all, there was still the noise.
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Old 8th July 2011, 09:58 AM   #16
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Not a good idea to leave inputs floating, this might have something to do with it. Try reconnecting those I2S bus inputs to the 7321.
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Old 8th July 2011, 10:19 AM   #17
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Got it now. I again disconnected my dac board with opamp stage and listened very carefully and most of the noise is gone now. I guess it has some to do with the Vref adjustment. I have 2k7 from Vref to GND and because of the distortion on the output I experimented with a cap parallel. I guess there is 150n parallel now but that might not be the good thing to do. I also bring Vref to the opamps like in the datasheet. Is there a better way to make it work? Passif? Maybe 2k7 as feedback resistor is not enough?
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Old 11th July 2011, 04:10 PM   #18
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Made passif I/V converter like Doede Douma in his ddddac. 1xtda1543 5V supply 1k as Vref and 1k as L/R output resistor to GND. Sounds awesome!
Mute doesn't work properly now, I already cut out analog mute transistors. Any other possibility to make mute work properly again?
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Old 11th July 2011, 04:24 PM   #19
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I haven't decoupled outputs to opa2134, maybe it is that what I hear?
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