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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
A story of mysterious interaction between a diy tda1543 dac setup and the human body.
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Old 12th February 2018, 10:05 AM   #1
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Default A story of mysterious interaction between a diy tda1543 dac setup and the human body.

Hello everbody!
Maybe someone could kindly explain what exactly is going on...
I am testing a diy 16xtda1543 based dac.
The dac is running on a 12V power supply and feeds a Primaluna Valve amp. The dac is connected via i2s to an sd card reader running on 4x1.5V AA batteries. There is so much noise that the music is hardly distinguishable.
BUT.
If I touch one battery with a finger (mind you: the outside plastic wrap, not the wires) the noise is reduced by 25%. When I add a second finger on the 4th battery the noise is down 50%. If I lift the battery pack and wrap my right hand around it, down 80%. With my left hand, I place a finger on each RCA jack exiting the dac, and the noise is virtualy gone. Listening to music this way is quite unconfortable. I am wondering what circuit my body is simulating in this setup and how can I replace it? (my body)
Thanks !!
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Old 12th February 2018, 10:37 AM   #2
abraxalito is offline abraxalito  United Kingdom
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Is the 0V wire in the I2S link (you should have 4 wires - 3 signal and 0V) connected at both ends?
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Old 12th February 2018, 10:38 AM   #3
luxury54 is offline luxury54  Romania
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the ground (-) of the sdcard reader's power supply must be common to the ground of the dac's power supply; is it in your case?
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Old 12th February 2018, 11:28 AM   #4
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Hello abraxalito and luxury 54.
Thank you for your reply.
No, did not connect ground.
I will do it as soon as I get home and let you know.
Thanks ver much !!!
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Old 12th February 2018, 09:17 PM   #5
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Hello again.
Yes that was the problem ! No noise now. Perfect.
(By the way, people designing the pcb could have added the ground pin next to the I2S )
Thanks again !
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Old 25th February 2018, 07:07 AM   #6
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Hello !
Whilst the previous problem was easily solved (grounded ) thanks to your suggestion, there is another little problem with the sd player/tda1543 combo.
I am experiencing a short burst of static in between tracks...Any idea where that might come from? ( SD card player playing .wav on 4x1.5V batteries, connected via I2S to single TDA1543 with passive IV conversion, @8V and straight to valve amp )
Thanks, Bart

Last edited by Bartb; 25th February 2018 at 07:12 AM.
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Old 25th February 2018, 08:01 AM   #7
abraxalito is offline abraxalito  United Kingdom
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Does the SD card player have its own analog output? If so, have you listened to it and discovered if the same static is present?
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Old 25th February 2018, 10:11 AM   #8
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Hello !
The SD card player has only I2S output fed right into the TDA1543, pin 8 is fed to 2.7k to ground, and 1uF cap to analog output...
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Old 25th February 2018, 10:16 AM   #9
abraxalito is offline abraxalito  United Kingdom
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My best guess then is that the SD player is generating the static between tracks.
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Old 25th February 2018, 10:20 AM   #10
Bartb is offline Bartb  Slovenia
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A story of mysterious interaction between a diy tda1543 dac setup and the human body.
Ok the main suspect is the CF player...was thinking the same thing...
Quite strange though...
Thanks for now !
B.
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