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Power Supply Noise Problem
Power Supply Noise Problem
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Old 18th August 2019, 12:55 PM   #11
thyristor44 is offline thyristor44
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Join Date: Jan 2013
phofman I wish I had seen your articles on your player before I started, they are very helpful, thanks.
I had a look at my TPA3116 board its too small for me, never worked on surface mount at all. I see exactly what you mean though.
Any ideas for cheap differential input amps that are cheap.
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Old 18th August 2019, 02:02 PM   #12
phofman is offline phofman  Czech Republic
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The cheapest differential input amp is a TPA3116 amp with available differential inputs, such as the one I use DC 12V 24V TPA3116 Dual Channel Stereo 50W*2 BTL Mono 100W Audio Amplifier Board 9934840364132 | eBay
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Old 18th August 2019, 03:13 PM   #13
thyristor44 is offline thyristor44
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You seem to have taken the inputs to the front of the TPA3116 board. Are the capacitors c1-4 the ones on the front, 1mfd if so that looks possible for me if they are.
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Old 18th August 2019, 03:20 PM   #14
phofman is offline phofman  Czech Republic
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Exactly, just unsolder the grounded pins of the two tantalum caps for cold lines (the ones on side, the middle ones are for hot line/signal). Since the grounded pins are on the board edge side, just bend them outside and solder the incoming wires directly to them, trivial modification.
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Old 18th August 2019, 03:30 PM   #15
thyristor44 is offline thyristor44
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That sounds ok for me.
Will I then be able to use the 12v psu for amp and the 12v-5v converter for Pi and 7" screen or separate psu's.
Thanks
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Old 18th August 2019, 03:36 PM   #16
phofman is offline phofman  Czech Republic
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I use the same adapter for the thin-client PC and the amp, using internal soundcard. No noise, after the mod. Unbalanced connection - every PC operation was audible. I hope it works for you too.
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Old 18th August 2019, 03:40 PM   #17
thyristor44 is offline thyristor44
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Thanks phofman I will send away for one.
thyristor44
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Old 20th August 2019, 01:14 PM   #18
den_hr is offline den_hr  Croatia
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As I wrote some time ago in another forum ("Class D"):
"You should connect all ground lines together ("star grounding").
I had the same issues initially when I set up my (similar) project (all three components - RasPi, DAC and amplifier - powered by the same power source).
Once I joined all ground lines to one central point, the noise disappeared.
BTW, my line out from DAC to amp has ground disconnected - I only have left and right channel signals from DAC to amp (i.e. two wires instead of three - ground is NOT connected).
Try that, and I think your noise problems will be solved. "


I addition to what I wrote above, I might add that in the end I *did* connect the amp signal ground: but again - not to the incoming signal ground from the DAC, but to the main "star ground". Without that last step, I still heard noise coming from wifi activity on the RasPi

This is the main and most common issue when powering both the RasPi (and DAC) and the amp from the same PSU (regardless of any step-down modules you might use).
Some "ground isolators" might help (a bit), but you won't solve the problem until you ground everything as described above.
No use in buying extra components (I also tried isolation transformers, and many other gadgets.... no use, nothing solved the issue completely): just gound everything into a central ground point, and your noise will be gone
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Old 20th August 2019, 09:55 PM   #19
peizi is offline peizi  United States
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Default Add PSU output EMI filters

Add PSU output EMI filters, and All output add a short ground wire to the motherboard metal base.
Click the image to open in full size.

Last edited by peizi; 20th August 2019 at 10:08 PM.
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Old 20th August 2019, 10:37 PM   #20
peizi is offline peizi  United States
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And
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Click the image to open in full size.

Last edited by peizi; 20th August 2019 at 10:39 PM.
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