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Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

Appendix F - MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

End of Answer

Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

Appendix F - MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

End of Answer

Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

End of Answer

Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

Appendix F - MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

MAX4466 Microphone Amplifier and 24 but HiFi Stero ADC

End of Answer

Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cableseparate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

End of Answer

Answer

(moved from comments, to tidy up later)

I appreciate you experiment results very much. I also have noise problems in my projects. (1) I often use Lipo power banks (18650 x 3) 12VDC and step it down to 5V for Rpi and other circuits. (2) I even avoid using switching power supplies (LM2596/LM2941) and use series regulators (7805) and LDOs, (3) I use huge bypass capacitor (electrolytelyte) 10,00 uF), 0.1~1uF tanlum/cermic caps. (4) I also use dedicated/separate PSUs for Rpi and power amps,

(5) Grounding is also very important, I separate my grounds into (a) power ground, (b) logic ground, and (c) audio signal ground, and of course shielded or double shielded AV cables. I even dedicate the Rpi's several ground pins into groups, for I2C/SPI/UART/GPIO (audio) etc. Of course I need to use "ground stubs" later. For also signals Audio or I2C etc, I have separate ground lines going with them,

(6) For power amps, I sometimes use differential input D type power amp. (7) I also have digital low/band pass filters (for my EEG/ECG/GPS etc) to try to reduce noise. (8) I use UGreen USB sound cards (OK, they are not very HiFi, but cheap, with button selection of raw/music/gaming band widths. (9) I also try dynamic/moving coil (Sony grade) and cheap pizo microphones.

References

(1) UGreen USB Sound Card Discussion 1/2

(2) UGreen USB Sound Card Discussion 2/2

(3) Rpi GPIO Push Button Circuit Grounding Problem

(4) Ground loop problems and how to get rid of them Written and copyright by Tomi Engdahl 1997-2013

(5) RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector

(6) Why Grounding is used - Epanorama

(7) Using bypass capacitors to reduce voltage spikes and noise causing I2C read/write errors

(8) Clean Power for Every IC, Part 1: Understanding Bypass Capacitors - R Keim 2015sep21

(9) Clean Power for Every IC, Part 2: Choosing and Using Your Bypass Capacitors - R Keim 2015sep27

/ to continue, ...

Appendices

Appendix A -

Appendix B -

Appendix C -

Appendix D -

Appendix E -

End of Answer