Arduino and sharing audio ground (Line Level)

[spiderdave]

If one ends up in a situation where there has to be a shared ground between an audio module and the Arduino, what is the consensus on the best way to decouple? Using a DY-SV5W voice playback module with the line level output through the earbud jack... My case, I'm just going MONO.

There was an old thread about this but just looking to learn a bit more on the why:

Sound module issues

Hi, I had exctaly the same issue controlling SV5W with arduino. I finally found the solution after hours of test, capcitors, isolating supplies, ... The problem is the arduino pin not delivering a nice LOW state, just add a transistor as interface for each control line and it will work without any noise. I used BC547 with 1k resistor between arduino pin and base, collector to SV5W module and emitter to GND. JP Belgium

It was mentioned that it is good practice to have a 1uF capacitor in series for our audio circuits. My question is can/should that capacitor be on the Audio+, Audio-, or Both? Any insight would be appreciated.

[johnerrington]

@spiderdave

there has to be a shared ground between an audio module and the Arduino, what is the consensus on the best way to decouple?

If there HAS to be a shared ground then what and why do you need to decouple?

I looked at the old thread, theres no schematic just all words.

[spiderdave]

If a picture is needed, here is a different source thread of the concept, but that was in the context of noise isolation and direct to speaker, but I think similar principles would still apply at line level?

Isolating an audio line connection with two capacitors

The why:

Some electronic equipment has only an audio high input(line level) but no audio low input for an external audio source. Said equipment also needs to interface directly with Arduino for some logic control so it can’t be a floating circuit as a ground has to be shared.