Audio Source Switching

[Braeden Hamson]

Hello,

I've been having a pretty persistent problem switching between two audio sources, one is a generic bluetooth radio from amazon, the other is an Adafruit Soundboard FX https://www.adafruit.com/product/2220

I'm using a Maxim Integrated source selector chip https://www.digikey.com/en/products/detail/maxim-integrated/MAX4525LEUB-T/2045105



This is part of a larger circuit, however the rest of the circuit doesn't involve the audio portions. Act here, is from the soundboard its the activity indicator on the soundboard and changes the source when the soundboard plays a sound.

The issue is there is sometimes cross talk between channels, for instance the bluetooth audio can be heard when the soundboard is playing audio. There's also a significant amount of electrical noise even though I'm using isolated power supplies, isolated grounds for the audio portions and capacitors between audio and digital signals.

My question is what is the proper way to swap between audio sources using an electrical signal.

Also, here is the full circuit if it helps.

 

[kellys_eye]

What does the datasheet for the device state? Does it indicate the crosstalk figures? It should. The datasheet (which may also have application data added or made available via the manufacturers website) will detail grounding and supply separation/isolation issues if there are any. Often PCB layout/design is a major failing when it comes to noise. Is yours a breadboard design at the moment?

Either way, if your design follows the datasheet recommendations/specs then it will work as it is designed to work.

 

[crutschow]

There's also a significant amount of electrical noise

What is the nature of this noise?
What does it sound like?

 

[Braeden Hamson]

What is the nature of this noise?
What does it sound like?

Its not white noise. It has a narrower frequency range, higher pitched generally. it sounds like very typical electronic audio noise.

 

[kellys_eye]

Try a cleaner supply to start with. Use batteries if you don't have a linear regulated supply. SMPS devices are notorious for injecting noise.

 

[Braeden Hamson]

did u manage to work it out yet ?

I did, it was all grounding issues. I connected the 12V ground to the analog ground, and I connected the digital ground to the analog ground in one place. I also added large electrolytic caps directly to the +/- of some of my noisy digital circuits. Now it's silent.