Purpose of the RCA - IN of Volt+ AMP ?

[cmoulliard]

Hi,

 

What is the purpose of the RCA - IN of Volt+ AMP ? Can we use it with a PI 3/4 ? How ? Is there a  bundle available ? 

 

https://www.allo.com/sparky/volt-plus-amp.html

 

Cheers

 

Charles