Speaker Hum

[Napalm44]

I recently bought a 4 way audio switch -

( Source selector RCA 4 to 1 / reversible - Audiophonics ).





A picture probably explains better than words - this is how its used.





When I turn the switch to output to the power amp, there's no hum.


When I turn it to output to the headphones, the speakers buzz - and if i turn the power amp volume up, the hum gets louder.




I've checked all connections, and everything is powered by the same power strip.


Any ideas to stop it?

Thanks,

 

[phofman]

IMO the unconnected amp input starts picking induced noise, unlike when connected to the low impedance of the DAC output.

 

[Napalm44]

Any quick fixes to stop that happening?

 

[phofman]

Perhaps connecting the selector outputs permanently to ground via some 5k-10k resistors inside the selector box would eliminate the induced voltage while not loading the DAC output too much.

 

[dangus]

I agree, resistors, but try higher resistors first, like 100k and higher. My reasoning: 10k is lower than the input impedance of most audio gear, and if the source has an output capacitor, it could affect the low frequency roll-off.