Passive zone controller loosing 6dB!?

[Eliani]

I built a passive zone controller for a friend, but I loose 6 dB in this ciruit and I don't know what I did wrong! Can anyone help me with this?

I'm connecting a normal line-level output to four amplifier inputs, each "zone" goes through a similar circuit, simple 15dB pad, mono/stereo switch and a volume control.

 

[joaquins]

I'll assume top input is left, bottom input is right and the mid point is ground.

In that case you are not making a mono mixing but only left selection, for mono you should sum both inputs and send that to both outputs.

I think your problem is you are using a 600Ω T-pad which is loading your input all the time, you should use an L pad, disconnect it completely to unload the line when not used and probably use a higher impedance. The caps in there are probably not necessary unless you have DC on your source and that will cause noise when switching, only in that case the caps should be here, if not I probably remove them.

JS

 

[Eliani]

I see that now...  :-[