Mono/stereo PAS control

I would like to replace the mono/stereo selector of the PAS with an Off/On switch.

How should the connection?.
Should any component be introduced?.

Thanks for your attention.

you can replace the rotary blend switch with a simple DPDT toggle or slide switch (just like the one used for SOURCE/TAPE).
For mono, you can use a couple of 4.7K resistors, one from left, one from right, to sum the signals together for mono.

Thank you very much.