Adding mute switch to PM1000 console?

Hey folks,

I'm trying to add some channel mute switches to my Yamaha PM1000 console. I think the best way would be to make the switch short the channel's 33k summing resistor to ground. However, in the schematics, it appears that there is a separate resistor for each bus, depending on which it's assigned to. This may complicate things because I'd need to switch 4 resistors with one switch.

The next best spot *seems* to be right after the amp stage that feeds the bus output assign switchbank. My question is, if I make the switch cut the output of that amp stage, should I just break the connection, or should I short that connection to ground?

I guess it would also be possible to cut the signal right at the channel input jack, though that's probably not ideal.

If anyone can think of a better way to do this, please let me know.

Schematics are attached, the area in question is right above the circled section.

Make a switch that does what the fader does when it's all the way down?

Doing that at the input will mute cue which I wouldn't like for my desk, but it will mute echo sends which is a good thing. Ideally for noise performance the switching would be done as close as the bus as possible.

With VE summing amp, as here, it's better to leave the resistor disconnected to the bus, so noise gain of the summing amp is lower, and it won't change the gain. Ideally the switch will be after the resistor, connecting that resistor to the bus or to ground, you should use 6 switches per channel, one for each program mix bus and one for each echo bus. The physical switching is good to be as close to the location, so using a FET switch is the best way to do so, some ICs with some of those are available, with maxim there bunch to select from, some SPDT. Make sure is break before make as shorting ground to the bus is not a good thing, also noiseless switches aren't good for this application since this is done or shunted to ground before switching which would be the same thing. As there's no DC at the bus (AC coupled both sides) you should not have pops or clicks but the audio signal switching fast. There are noiseless switches from maxim which are slow, those could be useful for you, the other way is to do it at zero crossing but more complicated than this needs, I would go for slow switches. There are other options instead of maxim but is the first which came to my head.

If you want a hard switch instead, you have some problems, first to find a 6PDT switch, but you could find it or just switch the buses and leave echo bus 1 and 2 always running and go for a 4PDT switch which is easier to find. But still you need to take the signal and the bus to the front panel which isn't good for noise, a lot of wiring acting as antenna to catch any noises around...

JS