@cheeseweasel 554534 wrote:

I only have a fairly basic understanding of electronics, but I’ve certainly heard of others making simple muting circuits by just shorting the two legs together. What is the advantage of using a resistor?

depends on what is at the distant end (i.e the op amp driving the mixer control room output) – especially there is already an existing series resistor on the output, or any DC offset. Op amps do not like being driven into a dead short, it knackers them. similarly with valve stuff. DC offsets cause thumps/bangs. Most Japanese amps use a bipolar transistor as a switch for muting but downstream of the series resistor.

That said most new kit does have these resistors but its hard to get the circuit diagrams, plus I was taught a lot my my electronics by old boys the BBC and British Telecom who always liked to do things the proper way (shorting an Openreach circuit (or any similar copper circuit) with DC signalling will cause it to flag as defective and the automatic testing will dis it at the exchange end to stop excessive loop current, which isn’t ideal if you are using it to send programme material down!)