I have amplifiers driving 100V Line speaker systems.

I have a need to "mute" these, and already have speaker switching/selection relays controlled by an Arduino.

To mute the sound, can I just disconnect the speaker systems and leave the amps running, or will it harm the amps in any way?

The amps themselves will still have the loads of the 100V Line output transformers, so I'm thinking it should be ok, but does anyone have other ideas ?

TIA

 

Assuming that they are semiconductor amplifiers, you can disconnect them with relays, switches or any means you like, before or after the transformers.
Valve based 100V line amplifiers remained common long after hi-fi amplifiers were superseded because the transformer output stage suited valves. Valve amplifiers should not be run without a load.

 

Def semiconductor amps, so should be good to disconnect ....

 

Def semiconductor amps, so should be good to disconnect ....

I have decided not to disconnect the speakers on this system, rather prefer to fade the sound out, and fade back up again when we want the sound.

I've decided to use a Wemos D1 mini mcu, and drive X9C104 digital potentiometers to control the input to the amps.

This might not be the best forum for this but here's the circuit I've designed. Since I'm going to be either all-in, or all-out, and nothing in-between, it should be easy to program the mcu.

Next I've got to design a circuit to detect the jukebox is playing, to trigger the muting of the in-house systems. I am thinking of just connecting something to the jukebox speaker terminals and using a resistor/zener configuration, but unsure what would be best....

 

It has been over 30 years ago when I last used a digi-pot for audio use, but I recall having it powered from +/-5 volts. Audio signals swing above and below ground.
Please post the digi-pot datasheet.
A way around is to bias them at +2.5 volts, but these could cause popping upon turn on/off.

 

Besides the problem of audio being a bipolar signal, a standard linear pot will give an apparent non-linear change of the sound volume with pot position due to the non-linear log response of the ear.
Might be better to use an audio taper (log) pot such as this, that uses a dual supply to handle the bipolar audio signal.

 

It has been over 30 years ago when I last used a digi-pot for audio use, but I recall having it powered from +/-5 volts. Audio signals swing above and below ground.
Please post the digi-pot datasheet.
A way around is to bias them at +2.5 volts, but these could cause popping upon turn on/off.

Besides the problem of audio being a bipolar signal, a standard linear pot will give an apparent non-linear change of the sound volume with pot position due to the non-linear log response of the ear.
Might be better to use an audio taper (log) pot such as this, that uses a dual supply to handle the bipolar audio signal.

Dont think it'll be an issue, all I want to do is completely mute the in-house sound when the jukebox fires up, and restore it when the jukebox stops. It'll probably be a 1 second fade either way, so won't matter if it's linear or log. The fade will be 100% to 0% to 100%, nothing else ....

Datasheet is online for the X9C104, the 104 just means it emulates a 100 K Pot and has 100 steps.