Automatic switching of power amps

March 28, 2012

The Furman Miniport 20-Q mounted in electrical box with ACR2 attached to the side.

The school I work at has a permanently installed audio system in the gymnasium/auditorium.

I am responsible for the upkeep and use of this system, and over the years I have attempted to streamline the system so it would be easy to allow other users of the facility to use this system.

To that end I have been searching for a way to automate the use of the audio equipment. I would love to be able to hand over a wireless mic or a patch cord and have presentations or music playing.

I have started this process by automating the switching on and off of the power amps.

To do this I purchased two items: a Furman Miniport-20Q Power Relay and an ST-ACR2 Audio Controlled relay.

What I have done is created a unit that will send power to a pair of outlets when it detects an audio signal. The audio signal runs into the ST-ACR2 which then closes a circuit triggering the Miniport-20Q. The Miniport is installed in a plastic electrical box with a

Unfortunately the Miniport and the ACR require different voltages to operate (24 volts for the ACR2 and 5-18 for the Miniport). I happened to have a couple extra wall-warts to run the unit, but ideally it would have been a single transformer with dual voltages. The Miniport might have been ok with 24v instead of 18v, but I didn’t want to chance burning it out.

Next step will be to install this unit in my audio rack and running a patch from my aux-out or even headphone jack.

The nice thing about the ACR2 is that I can adjust the input sensitivity and the delay time up to 50 seconds – so if there are lulls in the audio input my amps won’t be constantly power cycling.

ST-ARC2 with power and relay wiring.

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