Update3: This looks to be a good 12v trigger 30A relay for cheap. 144 ohm coil means ~83ma load. This will work with receivers with lower power triggers.
These also simplify the trigger output wiring, can just use one of these and any old wire.
Update2: These relays have a higher impedance coil, which means less current (100ma) required to trigger them. I haven't tried these, but it looks like a good option.
TE Connectivity KUHP-5D51-12
Update1: I ended up using amplifiers that required 30a service. I am now using the following relays and they work great. Omron G7L-1A-TUB-J-CB-DC12
According to the datasheet, the Omron G7L-1A-TUBJ-CB-DC12 consumes 158ma (1.9w)
I recently purchased two Marathon MA-5050 amps. The idea of having to power on and off gear with a toggle switch seemed archaic to me, so I sought out a solution. This is nothing new, or novel, but I've seen the topic come up enough I figured I would post up some pictures and explanations.
At first I was going to use a mechanical relay, but decided to use a solid state relay instead. Browsing the Mouser website it seemed they have a bunch of high current solid state relays to choose from. I went with the Omron G3NE-220T-US 240V/20A
relay with a 12VDC trigger. Since my receiver has 12VDC trigger outputs, this simplifies things a bit. If your receiver doesn't have 12V triggers, one alternative is to use the receivers switched outlet if it has one, and a relay with an AC trigger such as the Omron G3NA-220B AC100-120
The parts I used for this are below. You can get most of these at local stores (radio shack, home depot, etc). The only special order item here is the solid state relay.
G3NE-220T-US-DC12 240V/20A 12VDC Trigger Relay
or if using a switched AC outlet G3NA-220B AC100-120
12-Gauge Insulated Female Quick Disconnects
.110 Female Quick Disconnects
3.5mm Mono Plug to RCA Jack Adapter
12ft Male to Male RCA Cable
15ft 12gauge 2 conductor SJOOW Cable
(can get this from Home Depot or any other store like that)
NEMA 5-15P Plug
Square Box (metal)
Single Gange Square Box Cover
(I used a 1/2" knockout plug, but can't find a link online, HD)
bolts and nuts (2)
This is what the relays look like. There are two here since I built two of these boxes.
The first step was to mount the relay into the square box. The backs of the relays are metal so they can dissipate heat. I drilled two holes and mounted it up with some #6
bolts and nuts I had. Make sure its mounted flat so that it can use the box as a heat sink.
Once the relay is mounted up, you can wire everything up. Ground to green, neutral(white) to white(silver) screw, and hot (black) to brass screw. Make sure you have everything wired correctly and the same on both the plug and the outlet.
The hot wire will be cut, and run through the relay using the 12 gauge quick disconnects, instead of being directly connected to the outlet. The small terminals on the relay are for the 12VDC trigger, and the larger terminals are for the load (AC outlet). I cut the end off of an RCA cable, which I am using for the trigger wiring, and crimped and soldered some female mini quick disconnects on. I then shrink wrapped them since finding insulated versions in this size is near impossible. Red goes to +, and white goes to -. Make sure (with a voltmeter) that you don't have any current either shorting or leaking to the trigger wires before plugging it into your receiver. Bad things will happen if you feed a 120VAC current into the triggers on your receiver. Those who are paranoid may want to put inline fuses on the trigger wires.
This is the box all closed up and ready to go.
I'm using the Mono 3.5mm to RCA adapter to connect this to the 12V trigger on my receiver.
Here it is with the amp off.
And now with the amp on.