Since you do not actually know how much current draw will make your receiver into a boat anchor, even temporarily, do not even think of putting a real load on it.
The best and worst of this that I have seen is a Marantz projector that has 12volts out, but if you try to draw more than a couple of milliamps, it drops quite a lot. It acted like 12 volts with 50k ohms in series with it.
Even safer than having the trigger drive a relay -- the Marantz would not even do that -- is to make up a little control circuit using a 2N3904 transistor as a DC switch to trigger a relay. You get a power supply that will drive the relay, then connect the transistor as a common collector amp with the trigger voltage being the input through a 1K resistor. I can fax you a sketch if you like.
That GUARANTEES to isolate your real world loads from what might be a low-current source, or even worse, might have been designed by a well-meaning engineer who did not realize that the current output specs would not simply be published as part of the manual, and who did not bother to make it bulletproof....
A good answer is easier with a clear question giving the make and model of everything. "The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw