I want to evaluate whether I can switch an amplified audio signal (AC, load 8 Ohms, e.g. 20W) using a solid state relay. I already do this with mechanical relays. So I need an SSR with very linear behaviour, suitable for AC in the frequency range of 20 - 20K Hz, with very little ON resistance (ideally 0.1 Ohms or less), and very low leakage current when the relay is OFF. And I want to control the relay with a micro-controller, i.e. with a 3.3V or 5V signal. Disclaimer: I know very little about how a MOSFET works.
I was thinking about Omron G3VM-61AR1. What I don't understand is what kind of circuit I have to build "around" this component. It specifies LED currents and such things, but I need to ensure that I can apply a control voltage from the GPIO instead. Those components have four pins, which I also don't understand. "ready-made boards" usually come with stuff around the relay that gives you GND, Vcc, Control-Pin, and Load-In/Out, so five pins. Any help for noobie level would be appreciated. I guess my application is not unlike this.
My current understanding is, looking at the more detailed spec, that the LED "forward voltage" should be between 1.33V and 1.48V, so I could probably create a voltage divider, and just make sure I don't run more than the 15mA or so that the GPIO can handle. So instead of separate Vcc and Control-Pin, I just have a single control voltage input? Do I need to be careful about "reverse currents" or such things?
Edit: This related question would imply that I can just connect the GPIO if I use some 300 Ohm or so resistor.