Most multichannel equipment will have a "max volume" restrictor and " initial volume" for playback setting built into the software. Set those 2 settings appropriately to safe levels.
But, if you are a 2 channel 1 knob and no features kinda guy, look at your one knob’s position (volume) whenever you hit the power button. There’s not a whole lot there to distract your simple soul, i.e., all you’ve got is 1 knob.
Even if it was 2 secs of max volume, you most probably broke your speakers and ears. You are so screwed. All is lost for you. Renounce everything and become a wandering monk.