[jthew]

Right. So the headphone jack is unaffected by this type of switch, or is it a case by case thing, where one would have to get a schematic

 

[SilverEars]

Shouldn't be.

Don't know about current receiver amps, but receiver amps need high gain to drive speakers, and the headphone jacks for the old receivers(at least) were resistor attenuated to decrease loudness so that you are able to to adjust the volume knob at a reasonable range and prevent blowing your headphones. I heard of one that had 120ohms output impedance fixed for the headphone jack.

Headphone amps generally are tailored for the needs of level of power required for a range of headphones, lower gain(enough to drive headphones, not so high to drive speakers), and output impedance is ideally close to zero ohms to increase damping factor(but also, for specific headphones, people may desire less damped outputs).

Even for iems, there is a level of power that should be at a lower requirement that would be at another range.