[imackler]

Getting recommendations on headfi has been great. But there is a lot more i have yet to learn. Please teach me to fish for myself! Is there a way to know how much power I need to drive the ER4S as well as it can be driven? Is there a point where it maxes out? I'm not talking which amps synergize well with the ER4S but what kind of numbers would I be looking for as far as power output. And here, I'm going to show how much I don't know. Is it how many watts I need? or voltage swing? (Its impedance is 100ohms if that helps...) Thanks for any help!

 

[Mad Max]

Minibox-E+ (oir the newer ES version) is made for ER4S/P.
It pairs really well with bright and/or sibilant headphones in general.

 

[imackler]

Thanks for the suggestion, Mad Max! I know you're a big fan of the minibox/etymotic synergy!
 
But I'm still wondering not what amp would have enough power (there's a ton of them) but what is the technical specification that would guarantee I have enough power, no matter which amp I choose? I'm not sure if it would be in watts, voltage swing, etc.?

 

[Anaxilus]

You want something with an output impedance as close to zero as possible but up to 10ohms should be fine.  My amps are quite powerful with the Arrow rated 12-13V and the DACPort hitting 18V with dual 9V rails.  I believe that's correct.  My gumstick seemed to drive the ER4S quite well so the Hippo Gumstick, Cube C30, Nationaite N2 seem to fit the bill.  Not sure on their specs.
 
Hopefully a proper EE will step in and offer counsel.