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level matching question

post #1 of 3
Thread Starter 

i just got a multimeter yesterday and am trying to match volume levels between amps but having a little trouble.  i'm using the AC volts setting and matching the output of two amps to within .002V, but there's still an audible difference in volume in the headphones.  in googling i found a thread on a different site where the solution seemed to be to do "level matching loaded with headphones" but i don't understand what that means.  halp?

post #2 of 3

That's because the two amps have different output impedance.  Some voltage is being lost across that output impedance—a negligible amount if you're measuring with the multimeter, which effectively has a very high impedance, but apparently not negligible when compared to headphone impedances.

 

Connect the amps to the headphones using a splitter, and measure with the headphones attached.  The volume you should set to match them will then depend on the headphones used.  Furthermore, for many headphones (those with impedance varying over frequency), even if you can match the amps at 1 kHz or another given frequency, they may not be matched in volume at another frequency.

post #3 of 3
Thread Starter 

ok, thanks.  splitters are coming in my next little box from monoprice, hopefully tomorrow, so i'll try that.  not much i can do about impedance that varies with frequency (one of my pairs is k701 though which is reasonably flat).

 

one other unrelated question.  with the switch box i have right now, there's a tiny bit of static when flipping the switch between sources.  is it possible to build (or buy) a box that wouldn't have any static when switching?


Edited by scud80 - 4/20/12 at 10:24pm
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