John Woodgate jmw at
Tue Jun 3 01:52:06 EST 1997

In article <33935466.1CC at>, Luc.vanHoye at writes
>I am trying to figger out if the impedance of an audio device has
>something to do with how loud its signal can go...

No, nothing at all.

>for example:
>I have a Roland XP80 (the audio device) which allows headphones with an
>impedance between 8-150 Ohms.
>Now, is it so that if I should use an 20 Ohms headphone I will probably
>get a louder signal then if I should use a headphone with an 150 Ohms

One cannot tell: the sensitivity is not directly related to the
>Could anyone explain me how this works and what people mean if they say
>that a headphone is 'hard to drive'?! 

You must ask them not to use vague and unscientific phrases.
>Second, if I have the option, is it always better to chose a headphone
>with low impedance?
>I would really appreciate it if somebody could explain this to me!
>Thanks in advance!
>Luc van Hoye.

There is a thread going on this group about headphone 'matching',
including a description of the standard 5 V/120 ohm interface, which
attempts to feed headphones from 8 to 600 ohms with at least enough
power to give a reasonable listening level. I suggest you follow this
back in time, via DejaNews if you haven't still got the articles in your
local storage. But the Roland might not use the standard interface.
Regards, John Woodgate Tel. +44 (0)1268 747839
Fax +44 (0)1268 777124. OOO - Own Opinions Only
Alternative e-mail address: jmwa at
That means I get double spam with everything (;-(

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