Re: Optimal amplifier output impedance for headphones

On Aug 24, 8:00 pm, "Ian Iveson" <IanIveson.h...@xxxxxxxxxxxxxxxx>
wrote:
maxhifi wrote

What is the optimal output impedance for a headphone amplifier?

Zero is always best for driving anything that's properly designed to
respond to a voltage source. Optimisation as a concept requires at
least two parameters, surely. Here you have just one...and there is a
perfect answer.

Zero will always give you the widest frequency response, and the
lowest distortion.

The common practical rule of thumb for the upper limit is 1:10, which
is a good design starting-point for both frequency response and
distortion considerations.

I assume that if a minimum source impedance is required, then it
should be linear, meaning a resistor driven by a low impedance output.
In which case the resistor should be built into the 'phones. Or there
should be a warning sticker or something.


In practice, headphones were not necessarily designed for being
driven by a zero impedance source.

Also, tube amplifiers that put out any substantial power need to work
into some approximation of the expected load.

Probably a single ended triode amp would work fine for headphone
application if there were not the need to provide sufficient shunt
loading to keep it satisfied, assuming a conventional plate-to VC
ratio opt were employed. But the best results will invariably come
from an amplifier, tube or otherwise, specifically engineered for
headphone use. Several examples are available for study online.

.

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