[Elecraft] audio amplifier/speaker/headphone impedance matching

Thu Mar 7 17:17:00 2002

If the resistor is pure R and no X, it should have no effect on frequency 
response.

best wishes,

dave belsley, w1euy

--On Thursday, March 7, 2002 9:47 PM +0100 Sverre Holm - LA3ZA 
<[email protected]> wrote:

>
>
>
>
> -----Original Message-----
>> From: [email protected]
> [mailto:[email protected]] On >Behalf Of Rick Shindley
>
>> People sometimes are confused about impedance (Z) matching. They
> mistake the
>> need to do so at rf frequencies with the conventions used at audio
> frequencies.
> ....
>> The zero Ohm source impedance of most audio amplifiers assures that the
> speaker >voice coil will be forced into position with authority.  That
> means low acoustic >distortion. If the amplifer had a non-zero output
> impedance, the voice coil
>> would not accurately track the voltage signal and acoustic distortion
> would
>> result.
>
>> Rick  KC0OV
>> K2 1360
> -------------------
>
> This is an interesting topic that is raised here. I have often wondered
> about the practice used in most ham equipment of using series resistors
> to feed the headphones (e.g. separate 82 ohm resistors to feed the R and
> L headphones in the K2). It does make the output short-circuit proof.
>
> But what are the side-effects? Does it cause the headphone to ring at
> some undesired resonance frequency? Could it distort CW, by distortion I
> mean color it with some unknown frequency response which is the effect
> of the design of the headphone and the series resistor? At the very
> least we don't get the advantage of damping the headphone coil with the
> low output impedance of the amplifier.
>
> Any comments?
>
> 73 Sverre
>
>
> Sverre Holm, LA3ZA
> Asker, Norway (59.8N, 10.4E)
> ---------------------------------
> www.qsl.net/la3za
>
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----------------------------
David A. Belsley
Professor of Economics