[Boatanchors] Crystal Headphones

[J. Forster]

> Hi All,
>
> Just curious.
>
> When were crystal headphones first introduced? By whom? And why?

Crystal 'phones are very high impedance. Making permanent magnet biased
'phones w/ high impedance requires lots of very fine wire, which is
expensive and failure prone. Most 'phones are fairly low Z. If you want to
match to a HiZ amp output, you need a matching transformer, which adds to
system cost.

> Did they serve a specific purpose that other headphones of that era did
> not, perhaps could not?

Other than an easy match to HiZ, probably not.

> When were crystal headphones abandoned in favor of carbon headphones or
> whatever? What replaced them? Who made them? And why?

There is no such thing as 'carbon headphones', There is no piezoelectric
effect (mechanical stress <==> voltage)in carbon. It takes a material like
Potassium DiHydrogen Phosphate in a single crystal, cut properly. (Quarts
has a piezoelectric effect too, but it is much weaker than KDP.)

Carbon is used in some microphones, but in a mike, the diaphragm varies
the pressure on some carbon granules, varying bthe resistance of the
capsule. The effect is not reversible (voltage will NOT produce motion).

Mostly LowZ magnetic headphones. They are more rugged and not suceptible
to moisture. Magnetic phones likely took over most of the market in WW II.
During WW II a lot of engineering was devoted to the understanding and
development of electronics and a lot of people were trained in engineering
fundamentals.

> Given a vote, what type of headphones would you select as the best all
> around for voice, music and Code?

Voice or music, magnetic. Some crystal 'phones might have a resonance that
some might like for code. IMO, a tunable bandpass filter and magnetic
'phones would be a better choice.

> Thanks!
>
> FYI: Unrelated. The main computers that keep 'mailman.qth.net' operating
> also keep a running count on what subscriber posts the most each month,
> among other topics of fascinating interest. Should we post the top five
> subscribers who qualify each month? (Chuckle)
>
> Duane Fischer, W8DBF - WPE8CXO
> E-Mail: dfischer at usol.com
> Hallicrafters web site: www.w9wze.net
> HHRP web site: hhrp.w9wze.net
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>