After measuring the headphones with an LCR meter, is there a way to
take the inductance, capacitance and resistance to find the AC
impedance of the headphones at 1KHZ?

David wrote:
After measuring the headphones with an LCR meter, is there a way to
take the inductance, capacitance and resistance to find the AC
impedance of the headphones at 1KHZ?

If you measured all three at 1kHz, yes.

Otherwise you may find that the _effective_ L, C and R at 1kHz was just
that -- effective, not actual.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

David wrote:
After measuring the headphones with an LCR meter, is there a way to
take the inductance, capacitance and resistance to find the AC
impedance of the headphones at 1KHZ?
==============================================
the Thandar Electronics Ltd LCR meter model TC200 with LCD readout
(approx 20 yrs old) operates at 1kHz.

I use the instrument regularly ie once a week.

Thandar Electronics Ltd
London Road
St Ives
Huntingdon
Cambs PE17 4HJ

Now renamed Thrulby-Thandar Instruments Ltd
http://www.tti-test.com/


Frank GM0CSZ / KN6WH

On Apr 20, 5:46*pm, David wrote:
After measuring the headphones with an LCR meter, is there a way to
take the inductance, capacitance and resistance to find the AC
impedance of the headphones at 1KHZ?

Hay OM:

I wondered what the impedance of a crystal headphone would be. I guess
just the capacitance and inductance of the wire going to the crystal.
And at 1000 cycles that would be way up there.

I can bet for a certainty that 32 ohm headphones will be 32 ohms of
impedance at 1000 cycles. Just think how much the inductance and
capacitance will figure into the equation? Under 1% I bet at 1000
cycles.

73 OM

de n8zu

raypsi wrote:
On Apr 20, 5:46 pm, David wrote:
After measuring the headphones with an LCR meter, is there a way to
take the inductance, capacitance and resistance to find the AC
impedance of the headphones at 1KHZ?

Hay OM:

I wondered what the impedance of a crystal headphone would be. I guess
just the capacitance and inductance of the wire going to the crystal.
And at 1000 cycles that would be way up there.

I can bet for a certainty that 32 ohm headphones will be 32 ohms of
impedance at 1000 cycles. Just think how much the inductance and
capacitance will figure into the equation? Under 1% I bet at 1000
cycles.

73 OM

de n8zu


Impedance of xtal phones is often in the 10s of k. But their efficiency
stinks.

Regular old-time "2k" phones ohm out pretty close to 2k in DC
resistance and their impedance is in that same ballpark. They are all
over the place nowadays . May be fine on a regen set but suck horribly
on a crystal set.

"Bill M" wrote in message
...
Regular old-time "2k" phones ohm out pretty close to 2k in DC resistance
and their impedance is in that same ballpark. They are all over the place
nowadays . May be fine on a regen set but suck horribly on a crystal set.

Hmm... so a crystal radio would effectively perform better using a 1k--8 ohm
audio transfer than just using the "traditional" crystal earphones?

Are crystal earphones called that because they're used with crystal radios, or
because they really do have some sort of crystal in them (seems unlikely)?

---Joel

Joel Koltner wrote:

Are crystal earphones called that because they're used with crystal radios, or
because they really do have some sort of crystal in them (seems unlikely)?

---Joel



Not at all unlikely :-) Crystal earphones are piezoelectric devices
- the small electrical AF signal produces a small mechanical
movement. These devices have very high impedances so are ideal for
extremely low power circuits such as crystal sets.
See also crystal cartridges for playing records, these were some
what chunkier and would produce a lot of output and a typical cheap
record player might consist of a crystal cartridge (pickup) driving
the grid of a tridode / pentode arrangement (EL86 I think).



Charlie.

--
M0WYM
www.radiowymsey.org

Sign today!
http://petitions.pm.gov.uk/SaveShortwave/

"Joel Koltner" wrote in message
...
Are crystal earphones called that because they're used with crystal
radios, or because they really do have some sort of crystal in them (seems
unlikely)?

---Joel



The crystal earphone is called that because it does contain a crystal,
similar to some microphones.

The crystal in a crystal radio is the diode that does the conversion from RF
to AF. It started off years ago as a real crystal. A semiconductive
mineral crystal, usually lead sulfide (galena) or cadmium sulfide.

The impedance of the headphone is pretty much meaningless.
The sensitivity is critical. Impedance matching can be done with
high quality audio interstage transformers. The most popular
headsets are made from sound powered Deck-Talkers used on
WWII era military ships. They have balanced armatures and
are extremely sensitive, and very low impedance.

Pete K1ZJH

Ben Tongue's website offers exellent engineering analysis
and practical information on crystal set design:

http://www.bentongue.com/xtalset/xtalset.html

For good practical discussions try TheRadioBoard.com.
Lot's of xtal set experimenters over there to answer
questions...

Pete k1zjh