Günther wrote to me in an email with a lot more detailed information about how the earphone works and provides an interesting discussion about impedance.

The (classical) sound converter is the electro-dynamic version. It consists of a membrane made of thick paper or thin plastic (waterproof) which has a cylindric coil (some dozen … some hundred turns of thin isolated copper wire.

This coil is movable in a cylindric hole in the magnet, so that every AC voltage acts to move the coil (with the membrane) up and downwards (like a pump or a special motor) – this “generates” the noise / music etc..

A cross-section drawing is appended as #1.

This principle is used in all the classic microphones since ~ 1950 (not elektro-stats! That’s a complete other world, see later), loudspeakers of any construction and size (not high-tone piezo-tweeters!),  classic headphones (not special High-End constructions, see later) and EARPHONES (not piezo/crystal/quartz versions!)

=> ALL LECTRON earphones are ALWAYS electro-dynamic 300 ohms! Why?

Because they can be used instead of the loudspeaker block (you may measure: ~ 300 ohms, like the earphone!) Therefore all the year until today this are the two types in my photo to the right. The one version (newer) in white with metal plate, and the other (Miss) Piggy-colored for many years and today (with the two plugs) as part of the Buchlabor. The “universal component tester” can show you all values of this blocks / parts – so please use it…

And look at the electric symbol of the earphone block: what do you see? A thick black line (= membrane) on a square (= magnet with coil) – what does it mean?

YES – an electro-dynamic phone – similar to the loudspeaker symbol where the trapezoid means the funnel shaped membrane, see #3 + 4.

Therefore you cannot use the mass of cheapest earphones / earpieces with 6 / 16 / 32 ohms – the amplifier transistor will smash! These earphones were given with all the millions of pocket radios since 1955. Meanwhile these earphones (sometimes two for stereo) come in huge container ships from China and are not worth the money…

and cannot be used with Lectron, too.

Only some of my special circuits and applications may be used with these…

Forget the word “ceramic”! What does is mean common? I don’t know – perhaps a ceramic housing? Ceramic has no physical and not any electric properties!  I cannot make music with a ceramic tile! I may glue it on the bottom or on a wall in my house – but does it make music???

What could be meant is: a ceramic wafer with gold leaf membranes like in this version of a limited edition (300 units) of the best headphone of the world, together with this special amplifier (!) and an output of 400 V (!) to drive the headphones – called ORPHEUS HEV90 – for 30’000 DEM (1991) see appended advertisement of SENNHEISER Germany #2.

Last but not least: all crystal / quartz / piezo (= tiny metal plated ceramic strip, since ~1953 used as “saphire” pick-up in record players) have a no ohm value – because “stone” is not an electric conductor (!) sometimes it is so simple…  Perhaps more than 100’000 kohms but: forget it! Sensitivity: quite good, quality: bad – not / never for Lectron!

By the way: the symbol(s) of piezo/… whatever material phones / pick-ups / tweeters is a rectangle with a plate on each of the both long sides (like a capacitor  filled with a small brick and glued with a foil working as membrane…) – so simple can it bee in our life – see #5.

And now some words to “impedance”: depending on the construction, kind of metal / coil and weight of the metal components the coil may have different resistor values in the range of 35 … 20’000 Hertz/cps . Always at 1 kHz/kcps (= 1’000 Hz/cps) an impedance will be measured and offered in catalogs etc. as “Z = xxx ohms”, where “Z” is the impedance unit and ohms are the measured value at 1 kHz. This can be done only with expensive measurement tools in specialized  companies, drawn as a “curve over f”, f = frequency.  (low frequency = lower resistor value, high frequency = higher resistor value).

So the “real resistor value” may be 255 or 310 ohms, but the “impedance value” can be 350 / 500 or even 1000 ohms – never care! Everybody in the “background” knows it – and that is enough…Not to confuse all people 😉

Hope that helps,


  • This reply was modified 2 years, 3 months ago by Michael.