All Lectron earphones are – magnetic – 300 Ω versions -because they may be used as an alternative to the speaker block (with output transformer). The coil(s) are like the output working resistors for the transistor amplifier, and there is a current of some mA. Therefore no 8 Ω version must be used – the transistor will get hot and “die”!
The crystal version (sometimes called ceramic /piezo) is like a condenser / capacitor – there cannot flow any current, so this won’t work for a “normal” Lectron amplifier stage. No ohm value can be measured checking this kind of earphone, and they were bigger (used in the 1950ies and meanwhile very rare), see details in this photo:
Hope that helps.
- This reply was modified 3 years, 6 months ago by Guenther.
- This reply was modified 3 years, 6 months ago by Michael. Reason: Changed font and size styling for easier reading