[Lowfer] Tech question

[Ed Phillips]

check with the Antique Wireless Association AWA
you should be able to get a good set of old headphones
with very good sensitivity fer not much

the ones that use Mica as the diaphragm are good

Bob K3DJC

http://www.antiquewireless.org/

there is a mail reflector list as well

Bob"

	"The ones with mica diaphragms" are Baldwins and are relatively expensive.  I have a number of old stock "2000 ohm" headphones going back to the early 1920's and they all work well with crystal sets but the headbands and cords are getting kind of frayed so I usually use WW2 military types with R-14 elements which used to be easy to find.  Not sure now.  The ANBH-1 elements are much lower impedance and I wouldn't use them.  I've also used several of the common types [usually borrowed from the airlines after I'd "bought them" for an exhorbitant price] with a matching transformer.

	Another very simple and cheap solution is to use an opamp between the crystal set and the headphones - that will let you use low impedance ones and is probably the cheapest solution.  I have such an amplifier built into a little box and using a quad LM324 opamp which operates from a 9V transistor radio battery.  I can switch in from zero to four stages, the latter with a voltage gain of 10 each.  At max gain that really improves things!

Ed