>> Actually I'm pretty sure my PC microphone is a crystal mic...

> UH? do they still sell that? Usually they are electrets

Sure - why not? They sell crystal ear pieces too - very useful with 
home-made crystal radio sets. And let's not forget, picture speakers use 
crystals too...

>> [The microphone that works is marked as "dynamic", whatever that means.]
> 
> It means a moving coil microphone, no need for power

Right. So a reverse speaker then?

>> I had a go with my dad's test meter. At 0 Hz, the working mic has a 
>> resistence of about 600 ?, whereas the non-working one is about 1.2 k?. I 
>> don't know whether that has anything to do with anything. [I don't have 
>> the specifications for my outboard sound card to hand...]

> For the dynamic microphone you measure the DC resistance of the coil.

Right. So the working mic has a DC resistence of 600 Ω.

> Electret microphone are buffered by a FET and insulated from DC by a 
> capacitor.
> You can't measure a useable impedence at 0 Hz :-)

OK. So assuming it really is electret, I can't measure its impedence 
meaningfully.

I'm 70% sure this is the guy BTW:

http://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=24698&doy=12m6#spec

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message