Mic explaination

[John Frazer <jfrazer@xxxxxxxxxxxxx>]

HARMONICA JOHN	San Diego  PO Box 740613 SD CA 92174 (619)263-6826

God, family, music, fishing, work.	 Can blue men play the whites?

On Tue, 4 Jul 1995, Bobbie Giordano wrote:

> Awhile back I seem to remember discussions about switching out the innards
> of a JT-30/Blues Blaster with a Bullet cartridge, which gave a Bullet-like
> quality in a JT-30 shell and added benefit of volume control.  Why not try
> going that route with the idle JT-30/BBs?  

The cartridge has nothing to do with volume control. That is what the 
POTentiometer is for. You can have volume control on an Astatic. 

> One difference I've noticed is the Bullet weighs twice as much as a 
JT-30/BB. > 

There is a big difference in the weight because there is a big difference 
in the cartridge. The bullet has a "controlled magnetic" element- 
whatever that means. It is basically a dynamic mic with some kind of 
transformer on the back. The transformer may be there just to allow for 
impedance matching (hi or low).
	In case you don't know, a dynamic mic has 
a magnet with a slot in it in which a coil of wire is caused to vibrate 
by sound. The coil of wire cuts thru the "lines of flux" inside the 
magnet thereby inducing an electric current which varies with the sound 
input. 
	A crystal mic has an actual piece of rock(silicon or quartz, I 
think) that is attatched to a funnel-like piece of metal which focuses 
the sound vibration on it. This induces a voltage by the "piezoelectric" 
effect. Over time the crystal can soak up moisture and become less robust 
in its output. The piece of rock is quite small, and the sound focosing 
metal is lightweight to increase its vibrational qualities so it won't 
weigh as much as a big ol' magnet. 
	You probably didn't want to know, but there it is as I understand it.

Again, have a good Independance Day celebration! 

HJ