amp question

[Thomas Hinkle <hinkl_th@xxxxxxxxxxxxxxxxx>]

I just noticed that when I'm playing high notes on my amp (7 draw and up
on a C harp) I hear the octave below it playing.  It's pretty dramatic and
I'm not even sure if I can here the note I'm playing coming through the
amp or not.  Does anyone have any explanation for this?  I just got a new
speaker put into it (I think they actually put in a used one of the same
type as the old one) and I'm not sure if that has anything to do with it
or if I just started to notice it now. 

On an unrelated note, what mics do people have the least feedback
problems.  I've heard that ceramic elements are better at not feeding
back, but how dramatic is this difference?  Also, is it possible to
replace the crystal elevent in my JT30 with a ceramic ones, or are the
mics entirely different.  

Below is a bunch of information on my equipment for the tech guys to look
at if it helps with my question...

note: I don't really know anything, I'm just going to write down stuff I
see written on my amplifier, and hope you can interpret it.

First of all, my mic is an Astatic, JT30VC with a crystal element.  

My amp is an Airline (from Montgomery Ward :-) 
Model 8503
117V 60C 55W .5A
95GDR8503

has vibrato and vibrato footswitch jack.  4 inputs.  Contronls for
strength and speed of vibrato and volume and tone controls.

I'll type up the little tube diagram on the inside of it

Main Chassi Tube Diagram.  Control panel has one additional tube type 12AX7
				CABLE
12AX7	6v6GT	6V6GT	6AU6	6X5GT

The speaker has some little numbers and stuff along the edge, which read...

220112

P12S C5202


p.s. Even if this doesn't explain the stuff I asked about, could someone
tell me what all of this means.


				-Tom-