Re: Hot Rod Mic - Correction

[Mike Curtis <wd6ehr@xxxxxxxxxx>]

> 
> OOPS!  Thanks for pointing that out, Mike.  I was in a daze yesterday.
> The capacitor IS 150 pfd.... so that would be .00015 ufd. 

Aha!  It's a "loudness control", not a "volume control".  A very 
elementary one, but one nonetheless.

What's the difference?  Loudness also adjusts frequency response to 
correspond more with what the ear perceives.  Volume adjusts everything 
and takes naught the ear into consideration.

At 5 meg, 150 pF would give a -3 db frequency of around 2 kHz.  As
resistance is dropped (lowering volume), the frequency passed by the
capacitor @ -3 dB would correspondingly be raised.  At lower volumes, you
would get more high frequencies.  Whether this is done to compensate for
loading of the element, or???, I really couldn't say without doing actual
tests. 

Most hi-fi sets have a "loudness" switch that converts the volume control 
to a loudness control.  It boosts bass and treble frequencies at lower 
volumes.

> Thanks again for catching that!

No problem.  I thought it was a .15 uF cap, which didn't make a lot of 
sense to me.  But you're the one to be thanked.  You did all the work.  
All I did was find one minor detail.

Thanks from all of us following this most interesting and informative 
thread.  (Now, where's my soldering iron :-)

 -- mike