Subject: Re: Audio response of Exciters ( Was : audio hissing at high end)
Date: 1998/10/19
Author: C. Gould <tigercom@nacs.net>

The Panaxis is an OK exciter.
                  
As for the bass, I noticed the same decrease in LF response, and found that 
the PLL loop filter was set too fast, causing the PLL to mistake bass
for frequency drift rror, and cancelling it out. It was not a bad decrease.
The Ramsey FM 25 is horrible in this regard (no bass to speak of), and the
Ramsey FM 100 wads only slightly better than the 25.
                   
Anyway, after CAREFULLY studying the design, I modified the PLL loop filter,  
and increased the size if the input electrolytic capacitors to about 100 uF
to allow bass response down to 5-10 Hz, and that solved things.
                   
For those of you with an Oscilliscope, and a decent composite output from a 
tuner, you can see this quite easily.
                   
Just feed a square wave at about 80 Hz into the composite input of the 
exciter.  Then look at the demodulated waveform.  If the "tops and bottoms"
of the square wave is not perfectly flat, then you've got Low Frequency roll off
happening.
                   
                  C. Gould