[Drake] T-4XB audio improvement

[Chris Codella, W2PA]

In 2007 I made a very simple, reversible modification to the microphone 
amp in my T-4XB to improve the audio quality.  Since the affected 
circuit is practically the same in the other T-4 models and the TR-4, it 
should work in those rigs too.  I've confirmed the on-air improvement 
over a couple of years of using it this way, on both SSB and AM.

For details, go here: http://www.w2pa.com/drake-t-4xb-audio-improvement

73,
Chris, W2PA