To update....
I've been talking to Mike Pickett via email & phone (as well as doing a little research myself on the net) and the popping may be caused by a small amount of DC voltage on the outputs.
There is a DC Offset adjustment that can be done on the amps, if required. I tested all three (3) outputs on my 6B and they tested +/- 0.000 volts...perfect.
The 14B SST tested +0.005 & 0.011 volts on outputs. So, we'll do a little adjustment to bring them down to zero (which is where they are targeted to be) and hopefully that takes care of the popping

Keith