Loop Antenna broadband amp

I've been searching for some hints as to what may be in the resin-encased amplifier used on the Wellbrook loops without much luck. Their power demand of 130 mA at 12 volts is kind of high for any FET diff-amp, PNP level shift, into a balanced to unbalance output transformer arrangement. I'm using that configuration right now on a tuned loop that only requires 17 mA at 9 volts. Any ideas or links to useful information?

Thanks,

Chuck