Tom,
I beat you by 11 years, and in 1959, while I was a kid in the U.S. Navy, I purchased a Motorola stereo, one of those huge pieces of furniture that measures 8 feet from end to end. It used that exact system. Ironically, after all these years, the thing still works and I gave it to one of my sister's grandchildren. They had a party, spilled a soda into the amp, and that was the end of the system. I havn't had the opportunity to experiment with hooking the same system up from the keyboard amps yet, but with luck I'll give it a shot in the next few weeks and post the information.

Cheers,

Gary