As far as a source is concerned, one could use the tone generator in the True RTA program to find a steady 60Hz tone. Even the free/trial version of True RTA has a working tone generator. So if I feed a signal from a PC running True RTA into the 950 in Stereo7 mode and make the proper adjustments, I should be able to get a nearly identical voltage level from each output of the 770.

I’m still not sure about running a continuous 40 or 50 watts into a speaker’s voice coil, even if that speaker is rated to 300 watts.