Newbie here. I've had a pair of Dyna ST-70s since the late 1970s. I used them in stock form, set to mono and cross-wired, to drive a pair of AR 4-Xs for many years. I fed them with a PAS-II or III, I don't remember for sure. In 1991, Kevin Kennedy (KTA Audio) modified them to bi-amplify a pair of Audio Concepts, Inc. Sub-1s and Little Vs. After 32 years, including 6 years of dormancy, the system needs work and I've moved on.
I've isolated the various problems with my system, however. One of my ST-70s I was using to bi-amplify the ACIs has issues. It won't bias up and it hums, Tube swaps don't help, so I suspect it needs to be recapped. I rigged the other two amps (one of which uses one channel in triode mode for the LV and the other channel in ultra-linear for the Sub-1, and the third amp, which is set up in stereo triode mode to drive another set of satellite speakers), to test all four speakers. I've determined the drivers are done after 32 years, including 6 years of dormancy--when I press on them with my fingers, they feel stiff and make a crunchy sound.
Fortunately, my hand-made, tube preamp (also KTA) is still a gem, and It now feeds a used but new-to-me Mac MC152, which drives a pair of Revel M106s. I think I'm happy with the new gear, and the 33-year-old REGA II with the 19-year-old Semiko Blue Point Special EVO III is still remarkable! Vinyl really is the best!
So, my question for the brain trust is this: What do I do with 3 heavily modified ST-70s (the front end boards are designed and made by Kevin and utilize one 12ax7 and two 12Au7s), two Little Vs, and a pair of Sub-1s with crossovers modified for bi-amplification?