OK. Let's think this thing through.
Your Supratek had the left channel die.
Your left sub is dead.
Why?
The last time I checked, both channels were now dead on the Supratek. Jack wants me to hook it up one more time before I send it off to North Carolina under warranty and I was going to do that tonight.
To the best of my recollection, all of this started with the addition of the subs. By that, I mean the very loud and concerning thump in the left channel coming out of the sub when turning the Supratek on and off. I think starting off, I had the Rythmik toggle in the on position, then I switched it to standby mode for operation.
Now I will admit that my usual mo was to leave the Starkrimson amp on 24/7 and just turn the tubed Supratek preamp on/off every night for listening. Whether it was an interaction between these three pieces of equipment, I have no idea.