"I find a subset of people in the Analog section of the board who are terse, unhelpful and impolite if not outright rude and insulting. What could be more unhelpful than to present, as a fact, something that simply false."
Would you like a lollipop to make you feel better? I made an error in my preconception of the definition of the term "rise time", and I subsequently admitted as much. No insult was intended. Yes, things can get heated here once in a while. You came here with your mystery. Now you want to insist that you alone have solved it. OK. I read that your preamplifier uses no output coupling capcitor; instead, it uses a servo to balance out any DC offset in its output. So your preamplifier could in theory emit DC, IF and only if its servo corrector is not operating rapidly enough to prevent any DC offset in its output. But even then, the error in cancelling DC would likely be in the low mV range, perhaps not enough to move your woofer so obviously. (I say this because I use an Atma=sphere MP1 preamplifier that also uses a servo to cancel DC, and I have measured the error at 2mV, max.) I don’t know what amplifier you are using. If your amplifier uses a coupling capacitor at any point in its circuitry, then the amplifier cannot pass DC to your speaker, even the low level that might theoretically get past your preamplifier. Those are just facts. Not insults. I am only interested in getting the facts straight, because if you write something here that is just not possible based on facts, then some other reader may be misled. I operate on the assumption we are all here to learn.