I just found an old headphone amp that is cheaper and weaker that still works that I'd tried before this one. I couldn't get a single pop of static out of it anywhere in the car. Suggests something may well have gone wrong with the amp I've been using.
Next I'll try the staticy amp in some of our modern cars/van. If it is staticy there then I think it will be safe to conclude that it is, in fact, a probelm with the amp, not Old Henry.
After many months of chasing and fighting this static problem without success I finally gave up and just tolerated it. Then, recently, I found the ground strap from my engine loose on the firewall so tightened it. In addition to solving my starting problems and charging problems I'd had for months I was pleased to discover on my road trip last weekend that it also solved my static problem.
