![Confused :?](./images/smilies/icon_confused.gif)
I feel like such a slow learner. I'm getting the idea that something involving a negative feedback op amp between the source material and the amplifier is a far more efficient way to go, but it seems beyond my skill level at the moment.
At least I figured out what was causing the mysterious clipping. For some strange reason my amplifier goes from flat at 16 kHz to nearly 6 dB up at 20 kHz, which coincidentally is nearly perfectly matched by losses in the impedance-matching transformer. It does this into a dummy load as well, so it's not the transformer's fault. I suspect it may need servicing, and also that I'm asking it to do things it was never designed to do.