Yup... The amplifier has a 1.5 farad cap hooked up to it. The amplifier is a McIntosh MC4000M (1000 watts total across 6 channels). The spec sheet says it draws 7.5 at idle, 140 at the rated power. It is a lot of juice but even when the volume is turned up (which I rarely do), the charge LEDs on the cap never drop below the 2/3rd mark.

I was thinking it may be a voltage drop because Valentine One radar dectector owners who hardwire their detectors into E36 BMWs (previous generation 3 series) run into the same issue - flash of the high beams causes the detectors to power cycle. In fact, V1 will install a cap into the detector for E36 owners for free. They always claimed it to be a voltage drop.

Hmm... I'll have to hook up a multimeter and get some readings. Don't think my Fluke DMM will catch it though. I'll have to get an analog MM and some warm weather! Hopefully it won't happen very often until then. So far it only happened twice in 4 months. Thanks for the tip on the voltages...