FYI - Dave told me when I bought my 550B that the pop when using the "switch" was to be expected.
And no doubt, if you had everything turned up, it was a very annoying and loud pop. But having known that,
I never switched it with volume up, and other than that, the amp has always worked great for me. Never needed to switch it during a song - that would be a pedal's job.
Maybe same thing with the limiter light. You really had to bang on the bass for it to light up, and I think it
was more of a "heavy compression" vs. "any compression" light IF I remember right. Which is doubtful
I am still scratching my head over this whole thing. But I would be scratching a lot more if I got screwed as it sounds like some of you did. I guess Walter Woods kept service going longer than David did. Oh well.