Regarding the muffled crackling sound I mentioned earlier, and you just asked about...
It wasn't tube arching, no. But Aviator Audio in Edmonds, WA spent a LOT of time with the chassis removed. Here are some comments from an email sent to me:
"It turns out that the entire preamp pc board from one side to the other was contaminated with something that was not visible to the naked eye; you could see it only with high magnification. We ended up finding it by blowing with a straw across the pc board which induced moisture and made the substance conductive, thereby causing the amp to crackle.
My guess is the transition from your car to the house, a change in temperature in your house, or just enough ambient humidity in general was enough to get it going. For us here in the shop the only way we could get it going was the straw method, or letting it sit a couple hours in the other building where it’s colder than the main shop, and then bringing it back in were it would condensate enough to make noise.
Very long story short, we pulled the entire board and cleaned it, and decided while we were at it to hardwire a majority of the preamp connectors like we did in the output section for good measure and reliability. It’s been running solid over several cold/heat cycles and after today’s round we’re calling it done. Short of some pesky crackle or other sound rearing it’s ugly head, I would say it’s available starting tomorrow."
End of email excerpts.
As for the speakers in my A212, I'm hoping to find replacements soon, and bolt them in, not using wood screws. Eminence for replacements? Which model? I'm looking for high-wattage speakers, so they don't break up easily. I love this amp the way it is - loud and clean.
Tom Hanser