I suspect that your LS3 had some DC at its outputs which caused the popping in/from your SS amp. Not unusual with tube/ss combos.
This is relatively unusual with tubed amps as their transformers will not pass the DC. Some SS amps have built in protection from DC and also keep it from passing DC, but these are usually the expensive 'overbuilt' models. DC passed on to the speakers in excess can damage the speakers as well as the amps.
If you are talking about a tubed ARC amp that would be a safe combo but if you are talking about an ARC SS amp I'd check out how it deals with excessive DC.
FWIW.
This is relatively unusual with tubed amps as their transformers will not pass the DC. Some SS amps have built in protection from DC and also keep it from passing DC, but these are usually the expensive 'overbuilt' models. DC passed on to the speakers in excess can damage the speakers as well as the amps.
If you are talking about a tubed ARC amp that would be a safe combo but if you are talking about an ARC SS amp I'd check out how it deals with excessive DC.
FWIW.