I had the Radio Shack meters too, for the cool factor of course. I had them hooked up to a two channel receiver that had A/B speaker connects so naturally I bought a meter for each pair of speakers. Come to think of it they're still in use today on a system of leftovers put together in my parents basement that I left for them to use when I moved out decades ago. While they may not serve much function, they sure do last.
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Marantz AV7702 mkII
Outlaw Model 7125, Outlaw Model 2200 (3)
Oppo BDP-83, LG UBK90 4k
LG OLED C8
Directv
Sony PS4 Pro/PS3
Polk Audio RT800, CS400, FX500
Atlantic 44-DA (4)
Sunfire True Subwoofer, Epik Empire
APC H15
Harmony Elite remote
Blue Jeans and Monoprice interconnects