Audio Magic cables and YG Acoustics are all I can think of. But jetter nailed the biggest seller👍And oldest company and probably the Best audio tweek. Of course it goes with other enhancements available In Colorado
Colorado-Based Manufacturers
I'm trying to compile a list of manufacturers based in Colorado (amps, speakers, or otherwise)... I know about Ayre, Avalon, Boulder, & PS Audio. Any others people are aware of?