I've been using ESP cables in my studio since 2016. I use them on guitar amps, power supplies, powered monitors, synths, and mic preamps - essentially, every piece of gear that handles an audio signal.
Every single piece of audio gear I've tried with a MusicCord or MusicCord-PRO has sounded remarkably better with it.
The audio is more three-dimensional, the fundamental is more solid, the midrange is clearer, and the highs are beautiful. The placement of instruments in the stereo field in the studio monitors is rock solid. There's heft and weight to the audio that's missing without the ESP cables. Tube amps sound more liquid, detailed and powerful. There's less noise and hash.
I like my gear better. I'm more satisfied using it, and I'm not constantly looking at trading/upgrading it.
Clients coming into my studio tell me they love the sound I'm getting; but equally important, I love the sound I'm getting.
It doesn't get better than that.
Les Schefman (USA)