This tube is a version of the 0C2 voltage regulation tube. It's hard to describe the presentation these tubes produce in the Decware amps that utilize the 0_2 series of voltage regulation tubes, but ever since Will first mentioned these years ago and I tried them they are my GO TO, exclusively used, voltage regulation tube. They were just amazing in my SE84UFO3 monoblocks regulating the input tubes, and I use three in my SEWE300B amplifier and though I've tried all three 0_2 types in this amp in varying configurations and combinations including different brands of the same tubes, the three 75C1 just won't come out.
There's a certain appealing texture tot he music, a bit more "depth" to the sound and a darker (in a good way, blacker background, neutral nature) feel to the resulting sound. I just LOVE thiese tubees.
I have experimented with differeng versions and find that for my system and tastes those made in the UK are clearly preferred.
If you haven't experimented with them and have amps that use the 0_2 series of tubes try a 75C1!