The HI VOLT Ruby version has been tailored to players who like a lower gain more vintage JTM 45 type of sound with the abilty to go beyond. The 1st Black “HI VOLT CUSTOM” had 3 times the gain and a more modern Eq curve to it. The Ruby Hi Volt is more tame, vintage sounding but still takes advantage of the tube sound and feel of a  JFET circuit in cascaded form plus the powerful POST - 3 – band active Eq section The Hi Volt can take an amp of any size and give it an unprecedented amount of depth and mass. It works exceptionally well with both single coil and humbucking pickups.