He lives inside the box. Master builder Mark Bartel has focused on nothing but the design, construction and perfection of the vacuum tube amplifier for over thirty years.

Mark tests and retests countless wood, component and configuration combinations until he hears sound worthy of the name Tone King. Off the shelf parts? Not here. Mark works with USA-based manufacturers to develop custom components that meet his demanding requirements.

Mark's first vacuum tube amp model, the Imperial, is a trusted small venue standard. His Metropolitan model features Phase-4 power control, a breakthrough in vacuum tube amp technology that ensures consistent tone from 0.1W to 40W, clean or gained up, in big venues or small. Mark and PBG recently introduced the Metropolitan Head, in response to numerous requests from dealers and customers.