The Whitestone Audio P331 is designed by Dave Rosen and is a Class A fully differential tube amplifier (dual-triode 6SN7GTs). The all-analog circuit is digitally controlled and supported by an onboard ROM chip.
The magic happens on Loading control. Turning clock-wise, it increase the operation point of the vacuum tubes. Selectable feed-back or feed-forward modes give wide latitude to this process. Loading is not just “hitting the tubes“. Each rotary switch position affects the tube’s internal gain. It forces the audio to different points on the tube’s response curve. This essentially allow control the tube’s operation point.
A parallel filter sits beforehand Loading and can enhance highs, lows or even both. When engaged, the signal is passed through the tubes and blended back in with the unaffected input signal at a set percentage.
Two transformer options: This unit is designed to run fully transformerless. So, the transformers are here to serve as another tone shaping tool. A solid-state output stage is the last stop on this beautiful versatile piece of gear.
The P331 doesn’t work as a typical tube loaded unit. It is much more invsible without losing its charm and doesn’t shape transients additionally like traditional tube gear does. It brings both impact and detail to the source material.