PST-100 MKII

About the PST-100 MKII

The Ypsilon PST-100 MKII is a high-end tube line preamplifier aimed at audiophiles seeking maximum transparency and low coloration. It combines a no-feedback single-ended active gain stage with a custom transformer attenuator and offers both passive and active operating modes. The active stage uses one Siemens C3m tube per channel, transformer-coupled to the output, providing a gain of approximately 16.9 dB (x7). The power supply employs valve rectification (EZ81/6CA4) with a choke filter. Volume is controlled by a transformer-based attenuator with 31 steps, avoiding the sonic compromises of resistive potentiometers. In passive mode the signal is routed only through the transformer attenuator with no added gain, ideal for low-output-impedance sources; in active mode the C3m tube stage adds gain while maintaining low feedback and high linearity. The preamp provides six inputs (five unbalanced RCA, one unbalanced XLR) and three outputs (unbalanced RCA, unbalanced XLR, and a buffered Tape Out). Construction features point-to-point wiring with custom pure silver wire and in-house-wound transformers. It includes remote control for volume and input selection, weighs about 25 kg (55 lb), and measures roughly 400 x 180 x 410 mm (15.6 W x 7 H x 16 D). It is widely described as extremely transparent and quiet, approaching a straight-wire-with-gain presentation, and omits balance and mono controls in favor of a minimalist, purist design.