Preamplifier Ypsilon Electronics PST 100 Anniversary Silver

Tube preamplifier with transformer volume control and a zero-feedback signal path

The Ypsilon PST-100 Mk2 is a flagship tube preamplifier whose concept is built around custom 31-tap transformer volume controls. Unlike conventional resistive dividers, which introduce their own noise into the signal path and limit resolution, attenuation here is achieved by switching transformer taps. Such a solution helps preserve signal purity and microdetail across the entire volume range.

The active gain stage consists of a triode-connected Siemens C3m pentode in single-ended configuration, operating entirely without feedback and coupled to the load via an output transformer. A gain of 16 dB and an output impedance of no more than 150 ohms allow reliable driving of power amplifiers even with longer interconnect runs. The power supply uses tube rectification with a 6CA4 and a choke filter, which reduces residual ripple without the hard switching character of solid-state rectifiers.

Internal wiring is executed with hand-soldered point-to-point connections in pure silver wire, minimising the number of transition contacts in the signal path. The transformer attenuator is placed after the tube stage, so the active circuit always remains in its optimum operating range and dynamics are not restricted even at lower volume levels. This shows itself in stable instrument localisation, legible microdynamics and a low noise floor.

For users who prefer purely passive volume control, the PST-100 TA version is available without the active tube stage, built solely around the transformer attenuator.

Key features

• Volume control: Custom 31-tap transformer attenuators
• Gain stage: Triode-connected Siemens C3m pentode, single-ended
• Signal path: Zero feedback, output transformer, 16 dB gain
• Power supply: 6CA4 tube rectification with choke filter
• Construction: Point-to-point wiring in pure silver wire