First Watt SIT-5 Amplifier

The SIT-5 is the most recent amplifier produced by First Watt, and is the fifth to use a Static Induction Transistor (SIT) as the power amplifying device. It operates without feedback in single-ended Class A Common-Source mode to deliver 10 watts of power, emulating the characteristic of a Triode.

The amplifier uses large Tokin SIT parts with unique characteristics that closely simulate the Anode-current to Anode-voltage characteristic of Triode vacuum tubes. These devices allow operation on Class A "load lines" that determine the relative values of second and third order harmonics.

Key features include a single-stage output circuit without negative feedback, using a high-power SIT rated at 600 volts, 30 amps, and 400 watts with frequency response to 50 MegaHertz. The amplifier is current biased by a negative 60 volt supply rail through a P channel Mosfet.

These amplifiers are aimed at audiophiles who appreciate detail, warmth, depth, and imaging. They are designed to provide a unique sonic signature with a dominant second-order harmonic character.