The First Watt 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. In 2011, we introduced our first SIT amplifier using a custom Silicon Carbide (SiC) transistor part made by SemiSouth. The amplifier also used a single power device, operating without feedback in single-ended Class A Common-Source mode to deliver 10 watts of power emulating the characteristic of a Triode, but operating at voltage and currents directly needed by loudspeakers, eliminating the output transformer. The success of the monoblock SIT-1 led to the SIT-2, which offered similar performance at higher efficiency, and two channels in the same chassis. 2018 saw a production of the SIT-3 which operated the SIT transistor in Common-Drain (follower) mode, again without feedback which was available until 2023. Some years prior, SemiSouth suffered bankruptcy and we found ourselves unable to acquire more of this special part. However, there was a company in Japan Tokin, known for making industrial Silicon SIT parts suitable for audio use. Their production facility was destroyed in the Fukushima earthquake and tsunami, but we were able to acquire these parts from existing inventories of these devices over several years. These large Tokin SITs enjoy that same Triode character but at much higher voltage, current and power ratings than our original SITs. www.firstwatt.com
