The Gearhead: First Watt SIT 3

It’s not terribly often that we get First Watt amplifiers in at TMR, and they tend to sell quickly. The first thing you notice when you dip into the mad world of designer Nelson Pass’ funky side project (obviously the main gig is Pass Labs) is the fascinating variety of ways to make lower wattage amplifiers that operate in class A.

Ever the circuit magician, Nelson in this exquisite little First Watt SIT 3 amplifier uses something called static induction transistors to provide the power. These are custom made active devices that he has used in his SIT 1 and SIT 2 amplifiers.

In those, Nelson says he used the static induction transistors in a Common Source configuration, which meant the amp was phase inverting, and polarity had to be corrected by reversing the binding posts.

In this design, he’s switched up the way he uses the transistor, creating a Common Drain configuration for the SIT device. This way, he is required to include an input transformer to help it get the right voltage and current it needs, but the output is in phase, and, to my ears, downright heavenly.

True to First Watt form, the amplifier has no feedback, and uses every millimeter of those impressive side-mounted heat sink fins to dissipate heat. A class A amplifier uses a lot of power to make a little (very clean) amplification, and this SIT 3 is no different.

But listening to this beauty I can’t help but be struck by how sparkly clean yet eminently musical the sound is. Especially going from my testing amplifier, which is a class D with class A input stage kind of thing. Going back to it, it seems all I can focus on is harmonic distortion and its diffuse, if only minutely, sense of soundstage and separation.

Dang it! Sometimes this job isn’t much fun at all. Well, excepting those times when I can listen to great music through a great design of an amplifier from one of the legends in the industry. There is that, I suppose.