Jun 122018
 

Today’s exciting arrival is the First Watt SIT-3 stereo amplifier, which was designed by – and in the case of this particular SIT-3 amplifier – hand-built by Nelson Pass himself!

The First Watt SIT-3 stereo amplifier designed by Nelson Pass.

I consider Nelson’s First Watt amplifier designs to be an artistic expression of what is possible at the cutting edge of audio performance, and as such they are state-of-art minimalist circuits designed with the ultimate musical and sonic performance in mind.

Simplified SIT 3 topology schematic.

Nelson’s First Watt amplifiers also tend to be lower power designs, and in the case of the SIT-3 that means 10 watts into 16 Ohms (my vintage Altec loudspeaker collection) 18 watts into 8 Ohms (as with my Tannoy Westminster Royal SE loudspeakers), and 30 watts into 4 Ohms.

SIT stands for static induction transistor (i.e. a VFET), which is what the First Watt SIT-3 uses in its power stage, and Nelson says it has the character of a tube triode.

Static Induction Transistor

The SIT-3 is the 3rd iteration of Nelson’s First Watt SIT stereo amplifier design, thus the “SIT-3” designation, and it differs from the SIT-1 and SIT-2 in that the SIT-3 is operated in common drain mode, rather than common source mode like the SIT-1 and SIT-2.

Common source mode provided both voltage and current gain for the First Watt SIT-1 and SIT-2 amplifiers, but common drain mode in the SIT-3 provides only current gain, so Nelson utilizes an autoformer in the SIT-3 to boost voltage by 11dB.

Nelson says, “The SIT-3 has more power, more damping factor and less distortion than the
previous designs. It retains their desired second harmonic character with even fewer
higher order harmonic components … The SIT-3 has an organic quality that breathes more depth and
life into the music … This is one of those all-night, year-after-year pieces.”

As always, I’ll have a lot more to say about Nelson Pass’ First Watt SIT-3 stereo amplifier, and will be providing some first impressions before long, so stay tuned!

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Postscript 1: Yesterday my buddy Ron stopped by to listen to the new First Watt SIT-3 stereo power amplifier that had arrived from Nelson Pass, and we had a nice time listening to the rich, dimensional, nuanced, and natural sounding SIT-3.

First Watt SIT-3 (right) and vintage Fisher SA-100 stereo amplifier (left)

The SIT-3 was changing by the moment as we listened to it warming up and running in, and there’s still a lot of run-in that needs to occur, but suffice it to say that the not-quite fully-baked SIT-3 never sounded less than delicious and beguiling.

I’ll have a lot more to say about the SIT-3, but just as a word of advice, if you have an inkling that you would like to have a First Watt SIT-3 stereo amplifier of your very own, and have loudspeakers that can be driven with 18 watts or less, you may want to consider buying one of these quickly before they sell out, as there won’t be many made.

The First Watt SIT-3 is the first amplifier I’ve listened to in a long time that I thought could entice me away from my restored and hot-rodded vintage McIntosh MC30 monaural amplifiers – it’s really good, and it isn’t even completely run-in yet!

Much more to come about the First Watt SIT-3 in due time!

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Postscript 2: Well I’ve now got the First Watt SIT-3 properly installed into my Westminster Royale SE based system, and my vintage Mac MC30 monaural amplifiers are sitting forlornly off to the side of the room.

First Watt SIT-3 installed into the Westminster based system.

Nelson Pass’ First Watt SIT-3 is a ridiculously good amplifier, displaying both accomplished musicality and sonics.

I forgot to say in my last postscript that I put one of Mark Coles’ Sablon Audio Gran Corona power cords on the SIT-3 in place of the stock power cord, and as I’ve experienced with other Pass amplifiers, a really good power cord makes a huge difference in performance. If you’ve got a Pass or First Watt amp and are still using the stock power cord, you haven’t really heard what your amp is capable of yet, so you’ve got an adventure to look forward to!

I’ve been listening to the SIT-3 a lot with both the Soundsmith Zephyr Mk III and Carmen Mk II phono cartridges as I’m finishing up the review of the Carmen Mk II for Positive Feedback, and they are exquisite together!

I’ll have a lot more to say about the First Watt SIT-3, so stay tuned for more!

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Thanks for stopping by, and may tone be with you!

 Posted by at 9:17 am

  4 Responses to “Today’s Fresh Catch: The First Watt SIT-3! Postscript added x2.”

  1. Looking forward to hearing more!

    • There will be lots more to come, Joseph! I can tell you that I’ve now got it hooked up to my West’s and the SIT-3 is sounding mighty fine. The SIT-3 sounds rich, transparent, and musical, and at 18 watts has just enough power to make the West’s sing.

      Kind regards,

      Jeff

  2. Exciting news, Jeff — I’ve been waiting for the reviews of the SIT-3 to start coming in.

    Coincidentally, I only very recently bought a FirstWatt F7 just to try out, and so far I’m impressed.

    • Hi Richard,

      The First Watt SIT-3 amps are just starting to ship out, so you should start to hear more about them soon.

      My friend Ron and I had a chance to give the SIT-3 a good listen today, and it never sounded less than very nice. It changed significantly in sound even over the time we were listening to as it got some time on it, sounding rich, natural, transparent, and very nuanced.

      I’m going by memory here, but if I remember correctly, one of my friends – Rahul – has an F7. I thought it sounded really good when I heard it over at his house.

      These First Watt amps are really nice!

      Kind regards,

      Jeff

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