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PostPosted: 29 Aug 2016, 06:41 
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This is a once in a lifetime opportunity to build a very unique SS amplifier. This amplifier uses NOS SIT transistors called V-fets by Sony used in their 80's amplifier. Nelson Pass had a stock of them and designed an amplifier around these for diyers when they were still being offered for sale in Hong Kong. But as it goes as soon as he published the information someone bought the entire stock of the 2SK82's making the build impossible. Nelson in his generosity decided to put together a kit with board, V-fets and brackets with his stock for diy'ers to build. There was a limited offering of 200 kits which sold out in a few days. I was fortunate to acquire a kit and the first to post on the diyaudio forum of a build. What is unique about these transistors is they have curves that resemble a triode tube whereas mosfets have curves like a pentode tube. In other words a SS transistor that sounds like a 300B tube. You can follow my build here with tons of information. I know it is not polite to cross post other forums but this is the only place to acquire information on this build.

http://www.diyaudio.com/forums/pass-lab ... a-180.html

There are going to be another 200 offerings of these kits in the next few months. Nelson being a very busy man takes some time to cater to the diy crowd. If anyone is interested they need to keep a watch out at the other forum for information on availability. There will be a signup date preceding the sale.


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PostPosted: 30 Aug 2016, 06:13 
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Just a follow up on the sound. AMAZING. A SS state device that has the sound of a true triode tube and is one of the fastest switching transistors made. Being a Push Pull design the sound is different than a SE. I have both the SET 300B and 45 tube SET amps and the sound is different. It does not have the holographic sound stage of the SET's nor was it supposed to. Nelson has said his retail SIT amp does a good job doing that. The reviewers of Nelson's retail SE SIT amplifier has praised the sound as good as a 300B but much quicker. Some even say it appears too quick if there is such a thing. If you have speakers (90db or better) that can get by with 15 watts this is a must have build for diyer's.

A SE version has been promised by Nelson if you have some of these V-fets. I was lucky enough to obtain some when they were still available. One may still be able to find some 2SJ28's with some searching. Beware of counterfeits on Ebay though. The 2Sk82's are much harder to find. Nelson has promised SE designs for both in the future.

This design is an improved scaled down version of the Sony V-fet amplifier of the 80's. The terms V-fet and SIT are the same thing. Static Induction Transistor.


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PostPosted: 30 Aug 2016, 18:53 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Schematic?

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PostPosted: 30 Aug 2016, 19:57 
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mwhouston wrote:
Schematic?



http://www.firstwatt.com/pdf/art_diy_so ... _draft.pdf


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PostPosted: 30 Aug 2016, 21:19 
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I have a Yamaha B1 in need of VFET's. I wonder if Nelson would let a couple go?

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 30 Aug 2016, 21:39 
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Surely there is another power FET which can be used?

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PostPosted: 30 Aug 2016, 22:51 
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No :(

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* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


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PostPosted: 31 Aug 2016, 06:09 
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You can email Nelson at Firstwatt.com and ask. Also post at diyaudio.com about needing some, someone may sell you some as well. I noticed a set for sale in the last few days.


Last edited by wdecho on 31 Aug 2016, 06:19, edited 1 time in total.

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PostPosted: 31 Aug 2016, 06:19 
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mwhouston I know you are like me and do a lot of building. Do not let this chance get by. You will not be sorry. I believe the diyaudio store is selling the boards and brackets for those already having the V-fets. I actually have another set of them along with a pair of 2SJ28's but decided to buy the kit with V-fets and keep the ones I have. Better than money in the bank. They are only going to increase in value unless Russia dumps some surplus ones as gossip has said. But I have been hearing this for years. SIT transistors are still being made but only for the military. Nelson had some made at a cost of $300,000 for himself and they are available in the Firstwatt SIT amplifiers at a retail cost of $5000. Most manufacturers use mosfets or BJT's that are made for other purposes such as switching. You would have to sell a lot of amplifiers to cover the $300,000 cost just for transistors. The company that made the Pass SIT has since went out of business.


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PostPosted: 31 Aug 2016, 06:41 
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Not big on fet power amps. I lean more toward low power SE tube amps and lately Class Ds. I have too many tubes and too many nice ones to build with anything else. I really must stay with this theme - tube amps.

I have to confess I have some desire to build some low power bipolar transistor amps and have all the parts to do so but other builds are first.

Thanks for making the suggestion but I must stay on track. I'm distracted far to easily.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
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