Bargain VFET Amp 20 watts Class A @8ohms 40 watts class A@4 ohms Nelson Pass design.

cjfrbw

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Apr 20, 2010
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I bought one of these. They come as 230V, but a 40 dollar voltage scaling transformer on ebay can be used to adapt them to 120V use. They can also be rewired internally for 120V use, but I didn't want to bother and the step down transformer also acts as an isolation transformer for the unit. You might ask the manufacturer to ship it as 120V.

Compared to most of the hi end stuff that sells for very high prices here in WBF Audio Monaco, these are currently selling for chump change.

They are based on the Nelson Pass-Sony VFET designs, using NOS Sony VFETS. I heard the behemoth unobtanium Pass VFET at the California Audio Show, and loved it. I thought that if they ever built a scaled down version, I would like to buy one. This Thai manufacturer has done just that, using the Nelson Pass circuit designs and most of the same recommended devices.

As a Pass push-pull design, it likely goes into Class AB at a much higher rating than the nominal class A rating. Based on the number of devices, I would guess it does low distortion transients into the 80 to 100 watt range.

Playing it very loud, as much as I could stand, full range on the crossoverless 89 db@4ohms efficient panels of the Analysis Epsilon speakers, with classical music, it never showed any signs of stress or clipping.

Just when typical solid state amps of almost any description seem to go bitter, the VFET amps just go sweeter, deeper into the tonality, and faster, with uncanny 3D soundstage separation and ability to identify and isolate separate instruments and their signature tones. Solid State dynamics without solid state stripping, but even faster and more detailed. Use it with a directly heated triode preamp, and be prepared for an involving audio experience unrivaled by just about anything out there at any price.

Mine has build quality as good as my Pass Labs First Watt M2, and sounds a lot better. It is is basically in the identical fascia to the First Watt products.

I was going to buy a second unit, but I have a vintage Sony TAN 8550 being rebuilt, and I have no current use for an extra one.

Buy one before the prices start going up to where they usually go for top notch audiophile product. The main risk is difficulty with warranty and shipping etc., but my sample has been rock solid for the several months I have been using it and just sounds better and better.

http://www.ebay.com/itm/VFET-AMPLIFIER-2SK82-2SJ28-2SK170-2SJ74-/252244603631? Screen Shot 2016-01-12 at 11.37.19 AM.jpg
 
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even.twice

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Dec 4, 2016
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Can't agree more.
I bought one unit this Jan too. Very satisfied with the sonic beauty it brings and I bought one more unit two months later.
It seems stock out now.
 

cjfrbw

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Apr 20, 2010
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The nominal rating is 20W class A @ 8 ohms and 40W class A @ 4 ohms. I think transient peaks into class AB would be perhaps up to 60 or 70 watts rather than 80 to 100 as before stated, but still pretty powerful for the configuration.
 

even.twice

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Dec 4, 2016
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My two units are in different configuration. One is with NFB. Another is without. They sound differently. With NFB is more refine. Without NFB is closer to real thing.
 

uncola

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Nov 24, 2016
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Just received the same builders version of the f7, very happy with sound and build quality. Definitely sounds class A with super pure and natural vocals like a veil was removed between the singer and the mic recording them
 

even.twice

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Dec 4, 2016
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Yes, I owned the same builder version of the F7 too. Find the same as you.
 

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Phonixaudio

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Feb 15, 2020
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This's my latest Static Induction Transistor Amplifier 18W
 

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cjfrbw

Well-Known Member
Apr 20, 2010
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This's my latest Static Induction Transistor Amplifier 18W
That's very nice. Is that a Tokin SissySit? How does it sound? Can you compare it the the regular Pass SIT or Vfet DIY?
 

Phonixaudio

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Feb 15, 2020
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That's very nice. Is that a Tokin SissySit? How does it sound? Can you compare it the the regular Pass SIT or Vfet DIY?

No, It's quite different from SissySiT, I merged 2-3 version of an original SiT to get best THD, noise, and relative of K2,3

Also hard to get suitable SiT/Mosfet VGS matched from the first time (4 pairs selected for me)
 

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cjfrbw

Well-Known Member
Apr 20, 2010
2,836
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570
Pleasanton, CA
No, It's quite different from SissySiT, I merged 2-3 version of an original SiT to get best THD, noise, and relative of K2,3

Also hard to get suitable SiT/Mosfet VGS matched from the first time (4 pairs selected for me)
Nonetheless, it must sound wonderful. Transformer voltage gain?

Applause!

I was thinking of attempting to build a SissySit this summer, but I don't really know if I have the skills to make it work. Like you say, that matching of MOSFET and SIT is apparently very difficult.
 

Phonixaudio

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Feb 15, 2020
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Nonetheless, it must sound wonderful. Transformer voltage gain?

Applause!

I was thinking of attempting to build a SissySit this summer, but I don't really know if I have the skills to make it work. Like you say, that matching of MOSFET and SIT is apparently very difficult.
Yes, Cinemag is used fir 11.5dB gain and SiT+Mosfet is only current gain (buffer) without any negative feedback.

Its temperature is too hot with 1.5A biased and also sensitive from hum and noise from outside Chassis, AC INLET
 

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