The 40th Anniversary Sony VFET Amplifier from Pass Labs

[Odd]

At a special press briefing held during the 2014 International CES

http://blog.sony.com/press/sony-demo...fet-amplifier/

[1audiohack]

Those are super cool looking. Ill bet they don't sound bad either.

I want 'em!

[Odd]

Those are super cool looking. Ill bet they don't sound bad either.

I want 'em!

So do I.
I read somewhere they were not for sale, we have to wait and see.

[BurntIsland]

As mentioned in our report from the 2013 Burning Amp Festival, the veteran designer showed his "simplest amp," created with “two transistors, a [Jensen] transformer and wire—the fewest parts he'd been able to use to make it work.” The transistors weren’t identified back then but it turned out that they were Sony Vertical Field Effect Transistors or VFETs, a device Sony had developed 1972 to mimic the transfer function of a 300B triode tube. Sony and Yamaha both made amplifiers using this unique device, but discontinued them in the early 1980s when lower-priced power MOSFETs became available soon after.

Nelson’s Burning Amp used two complementary VFETs, part numbers 2SK82 and 2SJ28, the only ones Nelson had to hand, but he then set to work finding more. Eventually, he uncovered a stash in Singapore and bought all of them, enough to make the single pair of “Sony VFET Amplifier 40 Year Commemorative Edition” amplifiers at CES. This uses 24 pairs of VFETs as complementary followers and front-end/driver circuitry based on a Pass Labs’ XP topology. Output power is specified as 250W into 8 ohms—it sounded like more!

[gferrell]

Sort of reminds me of the old Ashly FET-2000 amps.

[Mr. Widget]

So do I.
I read somewhere they were not for sale, we have to wait and see.

There will be no more... Nelson found the last NOS supply of V-FETs to build them. He built the amps as a tribute and presented them to Sony as a gift.

Widget

[Dave_72]

There will be no more... Nelson found the last NOS supply of V-FETs to build them. He built the amps as a tribute and presented them to Sony as a gift.

Widget

That sucks...

[Cyclotronguy]

Not quite accurate Mr. Widget! Only the last known NOS stash of Sony Vfet's.

To beg a line from Kief; Gerber files and metal "Are only a shout away, a shout away, just a shout away!" So maybe a couple more channels.

And yes the sounded really magical in the Sony CES room on the Sony speakers. Best I've ever heard the Sony speakers sound.

Cyclotronguy

[SEAWOLF97]

My daily amp , connected to ESS Heil AMT bookshelves, is a Technics SU-G90 integrated (130 wpc). It is marked "FET direct coupling" and "new class A". Not sure what type of FET it is.

Running digi files from the computer , it is a great combo (prolly not worth much tho).

[Cyclotronguy]

If you like it, regardless, then I would think it's worth quite a lot!
The beauty of this hobby, is that whatever puts a smile on your face, works.

Cyclotronguy

[Allanvh5150]

Interesting. V FETS are still readily available. I use them all the time.

Allan.

[Ducatista47]

Interesting. V FETS are still readily available. I use them all the time.

Allan.

Are those power VFETs, or low power pieces like most JFETs are? Many preamplifier stages use JFETs, but power JFETs of recent manufacture were limited to, I think, two manufacturers, one being now defunct.

Only the defunct ones (Semisouth) were high voltage units, of interest to electrostatic listeners like myself. When a suitable high voltage amp can be built, no transformers are necessary to drive electrostatic speakers and headphones, eliminating significant distortion. The only common way to build such an amp is to use tubes as the high voltage devices. The available solid state units bootstrap lower spec transistors; not a great way to go. They end up either not producing enough voltage swing to make the high end headphones sound as designed, or operating the transistors out of their design parameters. This is why the only tubes I still use are in a Stax amp from Japan. It still didn't cut it, but a friend modified it for me with higher voltage tubes; he replaced dual triodes with single triode bottles with much higher voltage capability. Some rewiring was also necessary, and it all works beautifully now.

I could mention that while MOSFETs can make outstanding output devices for audio, JFETs have some remarkable advantages over them. Nelson Pass has all the good ones left. I am lucky to have two of his First Watt power amps equipted with them.

I would have thought that power VFETs would be big news. What sort of pieces are they?

[LowPhreak]

"At a special press briefing held during the 2014 International CES, Nelson Pass announces a few people have won the lottery, or have more money than brains..."


Good luck.

[1audiohack]

Hi Ducatista;

Just curious, how high is the output voltage of the modified Stax amp you speek of?

Thank you,

Barry.

PS. I have no idea why there is a frowny face on the top of this post and I can't get it off.

[Allanvh5150]

Although the classic 2SJ56 and 2SK176 and there smaller counterparts are not made now, they are still widely available from various sources. Also, the newer and higher powered 2SJ201 and 2SK1530 are in production and no problem at all to get hold of.

Allan.