VFET-X (or my 1/3 40th Anniversary Sony VFET Clone) - diyAudio
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Old 6th September 2016, 04:46 PM   #1
WalterW is offline WalterW  Netherlands
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Default VFET-X (or my 1/3 40th Anniversary Sony VFET Clone)

I always wanted to build a last special amplifier, and wanted it to be big and spectacular.
My big example is the '40th Anniversary Sony VFET Amplifier' Nelson presented at CES in 2014.
There are more members who told me they also want to build something like this so I opened my first thread
I will post a lot of pictures...
What I like to try is building a stereo version of this amp with 1/3 of the VFET's so 8 per channel instead of 24.
Then bias each a bit higher to get a 1/2 40th Anniversary Amp

The schematic is the original Sony VFET pt2 article with the two VFET's paralleled and then double it to get a fully balanced amp.
Both sides are connected with R24 to each other instead of to ground.

I will make my own PCb's, chassis and so on, just having a lot of fun.

On Ebay I found this nice Pass like heatsinks, so I will build the whole amp in a kind of XA160 chassis.
The heatsinks are 'Oxidised' according to the seller, is that different to 'Anodised'? Does somebody know?
They feel different and look more shiny than what I'm used to.
I tested one heatsink with around 100 Watts on the surface, but the surface was too rough, brushed, to get good results. After removing the black 'oxidized' layer and a lot of smooth sanding they transfer the heat better.
I estimate each heatsink can do about 80 Watts of heat. I have six of them so total of 480 Watts. I hope
Attached Images
File Type: jpg 40yearBIG.jpg (284.5 KB, 1215 views)
File Type: jpg Big-Sony-DIY.jpg (133.3 KB, 1182 views)
File Type: jpg NG7_Pass_VFET.jpg (251.0 KB, 1188 views)
File Type: jpg sinks-arrived.jpg (325.6 KB, 1147 views)
File Type: jpg sink-top.jpg (200.7 KB, 1073 views)
File Type: jpg sink-brushed.jpg (244.8 KB, 354 views)
File Type: jpg sanded.jpg (251.1 KB, 415 views)
File Type: jpg heat transfer.jpg (297.7 KB, 474 views)
File Type: jpg 100Watt.jpg (311.7 KB, 426 views)
File Type: jpg after-sanding.jpg (376.3 KB, 317 views)
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Old 6th September 2016, 04:49 PM   #2
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So wonderful
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Old 6th September 2016, 04:57 PM   #3
WalterW is offline WalterW  Netherlands
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Next the 15mm thick aluminum panels arrived. almost 5 KG each... that's where the heatsinks will be mounted on. The 15 mm sheet will act as a heat distributor. I hope .

On this big sink a T-bar will be mounted, the thickest I could get, 60x60x6mm. On each T-bar there will be 4 MOSFETs and 8 VFETs mounted.

The frontends are done already.....

A lot of work to do for coming winter
Attached Images
File Type: jpg 15mm-front.jpg (414.0 KB, 374 views)
File Type: jpg 15mm-panels.jpg (433.9 KB, 421 views)
File Type: jpg big-case.jpg (289.1 KB, 438 views)
File Type: jpg big-T-bar.jpg (270.4 KB, 385 views)
File Type: jpg PCB on T-bar.jpg (342.7 KB, 391 views)
File Type: jpg the-plan.jpg (275.5 KB, 461 views)
File Type: jpg frontend.jpg (233.6 KB, 508 views)
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Old 6th September 2016, 05:39 PM   #4
Zen Mod is online now Zen Mod  Serbia
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Old 6th September 2016, 05:48 PM   #5
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Fantastic project Walter! I'm looking forward to seeing this progress.

Sightly off topic, what do you guys think of a 1/4 40th anniversary amp with
just 4 vfets per channel? You can use one kit per channel but I don't know
if the bias will be too low to be feasible...

Cheers,
Dennis
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Old 6th September 2016, 05:49 PM   #6
Zen Mod is online now Zen Mod  Serbia
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better not

it'll have much higher voltage envelope than current one

well , at least not safe current one
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Old 6th September 2016, 06:03 PM   #7
WalterW is offline WalterW  Netherlands
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Quote:
Originally Posted by Zen Mod View Post
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I hope you can borrow me some of your brain cells during the process
I might need them...
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Old 6th September 2016, 06:19 PM   #8
Zen Mod is online now Zen Mod  Serbia
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all of them ,but two, are already floating through open space .......

so , you can count on these two
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Old 6th September 2016, 07:58 PM   #9
jama is offline jama  Spain
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Wonderful Walter. I am finishing other projects and soon I will start to follow your way...
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Old 6th September 2016, 08:23 PM   #10
MRupp is offline MRupp  Germany
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Interesting project.

Just looking at the DIY Sony VFET schematic: Taking two per channel - keeping their lower 28 V supply - mirroring one of them and tying the two feedback resisters R4/R4' together instead of connecting them to ground, I would then end up with the same topology, no? And the dissipation of the devices would stay the same as well. Just wondering what added advantage that would have over the unbalanced / unbridged original, all other things remaining equal.
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