VFET-X (or my 1/3 40th Anniversary Sony VFET Clone)

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WalterW

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Joined 2012
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Hi Superberg, you revived this thread worthy. I have great respect for your creative super build!
I like it very much.
You already achieved the highest possible 'Fugly' from Zen Mod, and even Papa responded.
Thanks.
I would like to go even further a bit with my build and use a balanced VFET gain stage with 2SK79's in it.
I will open a new thread for that.
 
mbrennwa

mbrennwa

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Joined 2005
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Sorry for necrobumping this old thread... I have been thinking of building this one, last, big, definitive amp. And I do have a bunch of Sony VFETs of both sexes. So...

...I do not (yet) have the time to actually go forward and build the thing, and I would also need to finally learn making proper PCBs (or find someone to do it for me). Also, I'd need to sort out a few design thoughts before pulling the trigger, and I hope you guys can provide some insight:

(1) The heat. Anything wrong with building this with active cooling? A "heat pipe" maybe?
(2) Using an optocoupler for biasing the output stage seems to be a thing recently (like in the FirstWatt M2 or Whammy etc.). Would it make sense to use this method for a Sony VFET push-pull amp, or is this is just a weird brainfart?

Would be cool to get some insights.
 
Zen Mod

Zen Mod

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Joined 2003
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1. why not
2. why not; but - reasons being? it behaves with biasing devised by Pa; options with optocoupler are all basically active, if done properly certainly more stable than passive biasing
but, if you want that, you must construct it - I'm not aware anyone (here) did that for Sony VFets
 
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plasnu

Member
Joined 2011
mbrennwa said:
Sorry for necrobumping this old thread... I have been thinking of building this one, last, big, definitive amp. And I do have a bunch of Sony VFETs of both sexes. So...

...I do not (yet) have the time to actually go forward and build the thing, and I would also need to finally learn making proper PCBs (or find someone to do it for me). Also, I'd need to sort out a few design thoughts before pulling the trigger, and I hope you guys can provide some insight:

(1) The heat. Anything wrong with building this with active cooling? A "heat pipe" maybe?
(2) Using an optocoupler for biasing the output stage seems to be a thing recently (like in the FirstWatt M2 or Whammy etc.). Would it make sense to use this method for a Sony VFET push-pull amp, or is this is just a weird brainfart?

Would be cool to get some insights.
Click to expand...
I actually installed 16 VFETs to an industrial heatsink like this: https://www.ebay.com/itm/166396991174?

I have not finished the project, though.

s-l960.png
 
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mbrennwa

mbrennwa

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Joined 2005
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That heatsink is pretty nice, but requires cooling water, which I don't have in my listening room.

More (stupid?) questions... looking at this thread I only found the simplified schematic of the VFET-X, but not the full circuit with all the glory details. I guess the circuit is essentially a balanced amp, where each half is a Sony Push-Pull 2015 VFET amp with more output devices. Is this correct?

If so, I could probably just use a pair of the 2017 PCB boards from the store to build a VFET-X, with the ouput devices not on the board. That would make life much easier for me, because I am a noob when it comes to making PCBs. And because I already have those boards floating around my basement.
 
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