DIY Sony VFET pt 1

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#261
Mark Johnson said:
That was a very common response on the other Nelson Pass class A power amp project which had a bunch of different, interchangeable front end cards: The diyAudio First Watt M2x

I estimate that around 40-50% of the people who built an M2x, used the front end card designed by Nelson (called "Ishikawa" in the M2x-osphere) and never built or tried any of the other possibilities. Not even the front ends whose PCBs were automatically included as part of the M2x board bundle shipped by the diyAudio Store. Of the folks who did try other cards, it appears that most of them found one that they liked best of all, and usually it wasn't Ishikawa. That may not be a shocking outcome, since Ishikawa was only one out of eight competing front end cards. A diversity of personal tastes, and idiosyncratic preferences among the builders/listeners, naturally results in a wide distribution of final choices. They likes what they likes, as Popeye the Sailor Man would remark.
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Mark,

That is certainly human nature. When I read that someone dismissed a design or device (or tube, for that matter) I always ask if they tried different operating points and did they measure distortion.

The salient point is that the hobbyists has to know what their taste is and how it is created: one cannot discard a device or design until experimentation of operating points is exhausted. Then, and only then, will you know that it will never be your taste.

Cheers,

Greg
 
#265
chromenuts said:
I’m trying to wrap my little brain around some of the design characteristics and put it in perspective with the other VFET amp designs that were offered and what I have built and listened to so far (ACA-with Semisouth @Q1 and F2J).

Let me know if I have any of it correct and what insights anyone may have.

This offering is a common drain follower. Which means it would normally offer current gain like the F2J except that the front end Papa designed for it will provide voltage gain via a transformer?
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The F2j is a common source design. The previous Sony vfet projects were common drain like this one, but push-pull. The choices were narrowed to this by scarcity of parts and the desire for consistent results.

:snail:
 
#269
Thank you, Mr. Pass, for this generous offering. It will be felt by many people.

Good luck to everyone in the lottery. Even if you don't win, remember that we, the members of diyAudio, have already won the big lottery in life.

As for the new amplifier, I think that I've already had a bit of a preview of it, although indirectly, as the last amplifier that I built uses basically the same output stage design. I have several SIT amps and this one is my favourite. 2SK82 -2SJ28 SE Amp
 
#273
Nelson Pass said:
Something similar. Details of mounting, biasing and such. The Tokins being N channel parts would look more like part 2 of this project, where the polarities are reversed. One interesting result for N channel follower is that you don't have to reverse polarity twice to get the 2nd harmonic phase negative.

Big upside is the potential for more power.
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Just wondering if the Tokin devices are as linear at the Sony? Any idea of how much more power is possible? Many thanks!
 
#278
Thomaudio said:
Just wondering if the Tokin devices are as linear at the Sony? Any idea of how much more power is possible? Many thanks!
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The Sony parts seem made audio and 8 ohms. The Tokins seem to prefer a
different impedance, although running at higher dissipation and/or adjusting the surrounding circuits will generally cover the difference.

You can even use feedback. Or so I hear...

:snail:
 
#279
Some load line tidbits there. Good stuff. If you play with the Sonys, you'll see "8 ohms", typical volts, being perpendicular against the gain of the parts, generally. At least thats what I've noticed. Other parts have different curves, sk60, pass-sit.... not so talked about.
 
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#280
vanofmonks said:
Any chance of getting a replacement deluxe 4u faceplate with the vfet logo?
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Unfortunately, no. I already asked the powers that be.

However I designed a pretty cool faceplate for my 4U that pays homage to Nelson, SONY and the VFET. It is printed, not etched. If you're interested, shoot me a PM and I'll share it with you. I suspect that Gianluca probably still has the file.
 
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