Sony vFET Amplifier Part 2

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#561
Nelson Pass said:
And here's the good news.

I have tested the single-pair version of the amplifier with good results.

It has a little more distortion and a little less power, but not by much. It
delivers 20 watts into 8 and 30 watts into 4 ohms. I am going with the
feedback version, but you can have the no-feedback version by changing
a couple resistors.

This will double the number of channels that can be built, and no matching
of the parts is required. I am planning to supply 400 pair of the devices
to the DIYAudio store. TO-247 IR parts will be used for the regulators.

I have drawn up a T-bar mounting bracket to fit the 300 mm deep heat
sink (also will fit the 400 mm) chassis offered in the DIYAudio store and
will be doing a pc board to fit it.

Presumably those who plan to use matched dual pairs can go with Tea
Bag's boards or they can bolt the extra devices in parallel. The performance
should be about the same either way.

On my end this will proceed over the next few weeks. Those with only one
polarity of VFETs will be addressed in a separate design after that.

😎
Click to expand...


Thank you Nelson. That's very kind.
What would it take to crowd fund a manufacturing run of boutique parts eg something like 2sk77 or Sony Vfets but with even more desirable properties?
Is this feasible or would it be far too expensive?
 
#566
Nelson Pass said:
And here's the good news.

😎
Click to expand...
@ Mr Pass
Woow i see bunch of happy Diyers with vfets amps in near future
all possible by generous mind and energy of Mr Pass thanks marvelous !

Could be possible to keep on new single pair pcb version
feedback or nonfeedback switch connection from original
vfet part2 schematic ? Please :happy1:
This is cool & interesting audiophile option for sound tests in real time :note:
Best regards
 
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#577
plasnu said:
The output impedance and voltage gain of single-pair version amp without/with feedback?
Click to expand...

Voltage gain w/o feedback is determined by the degeneration of the input
pair, and is whatever you want within reason.

With feedback, my prototype was 16 dB gain.

I didn't check it without, but with feedback, the DF is 40. I expect the DF
w/o feedback and the same bias current to be about 70% of the original 18,
about 12 or 13.

😎
 
#578
2 picoDumbs said:
What would it take to crowd fund a manufacturing run of
boutique parts eg something like 2sk77 or Sony Vfets but with even more
desirable properties? Is this feasible or would it be far too expensive?
Click to expand...

When Tokin still had the production line (apparently destroyed in the quake
and not rebuilt) I had an indirect (not from Tokin) nominal quote of
$250,000 for 2SK77B's. I had a comparable quote from SemiSouth for
more SIT-1 devices and almost made the down payment before they went
under.

The unfortunate fact is that there is not a big enough audience for the parts.
Digital Do Main had the 2SK77B's made originally, and I am under the
impression that its owner did not regard that as a lot of money.

Even with crowd funding, I don't know that you can convince Tokin to
spend the millions it probably would take to rebuild the production line.

I do have a small quantity of the 2SK77B's, and if any of you have some
quantities of the genuine parts, let me know. :wave2:

😎
 
#580
Nelson Pass said:
Voltage gain w/o feedback is determined by the degeneration of the input
pair, and is whatever you want within reason.

With feedback, my prototype was 16 dB gain.

I didn't check it without, but with feedback, the DF is 40. I expect the DF
w/o feedback and the same bias current to be about 70% of the original 18,
about 12 or 13.

😎
Click to expand...

Well, it can be tolerable to me.😎
 
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