Beast with a Thousand JFETs

[Nelson Pass]

Jam called me up and asked if I have ever paralleled up a
bunch of 2SK170's and 2SJ74's to make a power output
stage.

I guess it's time to unveil the Beast with a Thousand JFETs.

Here's the first teaser, a circuit panel to hold 588 JFETs and
associated resistors.

 

[Boris_The_Blade]

How do the capacitances compare with an equivalent group of power fets? I'm curious to see what you can do with this Will you need to do any matching? (or just wing it) Pardon my ignorance, I'm not a huge ss designer.

 

[Salas]

Jam called me up and asked if I have ever paralleled up a
bunch of 2SK170's and 2SJ74's to make a power output
stage.

I guess it's time to unveil the Beast with a Thousand JFETs.

Here's the first teaser, a circuit panel to hold 588 JFETs and
associated resistors.

He, he, mega!

 

[Bigun]

Wow, that's impressive - I hope you're using a Pick n Place machine, no hand soldering on that thing.

How does the cooling work ?

 

[Nelson Pass]

Wow, that's impressive - I hope you're using a Pick n Place machine, no hand soldering on that thing. How does the cooling work ?

Hand soldered. Hand matched.

What cooling?



currently ripping: Outernational Sound, Thievery Corporation

 

[mjf]

How does the cooling work ?

perhaps with a few (cpu) fans.........
and if that does not work put it into a refrigerator.
greetings.........

 

[gl]

Nelson,

As I recall you did something similar once before many years ago - paralleling lots of JFET's.

If this beast has a thousand JFET's then there must be two of these panels required? And with 2SJ74's the voltage rails will probably have to be in the Firstwatt power amp range?

By golly the thing is starting to look like a simplified version (did I actually say that out loud?) of the F4.

Graeme

 

[jacco vermeulen]

Hand soldered. Hand matched.

EEEK

 

[wicked1]

Hand soldered. Hand matched.


currently ripping: Outernational Sound, Thievery Corporation

Doing that by hand is almost crazy, but I've gotta tell you... Thievery Corp is the perfect music for such activities.

 

[maxlorenz]

Since J74 is not that easy to source, I will go single ended.
In fact, as a premonition, I started to source the 170 months ago...

Heat? I heard someone immersed some amp on oil...maybe vaseline, with its many uses , could also work.

Regards,
M

 

[SY]

Didn't someone (maybe Tim de Paravicini) do this with 12AX7s?

 

[Nelson Pass]

As I recall you did something similar once before many years ago - paralleling lots of JFET's.

Actually I did it many years ago with TO-92 bipolars, and later
with ZVN3310 and ZVP3310 Mosfets.


The single-ended version typically requires four times as
many devices for the same performance - 2 X in parallel and
then balanced.

It's actually more economical to go complementary when you
consider your time and the costs of the extra transistors,
resistors, and pc boards.

Oh, and it will not be an F4.

 

[Michael Rothacher]

The name alone makes me all giddy.

 

[DigitalJunkie]

That's Nutty -I Like It!

 

[alazira]

Doing that by hand is almost crazy, but I've gotta tell you... Thievery Corp is the perfect music for such activities.

I concur, about Thievery Corp that is

Garrett

 

[Nelson Pass]

Variac and Elena and Jill and I all went to see Thievery Corporation at the Warfield a couple years back.

The performances were awesome but the sound system sucked.




Tosca / Suzuki

 

[iko]

The kilofet; a new unit of excellence?

 

[tomtt]

Beast with a Thousand JFETs.

maybe Brad Pitt, to play your part, in the movie...

 

[MashBill]

Very interesting! I look forward to following the progress on this.

 

[Diomedian]

Jeez - how many 2sk170s do you need to come up with a matched millennia?