[Big Bad Bob]

On 2021-02-09 16:41, Lord Valve wrote:
It actually *is* a vacuum tube, but it's pretty flaky. There are a bunch
of effects pedals out now (and an amp or two) which use it. Here's
a couple of URLs on it, one from the manufacturer:

https://korgnutube.com/en/

they would e-mail the data sheet to me but I have to give them sales
contact info first. Naaah. I'll wait until digikey has them.

https://diyaudiostore.com/products/korg-nutube

The second one has some numbers and graphs and stuff.
If you want to mess with one, they'll be glad to sell it to you
for only fifty bucks US. (OUCH!)

if I wanted to build an amp to test a design it's probably worth it.

Looking at the curves, it runs with a positive grid voltage in most of
the examples. that's not entirely ideal [obviously] especially when
plate current is measuree in microamps.

apparently the ref circuit solves that by using a JFET front-end as a
voltage follower.

Still interesting, but I can't see any advantages of this over using a
MOSFET other than to say "it is a tube". HOWEVER... I would definitely
expect the technology to improve and at some point use an indirectly
heated cathode.

Having a mu factor of 14 isn't all that exciting either. I'd expect 50
or 60 to be of real use (like a 12AT7) in a preamp, or 100 like a 12AX7.

still - the low volts, low heater power, and small physical size
definitely have an appeal.