Korg 'Nutube' - next generation vacuum tubes

[GGBB]

A colleague dug this up: http://hackaday.com/2010/04/22/vfd-as-a-sound-amplifier/.

[merlinb]

Also this:
http://www.hpfriedrichs.com/radioroom/vfd/rr-vfd.htm

[PRR]

> Also this:

Interesting.

Most notable is the low-low-low current up to 40 Volts on the plate. I wonder if there is a mis-interpretation of the data. The wobbliness of HPF's curves is also curious; we expect small "contact potential" offsets and possible saturation, but not a lot of inflections.

Also the data extends far into the Positive Grid range. In conventional tube work this is a No-No for small-signal amplifiers. Yes, we can bend this rule, especially if we know the grid current and if we have powerful drive (19 penny opamps?).

Assuming "large" plate voltage and non-Positive grid, I get numbers like:

Mu about 20-30 (HPF gets ~15, noting it depends on op-point)
Transconductance about 1V/0.16mA = 160uMho = 0.16mS
Plate resistance near 160K

Plotting a loadline like 140V, 140K resistor, I squint a swing like 105V-135V or 30V p-p with a 2.5Vpp input, or gain near 12 into infinite load.

Certainly a useful Audio Amplifier. But we have these, cheaper. Is it a Tube Amp? Technically yes, but the data does not allow any guess of distortion or grid-blocking to say if it has "the mojo". If I smooth HPF's curves I do get the expected ~~5% THD near clipping; oddly if I use the raw data it looks like very low THD. And there is more to a tube than plate clipping, grid clipping, and 5%THD curvature.

[patricks]

Cool. Do you think they'll make a pentode version?

[pmillett]

The NuTube 6P1 is available to buy online now on eBay and www.nutube.us.  It should be an interesting part...

[PRR]

Good to see you here, Pete.

I think your link got clobbered in the innernet. (";" s/b ".")

Seller site: http://www.nutube.us/

More links--

eBay store: http://stores.ebay.com/nutubeusstore

KORG site on NuTube: http://korgnutube.com/en/

Quite complete datasheet: http://www.nutube.us/downloads/Nutube_Datasheet_31.pdf

More app-notes: http://korgnutube.com/en/guide/

[stonerbox]

I guess all of you already seen this?   

[potul]

And the first VOX amps using Nutubes are here

http://www.voxamps.com/MV50

[vigilante397]

And the first VOX amps using Nutubes are here

http://www.voxamps.com/MV50

The store I work at is a Vox dealer and we just put in an order for a few of these. Eager to hear how they sound (and open one up so I can see these things) in person.

[vince76]

Hi,
did you heard it?

[vigilante397]

Hi,
did you heard it?

Not yet. Vox says they won't ship until the end of the month 

[TejfolvonDanone]

Those datasheets look really badly made. For example several plots have conflicting title and axis label.

[biogk]

Guys, I got some news that Nutube is on sale in Japan.
Here are addresses of these shops.
http://korgnutube.com/jp/dealer/

BTW, what is the relation between the nutube 6p1 and the Chinese 6p1?

[PRR]

Welcome.

> what is the relation between the nutube 6p1 and the Chinese 6p1?

Probably none at all. The NuTube is really a display tube. Used as an "amplifier" it would be too pathetic to put into production. However Noritaki has excess production capacity, and KORG likes it, so it is being offered.

That link is Japanese and seems to be Japanese shops. I know I have seen a US/EU sales site but am not finding it now.

[GGBB]

http://www.nutube.us/ - which has a link to an eBay store for sales.

[GGBB]

Spotted these amp kits which may be of interest to some - schematics are included.

https://www.tindie.com/products/microwavemont/nutube-amp-kit-a-vacuum-tube-in-new-century/
https://www.tindie.com/products/microwavemont/nutube-based-15wx2-amplifier-kit-with-class-d-amp/

[biogk]

Welcome.

> what is the relation between the nutube 6p1 and the Chinese 6p1?

Probably none at all. The NuTube is really a display tube. Used as an "amplifier" it would be too pathetic to put into production. However Noritaki has excess production capacity, and KORG likes it, so it is being offered.

That link is Japanese and seems to be Japanese shops. I know I have seen a US/EU sales site but am not finding it now.

nutube.us is the English site, and it is expensive a bit.
I will try to buy one the next time I go to Japan.

[rezzonics]

Just received in the post 2 samples of KORG NuTube 6P1 triode for a DIY guitar preamp project:

[rezzonics]

According to the Application Notes the gain is 14dB at 12V and 17dB at 30V, I would like to make a boost channel guitar preamp with some cranked distorted output. I plan to cascade two of them at 24V, should I add additional gain? Opamp or JFET amplifier? Where to place the additional amplification, before, after?

[wavley]

According to the Application Notes the gain is 14dB at 12V and 17dB at 30V, I would like to make a boost channel guitar preamp with some cranked distorted output. I plan to cascade two of them at 24V, should I add additional gain? Opamp or JFET amplifier? Where to place the additional amplification, before, after?

Personally, I'd breadboard this one and see what it sounds like.  That way you can try all the things you would normally do with a twin triode, for example: series for more gain, parallel to see if it gets that jumpered Marshall sound (plus 30% more gain and lower output impedance), cathode follower for lower output impedance... you get the picture.  Then I'd probably throw a Fetzer valve on the breadboard with it and see how it sounds before and after.

That's what I would do if I ever had the time for such things.