Has anyone had a play around with these devices? Based on 'old school' vacuum fluorescent display technology we have effectively two triodes in a compact component without the need for screaming hot high current filaments. I've just bought one, let the experiments begin....

Not played around with them but have heard them in a digital audio player that has the capability of switching from solid state to tube output

The tube out sounds incredible compared to the SS on the player

Manager & Product specialist at Rapallo AV & HI-FI

Interesting.
Not inexpensive at ~US$50 I believe, but I see that Nelson Pass designed a preamp using one....

diyaudiostore.com/products/korg-nutube-b1-pcb-and-jfets

DarkLantern blog - darklanternforowen.wordpress.com

May 5, 2020 18:24:02 GMT 12 Pete Bronlund said:

Has anyone had a play around with these devices? Based on 'old school' vacuum fluorescent display technology we have effectively two triodes in a compact component without the need for screaming hot high current filaments. I've just bought one, let the experiments begin....

What are going to build with the korgs Pete?

Manager & Product specialist at Rapallo AV & HI-FI

My previous comments under “Nelson Pass - interviewed by Steve Guttenberg”:
“ Yes I have some here but didn’t like them much. They have very low current capability in the order of tens of micro amps instead of milliamperes like normal triodes like the 6dj8. You can get far lower distortion and noise out of conventional triodes without resorting to jfets for impedance matching. As a hifi device the Korg 6P1 has a bit too much distortion and/or noise, depending on the situation it’s in. A 6dj8 SRPP circuit has more than an order of magnitude lower distortion, also an order of magnitude lower noise and much higher output voltage swing. The Korg seems to be a bit prone to microphonics as well, necessitating attention to how it’s mounted. It might work ok as the input stage of a poweramp where a bit of noise at low voltage swing wouldn’t be so noticeable.
But as an instrument device, ie, designed to modify the sound of a synthesizer or electric guitar etc. it would work very well I suspect. In that case the noise wouldn’t matter so much and the tone and overload/overdrive characteristics would be important.
But what I like about Nelson’s circuit is that he operates it at the point at which 2nd harmonic nulls out. I made a circuit in the 90s with 12au7s in which you could null out the 2nd harmonic also. But the third harmonic was still quite variable with input signal voltage so nulling out the second didn’t seem to make the circuit sound much better. So I concluded that a low distortion circuit with the right harmonic structure, including low amounts of upper harmonics including the third, sounded better ultimately.”

AMR-iFi R&D

Of course it would be fun to build one though!

AMR-iFi R&D

Great reviews of the pass kit, I'm sure with Mr Pass behind the design it will sound pretty darn good

Manager & Product specialist at Rapallo AV & HI-FI

While i really want to get stuck in and begin experimenting with this thing i have never personally heard one working. I'd be very disappointed if it performed sound-quality-wise just like any bipolar transistor design, ie minus that infamous magic "warm triode sound" so i did a bit more research overnight.

Stumbled upon a range of kit-sets that Korg do using their 6P1, the one of interest is a headphone amplifier (HA-KIT) which includes a MUSES01 output OPAMP (that can be rolled for the NJM4580). I note that Mouser Electronics list the MUSES01 at NZD$84.64 unit price! All parts look to be Japanese as in Nichicon electrolytics as opposed to one-hung-low branded devices so probably a nice unit to add to my personal audio setup. It's not too eyewateringly expensive either. Think i'll give the credit card a bend.

www.nutube.us/HA-kit.html

www.head-fi.org/threads/portable-headphone-amp-kit-with-korg-nutube.892146/

pmillett.com/

From reading around the Pass 3 with korg tube threads, reports seem to be pretty positive.
Most seem to enjoy the tubeyness.

The biggest issue seems to be around microphony. Great care must be taken to stabilise and damp the 6p1 to prevent ringing.

Things like using double sided foam tape under 6p1. Some have tried magnets etc.

They also appear to be a very long life device so whilst not the cheapest tube up front, you only need one and hopefully you won't ever have to replace it.

In April, I was notified of pre-orders opening for KORG NUTUBE B1 Preamp Complete Kit.

This is a Nelson Pass (Pass Works DIY) design, offered at the 2-17 Burning Amp Festival.

" At the Burning Amp Festival in 2017 Nelson Pass presented a pre-amplifier using the Korg Nutube dual triode. After more than 4,000 discussion posts, a successful prototype run, and many successful builds, the Korg Nutube B1 complete kit is now available for pre-order. "

The KORG NUTUBE B1 - Pre-Order Status Page says:

" All pre-orders are looking like they will ship by late September. "

Nelson Pass:

" Besides pure novelty, the attraction of the Nutube in an audio circuit is the Triode character. "



In addition to this PCB + JFETs kit, you will need:

Nutube (US$49.99)
Chassis (US$129)
Completion Kit (US$99) - everything else needed to join the bits together..

Or buy all together as a "full kit" bundle for US$299

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