Review and Measurements of KORG NuTube HA-KIT Headphone Amp

[NTomokawa]

Yikes, forty-four decibels of SINAD !?

I am speechless.

 

[restorer-john]

These 'tubes' appear to be derived from VFD construction/technology. A VFD can behave somewhat like a triode. Is the brand Noritake Itron?

It is:

https://hackaday.com/2015/02/02/tubes-on-a-chip/

Noritake's history : https://www.noritake-elec.com/about/history
The other big player in VFDs out of Japan was Futaba. http://www.futaba.co.jp/en/corporate/company_i/history.html

 

[jsrtheta]

Years ago there was a small tube called the Nuvistor. Looks like these guys were trying to reinvent the wheel.

https://en.wikipedia.org/wiki/Nuvistor

Musical Fidelity came out with a number of "Nu-Vista"-based components, including DACs and preamps. They claimed they had bought all the nuvistors in existence (and then doubtless went on to corner the market in Siberian tigers), which made me wonder why I'd buy one of their products since they claimed they were the only game in town for replacement nuvistors.

Behold: https://www.musicdirect.com/integrated-amp/musical-fidelity-nuvista-800-integrated-amp $12,000 for an integrated amp that they claim outputs 330 watts per channel into 8 ohms.

Pass.

 

[amirm]

Here is a video on how to assemble the kit by the way:

 

[Sythrix]

I built Pete Millett's Nuhybrid Headphone amp, if you're interested in measuring a different product with this tube.

 

[amirm]

I built Pete Millet's Nuhybrid Headphone amp, if you're interested in measuring a different product with this tube.

Thanks for that link. It seems to have the same horrific distortion of the one I tested:

Second harmonic is down less than 40 dB putting its SINAD in high 30s.

I don't think it is worth sending it back and forth but I am open to more feedback.

 

[restorer-john]

...but I am open to more feedback...

Positive or negative? Keep you in the loop, so to speak?

 

[Sythrix]

Thanks for that link. It seems to have the same horrific distortion of the one I tested:

....

I don't think it is worth sending it back and forth but I am open to more feedback.

Yeah, he mentions it’s not a low distortion amplifier.

It was fun to build and has a unique sound, but I doubt it would be special in terms of measurements.

Just thought I’d let you know in case you wanted to explore further.

 

[Ralf Stocker]

What a distortion crap.

 

[vitalii427]

So we have one cute little distortion box. I think some genres of music could benefit from it. Reminds me of Lomography.

 

[restorer-john]

So we have one cute little distortion box.

This one had more control for less money:

Made in the 1980s, still sell for good money.

Or just go extreme with Hyper Distortion:

 

[Jimster480]

I have a different nutube headphone amp and if I so much as brush against the headphone cord I get a ringing sound from it. I guess I got an extra microphonic nutube.

I don't have any power hungry headphones so I don't really need an amp, I just like building things but I quit using it because of the ringing.

I like tubes but I'm not a fan of adding them into a circuit just for the 'sound'.

I bought the kit to build the Pmillet Nutube hybrid.
But I never finished soldering it.
My soldering iron sucks and I gave up after a few hours....

 

[vitalii427]

I remembered where I saw this Nutube. $3300 DAP I got my hands on recently:

 

[Dogen]

I have a different nutube headphone amp and if I so much as brush against the headphone cord I get a ringing sound from it. I guess I got an extra microphonic nutube.

I don't have any power hungry headphones so I don't really need an amp, I just like building things but I quit using it because of the ringing.

I like tubes but I'm not a fan of adding them into a circuit just for the 'sound'.

I like tubes too, but why would you add them to a circuit if not for the ‘sound’?

 

[Audioagnostic]

Many thanks for introducing me to this flabbergasting product! I watched the video in amazement as well, it seems you have to unscrew the whole front to replace the batteries.
Nothing seems to be too far fetched in esoteric hifi products.

It has inspired me with a product idea. Why not make fake tubes with led's in them? You could construct a class D amp with "tube sound" filter and power the whole thing over usb. Or maybe such a product already exists...

 

[Jimmy]

Many tube amps (mainly cheap ones), are hybrids, often the tubes are just used for voltage gain to add a certain flavor to the sound.

So if what comes in is different from what goes out by a fair amount, SINAD won't be very good, but it doesn't mean it should sound bad, triodes (good ones) add even order harmonics to the signal and when implemented properly add a certain richness and warmth to the sound, but certainly are not neutral.

The Nutube is an interesting device from a technical point of view, but I doubt that it can compete with a functionally equivalent good NOS tube.

Many thanks for introducing me to this flabbergasting product! I watched the video in amazement as well, it seems you have to unscrew the whole front to replace the batteries.
Nothing seems to be too far fetched in esoteric hifi products.

It has inspired me with a product idea. Why not make fake tubes with led's in them? You could construct a class D amp with "tube sound" filter and power the whole thing over usb. Or maybe such a product already exists...

 

[SIY]

Musical Fidelity came out with a number of "Nu-Vista"-based components, including DACs and preamps. They claimed they had bought all the nuvistors in existence (and then doubtless went on to corner the market in Siberian tigers), which made me wonder why I'd buy one of their products since they claimed they were the only game in town for replacement nuvistors.

Behold: https://www.musicdirect.com/integrated-amp/musical-fidelity-nuvista-800-integrated-amp $12,000 for an integrated amp that they claim outputs 330 watts per channel into 8 ohms.

Pass.

I had a pile of Nuvistors of various sorts. Noise was all over the place and they were all microphonic. Gave 'em all away and stuck with high quality conventional tubes after that.

 

[invaderzim]

I like tubes too, but why would you add them to a circuit if not for the ‘sound’?

In my tube amp they are there for the amplification. I like building point to point wiring and that doesn't tend to be good for solid state. The goal with the tube amp I built is to get the best performance and according to the blueglow electronics build of the same amp it is possible to get decent performance out of it.

Taking a printed circuit board amplifier and adding a low voltage tube just to have a tube mixed in with the solid state amplification isn't high on my list anymore. Yes it is ironic that i built both the headphone amp and the buffer. And building a tube amp and trying to get 'clean' sound may be an exercise in futility but I enjoy it. Maybe I'm jaded against the nutube due to the microphonics of the ones I have but it seems like adding a noise maker to a system.

 

[SIY]

I like tubes too, but why would you add them to a circuit if not for the ‘sound’?

Entertainment. I often analogize it to driving an Avanti or a T-Bird instead of a Lexus. It won't get you there any faster, but it can be fun if that's your mindset.

 

[invaderzim]

Entertainment. I often analogize it to driving an Avanti or a T-Bird instead of a Lexus. It won't get you there any faster, but it can be fun if that's your mindset.

which probably explains why I listen to tube amps and (on nice days) drive this for a hundred mile round trip commute: