Review and Measurements of KORG NuTube HA-KIT Headphone Amp

[antdroid]

I understand the site is trying to measure to see how clean the sound and distortion are, but isn't the point of some of these tube and tube hybrids to distort the sound to a different character? I'd be interested to see measurements (freq response, decay, phase, impulse, etc) of a few headphones using a clean reference solid-state vs the review tube amp to see the change in sound characteristics.

 

[amirm]

I understand the site is trying to measure to see how clean the sound and distortion are, but isn't the point of some of these tube and tube hybrids to distort the sound to a different character?

I included listening tests for that reason. I detected no positive effect from the distortions. They just made things well, distorted. It added no character that I noticed.

 

[antdroid]

I included listening tests for that reason. I detected no positive effect from the distortions. They just made things well, distorted. It added no character that I noticed.

I guess, if the Korg, in this example, truly is making the response an increase in upper mids and treble, and you are listening to already known bright headphones (ATE, Grado, MDR-7506), it seems like they aren't the right headphones to be testing an amp that injects more brightness into the sound. Is that what your listening test concludes? Let's say I were to listen to a darker headphone, would the tube distortion that cause your bright headphones to sound more shrill, help bring up the treble in a dark headphone?

Most tubes typically lose some detail for some other character in my subjective listening and I'm expecting that when I go into using a tube vs a solid-state.

My comment is basically, it would be neat to see some measurements of the headphone changes too. In my DIY-type headphone measurement gears, I've seen some tube-hybrid amps make very minor and some make audibly different changes to the sound profile of the headphone. As this has never been really quantified before by the tube manufacturers, it would be nice to see if there are truly changes being made by measurements of headphones.

 

[Gomjab]

I included listening tests for that reason. I detected no positive effect from the distortions. They just made things well, distorted. It added no character that I noticed.

I assume this is the same Korg that makes synthesizers. Perhaps this miniature tube was created to include in a product as an effect for music creation and not playback?

 

[solderdude]

I understand the site is trying to measure to see how clean the sound and distortion are, but isn't the point of some of these tube and tube hybrids to distort the sound to a different character? I'd be interested to see measurements (freq response, decay, phase, impulse, etc) of a few headphones using a clean reference solid-state vs the review tube amp to see the change in sound characteristics.

You won't see any differences in headphone measurements using either tube(hybrids) or SS.
The distortion levels are lower than those of the headphones and FR is not affected.
That is with a well designed tube hybrid, cheapo Chinese crap and all tube amps with measurable roll-off will of course also show the same roll-off which is not surprising...
The audible effect of phase shifts at the ends of the spectrum is wildly exaggerated and often similar to that of SS. Measurable but not audible.
Impulse response is limited by the driver of the headphone. Not the amp.
Have done those measurements in the past.
In this particular case you will see an increase in 3rd harmonics most likely, when measuring high impedance headphones.
Have never seen any tube hybrid measure this bad.

 

[SIY]

I assume this is the same Korg that makes synthesizers. Perhaps this miniature tube was created to include in a product as an effect for music creation and not playback?

That is exactly the case. If memory serves, Pete Millett jumped on this for audio use because he thought it would be interesting, and others have followed.

 

[Gomjab]

That is exactly the case. If memory serves, Pete Millett jumped on this for audio use because he thought it would be interesting, and others have followed.

It makes sense then. You don’t buy a distortion effect to not hear distortion. But in its intended case the distortion is being applied to one instrument when desired not the whole mix.

 

[maxxevv]

Interestingly, iBasso has actually made a amplifier module for its DAP range with the KORG nutube.

 

[Jimster480]

Interestingly, iBasso has actually made a amplifier module for its DAP range with the KORG nutube.

View attachment 27494

That looks cool!

 

[cjfrbw]

I would suspect that the device Amir measured used the NuTube to drive an op amp, because the specs of the NuTube itself are abysmal for headphones i.e. very low power of about 1.7 mW and high output impedance. Also, as has been intimated by previous posters, the original PURPOSE of this device was to add tube distortion to musical gear, because many musicians who use amplified instruments love tube distortion. You probably hear these distortions in a lot of the pop, rock and synth music you listen to routinely. The fact that Korg NuTube has been hijacked for audio use wasn't part of the plan.

Another thing for ASR to go after with a hatchet on the Pass DIY site is the love for Pass' giveaway gift: B1 Korg NuTube preamp boards and plans. I built one of these, and I am listening to it right now as a buffer for my Sony MDR Z1 headphones and it certainly sounds nice. Expands the soundstage or something or other. Even with the impedance mismatch (MDR Z1 about 80 ohms, NuTube out put about 170 ohms), which probably alters the frequency response profile as well. A pair of 300 ohm Senn HD580's also sound great, and at least have higher impedance compared to the NuTube.

http://www.firstwatt.com/pdf/art_diy_nutube_preamp.pdf

It is the only DIY thing I have ever built and I was amazed I got it to work. It also has the intended purpose of adding second harmonic distortion to the signal because that's what some listeners like. Pass makes a distinction between positive phase second harmonic distortion and negative phase second harmonic distortion, and has adjustments to swap back and forth to taste. The Pass device has an output impedance of about 170 ohms, reverses phase, and has said power spec of about 1.7 mW, Heh, Heh! It also 'brags' a two percent or so harmonic distortion figure at 1 volt output, with a gain of 16.

The DIY guys love the damned thing, just like they love the ACA amp, so it's horses for courses. I like it, too, but maybe just because I built it and it works.

My baby, my monster!:

 

[lkong]

I would suspect that the device Amir measured used the NuTube to drive an op amp, because the specs of the NuTube itself are abysmal for headphones i.e. very low power of about 1.7 mW and high output impedance. Also, as has been intimated by previous posters, the original PURPOSE of this device was to add tube distortion to musical gear, because many musicians who use amplified instruments love tube distortion. You probably hear these distortions in a lot of the pop, rock and synth music you listen to routinely. The fact that Korg NuTube has been hijacked for audio use wasn't part of the plan.

Another thing for ASR to go after with a hatchet on the Pass DIY site is the love for Pass' giveaway gift: B1 Korg NuTube preamp boards and plans. I built one of these, and I am listening to it right now as a buffer for my Sony MDR Z1 headphones and it certainly sounds nice. Expands the soundstage or something or other. Even with the impedance mismatch (MDR Z1 about 80 ohms, NuTube out put about 170 ohms), which probably alters the frequency response profile as well. A pair of 300 ohm Senn HD580's also sound great, and at least have higher impedance compared to the NuTube.

http://www.firstwatt.com/pdf/art_diy_nutube_preamp.pdf

It is the only DIY thing I have ever built and I was amazed I got it to work. It also has the intended purpose of adding second harmonic distortion to the signal because that's what some listeners like. Pass makes a distinction between positive phase second harmonic distortion and negative phase second harmonic distortion, and has adjustments to swap back and forth to taste. The Pass device has an output impedance of about 170 ohms, reverses phase, and has said power spec of about 1.7 mW, Heh, Heh! It also 'brags' a two percent or so harmonic distortion figure at 1 volt output, with a gain of 16.

The DIY guys love the damned thing, just like they love the ACA amp, so it's horses for courses. I like it, too, but maybe just because I built it and it works.

My baby, my monster!:
View attachment 47155

Other things aside, you might want to switch location of your ps and amp board.
Having that 120v main running close to un-shielded signal is very spicy.

 

[cjfrbw]

Other things aside, you might want to switch location of your ps and amp board.
Having that 120v main running close to un-shielded signal is very spicy.

You are absolutely correct.

However, wire is shielded and the unit is completely quiet, so I got a pass for bad ergonomics. If there is any influence, I can't hear it, and I use it frequently.