KORG NuTube Portable Amp Kit

Discussion in 'DIY' started by highflyin9, Oct 31, 2018.

  1. highflyin9

    highflyin9 Facebook Friend

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    Pete Millett has the latest Korg NuTube Portable Kit from Japan. I did a review at Pete's request but wanted to share here as well just in case anyone would like to build one. You can get the kit here. Pete translated the instructions to English so it's a pretty easy build, you just have to have a little bit of experience with an iron so you don't accidentally short any of the smaller solder eyelets.

    [​IMG]


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    Bottom line: fun build with great tube amp sound on the go, and zero microphonics. I'd love to see a built-in DAC with the next version. If you decide to build one and need help, please feel free to post here.





     
  2. Cspirou

    Cspirou They call me Sparky

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    I knew he was doing a Class D project. I did not know he was doing an altoids mint NuTube too!

    I read that the NuTube can be microphonic. Not sure how well it performs for portable use.
     
  3. HAL9000

    HAL9000 Almost "Made"

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    Looks like fun... How much power out?
     
  4. highflyin9

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    That's what floored me, the kit came with a bit of foam damping (not a lot), and the Nutube is mounted off-board. I shook it pretty hard a few times while listening and heard absolutely nothing.

    Pete didn't actually design this one, someone in Japan did. He just did the translation and is selling.

    I have a couple of the Class D units forthcoming. I'm really looking forward to putting them together. They're on his main ebay page now.

    Regarding the power out, I need to check the manual and see if it's in there.
     
  5. Cspirou

    Cspirou They call me Sparky

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    Is there a schematic available? Is it basically a CMoy with a 6p1 in between the opamp and the pot?
     
  6. highflyin9

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    I dug through the manual but did not see anything about power output. In the specs, the output impedance is 10R and recommended load is 15R or higher, and the AAs should last about 9 hours.

    Here's the schematic (copyright Korg 2018)
    [​IMG]
     
  7. Cspirou

    Cspirou They call me Sparky

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    Looks like the volume control is from adjusting the feedback of the opamp?
     
  8. highflyin9

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    Good eye. There are four pots on the inside, two are for adjusting the load on the anodes to your preference, two are for gain.
     
  9. Sqveak

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    @highflyin9

    What range of gain possible on this? I lack sufficient circuit-fu to answer my own question.

    What headphones and IEMs have you tried with it?
     
  10. Cspirou

    Cspirou They call me Sparky

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    The schematic shows a 26v single rail which is equivalent to +/-13v. You should be able to use HD6xx headphones fine with this. The 10 ohm output means no BA IEMs

    Here some more info

    http://www.nutube.us/HA-kit.html
     
    Last edited: Nov 1, 2018
  11. highflyin9

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    So far I've only listened to it with the KEF M500 (albeit for several hours). It was satisfying enough that I didn't have the urge to immediately try something else.
     
  12. Sqveak

    Sqveak Friend

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    That's a fair assessment.

    I'm thinking it would be interesting for DDs such as the Future Sonics G10 or MEE Pinnacle P1 as they are both higher impedence with higher than average power handling.

    @highflyin9

    How does the sound signature of the Nu:Tekt compare to the NuHybrid?

    I have previously built a NuHybrid and found it to be a bit too Warm McLush for my liking.
     
  13. highflyin9

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    From memory the NuTekt is warmer than the NuHybrid.

    Edit: I should add however that the load on the anode is adjustable (and you can swap the op-amp), so the harmonic distortion can be tailored a decent amount. When I'm not listening critically, I like rich, warm, full sound, so that's the way I tuned it. I'd imagine you can dial it back quite a bit. I'm a little tired of opening and closing it at the moment to adjust, but will experiment more later and report back.
     
    Last edited: Nov 1, 2018

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