"Millett Hybrid" redux: NuHybrid headphone amp, using the Korg Nutube

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  1. silverfishla
    Thank you @pmillet, I will check that out. I'm so curious to hear this amp!
  2. silverfishla
    I am at the very end stage of my build! I just need to finish wiring it up. I've got a few last questions though that I want to make sure I get right...
    I've decided to install a stereo jack off board and want to make sure I wire this up right. What numbers correspond to the Ring, Tip, and Sleeve of the jack? The PCB has six soldering points, but I assume that I only have to use 3 of them. Can anyone tell me which ones correspond to the Ring Tip and Sleeve?
    I've also decided to install the 24v DC jack off the PCB. Can someone also confirm which numbers correspond to the Ring Tip and Sleeve of the back of the installing DC jack?
    Lastly, do I need this third wire connected to the On/Off toggle switch? Or can I just leave it off?

    My thanks in advance.
  3. pmillett Contributor
    On the headphone jack: 2 = tip, 4 = ring, 6 = sleeve.

    On the power jack: 3 = tip = positive, 1 = sleeve = negative.

    On the power switch: You only need the two pins farthest from the PCB edge
    (green and white wires in the pic).

  4. SasaKudo
    @pmillett : It seems that the dimension of the upper left hole in the PCB drawing is wrong (it's 2,8125 right now, bigger than the PCB itself).

    The assembly guide also mentiones that I could find the DXF file of the PCB on your website, but I wasn't able to find it (Wanted to use it to design a 3D printed case).

    Thank you for the hard work!
    Last edited: Oct 20, 2017
  5. Daniel Bauza
    Hello all, first off I'd like to thank you for all the valuable info you post and discuss which helps further noobs such as myself learn more about DIY projects. I built the Nutube a couple of months ago and I noticed an imbalance in the right channel. I'd have the volume at zero but could still hear right channel. Today all hell broke loose. The right channel is blasting even with the volume all the way down. Could use some guidance?
  6. pmillett Contributor
    That's pretty much always the symptom of the grounded end of the volume pot being disconnected from ground. Check the solder on the volume pot. Or, it could be defective or broken.

  7. pmillett Contributor
    Sorry for the delay, I've been traveling again. When I get home tomorrow I can generate a DXF file for you.

  8. HiGHFLYiN9
    I'm surprised the NuTube hasn't found its way into a tube overdrive pedal yet. The only guitar pedal it seems to be in right now is a strange Miku anime sing along pedal.


  9. Daniel Bauza
    Thanks Pete, resoldered the contacts and It cleared up considerably.
    Very low signal coming from right channel but only noticeable with my Grado’s
  10. silverfishla
    Have you checked your gain settings and are they of equal value?
  11. Daniel Bauza
    Yes I have and they appear to be exact
  12. pmillett Contributor
    Unfortunately that's pretty common for small volume control pots. They all... suck. Lots of channel imbalance at low volume settings.

  13. Daniel Bauza
    bummer... other than that I love the sound. Going to put it up against audio-gd R2R later this week.
  14. silverfishla
    So, I finally finished my Millett Nutube amp a few days ago. I think it sounds great and getting better. I'm running a couple of SparkosLabs singles in there at the moment and from initial comparisons with the ones on the BOM, I think that they are fantastic. I don't have a final assessment yet, as I'm still letting everything settle in and trying different headphones. Here are a few pictures though.
    I also have a couple of Burson V5i singles coming in to try out. I'll post my op amp impressions when I get a little time with them...
    millinside2.jpg millampfront2.jpg millback2.jpg
    Thanks @pmillett , that was a really fun build and the amp sounds great!

    *There's supposed to be a little green rabbitt that shows up on the front of the amp when ON. I'll have to change to a stronger LED to make it show up though...but I'm going to make that happen! I call this amp my Millett Nutube "White Rabbit" amp. :)
    Last edited: Oct 23, 2017
    WoodyLuvr and Daniel Bauza like this.
  15. pmillett Contributor
    Yeah, that dimension should be 3.125. I grabbed the 'x' location instead of 'y'.

    I'm attaching the DXF file (inch units, zipped).

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