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

  1. pmillett Contributor
    Well, I'm not real sure what would be causing this. I didn't notice noise like that on the one I built with the upgraded pot.

    The noise that was caused by oscillation using the FET was very loud. I would expect a little noise as the pot hits its limits, but nothing terrible.

    Sythrix likes this.
  2. Sythrix
    Not a big deal. I might tear it apart one day to see if I can figure it out, but for now it's just not enough of an issue for me to bother. The sound is so good that I am making it my main bedroom amp for music and TV/movies.

    Anyways, thanks for getting back to me! I am a fan of your work and am just about ready to start the Butte to accompany my PC.
  3. trevmex
    I have the upgraded pot as well and grounded it as well, it hisses at the very bottom and crackles at the very top. I don't get distortion when tuning, though (I used all the recommended upgraded parts on the BOM/site).

    The amp is hyper-sensitive to any jostling, though. I put EARs on it, which seems to help, and I bought the enclosed version of the box Pete recommends (but haven't gotten around to putting the top on yet).

    Still, I love it, though. I am thinking of making a DAC to complement it, but haven't decided what to build...
  4. Sythrix
    The distortion while turning and at the bottom and top seems to be fading away with time. I think I was shipped a substandard pot, but since I already soldered it, it's not eligible for return.

    I used "Isolate It!" Sorbothane feet to steady it, which seems to limit ringing to when I plug in a pair of headphones or very slight when I am adjusting the volume.

    I also am going to build a DAC!

    I decided on the https://www.amb.org/audio/gamma2/ (which requires that you also build the γ1, as it's an extension to it). It's basically two DACs and outputs in one case. That way I'll be able to wire two different amps (if I want) to the one brick housing the γ2 and γ1 (with one slightly higher quality output, given the more advanced γ2). Came out a little over $300 after all parts and a σ25 power supply with the σ78 regulator (optional, but lower noise than wall-warts). Could probably easily do it in the low to mid $200 range if you just used the USB power or something. There really aren't a lot of options for DIY DACs out there.

    I was going to go for the γ3 but the cost of all the parts and the front panels, on top of my non-existent knowledge of building power supplies, led me towards these builds instead. I'm going to have someone guide me through putting together the σ25 power supply so I at least get some familiarity with building them before attempting something as complicated as the γ3's.

    I'm just a little concerned about the reports I've been reading of the old SSMH and how it sometimes damaged the γ2 and γ1 because of some kind of power problem. I'm guessing it's not going to be an issue, but Pete did say the NuHybrid was based on the old Millett Hybrid design... All the parts are already on their way, so I hope it doesn't have the same problem or I'll be building another DAC soon enough after this one, lol.
    trevmex likes this.

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