Nelson Pass DIY H2 "injector" for loaner tour

Discussion in 'DIY' started by dBel84, Dec 8, 2019.

  1. cameng318

    cameng318 Friend

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    The FET Aikido from this TubeCAD article is also nice circuit for solid state tuby preamp. From my measuremet, the J113 JFET actually follows tube's 3/2 power law pretty well between 6 to 16 mA. So bias it around 11 mA and degenerate it with a 680 ohm resistor should make it sound pretty close to a typical triode amp with damping factor of 10.
     
  2. skem

    skem Friend

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    I’d like a distortion circuit but one with less IMD than this circuit produced.

    I seem to recall Nelson has a variable H2 component to his B1 w/ Korg NuTube
     
  3. dBel84

    dBel84 Friend

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    Yes, the B1 nutube has some degree of adjustment.

    "If you increase the Plate voltage, the circuit takes on a positive phase 2nd harmonic distortion character, and if you lower the Plate voltage it has negative phase 2nd harmonic. These distortions increase as you adjust the Plate voltage farther from the null point."
     
  4. dBel84

    dBel84 Friend

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    If anyone is interested, NP is making boards and matched Jfets available as part of a GB on DIYA.
     
  5. mitochondrium

    mitochondrium Friend

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    For those in Europe (postage elsewhere being quite expensive at the moment) interested in this, there is a guy in Germany who built a little device based on this:

    https://www.nixiekits.eu/product.php?key=renew

    He used to work for Klein&Hummel before they were bought. I own his Phono pre which I enjoy very much.
     
  6. dBel84

    dBel84 Friend

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    @E_Schaaf did you ever get to hear this, would be curious of your thoughts.
     
  7. E_Schaaf

    E_Schaaf MOT: E.T.A Headphones

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    Not yet, but I'll be traveling off and on for the next month or so. Would love to take it for a spin in October or beyond.
     
  8. CEE TEE

    CEE TEE MOT: NITSCH

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    Okay, I am posting old stream-of-consciousness impressions that I wrote but are not exhaustive.
    I listened enough to know I wanted to build one. I think it will be fun to have around.
    (I want to see if I can use it to make my Parasound Phono Preamp listenable, for example.)

    In fact, I have two kits and will send one free to someone who wants to build one and will post impressions if they do. PM me. @penguins or @skem that includes you!

    Figured I would build one, use it more and then post. But let's not wait for that!


    Only listened with headphones...will let others say if this is good for speakers too. (NOTE: @skem did listen with speakers.)

    GRACE SDAC Balanced > H2 Generator with high level 1% > Black Widow > HD800

    Seems to thicken/warm up the sound overall with noticeable weight and longer decay down low, creating a somewhat persistent feeling of "floor" that isn't there without the generator.

    Bass floor is more present- a bottom end. (Versus only hearing bass hit and disappear when more energy is present.)

    Lush decay- a plush constant pressure rather than faster, greater range/dynamic attack.

    I think it is pleasing, but some may not like what they have to give up...will some call it a bit of veil?

    In the upper mids, slightly rounds a thin/wispy whistling? (off of a narrow sibiliant peak in something like Cowboy Junkies.)

    Brings the sound in closer, filling in a bit more...less space. Richer but less emphasis on resolution and space.

    Grey background due to lingering decay?

    Physicality of the sound is more of a punchy-blunt-Crack-like-perpetuating wavefront. A steel rod with a shorthaired terry cloth wrapped tightly around it? The decay envelope is rounder/wider and trails longer.

    Ha, brings my modded HD800 closer to my Phillips X1...in warmer lower end and sub-rumble.

    HD800 still gives sense of some 3D space on the Black Widow but everything is closer/more concentrated. I wonder if the negative phase of the H2 keeps the headstage from being too narrow/congested/claustrophobic. I'll test with HD600.

    Wow- with HD600, notice much less difference at first but with A/B/A/B:

    HD600 without H2 = more coherent quality across the FR. Vocals a tiny bit further away, the control, tone, attack and decay more similar with bass & up.
    HD600 with H2, vocals a bit closer and more up-front with mid-bass a bit more diffuse and low bass more hit/rumble. Some might think this makes vocals stand out more. (People use the term "shouty" to mean different things, is this one of them?)

    SOME THOUGHTS:
    I feel like this is a potential tool to have on hand for "adding Crack" to amps that are too quick/spacious or thin or need bottom end or leading edge overshoot is fatiguing or peaks are too narrow/resonant in the wrong places. Or for DACs with digititus or glare. The volume pot/pre-amp funcationality might be helpful so people can also play in a usable and channel-balanced area of their amp pot.

    If stereotypical "Hi-Fi" sound is faster overall & more treble...is this possibly "Low-Fi" to "Warm-Fi"?

    Has some bassier/warmer sound while retaining some adjustable degree of the original component quality/strengths?

    This might be a particular characteristic of some tube amps (like the Crack). Consider that people do enjoy the Crack and the sound is seductive + punchy at the same time. But they also end up modding it to try and reduce some of those effects over time. A great Crack+Speedball sits in between stock Crack and the best tube amps. Being able to sit at different spots on the continuum, gear-match, or just isolate and control more elements of sound is a good thing.

    Instead of listening to two complex, different pieces of gear to try and compare differences in one aspect...using this device allows you to tweak your singular component and hear/know what you are tweaking much more easily.
     
  9. skem

    skem Friend

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    Totally agree. Push pull amplifier designs have H3 by default. Adding H2 helps. Not having the H3 in the first place helps more.
     
  10. CEE TEE

    CEE TEE MOT: NITSCH

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    Somebody on HF reached out to share an H2 product that you can buy:
    https://www.nixiekits.eu/product.php?key=renew

    You can adjust the phase and there is also a high-pass filter so you can bypass the bass if desired. Interesting.
     
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  11. penguins

    penguins Friend, formerly known as fp627

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    Thanks but I'll pass for now (no pun intended).

    I'm curious about a H2 + H3 + H4 generator now though as an educational listening tool though. Mix and match the different harmonics and see what we individually perceive. Ex adding a little H2 was fun, but it almost felt like something was missing without a little H3 and possible H4 as well... but I may also be completely wrong and I just don't like "large" amounts of H2 as much as many do.
     
  12. Cspirou

    Cspirou They call me Sparky

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