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Check the Korg Nutube 6P1 Out!!

Discussion in 'Home Brew' started by Onelasttime, Apr 10, 2018.

  1. Onelasttime

    Onelasttime Well-Known Member

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    https://korgnutube.com/en/



    By itself, you could create a small tube preamp that could be used to create a tube mic sound especially on direct inject app's. It compact size and low power requirements are crazy cool! Headphone amp would be another very practical use. Ultimately you could use it before a well-designed transistor amp to reproduce the sound of a single end high power tube amp.

    As I understand it microphonics is still an issue so maybe base station use first. You can fit 5 or 6 of these in one mans hand. The power and current is so much lower than what is needed for a 12AX7.
     
    Shadetree Mechanic likes this.

  2. LeapFrog

    LeapFrog Sr. Member

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    Brad the "Guitologist" did a nice review of these, yes they will exhibit microphonics if allowed to vibrate.
    But I do think they are kind of neat, I wonder what CB manufacturer would include this in a radio?


    The VOX MV50 uses this part!
     
  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    LeapFrog likes this.
  4. Mars

    Mars New Member

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    Interesting!
     
  5. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Fun little device, but brings back the issues around "tube ringing" as others call it, microphonics. - so this makes a modular unit, but limits you to that particular design and strip. So even the socket is not around they use a header - but would seem to fit a niche in the analog world of turntable preamps and such.

    Makes this more of a novelty than a useful device.

    As said in the vid, the "compression and hum" did come up - so the "wall wart" would have to be upgraded. And with the required noise abatement and isolation stuff you would have to put in, else this thing picks up on its own - would make an interesting "reverb" device but using a switching power supply on it - not a good idea.

    Thanks for the heads up on this.

    :+> Andy <+:
     
  6. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Went back to the Vid and then went to the site.

    Got this as some ideas...

    The Evaluation board...
    6P1Evaluationboard.jpg

    This "kit" if you watch the vid above - comes with a header to mount the tube...

    Top side, where the tube will mount....take note that the board has a "blank header" to reduce microphonics ringing - as demonstrated in the vid...

    NuTube6P1Header.gif

    Bottom side - showing solder traces...

    NuTube6P1HeaderView2.gif

    Soldered in place...
    NuTube6p!Solderedinplace.gif

    Ok, the finished product...
    NutubeMountedHeaderCloseup.jpg

    It's a wild rebuild of an idea the Vacuum Tube Fluorescents can also be used as amplifiers.
    NuTube6P1.gif

    The Phosphor as an emission electrode, wild idea but when you look at how these function on paper - they make sense.

    6P1NuTubeCircuitIdeas.jpg
    Just remember not to overcook the filament that lights the phosphor.
    OverdrivenCathodeFilament.jpg

    Else can be made as small signal tube amplifiers.

    Very Novel idea - especially for compact stereo equipment using a Vintage technology platform.

    Nutube6P1KitNKaboodle.jpg

    One small drawback, uses FET outputs - may be an issue on the breadboard for interfacing an analog device that may not like the shot noise and non-linear output of an FET directly.

    Note the use of 330K resistor on the FET Strappnig Gate to Drain - for some linear operation. Frequency response notwithstanding - can produce some good fidelity. The 330K can be reduced will some improvement that comes with a loss of output - with improvement in bandwidth products.

    Now remember - this is their plots, your mileage may differ...
    Nutube6P1Responses.GIF

    Not sure of the actual signal level you can drive this - but looks like low-level dynamics would be just fine - the -2dB output at 12VDC is pretty good - but remember this output can be duplicated with a typical Electret - so again the Novelty and the glow - would be a nice addition to any system that uses low-level dynamic mics and cartridge outputs for entertainment.

    Looks like the filaments are the biggest bottleneck, 0.7V 17uA - note one photo showing the red-glow - you have seen this on typical Calculator Vacuum Fluorescent Displays (VFD's) as normal, but remember that was for a display for considerable brightness, and digital drive output. So these do have a "headroom" dynamic issue of power input, so Filament aside- again low-level dynamics seem to be the best suited for this application.

    Just not a lot of drive output - see the use of the FET output for line level. So its' possible; that with some rework even Germanium can be he next stage of the amplifier. Just watch the output of the ANODE - doesn't appear to summate the grid values - but can be driven with plate voltages quite high up to over 18 volts - can be a bit of a poke on the other end.

    Noise? Note above in the graphics, a 10uF cap can be installed ABOVE BOARD - see photos above for location as C1 - for noise abatement - again, not a clear cut and dried use but can provide dampening of noise.

    All the above - was from here...

    https://korgnutube.com/en/guide/

    Note the FET symbol - the GATE points to SOURCE lead - so bias feedback on Gate To Drain or Pins 1 to 2 on schematic reference.

    Have fun!
    :+> Andy <+:
     
    #6 Handy Andy, May 29, 2018
    Last edited: May 29, 2018
  7. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    I'd love to see this take off...

    See attached...

    Now if anyone had ever heard a mechanical reverb unit, these "tubes" can easily reproduce that effect thru springs - so it's like we've gone back in time...wild - like turntable "rumble" when Bass is set high - so can these "reverb" to a degree using the tubes as a feedback device.

    Evaluation board PDF and TUBE spec PDF
     

    Attached Files:

    #7 Handy Andy, May 29, 2018
    Last edited: May 29, 2018
  8. Onelasttime

    Onelasttime Well-Known Member

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    Some seriously high-end hifi audio amps use a nice clean tube preamp feeding into multiple class D discrete component amp boards. The trick is getting the filtering right. If you can do that than class D audio amps can be not only efficient but sound great. The filtering will take most of the time in R&D. Most people will tell you that you can not do a Class D audio amp and get great sound but it can be done it is just not easy.

    So why did I bring up the above? Well doing the impossible is what small independent inventors and hobbyists have been doing for years they innovate. They can often take things that should not work and by diligence and sweat equity do what other's have failed to do. So I have no doubt at some point this will work it's into the fabric of many different hobbies. Why? Power requirements are low. If cost and reliability can be brought inline the microphonics issue solved it has a ton of potential. A lot of people love the tube sound but hate the lack of efficiency and the huge power consumption. Usually when people do a hybrid with tubes and transistors the tubes are power hungry and generate a lot of heat. This is especialy true when you have multiple gain stages say dual triode tubes. Tube modeling is still not as good usually as having an audio tube stage feeding into discrete transistors. This is especially true with guitars where you want some crunchy dirty slightly overdriven sound. Even really well designed discrete components amps often lack that sound you get from a tube amp. Now obviously when talking hifi not guitars it is a different story the less power your tube preamp section needs the smaller your transformer can be which means less steel and copper this is not 1950's copper and high silicone steel is not at all cheap today!

    THe trck would be to use the perfect transistors after this that have nice clean sound that is not harsh which means a lot of tinkering with impedance on the input side of the transistors to make sure they sound nice and full of harmonics not harsh and thin. I just think it has potential is all too early to tell much for sure.
     

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