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Nutube vs Nanotube

Discussion in 'Amp Central Station' started by doghouseman, Apr 15, 2021.

  1. doghouseman

    doghouseman Tele-Holic

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    Anyone know if the Nutube technology that Vox/Korg uses is the same technology as the Nanotube stuff that BluGuitar uses?
     
  2. metalosophy

    metalosophy Tele-Meister

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    They are different. Nanotubes are smaller stable conventional ones, Nutubes are a new design.

    The Nanotube is a Subminiature tube.
     
  3. doghouseman

    doghouseman Tele-Holic

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    Arent the Nutubes like little florescent bulbs? or not?
     
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  4. metalosophy

    metalosophy Tele-Meister

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  5. doghouseman

    doghouseman Tele-Holic

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  6. gusfinley

    gusfinley Tele-Afflicted

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    The Nutube is both lower voltage and lower gain than the 12AX7s that are used in traditional amps.

    To me, they sound like a 12AX7 that is being run at low voltages like the Marshal Valvestate or the Orange Micro amp series. A lot of compression and saturation - too much in my opinion.
     
  7. radiocaster

    radiocaster Poster Extraordinaire

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    Also I'm not sure they ever made a 100% Nutube preamp, I bet they are hybrid designs with some IC/transistor stages. Not saying it can't be done, just what probably has been done so far.
     
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  8. DougM

    DougM Poster Extraordinaire

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    The Nutube was derived from fluorescent display technology
     
  9. uriah1

    uriah1 Telefied Gold Supporter

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  10. DeepDangler

    DeepDangler Tele-Meister

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    I have a Vox MVX150C1 which is their 150 watt nutube combo. It’s all analogue and uses nutube in the preamp and power amp but it is a hybrid. The nutubes change the sound and are integrated into the power stage for tone but they use class D solid state amplification for volume.

    Overall, I think the technology is great! I can get saturated sounds with dynamic compression and drive like a real tube but I’m not dependent on volume to do it.
     
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  11. 11 Gauge

    11 Gauge Doctor of Teleocity

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    I have a Vox MV50 Boutique that uses the NuTube. It stays pretty clean for most of the rotation of the gain control, but then comes on really strong kind of suddenly, for the last bit of knob rotation.

    It's been awhile since I've played a Valvestate anything, but the MV50 Boutique IMO doesn't really sound the same, albeit going from memory.

    I'd say max gain with the MV50 Boutique sounds kind of like the old 12A_7 preamp tube amps of yesteryear, like the Valvestate, or maybe kind of like what you'd get from an overdriven SS preamp, but at less than max gain, there's not a ton of compression or saturation.

    I haven't tried a MV50 Clean or MV50 AC, so I can't speak to how they sound/feel when pushed to the point of clipping. I wouldn't be surprised if the MV50 Rock or MV50 High Gain didn't sound/feel similar to some old Valvestate sort of thing, just given their design.

    Edited to add - here's how the MV50-series look under the hood:

    [​IMG]

    ...The NuTube is the rectangular-shaped thing in the middle.
     
    Last edited: Apr 16, 2021
  12. 11 Gauge

    11 Gauge Doctor of Teleocity

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    A little while ago, I was looking into the NuTube tech in a bit of detail, and it's not possible (IMO) to create a circuit that's 1:1 with what's happening with your typical 12A_7-based preamps.

    The long and short of it is that it looks like it makes much more sense to keep at least the initial driver stage as SS, as well as the EQ circuitry and such. And I guess that depending on what kind of power amp you intended to marry it to, you wouldn't probably want to use the NuTube for something like a phase inverter, either (if it's even possible).

    I think you can get a NuTube chip for around $12 or so, so making prototype preamps should be do-able for those who are DIY-inclined.
     
  13. Festofish

    Festofish Tele-Afflicted Silver Supporter

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    I’ve had a Vox MV50-AC for half a year or more and it’s absolutely great. Light on features but they were meant as an inexpensive way to introduce the technology to the market. I don’t recall if it’s replacing the preamp or power amp tube. Last I heard they were just around the corner from having both.
     
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  14. radiocaster

    radiocaster Poster Extraordinaire

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    Well, what if you want to make something like a 4 triode preamp, so you use 6 or 8 Nutube triodes?

    I think they also got used for something in the power stage of some amp, I remember reading about that.
     
  15. 11 Gauge

    11 Gauge Doctor of Teleocity

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    Unfortunately, just using the NuTube triodes by themselves will probably not be sufficient. Read this for details - https://diyaudiostore.com/products/korg-nutube

    I'll copy the most relevant bits here:

    The basic application circuit provided by Korg (Figure 4) uses simple JFET source followers to buffer the signal in and out of the Nutube. An input buffer is used to support the relatively low impedance looking into the grid and bias source. The output buffer is needed to drive anything but very high impedance loads, due to the low transconductance and resultantly high plate resistance of the tube.


    [​IMG]
    Figure 4- Korg Application Circuit

    This circuit is intended to operate from a single power supply between about 5V to 30V, plus a regulated 3.3V supply (typically from an LDO regulator). Bias is adjustable from 0 to +3.3V. To support the grid current, a relatively low value resistor (33kΩ) is used to provide DC bias to the grid. This then mandates that a large (10µF) coupling capacitor be used to couple the audio signal. There is no doubt some bias shift with signal level in this arrangement, but with the values shown it doesn’t appear to be significant.


    Filament power is obtained from the 3.3V supply with a dropping resistor.

    The article also contains data on what happens for given bias points, plate loading, etc.

    I guess you could theoretically use a NuTube triode as a cathode follower, but a jFET or op amp probably makes more sense. The more important thing IMO is getting the input Z sufficiently high, and that's easily done with either a jFET or op amp. Since the whole circuit is working off of relatively low voltages vs. typical guitar triode-based preamps, there's no need IMO to avoid using SS components where they will definitely help, and shouldn't contribute to distortion/clipping in any way.
     
    Last edited: Apr 16, 2021
  16. The Angle

    The Angle Tele-Holic

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    Nutubes have far, far less gain than a 12AX7 - something like 10 to 15 percent or thereabouts. So while it may be possible to make an entirely nutube preamp, it would take a ton of them and I doubt it would sound very good. They typically combine nutubes for their saturation/compression characteristics with SS for primary amplification. This quote sums it up: "I view the Nutube not so much as an active amplifying device as a signal processing element. Yes, it does provide voltage gain – but if accurate voltage gain is your goal, you are much better served by using other devices, both tube and solid state. In a guitar amplifier, it can be used to provide distortion similar to that of a conventional tube, with much lower voltage and power requirements." (source)
     
    Last edited: Apr 16, 2021
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  17. 11 Gauge

    11 Gauge Doctor of Teleocity

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    Wow, that's even less than a 12AU7!

    Yeah, it would clearly make sense to reserve them just for gain stages where you purposefully want to add clipping, and then just make sure the SS bits are never driven into clipping on their own.

    Runoffgroove.com did something like that for their Thunderbird - http://www.runoffgroove.com/thunderbird.html - it uses 24VDC supply voltage, to ensure that none of the op amp stages are ever driven into clipping. You could probably alter it to sub in NuTubes in place of their use of clipping diodes.
     
  18. DeepDangler

    DeepDangler Tele-Meister

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    The NuTube sound is somewhere between solid state and tube and has positive aspects from both. The wattage is usually high on the Vox NuTube amps because they need the class D solid state amplifier to stay clean and keep the nutube around in tact. It seems like the amp creates an extremely quiet “line level” sound using its analog circuit if you will and just boosts the volume. Tube amps use the tubes themselves to create sound and volume at the same time so you end up with interesting reactions between the two but you’re tied to high volume playing or attenuators. Most tube amps tend to have a “sweet spot” for volume and gain.

    I’m hoping the technology catches on and more companies use it. I’d love to see more new technology outside of modeling. If everything goes to modeling, there will be nothing new.

    Is a nutube amp the same as tube in sound? Certainly not. But they sound good and are responsive to playing dynamics and guitar controls. It just so happens they’re lighter and easy to dial in :cool:
     
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  19. The Angle

    The Angle Tele-Holic

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    The Guitologist has some interesting YouTube videos in which he investigates Nutubes. They get a little technical at times, but not too much. His demonstration of how microphonic Nutubes can be is sort of startling. It's hard to see how they can function in a guitar amp when they're that sensitive to physical vibrations. I've never had the chance to try a Nutube amp; I can only presume manufacturers deal with that issue somehow.
     
  20. DougM

    DougM Poster Extraordinaire

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    The little MV50AC head nails the AC30 sound better than any other attempt at it that I've played through, including any Vox (or other makers) modeling amps, or any pedal.
     
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