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    WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.​

New tube tech from Korg

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That's cool.

I'm a little wary of the press release stating, "The Nutube 6P1 is designed specifically to generate rich harmonics when used with a musical instrument," which implies that has high harmonic distortion.

I think it's sonic signature will preclude its use outside of guitar and synth effects.
 

Newk_Yuler

Member
2007-07-14 7:17 pm
Isn't harmonic distortion in tube guitar amps caused by hard driving the tubes? If these Nutubes are designed for distortion circuits (by description) wouldn't you think there is a possibility they can be driven in other applications for clean but harmonically enriched sound? You can run guitar tube amps at levels that produce clean sound.

With a 30,000 hour longevity these things could be awesome for little preamp or buffer projects if they turn out to have a decent potential for that sort of thing.
 
Noritake makes Vacuum Fluorescent Displays. These were common in 80's vintage cars, and consumer electronics. If you take a good look into a VFD you will see guts that are very similar to the device in the picture. There is one or more (mine had 3) filament wires suspended over a plate that is coated in electroluminescent material. There is a separate grid between the filaments and each segment on the plate.

In operation the filament is heated, the plate has about 30 volts on it, and the grid bias controls the plate current, and hence the brightness of the EL material on the plate.

Can a VFD display ripped out of a 1985 Dodge 600 be used to make a tube amp? YES, it can. The gain was a bit low, the Mu was maybe 5 or 10, but the VFD can amplify.

It should be possible to optimize one of these things for amplification, after the market for VFD's isn't what it used to be.
 
Interesting that it claims long life, in preference to a 12AX7. I always thought that VFDs fade long before the valves do, but perhaps it is just the phosphor wearing out. Or are they comparing with modern valves rather than NOS? Will the curves be anything like a real 6P1?

I suspect just a firm with vacuum technology trying to extend their otherwise obsolete skills for a few years. That lot in Blackburn tried it but it came to nothing.
 
Never thought of magnets.....I have chased the blue glow around the envelope in a KT88 with a small magnet, but didn't notice an effect on the sound. Maybe it would be more pronounced in a current starved VFD.

It's been a long time since I tinkered with the Dodge VFD, but I remember very low plate current, and the dark segments would start to glow if I fed it more than 30 volts on the plates. Don't remember the filament voltage, but I turned the supply up until I saw about the same faint glow that I saw in the car I took it from. Maybe a bit more filament voltage would help.

Maybe it's TIME to experiment a bit????

Electronic Goldmine - SALE! - Vintage Fluorescent Automotive Clock (Pkg 2)
 
I've used VFD's in synth modules to distort the signal.

The Electronic Goldmine sale ad appeared in my inbox this morning. Coincidence? I don't know, the VFD has been listed for a while, but the 50 cent rotary encoders are just right for a PIC chip MIDI controller along with the slide pots I got in my last order, so I ordered a pair of these VFD's.

These have 4 large digits where the odometer out of the old Dodge had 7 small ones. I should be able to rig up an audio generator, scope and power supply for a simple test. Much beyond that isn't going to happen soon.
 
About the magnets, I think they were physically moving some of the little wires inside the VFD... That would best explain the effect it produced.. On the module I built, I have what looks like a slide pot, but it's actually physically moving a magnet along the length of the VFD. No CV on that one.. Although, I suppose w/ an RC servo or something, I could automate that, too :). My VFD's were out of old clocks, I believe.. They're big!
 
There is no doubt that magnets will bend the electron stream. That's how the sweep section in a CRT "sweeps" the electron beam. The deflection yoke is a big electromagnet.

Note: resist the temptation to bring a magnet near the face of a COLOR CRT. The shadow mask in the face can become magnetized causing color splotches. The TV has a built it degaussing system to demagnetize the CRT, but it is only so strong. Magnets on a black and white set are no problem.

I doubt that the little magnet that I used on the KT88 in the SSE exerted much influence inside the steel plate. That's not the case on a VFD. The "insides" are exposed to the magnetic field.

No CV on that one..

You can vary the filament or plate voltage with a mosfet for voltage variable distortion.
 
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Yeah, I found a few sites on VFD amps now.

I wonder if AC could be made hum free for the filaments? I'm playing w/ one now, and it lights up unevenly w/ DC. (I don't have a suitable transformer for AC at the moment)
One site said high plate voltages sounded better, and they were going up to 90v (I think it was supposed to get 30v in its intended use).
Someone used a 5k transformer at the output, too.

Edit to add link. This one is fairly comprehensive
https://web.archive.org/web/20111130050742/http://www.hpfriedrichs.com/rr-vfd.htm
 
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I don't doubt that it works. It's a real triode, in a sense, and I've seen youtube clips of an ordinary VFD wired as an audio amp stage. I don't doubt that they get at least some kind of distorted tone out of it. Since Korg probably plans no other applications for it... fine.

But it's never going to replace ordinary vacuum tubes, just like anything alike it hasn't done so far. When even things like OTA's and BBD's are obsoleted what do you think are the chances for finding a replacement part after, say, ten years? I have a hunch thse VFD tube thingies won't be repairable in practice. That's a huge turn off when it comes to guitar amps, whose buyers expect them to be built bombproof and live thousand years without giving problems that couldn't be solved by a tube swap/replacement.

Nice idea. Fascinating new way to use old technology, but overall this doesn't bring anything "new" to the table. If people wanted to mimic vacuum tubes in smaller size, lower voltages and current consumption there has been various technology to do it for decades (including even this VFD).

But obsoleting traditional vacuum tubes with this won't happen. People hype it for a while because it's new and because it's seemingly a real triode. Few years and these things are buried and replacement parts nowhere.
 
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Somewhat reminds me Blackburn's (failed) attempt to recycle/re-use obsolete CRT guns into audio triodes some years ago. Remember the E813CC ? It soon disappeared and never went into mass production despite the huge marketing hype... Like CRT's, VFD's are a dying/dead technology and re-using the now obsolete machinery for making something with a greater potential market may make sense. VFD's could be used to build triodes (which basically they are), but lousy ones. I don't think these will go any further than distorsion generating devices for electronic instruments but still with a major drawback: they will be impossible to replace within a few years when they fail and production has stopped.
 
Is there a reason everyone is saying these could only ever make bad triodes?
It seems there is quite a bit of precision involved, compared to standard tube construction.
These could be made with extremely tight tolerances, everything etched and aligned perfectly.

I think everyone is right that there's no market and the idea won't really progress. But lets say there is a market and reason for further development, do you think the idea could be refined to a very good tube if they tried?
 
I think everyone is right that there's no market and the idea won't really progress.

I'm sure there is a market: Korg's own products use thousands of tubes. They must have poured money into this a for a good reason.
What I doubt is whether these will be available in the open for diy-ers and such; most probably not. Korg would be stupid to provide this to the competition - this gives them the edge.

Jan
 
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