A Korg 6P1 “Nutube” kit, part 1: Let’s look at the kit.
Thursday, June 4, 2026 at 07:30:49
I’ve known about these devices since they were introduced a decade ago, but never really had access to one. I decided to get one to see how it works. There’s a seller on eBay that has both the tube and a PCB for a buffer amp, and I decided to pick one of those up. Here’s the good stuff:
The device itself is kind of interesting - if you said that it looks like a vacuum-fluorescent display, you’d be correct. That’s exactly what it is.
What is this, exactly?
A vacuum-fluorescent display, or VFD, is a type of display that uses a filament, grid, and plate - just like a normal tube. The plate in this case is a painted substrate that is flooded with electrons, and this flood is either allowed or prohibited due to the charge on the grid. It’s and on-off device, but it still fulfils the basic requirements of a triode tube.
The Nutube takes that idea one step further. Instead of a painted substrate that’s a numeral or symbol, the plate on this one is just that - a rectangular plate that is flooded with electrons from a filament, modulated with a grid in the middle. It does glow in operation, but that’s not the point - this is a flat-pack tube that can amplify audio. It was designed, AFAIK, for Korg’s musical instruments because “tubes!” and because this device doesn’t need the high voltages that something like a regular 12Ax7 device would need - even though those higher voltages are trivially easy to generate these days.
The tube’s numbering doesn’t really follow standard conventions, but whatever.
The vendor provides a BOM for this device’s board, but it’s out of date. I’ve created a new one and will post it as I build this device. In the meantime, I’ve ordered parts and hopefully will have time to assemble this device in the next few weeks:
Stay tuned for an updated BOM and assembly thoughts.
Next part of this series: Coming soon.