NuTube - new tube design based on vacuum fluorescent display - Page 1
Forum section: electronics / projects

author: vwestlife
author_rank: Regular Contributor
timestamp: January 04, 2018, 10:34:02 pm
content: Apologies if this has already been discussed:http://korgnutube.com/en/"A new vacuum tube which puts vacuum fluorescent display technology to practical use. Nutube, similar to a conventional vacuum tube, has an anode grid filament structure, and operates exactly as a triode vacuum tube."Guitologist's video about it:

author: Len
author_rank: Frequent Contributor
timestamp: January 04, 2018, 10:46:58 pm
content: Here's an earlier discussion:https://www.eevblog.com/forum/projects/korg-and-noritake-develop-modern-vacuum-tube/25/

author: chris_leyson
author_rank: Super Contributor
timestamp: January 04, 2018, 11:37:48 pm
content: QuoteI remember reading somethink a long time ago, might of been "Wireless World" possibly in the 70's or 80's, I can't remember who was developing field emission cathodes.

author: ikrase
author_rank: Regular Contributor
timestamp: January 05, 2018, 05:26:21 am
content: Intriguing. Now if only they would make an electrometer tube with this...

author: Cyberdragon
author_rank: Super Contributor
timestamp: January 05, 2018, 07:16:08 am
content: Quote from: ikrase on January 05, 2018, 05:26:21 amNever going to happen. It won't work, the gain of these tubes is trash at only 5 per segment.

author: Ian.M
author_rank: Super Contributor
timestamp: January 05, 2018, 09:31:15 am
content: The gain is crap because they cant get the grid close enough to the filament. That's the problem with using a long filament (+tensioning spring) as a directly heated cathode. If they used MEMS technology processing to build up a heater, insulating ceramic coating, cathode metallisation, high emission rare earth layer on the cathode, then control, screen and suppressor grids supported by islands or walls of ceramic insulation, then they could construct multiple high gain isolated cathode Pentodes in the same form factor package. However, that would involve developing a lot of new technology, not just running batches down an under-utilised un-modified aging VFD production line, for maximum R.O.I for minimum effort from the deep-pocketed Audiophool market.

author: Gyro
author_rank: Super Contributor
timestamp: January 05, 2018, 10:29:13 am
content: Quote from: Cyberdragon on January 05, 2018, 07:16:08 amElectrometer tubes also go to great lengths to minimise stray leakage current to the grid via the envelope, a planar VFD type envelope just isn't going to hack it.

author: ikrase
author_rank: Regular Contributor
timestamp: January 05, 2018, 08:36:25 pm
content: That's really too bad.I would love to have new production dual electrometer (or even just high input impedance) tubes in a compact low power package.(Most of the new production tubes, iirc, are audio amp tubes. This is unfortunate for those of us who don't like the inability of FET gate oxide to survive 10kV overvoltage.)

author: Gyro
author_rank: Super Contributor
timestamp: January 05, 2018, 09:04:32 pm
content: You could always pick up a real electrometer tube off ebay if you want to play - easier to source and probably cheaper too. Electrometer tubes always have very low power requirements (they work under starvation conditions), if anything, lower power than the NuTube:https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=electrometer%20tube&_sop=15&_clu=2&_fcid=1&_localstpos&_stpos&gbr=1&_zpclkd=1

author: Cyberdragon
author_rank: Super Contributor
timestamp: January 05, 2018, 09:28:45 pm
content: Quote from: Ian.M on January 05, 2018, 09:31:15 amNo, that's exactly how you make a low voltage filament. It's the same in all low voltage directly heated tubes. They already have an emmisive coating on it, otherwise it wouldn't work at all (not sure how good it is though). The problem is the grid and plate need to surround the filament to gather the most electrons, not just be beside it. Subminiature tubes were invented 60 years ago, new tech would help (better cathode coatings), but it would not require radical tech. As far as isolating them from each other, you just put grounded metal plates between the sections. The problem is, properly constructed subminiature tubes wouldn't look all that interesting to an audiophool.

author: coppercone2
author_rank: Super Contributor
timestamp: June 16, 2024, 03:52:58 pm
content: did anyone try to make circuits with this? I got one. Not sure what I want to do with it. Looks like a very interesting bit of technology.even if for just learning about triodes on a bread board

author: LaserSteve
author_rank: Super Contributor
timestamp: June 16, 2024, 04:52:09 pm
content: 6977 aka DM160 tuning indicators make an "ok" AM radio. They are cheap, and much closer in design to an audio tube then a VFD. Fun on the bench and don't need fussy power supplies for the cathode heater. Great toy.If I did it again I might choose DM70 or one of the miniature magic eye tubes. Simply because of larger plate area. 6977 was cheap at the time.Steve