A new twin triode 6P1

[chriswood1900]

I was reading the latest edition of Silicon Chip the Australian electronics magazine; the January issue had an article on a stereo preamp using a double triode, nothing unusual about that you would think until you read a little further. Whilst the number 6P1 has been used before by Mazda for an audio output beam tetrode introduced in the mid 1950's and obsolete a decade later.
This 6P1 is rather different it is a very low voltage low power unit built in the same way as a vacuum fluorescent display and actually glows in the same way. Operating from low power supplies 9-12V and a heater current of 17mA at 0.7V.
I am assuming that this method of construction has been chosen as it is still a current method.
They are marketed by Korg the audio company. It will be interesting to see how they develop and the price in the future.
Who wants to build their own project using one!
Full specification here https://docs.rs-online.com/200b/0900766b815db1b5.pdf
If you want to buy one they are available here https://uk.rs-online.com/web/p/produ...-188&gclsrc=ds
Mods I hope this is an appropriate section if not please move it.

[G6Tanuki]

There was a thread about those some years back.

https://www.vintage-radio.net/forum/...d.php?p=742821

[chriswood1900]

Thanks, I didn't spot that or find it when I searched.

[Radio Wrangler]

Don't rush in.

Why should anyone want to build something using one? It might not do whatever it is that people think normal valves do. It could even be better, but it's worth finding out before acting. The one valid reason for building something new is to find out what it's like. If so, go into it with an open mind. People who assume it's junk and people who assume it's the answer to all their prayers are liable to each find that it is so.

With such low voltages and currents it is not going to be a power amplifier device, and it's not going to have the dynamic range at the top end that volves running with a couple of hundred volts on their anodes can achieve.

I think it may be a device which was made simply because they could make it. It remains to be investigated whether it has a use.

David

[high_vacuum_house]

With a maximum anode dissipation of 1.7 mW I cannot see using one as an output valve for an amplifier except maybe for use with an earphone !!

Christopher Capener

[turretslug]

I was puzzled by that in the original post- could they actually mean 1.7W? 1.7mW is piteously low, many times lower than a plastic-case BC548! Something made of glass and metal, as opposed to doped silicon sliver and plastic surely, surely can do better than that.

[Radio Wrangler]

Transistors, used properly, aren't actually bad. But some people act as if any valve circuit is always better than any transistor circuit. But there are good and bad varieties of each.

I care about whether a circuit is good or bad. What technology it uses seems less important. But it's a lot easier to spot whether there are transistors or valves than it is to determine whether a circuit is good for its intended purpose. Too easy, methinks.

The ratings of this new device make it look like some of the valve world's desirable properties might not be there in these parts.

1mW was the standard operating level for a telephone signal into an efficient (IE not high fidelity) earpiece. So the new vacuum fluorescent valves look to be limited to either preamp uses, or else as token parts for their placebo effect.

David

[Diabolical Artificer]

Pete Millet built a headphone amp with one - http://www.pmillett.com/Nutube_bal.html

Andy.

[Radio Wrangler]

Yes, but that circuit has an opamp doing all the work. The inputs are buffered by JFETs and the valve seems to have an entirely cosmetic role.

David

[Refugee]

These devices are made up using equipment obtained very cheaply on left over production lines after LCD took over for displays.
I suppose it is better than just crushing it all for scrap.

[turretslug]

The guy's put a bundle of effort into making a PCB for a rather puny valve and its life-support of a whole load of crutches- not only the in/out buffering but DC-DC conversion for the directly-heated filament. It's a shame that so much effort has gone into style over substance.

It would be instructive to know just how well this device has sold in the 5-odd years since the previous thread, and what a spectrum of actual users think of it. If they weren't aware that various products had this valve in it and just treated them as "black boxes" for parameter measurement, the reports might be a little underwhelming. I'd rather any active device was employed because it was good, as opposed to complying with religious stricture.

I'm reminded of questions as to whether 5V SMPSUs could be used to power 5V filament/heater thermionic rectifiers. High voltage rectifiers and a whole load of control circuitry being used to power.... high voltage rectifiers.

[ionburn]

They look a bit too expensive for me to even consider. I may be wrong but it seems the main thing about this is that it is different,but not particularly groundbreaking in valve technology.

[Diabolical Artificer]

Aye David & Mr Turret, I never said it was a good amp. Part of the beauty of valves is the low component count and relative simplicity of the circuits. Like with the Nutube there's a lot of headphone amps, guitar type FX and whathaveyou where a valve is chucked in and displayed prominantly, underlit with an LED as a selling point, like here - https://gearpatrol.com/2018/05/10/ib...-tubescreamer/

Nelson Pass also designed an amp with it, there's a thread here - https://www.diyaudio.com/forums/pass...rg-triode.html if you feel like wading through over 4000 replies. there's also some discussion here on the EEVblog forum - https://www.eevblog.com/forum/chat/korg-nutube/25/

Andy.

[chriswood1900]

I think it is fair to say the primary purpose of this valve is to produce the “valve sound”, in the Silicon Chip article as in the Pete Millet article it is surrounded in Op amps to make use of it, which I think personally is a bit of a waste of time. Clearly the commissioning of this device from Noritake by Korg is geared to audio markets and there is more material around geared to guitar applications.
For those interested there is some more info on the links below;

https://www.rs-online.com/designspar...-1-tube-basics
https://rezzonics.blogspot.com/2017/...rved-tube.html