The Tube Computer

Brilliant! and warming. ( literally and figuratively. )

"My family was homeless when I was born. But my parents found work, the council found us a flat, and 20 years later my dad was the managing director of a very large engineering firm, and my parents built a fabulous home.

To cut a long story short, much later my parents had a few personal problems, and sadly my mum finally killed herself. I don’t think you ever get over it, you really just learn to live with it.

My life then went a bit pear shaped. I trusted bad people and guess what, really bad things happened. Very kind friends managed to put me back on my feet, and then, at 55, I met Judy and her family, and we’ve had the most wonderful 15 years together.

So please, what ever happens, please don’t give up."

From the website: The person who built this appears to be (at least) 70 years old. Amazing!

> My family was homeless when I was born. But my parents found work, the council found us a flat, and 20 years later my dad was the managing director of a very large engineering firm, and my parents built a fabulous home.

> To cut a long story short, much later my parents had a few personal problems, and sadly my mum finally killed herself. I don’t think you ever get over it, you really just learn to live with it.

> My life then went a bit pear shaped. I trusted bad people and guess what, really bad things happened. Very kind friends managed to put me back on my feet, and then, at 55, I met Judy and her family, and we’ve had the most wonderful 15 years together.

> So please, what ever happens, please don’t give up.

For a long time I've been thinking about building one based on relays. The problem is that I would need a lot of relays just to achieve anything very simple. My solution: think about the simplest computer architecture I could come up with, and the simplest one was a NAND computer. In this architecture, the program is a simple loop with instructions all in the same format: input addess 1, input address 2, output address. The only supported instruction simply writes at the output address the result of a NAND operation of the input addresses.

Since any circuit can be built using only NAND's, this computer can simulate any circuit, including the circuit of a Turing complete CPU. It certainly would be very slow, but relatively simple to build. I still have to think about a good type of memory for this machine. Maybe one day I'll take the courage to build it.

Bit of an aside but I wonder how far tube technology might have advanced, without semiconductors intervening. In the late 1950s and early 1960s, GE, IBM, and RCA, probably other companies, were working on "integrated tubes" with many components in a single envelope, as well as techniques for easier and more automated manufacture. For example, introduced in 1959: https://upload.wikimedia.org/wikipedia/commons/b/ba/Nuvistor...

> Vacuum Tubes require high voltages to work efficiently and are not for the faint hearted.

People used to build vacuum tube circuits on breadboards at home back in the 1950s. They seem pretty frightening by today’s standards, but they’re a lot like big, hot, high-voltage, low-current transistors. The low-power tubes used for signals are not that hot, just kind of warm.

I’m not really criticizing here, I just want people to think of vacuum tubes as accessible to people with any kind of electronics background, and just more inconvenient than transistors.

Wonderful project. I learned vacuum and solid-state electronics in parallel so I'm familiar with tube electronics. My fascination with valves go back to my early childhood when I used to move our console-type radio from the wall and touch the grid-1 spigot connection which would make a loud humming sound much to the horror and chagrin of my parents.

One of the problems I've witnessed with training in electronics these days is how little time is devoted to vacuum tube electronics. Perhaps that's a necessity given constraints of course time etc. but without an understanding of how vacuum tubes work an important part of one's understanding of the subject is missing.

Vacuum tube technology is still a vitally important part of both electronics and of physics experimentation. For instance, magnetrons (microwave ovens, radar, etc.), klystrons, TWTs (travelling wave tubes), high power transmitting tubes (TV, FM) all rely on vacuum tech. So too do PMTs (photomultipliers) and imaging devices such as vidicons and orthicons. In physics, understanding thermionic emission is essential to understanding thermodynamics, so too cold cathode emission and related tech such as vacuum deposition, etc. Even electron microscopes and similar instrumentation relies on vacuum technologies.

Unfortunately, now since the widespread adoption of semiconductor electronics much of that vacuum tech tends to be rather specialized so those who've an interest in learning the subject don't get any hands-on experience at an early age.

What's great about this project is that it brings vacuum technology to the fore where it can be not only seen but also demonstrated.

Learning the transfer characteristics of thermionic diodes and triodes is an excellent way to gain such experience. And to begin one doesn't have to go to such lengths as this amazing project, starting with a single tube superregenerative FM receiver is a good place to start.

Tommy Flowers (https://en.wikipedia.org/wiki/Tommy_Flowers) knew a thing or two about valves (and how reliable they were if not switched off!). We have him (amongst many others) to thank for the success of Bletchley Park.

Fuses help with the "bang", as do using 5U4 or other vacuum tube diodes in the power supply, which limit current. I've learned not to be absolutely frightened of B+ at 200-300 volts, though I definitely respect it. Once you get above 500 volts, and an amp... the danger is very real, and the fear returns, in spades.

"The basic, domestic quality thermionic tubes have codes for a projected life span of either 1500 (6Н3П-Е) or only 500 hours (6Н3П). Many were used and then stored for over 50 years, quality stamps may have been accidentally altered, so life expectancy may be questionable, both for the tubes and for me!"

I love the idea of an expiration date, or at least an ever-present need for repair. It emphasizes the idea that the computer is a machine, subject to the constraints of the physical world. There's something charming about that.

And future proof! Made me question my sanity for a moment.

"© 2025 TheTubeComputer.com"

It's possible to build a switch so that these 62NP tubes are interchangeable with 12AX7 (or ECC83).

Instructions in this thread:

https://www.diyaudio.com/community/threads/6n2p-ev-vs-12ax7....

Pins 9 and 5 of the tube socket must be galvanically disconnected from the PCB. The switch is then interposed there.

I build Vacuum tube audio amplifiers, mostly Push-Pull class A's with EL84s. This is next level. Absolutely awesome!!

> They can switch several hundred million times a second, and in the 1950s they were combined with germanium diodes as the basis for many incredible computer designs.

Whoa, I didn't know they could switch that fast! Because afaik vacuum tube computers were measured in thousands of mathematical operations per second

>using 18 bit instructions, it could be rented for $12,000 a month.

Release of the IBM700 utilized 6N3P diodes, that tend to burn out due to voltage alterations, until the 7000 series, with System 360 was transistorised.

> The IBM700 series was the most successful 1950s computer system. ... Able to handle 36 bit words using 18 bit instructions, it could be rented for $12,000 a month.

That's cheaper than an AWS p4d.24xlarge.

“So please, what ever happens, please don’t give up.”

Love that - thank you!

How long before an audio manufacturer will implement some kind of DSP on this thing and marketing it as having "tube warmth"?

So, if this became sufficiently popular to a degree in which many more units like these were produced and released, and it was decided that they all should be connected somehow, in a sort of inter-network...

...it would finally be a series of tubes.

>They can switch several hundred million times a second

Huh. Wasn't expecting that.

> © 2025

Plus, we get free time travel to boot! Great project, I love it.