> Would a guitar amp built with these sound like a tube amp?
It would be nice, right? Most folks worry about getting vacuum electronics to simply work, so I couldn't dig up anything on the nonlinearities of a vacuum transistor amplifier. (For those who don't follow such things: The nonlinearities of guitar amps are intimately related to how it sounds. Many musicians still use tube amps because the world has become accustomed to that sound. It is the gold standard of distorted amplifiers to some of us.)
That said I'm not optimistic. A quick check of a Fender Twin Reverb schematic (http://support.fender.com/schematics/guitar_amplifiers/65_Tw...) shows that that the final amp has pentodes, different than the triode that the OP's article is talking about, and those pentodes have separated heaters for the cathode. So the temperature of the electrons coming off the cathode are going to be much hotter. (Another name for the monolithic vacuum devices used to be "cold cathode", because it acted like a thermionic emitter but without a heater.)
There's a lot that's different. Of course, the only way to know for sure is to plug it in and crank it up to 11.
I'd bet computers will be emulating the sound of vacuum tubes way before any of those things get into market.
You can get the correct vacuum tube-like amplification from a computer today, it's just that tubes are still cheaper. A/D converters and first stage linear amplifiers are only getting cheaper (even at this, post Moore's law era), thus it's only a matter of time before computers retire valves on yet another application.
EDIT: Also, tunnel devices have a completely different behavior from macroscopic valves. They are very non-linear, what makes them great at digital applications, but horrible sound amplifiers.
> You can get the correct vacuum tube-like amplification from a computer today, it's just that tubes are still cheaper.
It is absolutely not the case that tube amplifiers are still sold because they're cheaper than solid state amplifiers + DSP. Their sounds is preferred and they are much, much more expensive to produce.
The valves (which don't enjoy the economies of scale they once did) are only part of the cost. The power supply of a tube amp is usually more complex than a solid state amp and they generally need output transformers because of high output impedance -- transformers that are linear through the audible band are expensive to produce.
At scale you could easily build a SOTA DSP card suitable for emulating "tube sound" for less than the cost of a single channel output transformer. Line 6, among others, have built businesses based on that fact.
Won't prevent audiophiles from being audiophiles. I remember reading a screed against double-blind testing on some magazine (would link to, but can't find it)
I had a huge problem of making an D/A converter with enough precision for instrumentation a while back, but designing some digital I/O with enough bandwidth for it was a nightmare. Then I looked at the Internet and saw an audiophile complaining that a soundcard[1] with 20dB less noise than my design was crap.
1 - A PCI express card, of course. Didn't try that bus. I'd have a really bad time manualy creating a board for it.
It would be nice, right? Most folks worry about getting vacuum electronics to simply work, so I couldn't dig up anything on the nonlinearities of a vacuum transistor amplifier. (For those who don't follow such things: The nonlinearities of guitar amps are intimately related to how it sounds. Many musicians still use tube amps because the world has become accustomed to that sound. It is the gold standard of distorted amplifiers to some of us.)
That said I'm not optimistic. A quick check of a Fender Twin Reverb schematic (http://support.fender.com/schematics/guitar_amplifiers/65_Tw...) shows that that the final amp has pentodes, different than the triode that the OP's article is talking about, and those pentodes have separated heaters for the cathode. So the temperature of the electrons coming off the cathode are going to be much hotter. (Another name for the monolithic vacuum devices used to be "cold cathode", because it acted like a thermionic emitter but without a heater.)
There's a lot that's different. Of course, the only way to know for sure is to plug it in and crank it up to 11.