Solid-State TUBES !!

[GlennSprigg]

A lot of places are now developing Solid State 'Tubes', although with no need for a vacuum inside.
We are not talking about modified circuitry to change over to semiconductor equivalent circuits, but a solid state construction that is inside of a glass envelope, (for looks), and with the standard 'Tube' BASE, that just plugs right in to replace the original tube!!  Of course there will be the arguments about purity/quality of sound, (for true valves), but these just plug right in to the original socket, as a replacement!
"Bones of contention" expected... Need a light globe inside, to look like a Filament!!   

[frozenfrogz]

A lot of places are now developing Solid State 'Tubes', although with no need for a vacuum inside.

Please define "a lot of places" and "now".

A several years ago some of those solid state 12AX7 / ECC83 retrofits have been on the market, AMT being one of the more prominent manufacturers.
https://amt-sales.com/other/tubes/amt-12ax7-warm-stone-tube/

However, in the past couple of years (3-5?) I was not able to track down anything on the market.
I would have been interested in buying a couple of these to knock down the current consumption of the +15VDC rails in several Ampeg SVT 7 pro amplifiers (pretty buggy designed). These are solid state Class D amplifiers with a single 12AX7 in the preamp stage. Getting rid of the heater current by replacing the valve with one of those solid state retrofits would have saved me a lot of trouble.

[Gyro]

Look up 'Fetrons', they were manufactured over 50 years ago! 

[Cyberdragon]

I hate these things, t throw em away if I see em in anything.

Get your damn trannies outta my shit.

[TimFox]

I remember when the Fetrons first came out.  One was a cascode device to replace 6AK5/5654 pentodes, which were extremely common in military RF devices.

[wraper]

Solid state replacement for tubes is ridiculous. You get the worst of two worlds. Not to say operation voltages are very sub-optimal for semiconductor amplifiers. You'd be far better with conventional semiconductor amplifier and fake tubes with fake LED filament for aesthetics.

[T3sl4co1l]

What's suboptimal about it?  Transistors amplify hundreds of volts just fine.

The main difficulty is, commercial devices aren't usually dimensioned to cater to such applications.  There aren't many 600V 100mA 10pF 20W MOSFETs, for example.

You are quite correct, it is easier to re-engineer the application, than design and order custom transistors with such ratings, when a suitable match is unavailable.

Tim

[wraper]

There aren't many 600V 100mA 10pF 20W MOSFETs, for example.

Another issue is how are you going to dissipate that power in tube package. Semiconductor operation temperature is much lower compared to tubes.

[6h8c]

Personally, I am against such substitutes. It's like choosing a cheap wine instead of Château Margaux from 1787

[james_s]

Some tubes such as power rectifiers are easily replaced with solid state, others are much harder. I recall there having been several attempts at making solid state tube replacements but only a few types had any real success. While they perform similar functions, the characteristics of tubes and transistors are just too different in many ways to make a direct substitution work.

I think it's largely kind of pointless anyway though. I mean if you want solid state gear just buy solid state gear, it's cheaper anyway.

[bob91343]

I have one of those fetrons meant to replace a 12AX7 if I remember correctly.  It is all metal outside and smaller than a tube, with no intent to fool anyone.  I suppose it works, never tried it.

[John B]

What's the market for them? Due to the packaging of them, it looks like it's supposed to have aesthetic appeal along with function, so is it aimed at the audio market? If so, that market would be the most likely to keep valves for the reason that they are valves, myself included.

If it was a retrofit to get an old piece of test equipment working, it could be done with a PCB with pins out the bottom or right angle to plug into the existing socket.

[Red Squirrel]

This could be a new trend in audiofoolery.  "Built with solid state vacuum enclosed audio grade transistors".  Essentially a transistor inside a vacuum tube with an actual vacuum.  The vacuum could somehow be said to affect the performance of the transistor by providing it a consistent atmospheric environment, or some wizbang theory like that. 

[Cyberdragon]

Some tubes such as power rectifiers are easily replaced with solid state, others are much harder. I recall there having been several attempts at making solid state tube replacements but only a few types had any real success. While they perform similar functions, the characteristics of tubes and transistors are just too different in many ways to make a direct substitution work.

I think it's largely kind of pointless anyway though. I mean if you want solid state gear just buy solid state gear, it's cheaper anyway.

The original FETrons weren't meant to fool anyone. But these fake tubes with the terribly painted on "getter" just are just for hipster audiophile wannabes (or potentially audiophools as mentioned). These also seem a lot more dangerous. With tubes if something goes wrong it gets hot and eventually burns out, with this crap is seems like one problem and BANG! , total carnage, goodbye to itself and any transformers if the FETS short due to improper bias or internal failure.

[GlennSprigg]

Personally, I am against such substitutes. It's like choosing a cheap wine instead of Château Margaux from 1787

'Wine' like most things in life is very SUBJECTIVE...   
I personally am NOT a fan of 'vintage' French/Italian wines. And I'm not talking about the taste of Toe-Nail clippings and uncontrolled Toe-Jam Fungai in their home-stomped 'vinegar'/bowel-clensers!!   
I know such 'tubes' are not for everyone, especially for serious 'restorers', but when someone wants to just 'plug-in' a replacement without historical genuine parts to make something work, then the alternatives are there.
MY 'reds' are full-bodied, dark, black-currant flavored, with no sharpness...  You can drink your own poison 

[peter-h]

I used to design with valves. EF80, ECC83, EL84, KT66, KT88, even the big 807 for pirate radio transmitters

A valve is basically a depletion mode N channel mosfet. Like the mosfets we have today but if Vgs=0 it is fully conducting, so the gate needs to go negative to get into the controllable region.

Hence valve circuits, to avoid a negative rail, have a resistor in series with the cathode, which lifts the cathode up by some 10-20V, so if the grid is near ground you have in effect a negative Vgs.

The only advantage of valves is that they were electrically very robust, and short of mechanical destruction they would be very hard to damage. This was good for rudimentary EMP protection

Valve amps are crap. It is purely a fashion thing. Many years ago, QUAD did a blind test of their 1950s valve amp and the then state of the art 405 amp. The audience was a load of hifi press VIPs. Nobody could tell the difference, statistically, between the two amps. The THD was a few % versus 0.01% or so...

[T3sl4co1l]

The audience was a load of hifi press VIPs. Nobody could tell the difference, statistically, between the two amps. The THD was a few % versus 0.01% or so...

And double-blind tests have been banned in hi-fi circles ever since.*   That tells you, basically all you need to know.

*I mean, I don't know that this story is true and the origin of that aversion, but it's the general idea in any case.

Tim

[engrguy42]

Anyone notice how discussions of analog stuff like scopes and tubes invariably end up with justifications like "it's like a fine wine" or "it's like driving a Bentley or a Mercedes" or  dissing those who buy "cheap plastic toys from China"?

Please, tell me there's more to it than that 

Look, if you like it just cuz you like it then admit it. No need to search for irrelevant and meaningless justifications to make it look more honorable.   

Reminds me of the PC techies who pee in their pants when a "faster" GPU with more fans and shiny lights comes out. Even if it's only 10% faster, with software that hasn't been developed yet. "Ooooo, more POWER !!!"   

[Tomorokoshi]

I don't need solid-state tube replacements. I tracked down the problem 2D21 just fine. What I really need is a schematic for the thing. Otherwise obscuriorata is difficult to fix.

[frozenfrogz]

Valve amps are crap. It is purely a fashion thing.

I do not fully agree.

For hifi stuff, I do not see much benefit in tube technology either and there is a sh*tload of voodoo devices with tubes in it, that do not actually give any benefits aside from looks and marketing blerb. However, I really like playing tube amplifiers on electric bass and electric guitar.
Yes, there are some digital modeling amps that can pretty much reproduce what the original tube amplifier sounds and feels like. However, these are expensive AF and just do not "click" with me. It is a bit like using the screwdriver on a multi-tool. It gets the job done, but a dedicated screwdriver with a nice wooden handle makes the job more fun.
There is nothing more satisfying than playing through my Mesa Bass 400+ or Peavey 3120.

[peter-h]

This is old stuff but valve circuits generate lots of even harmonic distortion which sounds less harsh than the mostly odd harmonic distortion from badly designed transistor stuff.

But anything that valves do one can do with transistors, fets, software, etc

[Cyberdragon]

But anything that valves do one can do with transistors, fets, software, etc

Except survive an EMP.

[retrolefty]

I don't need solid-state tube replacements. I tracked down the problem 2D21 just fine. What I really need is a schematic for the thing. Otherwise obscuriorata is difficult to fix.

 Boy the 2D21 brings back memories in the Air Force 66'-70'. They had a handful of them in the off-line KL-7
off-line cipher machine that were used to step the rotors.  https://en.wikipedia.org/wiki/KL-7

[Tomorokoshi]

I don't need solid-state tube replacements. I tracked down the problem 2D21 just fine. What I really need is a schematic for the thing. Otherwise obscuriorata is difficult to fix.

 Boy the 2D21 brings back memories in the Air Force 66'-70'. They had a handful of them in the off-line KL-7
off-line cipher machine that were used to step the rotors.  https://en.wikipedia.org/wiki/KL-7

The failed 2D21 was in the reset circuit of a counter I'm working on. The plate shorted to the heater, so it took down the +100V supply every time it triggered. It glows a nice purple from the xenon fill when that happens. I borrowed one from the HP 405CR, where it runs the autoranging stepper, so now I need to get a couple replacements. And to think I replaced a Nixie in it only a week ago, and now I'm borrowing parts out of it already.

[james_s]

Anyone notice how discussions of analog stuff like scopes and tubes invariably end up with justifications like "it's like a fine wine" or "it's like driving a Bentley or a Mercedes" or  dissing those who buy "cheap plastic toys from China"?

Please, tell me there's more to it than that 

Look, if you like it just cuz you like it then admit it. No need to search for irrelevant and meaningless justifications to make it look more honorable.   

Reminds me of the PC techies who pee in their pants when a "faster" GPU with more fans and shiny lights comes out. Even if it's only 10% faster, with software that hasn't been developed yet. "Ooooo, more POWER !!!"

This just sounds to me like someone who either can't afford nice things or who has never bothered to try complaining about others who do see value in it.

Have you ever driven a high end luxury car? Have you ever had good wine or an expensive steak? Have you ever used top quality tools? It has nothing to do with honor, some of us just enjoy nice stuff and I don't see what the issue is with that. Is there nothing in this world that you are enthusiastic enough about to dig into the finer nuances? Have you really never been tempted to spend more to get that extra 5%? Do you see no value in quality, fit & finish and attention to detail? Do you not appreciate the engineering and craftsmanship that goes into it? Or are you one of the masses of people who always shop purely by price and buy the cheapest stuff you can find in all categories while pretending it's as good as anything else around?

I don't mindlessly "diss" people who buy cheap toys from China. I mean I also buy cheap toys from China, a lot of cheap crap is completely usable within its limitations. I do look down upon those who mindlessly sneer at anyone who can see the value in better quality equipment though.