Conventional wisdom has it that the solid state era in electronics began in 1948 with the invention of the transistor, or if you wish to split hairs, with the 1930s invention by the Russian [Oleg Losev] of an early form of tunnel diode. But there’s an earlier amplifier technology that used a solid state circuit which is largely forgotten, and [AWA Communication Technologies Museum] has featured it in a new video. We’re talking of course about the carbon microphone amplifier, a piece of telephone technology which made its way into consumer electronics.
The carbon microphone is a container of loosely packed carbon granules acted upon by a diaphragm. Vibrations from sound compress and decompress the granules, changing the electrical resistance of the carbon. It was the standard microphone used in telephone handsets for most of the twentieth century. Being a resistor it can be placed in a potential divider circuit that produces some significant voltage swings, so when the vibrations come from a high-impedance earpiece it can make an amplifier. It’s not a very good amplifier, it has lousy bandwidth, distortion, and noise characteristics, but it was just about good enough to be paired with a 1920s crystal set. In the video below the break we see a variety of the devices, and even hear them in action sounding very tinny indeed. At the time it must have seemed miraculous to be at the forefront of the new technology though, and we can’t help admiring some of the construction intricacies.
Carbon microphone amplifiers may be rare today, but for all that we’ve touched on them before.
Is this really solid state? Like it relies on mechanical compression of particulate to work.
Isn’t a vacuum tube just about as solid state?
I’m speaking under correction, but I think that the article could mean “active component” in contrast to a passive one.
And because it’s not involving a thermionic valve, so the logic goes, it must be solid-state. It’s not a semi-conductor, though.
If it’s a solid-state part or not also depends on how we define “electro mechanical device”, maybe. An classic relay is electro-mechanical.
Is the carbon mic amp electro-mechanical? If it is, then it’s not solid-state?
(To my knowledge, in my country we use electron tube/semi-conductor distinction rather than electron tube vs solid-state. I’m not used to solid-state term.)
Except that a variable resistor (which is what that was) is still a passive device. There is absolutely nothing about it that is “solid state”. And as you say, of course, the term “solid state” is a very poor one anyway.
An electret microphone varies capacitance as it is affected by incident sound waves, and that is every bit as “solid state” (i.e., none) as a carbon microphone.
heh i agree and just wanted to pedantically point out that it is most definitely a semiconductor in that its interesting properties come from its variable / reactive behavior between conducting and insulating.
which just goes to show how hard it is to talk about these things in a world where ‘semiconductor’ has come to mean ‘silicon’ and ‘solid state’ has come to mean ‘not a tube’. :)
Crunchy state?
A semiconductor is solid state device, but not all solid state devices are semiconductors.
Solid state is just a very old confusing marketing term that was intended to indicates to potential buyers that a device doesn’t include “old technology” vacuum tubes. That it is made from non-hollow components, hence the term solid. You could argue that components with moving parts are not solid state, but how microscopic is the movement allowed to be in order to pass or fail that definition? But keep in mind that “solid state” is just a marketing term and not a scientific definition.
Regarding the article/video, I was pleasantly surprised to hear about this technology. I was expecting an early implementation of magnetic amplifiers which is also a very cool concept and more serious and practical than you’d might expect.
“Solid state is just a very old confusing marketing term that was intended to indicates to potential buyers that a device doesn’t include ‘old technology’ vacuum tubes.”
By that logic, a magnetic amplifier is also solid-state. But if you said that to anyone in the electronics field, I’m sure they would be quick to correct you – throughout the industry, solid-state is synonymous with “employs semiconductor devices”.
Cool though the Brown Microphone Amplifier is, it’s no more “solid state” than a magnetic amplifier is. In fact, I can make a better case for the mag-amp being solid-state. At least it doesn’t require a moving mechanical element to perform its task.
If the amplification process requires mechanical motion, then it’s not solid-state, regardless of how “solid” the parts might be.
we are facing two problems here:
– marketing terms do not follow real logic
– the meaning of words in all languages are fluid
I fully agree that “throughout the industry”, solid-state is synonymous with “employs semiconductor devices”. However Hackaday isn’t the industry and the title and term are used more as a joke than it is to be taken seriously, but given the original concept and origin of the term you have to give the author some slack here in referring to the term “solid state” as in some way there is a point to it or at least food for thought (hence our comments).
But since language is fluid, we tend to forget the origin of words and sometimes add more weight to it’s meaning. After all, in the beginning it was just marketing term intended to indicate that a more “solid” technology (transistors) was used in a device instead of old technology “hollow” radio tubes. A TV in the 70’s marketed as completely “solid state” therefore is a lie, after all there is a huge tube in it, namely the CRT, but since there was no alternative for a CRT nobody cared and they all knew what was meant.
I do not consider the magamp to be solid state either, but before fully reading the article / viewing the video, it was the only thing I could imagine it could be. Therefore I was nicely surprised it to be something completely different and I found it interesting that it was actually used in some serious applications.
I’m happy to ‘agree to disagree’ if you are as well. And
I do love a spirited discussion, so thanks for your thoughtful and well-worded rebuttal!
I remember listening to radio ads about stereos, describing the “quantum leap” in the “State of the Art”.
So, people didn’t know that a quantum leap is the smallest change between an electron’s orbit that has any effect.
(I mean it’s really tiny! But it sounds impressive!)
B^)
Fluid language. That reminds me of the term “CPU”.
Nowadays, we associate it with the main microprocessor on a motherboard.
Back in the 80s/90s, though, certain people (not me) called a PC tower a “CPU”.
That’s because in the 1960s, the CPU was still a dedicated unit in a metal chassis containing the ALU.
That’s why certain people kept calling the PC tower a “CPU”, as well.
They applied the old terminology here, because in their eyes the PC tower was the central unit which all peripherals such as monitor, modem, external drives (CD, ZIP, streamer etc), keyboard and printer do connect to.
“Solid state is just a very old confusing marketing term that was intended to indicates to potential buyers that a device doesn’t include ‘old technology’ vacuum tubes.”
By that logic, a magnetic amplifier is also solid-state. But if you said that to anyone in the electronics field, I’m sure they would be quick to correct you – throughout the industry, solid-state is synonymous with “employs semiconductor devices”.
Cool though the Brown Microphone Amplifier is, it’s no more “solid state” than a magnetic amplifier is. In fact, I can make a better case for the mag-amp being solid-state. At least it doesn’t require a moving mechanical element to perform its task.
If the amplification process requires mechanical motion, then it’s not solid-state, regardless of how “solid” the parts might be.
Apologies for the second post – I didn’t knowingly make it. Lately I’ve found that this happens to me here. I had thought that it occurred only when I refreshed the page to ensure that a post had actually appeared, so lately I’ve been religiously avoiding doing so. But early this morning it happened anyway. Are others experiencing this, or is it perhaps a quirk of my browser setup?
I’ve seen it happen a couple of times with other commenters. Not entirely sure what causes it, I was under the same presumption that it was caused by page refreshes.
Talk about it’s use in the first long line voice operation. How much gain? Then there is the Amplidyne and other weird tech, hint for another story. Tubes couldn’t handle heavy currents. How do you run motors to aim a naval gun turret? Perfectly. In some of these amplifiers a rotating shaft is involved.
I found a antique impedance bridge with 3 decades of selectors, a slab of bakelite with stud and surface wiper controls precision resistors and no back or sides just busbars. Headphone output. There was some broken thing spilling carbon granules and a electro magnet at a vibrating reed of steel. I figured out it was an oscillator to provide the AC drive signal to the bridge. The “mic” modulated the current through the coil which vibrated the reed that the “mic” was attached to the end of the reed. It probably ran on one cell for power. Nifty for the time, 1910’s era.
While not semiconductor based, magnetic amplifiers, which date back to the 1880’s, are unarguably “solid” state. I encountered them in 1960’s in regulated power supplies. They were used in the early 1900’s in the transatlantic telephone cable systems.
Would love to learn more about these
Publication of O. V. Lossev’s work predates the 1930s by at least five or six years. The first US publication of his work that I’m aware was: “The Crystodyne Principle,” Radio News, Sept 1924, pp. 294-295, 431. (available here: https://www.worldradiohistory.com/Archive-Radio-News/20s/Radio-News-1924-09-R.pdf). There may have been some earlier European publications.
While everyone is debating over whether this is solid-state or not. I am questioning whether or not it is an amplifier. It seems that all it does is convert movement to resistance. How is that amplification?
It can provide voltage gain when used in conjunction with a whetstone bridge. I would say it is more like a component of an amp, but interesting none the less. I would like to see more work on the magnetic amp, perhaps one powered by an linear HF power source. The magnetic amps I have see had very poor noise and distortion characteristics because they used 60hz power and relied on canceling the 60hz in the output. One built using a RF power source might be capable of impressive bandwidth and noise performance. It is the sort of think I would do if I had the space to work on a project.
There is another early solid state amplifier technology, the magnetic amp. Magnetic amps can be powerful enough to drive a speaker and two stages can be enough to produce a usable voice or instrument amplifier.