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Alternatives to the vacuum tube and transistor?
Alternatives to the vacuum tube and transistor?
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Old 24th October 2021, 02:30 AM   #1
BasicHIFI1 is offline BasicHIFI1  Sri Lanka
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Default Alternatives to the vacuum tube and transistor?

As I build my class A simple amplifier, and delve into the current-controllable-variable-resistor concept which is the transistor, I keep wondering if a similar device could have been invented earlier? This is for audio amplification applications.

Has anyone come up with a variable-resistance relay that will do a similar job? Of course reliability will not be the same as a transistor, and performance may degenerate. Maybe a motor controlled by a small current moving a mechanical potentiometer?

The circuit I envisage is a simple amplifier circuit. (Single ended etc)

Alternatively, could a simple oscillator circuit using a capacitor be set up, with the input audio somehow made to vary the pulse width of the signal, this in turn used to create an amplified signal at the output sort of a class D without the transistors?

The first idea is within the realm of possibility, and I intend to try it out sometime. The second one...

There is also the magnetic amplifier but sound quality is said to be not so great, aka distortion.
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Old 24th October 2021, 03:05 AM   #2
rayma is online now rayma  United States
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Mechanical parts would wear out very rapidly.
The first digital computer used relays, but they gave up and went to tubes.

Last edited by rayma; 24th October 2021 at 03:25 AM.
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Old 24th October 2021, 03:12 AM   #3
HeyBill is offline HeyBill  United States
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Alternatives to the vacuum tube and transistor?
I suppose some sort of fluidics device might work. Probably slow. HeyBill
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Old 24th October 2021, 03:57 AM   #4
jjasniew is offline jjasniew  United States
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Alternatives to the vacuum tube and transistor?
They made very powerful speakers using an air compressor, a modulated valve exiting into a giant horn.

Maybe you could get the grooves of a record to modulate a micro-machine valve with some air pressure behind it - and get that into a horn (or a pair...) in a way similar to the 78 players of old. Have two conduits running down the tone-arm into separate horns. No electronic at all - just a little background hiss.

I once owned a portable Victrola wind-up. Replaced the mica diaphram with a plastic one having more compliance. Changed the sound! Became just a bit less squeaky.
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Old 24th October 2021, 05:26 AM   #5
NickKUK is offline NickKUK  United Kingdom
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You could use magnetics and use opposing currents to control other currents - similar to controlling arc furnaces.

Do missed the latter point.

The option then is digital but then you have the fun of modulation and filtering.

You could use light but the cost of a lab setup and the reality of usability would be an issue. An open optics bench also has safety requirements whereas a solid state “on a chip” is both immature with only a few universities being able to creat test designs..
For example you could use parametric downconcerstion to create a quantum entangled photo pair the. Sent one downs fiber optic to the read head and the other to the sensor. Then you count the photons and you know what happened in the read head.

That replicates the Chinese quantum camera/radar.. so cutting edge
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Old 24th October 2021, 06:08 AM   #6
JMFahey is offline JMFahey  Argentina
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Quote:
Has anyone come up with a variable-resistance relay that will do a similar job?
Relays are variable resistance, either infinite or almost zero, so conceptually they can be used to build a Class D amplifier.
Now given switching rate limitations, only sub-Hertz signals can be amplified.

Quote:
Maybe a motor controlled by a small current moving a mechanical potentiometer?
Also conceptually possible, again only practical for sub-frequencies.

Pneumatic/hydraulic amplifiers have been used for decades.
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Old 24th October 2021, 06:17 AM   #7
Enzo is offline Enzo  United States
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There were these:
Plasma speaker - Wikipedia

And for lots of fun google "tesla coil music"

Bohemian Rhapsody Meets Singing Tesla Coils - YouTube
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Old 24th October 2021, 06:33 AM   #8
freddi is offline freddi  United States
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Alternatives to the vacuum tube and transistor?
The Auxetophone.

Victor Auxetophone - YouTube

Category: - From an Oblique Angle
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Old 24th October 2021, 08:06 AM   #9
benb is offline benb  United States
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Quote:
Originally Posted by NickKUK View Post
You could use magnetics and use opposing currents to control other currents - similar to controlling arc furnaces.
Magnetic amplifier - Wikipedia
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Old 24th October 2021, 08:11 AM   #10
benb is offline benb  United States
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Quote:
Originally Posted by BasicHIFI1 View Post
There is also the magnetic amplifier but sound quality is said to be not so great, aka distortion.
All active devices create distortion. Various circuit topologies are used to reduce and minimize it.
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