Early history of High Fidelity amplifiers

[Nikolas Ojala]

First two historical facts:

1. On 1927 H. A. Hartley coined the phrase "High Fidelity" which meaned "... a type of sound reproduction that might be taken rather seriously by a music lover".
2. On 1937 Harold Stephen Black invented how negative feedback could be used in amplifiers without making them oscillators.

That means there was a ten year period of early Hi-Fi amplifiers while use of negative feedback was absolutely out of question. How was audio amplifier development within that 1927–1937 period? I am sure that patents, books and scientific articles about improved amplifiers were published during (and before) that ten years period.

[20to20]

Originally Posted by Nikolas Ojala

First two historical facts:

1. On 1927 H. A. Hartley coined the phrase "High Fidelity" which meaned "... a type of sound reproduction that might be taken rather seriously by a music lover".
2. On 1937 Harold Stephen Black invented how negative feedback could be used in amplifiers without making them oscillators.

That means there was a ten year period of early Hi-Fi amplifiers while use of negative feedback was absolutely out of question. How was audio amplifier development within that 1927–1937 period? I am sure that patents, books and scientific articles about improved amplifiers were published during (and before) that ten years period.

Since the first electronic phonographs used radio amps you could research the development of 1930's radio circuit output stages to find what you are looking for.

[ChrisA]

Originally Posted by Nikolas Ojala

..[/LIST]That means there was a ten year period of early Hi-Fi amplifiers while use of negative feedback was absolutely out of question.

You likely can't imagine how poor the sources were in the 20's. There were no tape recorders, no LPs not even decent phono cartridges or even good microphones.
HiFi back then was live AM radio, not what we'd call HiFi but compared to what was before it must have sounded great.

[kevinkr]

Also take a look at what Western Electric and RCA were doing with theater sound technology in the early 1930's - this was where a lot real innovation was occurring, and arguably marked the appearance of the first speakers, amplifiers and a source even vaguely capable of performance close to what we would consider high fidelity.

Comment: The use of (global) negative feedback is not universally considered a requirement for high fidelity. Look at both tube and solid state (FET) SE amps for examples.

[Globulator]

Originally Posted by Nikolas Ojala

How was audio amplifier development within that 1927–1937 period?

Here is some of the missing period I think - majoring on the purity on the Western Electric line driver stages.

[piano3]

Originally Posted by ChrisA

You likely can't imagine how poor the sources were in the 20's. There were no tape recorders, no LPs not even decent phono cartridges or even good microphones.
HiFi back then was live AM radio, not what we'd call HiFi but compared to what was before it must have sounded great.

The voice was often captured acoustically with great realism from the earliest days .The first commercial electrical recordings from 1925 had teething problems,mainly,I think, due to resonances in the early Western Electric microphones. However by the late 1920's/early 30's consistantly excellent results were being obtained in instrumental music which would,I imagine, shock many listeners today if they were to hear them properly reproduced-and I do not mean filtered beyond recognition to eliminate surface noise. AM radio can also be a very high quality source. Surely the reason for the great linearity of some of the early triodes was because they had to rely on this quality without feedback to help out. The fact that most people still listened on wind up gramophones with steel needles or cheap radios was an economic matter not because high quality reproduction was impossible.

[Merlinb]

Originally Posted by Nikolas Ojala

First two historical facts:[*]On 1927 Harold Stephen Black invented how negative feedback could be used in amplifiers without making them oscillators.

I think you mean 1927. 1937 is a bit late! (After all, Nyquist published his stability criterion in 1934!)

[leadbelly]

Originally Posted by Merlinb

I think you mean 1927. 1937 is a bit late! (After all, Nyquist published his stability criterion in 1934!)

Wikipedia says 1927 Harold Stephen Black - Wikipedia, the free encyclopedia

[barrymagrec]

The early history of Hi Fi involves many aspects other than just amplifier design, look up Alan Blumlein and Paul Voigt, just for a couple of really significant names.

Barry

[Nikolas Ojala]

Originally Posted by Merlinb

I think you mean 1927. 1937 is a bit late! (After all, Nyquist published his stability criterion in 1934!)

Is this the patent? Wave translation system