Wikipedia article: Tube sound
The English Wikipedia article http://en.wikipedia.org/wiki/Tube_sound is in a sorry state.
Recently some writer said:
"This article needs either a massive and strictly methodological re-write, with solid citations -- or simply to be discarded. Folks need to understand that an effort like Wikipedia is not the sort of place where one can just pontificate off the top of one's head without citation."
I quite much agree with that writer. I also thought that obviously the article needs more and new contributors. So I thought that usually here some experts and semi-experts meet and discuss about tube amps, sometimes referring to interesting literature sources.
I'm not saying what anyone should or should not do, but there is an article that needs few helping hands.
I guess that is enough. :smash:
Yes, I agree too: that article is the usual series of common beliefs......
Also those few claims that would seem correct at a first glance are wrong!
The term High Fidelity was already in use before the feedback era.... for example if you look at the original schematics of the RCA-Victor D22 amplifier, presented in 1935 , you will read : " Two 30cm Hi-Fi Dynamic Speaker"
I have the schematics on paper and is available somewhere on-line (not for free, however).
It has an input transformer loaded 6C5 tube. The transformer is SE to PP and drives the output stage which is made of 4x2A3's (parallel PP) for 22W output and very low distortion!
Zero feedback obiviously......
Or does anyone remember about the great Harry Olson 5W Class A amp at RCA studios??
You seem to have the required source that could be included in the reference list.
A quote from the book: Audio Design Handbook (H. A. Hartley), page 200
"I Invented the phrase "high fidelity" in 1927..."
You can download the book from http://pmillett.com/
Re: Would you?
it would take time to do things carefully. In any case if you go on the Lynn Olson site there are already plenty of historical info. You can link that site if you like and Lynn gives his approval.
Anyway, the main point about amplifiers is: they have always been, and still are, the strong link in the audio chain.
Hi-Fi in the 1930's was practically the same concept as today only with different results. It is true that the quality of magnetic materials for transformers was not good as today but this was not a problem at all.
Until the birth of the stereo LP (with high quality MC cartridges) the limits came all from the sources.
In fact, if you build today this amp,
you will be amazed by the sound and the measurements, even if using the original trasformers that were multi-purpose types and cheap!
Except for some high quality small signal JFET's and BJT transistors, the linearity of solid state devices (especially high power devices) is more pentode-like when used at the same time for voltage & current amplification (i.e. output at the drain or collector).
The best of these power devices only can have excellent linearity if used solely as current amps (emitter or source followers).
So, as you need substantial voltage amplification too, you need to go for more complex circuit structures if you need more than few volts output swing (such as cascodes or totem poles).
However, everything has a price and a good perfoming circuit can sound bad!
Having 0.001% distortion is not assurance of quality at all.
Otherwise we all would buy cheap op-amp based amplifiers because they sound better than an Audio Tekne with 300B's, only because of lower THD.
In fact there is, for example, a threshold for distortion perception.
For a triode-like (i.e. increasingly lower levels of higher harmonics) pure harmonic distortion this threshold is approx 0.2% around 75 dB SPL and for the most sensitive subjects.
At higher or lower SPL's the threshold increases quickly.
At 90 dB SPL, for example it is 2-3%......
A different harmonic content has a different threshold. The triode-like has the highest threshold.
It is not the same thing getting:
1) Low triode-like THD distortion just using the natural high linearity of a device.
2) The same as above but using tricks (like feedback, harmonic cancellation or other active circuit linearization). This almost certainly has a price to pay.
Also: test signals (like sinusoidal, square and triangular waves) or any other instrument in general, will never tell about the sound.
First because there is no instrument in my knowledge working like your hearing and then because music is basically an impulsive signal and not a standing wave.
The above periodic signals, however, remain useful for preliminary tests when looking if everything is working right.
What could be done quickly
Some things that could be done rather easily:
If you found a questionable claim, especially one you believe to be a false statement, then add a tag or delete the claim instantly.
Some of those claims are already tagged and they are only waiting for strict actions.
Some improvements detected
I detected some improvements have been done after january.
I hope that if someone contributes to the article that they include the effects of the magnetics in the signal path, not only in small signal but in overdriven sound as well (ie musical electrical instruments as a source). AFAIK There are documents on this from John Murphy.
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