Analysis of information sources in references of the Wikipedia article "Tube sound" in English language version.
This paper, however, points out that amplifiers are often severely overloaded by signal transients (THD 30%). Under this condition there is a major difference in the harmonic distortion components of the amplified signal, with tubes, transistors, and operational amplifiers separating into distinct groups
{{cite web}}: CS1 maint: archived copy as title (link)But, as I was about to disassemble it and put the parts away, I wondered what the circuit would sound like without any feedback. That is, just a pentode with a transformer load. I figured it was going to be awful, so I was not prepared for what I heard, which was near sonic bliss. From note one, this was something special. Turns out, I had built a transconductance amp more or less by accident.
It effectively bridges the gap between solid-state and tube sound, blending tube and transistor virtues into a musically satisfying whole.
The job of the amplifier is very simple. It must multiply the incoming signal voltage by a factor of about 20, and deliver a perfect replica of the signal to the speaker, independent of the impedance that the speaker presents to it.
Tube amplifiers sound better because of the euphonic distortions they add to the music, as well as plenty of other reasons I'll cover below.
Crossover distortion generates unpleasant high order harmonics with the potential to increase in percentage as signal level falls and is much more objectionable to the listener than distortion resulting from a smoothly curved characteristic, even if they have the same THD. Therefore it is desirable to reduce crossover distortion to a minimum amount.
The smooth transfer curves of Class A amplifiers have a characteristic which is monotonic, that is to say the distortion goes down as the output declines.
One interference which may reasonably be drawn is that any sharp kinks in the linearity curve, as usually occur in any class-AB1 or AB2 amplifier, have a far more serious subjective effect than is indicated by any of the standard methods of measuring distortion –whether total harmonic distortion, conventional weighted distortion factor or the standard form of intermodulation testing.
Crossover distortion generates unpleasant high order harmonics with the potential to increase in percentage as signal level falls and is much more objectionable to the listener than distortion resulting from a smoothly curved characteristic, even if they have the same THD. Therefore it is desirable to reduce crossover distortion to a minimum amount.
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