If you buy an amplifier, then typically these parameters are shared:
Frequency range, signal to noise, harmonic distortion, power rating, impedance, damping factor. (quick and dirty explanation what are these below.)
You compare all the above data and realize that a transistor amp is superior then a tube amp. In all aspects, in all cases.
You may start to feel bad, that you better liked that less high fidelity sound of a tube amp. While you may wonder how the transistor people, hear any difference between their already perfect (at least on technical specs) amplifiers. Actually the issue is not with you. The whole approach with these parameters is simply WRONG and misleading.
Let’s begin with the most cited data, the distortion: tubes are at 0.1%-1%-2%, while the transistor amp is 0.0001% or less… Hope in the bottom explanation I am expressing well that the measurement is really with a single frequency, so these values are not telling, what we as human beings mean really under distortion. So we have practically no idea how the amplifier really sounds with the various frequencies of music. And by the way, as nobody measured the distortion, the manufacturer started to simply lie, so the transistors at THD are better, but not that much.
Real amplification has to fight with upper harmonics, 2nd, 3rd, 5th… grade of a single source frequency. Real music has various frequencies at the same time, so called intermodulation occouring all the time also. Of course intermodulation can be also measured, but that person should hold the hand who saw such data recently within the technical specification of any amplifier. But even if that is measured, tells just the amplitude of unwanted frequencies, created by the amplifier, when supplied 2 frequencies (f1 and f2) and measure : f1+f2, f1-f2, f1+2xf2, 2xf1+f2, and and and. And even if you measure it, who can tell which combination of this distortion sounds less painful…
I am not claiming that things are not measurable, but there is no standard complex measurement that would really tell if an amplifier is sounding better or worst while reproducing music. The existing basic measurements in which results are shared as technical specifications can tell if an amplifier does sound really-really bad. But that’s the outmost what you can see from these data’s. So if you accept this, then tubes or transistors race is not decided based on the poor measurement possibilities.
But why do I say tubes are superior?
Transistor amps work with high current, so power supply is rarely flat. If I disable my Philips AG9015 it does continue to work for 10seconds. The typical transistorized amp has not a second time of reserve before it’s depleting the capacitor reservoir… Just measure out the triangle waves at the power capacitors with 100Hz and start to wonder about harmonics, intermodulation and similar what these are causing.
If you would put transistors in the circuits of tubes (after matching voltages, work point of course), then the measurable harmonic distortion would be 2-15%. Yes, transistors are absolutely far from the linearity of a tube.
The trick of the transistor amplifiers is in their circuit: Uses a massive amount of negative feedback, which resolves the huge distortion, increases frequency range, reduces impedance (better damping factor). So the distorted signal produces a negative correction at the input, so that the outcome looks fabulous. This works awesome. On a single frequency! But due to timing difference between low and high frequencies, this is not working as expected. Works well in the total harmonic distortion measurements, but the benefit with real music isn’t that advanced as measured.
Of course, there are areas where transistor amps are better: You can avoid capacitors in the signal path. Negative feedback is more hard to implement in the tube world due to bigger latencies (would help the same way as in the transistor world), mainly due to the latency of the output transformer which time constraints simply does not allow such. Oh, before I forget… The output transformer, that is again not helping in the sound… But a must have as tubes have to high outgoing impedance.
So as a conclusion, do not believe technical specifications. Do not think this is some kind of magic or mystery, is just the fact that real world is very complex to be measured. Even if measured, hard to interpret data and tell a very subjective info, if this sound better or that…. Due to the lack of easy to understand measurement methods, you have to trust your ears.
My verdict is that tube amps if well built better then any transistorized. Of course not all tube amp is better then a transistorized! Live with it and do not get fooled that you started to like a “distorted” tube sound. Most probably it is closer to high fidelity and that is why you like it, so no shame and nothing wrong with you.
A quick and dirty explanation of some parameters:
Frequency range: example 20-30kHz -3dB – wider the better? These are the frequencies, where the amplifier is fed with an sinus signal and starts to deliver just half (-3dB) of the output compared to the amplitude of 1kHz (0dB). So beyond and below these frequencies, the amplifier gets less an amplifier… In reality, this tells not how flat the amplitude response looks over the frequancy range. It could be better represented with a graph, but rarely done. Maybe +-1dB or something specified… But have to highlight: Results are valid with a single sinus input, so this is again not real life music.
Signal to noise: Again a nice data, where the more is better. Heavy to hear noise above 80-90dB, but depending on thy type and the circuit, such noise can be felt as it interacts (intermodulates) with the listened music
Harmonic Distortion: You drive with a very exact 1kHz (so has no measurable distortion, noise or anything) an amplifier. You measure at the output with a filter (limited bandpass, allows 1kHz to pass) the power of this 1kHz and then measure with a filter (limited band stop, allows everything outside 1kHz) the energy of all the rest signals. Then you express the ratio of this and tell the total harmonic distortion + Noise. While the load is a resistor, which far from real-life impedance of a loudspeaker. And also you do this on a given power. Tube amps without negative feedback have more and more distortion as you power up, while the transistors with the negative feedback maintain a low distortion and start to just heavily distort after a certain level.
Power rating: Tells the amount of energy the amplifier can feed into a resistance (badly simulating a loudspeaker). You can share this value when the harmonic distortion is at 1% or. Example 40W@1%
Impedance, damping factor, and nearly that are the most you get as technical specs. Here lower impedance, higher damping factor may mean better, but how this cooperates with a real life loudspeaker is a different story.
Philips AG9015 
You must be logged in to post a comment.