Now that I have your attention, I'm going to explain a theory for why tube amps sound different (and better) than SS from 40Hz and above. And 40Hz is somewhat arbitrary so don't get hung up on the exact bass frequency. The reason why tubes amps sound different than SS amps has been debated for many years and those that don't like tube amps usually cite distortion of one type or another to explain why people who like tube amps like tube amps.
For those that have at least a rudimentary understanding of electronics, you are familiar with Ohm's Law. With regards to power output, Ohm's Law is simply stated as P=IxE. For those that don't know the terms of this equation, "P" is power measured in watts. "I" is current measured in amperes, and "E" is voltage measured in volts. You can see by the formula that "P" doesn't care what combination of current and voltage exists because "P" will always equal the current times the voltage. However, Ohm's Law can only state that P=IxE. Ohm's Law can't tell you how those watts will sound, only that the watts are equal from a current times voltage perspective. And, there is a reason why its called "Ohm's Law" and not "Ohm's Best Guess." Ohm's Law has stood the test of time and is the backbone of how electronics are designed. Again, what Ohm's Law can't tell you is that two power amps that have the same power rating will sound the same. And they don't.
Many people realize that tube amps make their power with high voltage and low current and that SS amps make their power from high current and low voltage. I proffer that although a SS amp and a tube amp can have equal power output (and they can and do), they will not sound the same because of how that power output is created. Watts created from high voltage and low current sound different than watts created from high current and low voltage. David Manley actually should get credit for pointing this out to people who cared to read about it. David Manley wrote a book called the Vacuum Tube Logic book and he discussed how tube amps made their power from high voltage and they sound like it and the effect of using high voltage was readily audible. I personally would describe the difference in sound between tubes and SS as tubes sounding more live (more 'charged' with the energy of life) and thus more real and involving. It's another step closer to the microphone and away from the reproduction chain so to speak.
People often talk about how tube amps sound twice as powerful for a given output power rating than a SS amp does. We know from Ohm's Law that for a given output power, a tube amp can't be twice as powerful as a SS amp with the same output power rating. I think what people are really hearing is the effect (and sound) of watts that are created from high voltage. I'm specifically not talking about driving either amp into clipping and how tube amps behave differently than SS amps do (tubes tend to compress the top of the waveform and SS tends to shear off the top of the waveform when overdriven). I'm talking about operating both amps at a level that is within their output power capability and not driving them into clipping.
In order to give credit where credit is due for SS amps, we need to talk about the bottom two octaves. Many people are aware that the majority of subwoofers and large woofers sound their best when driven by SS amps due to the high current and high dampening factors of SS amps compared to tube amps. If you want iron fisted control over your large cone woofers that results in deep, tight, and accurate bass, that is really only going to come from the output of a SS amp. Tube amps can have decent bass, but I have never heard one that has great bass that extends to the bottom octave. Tube amps simply lack the current drive of SS amps as well as the high dampening factor of SS amps that most woofers need in order to sound their best.
In summary, there is a reason why some people prefer the sound of vacuum tube electronics over SS and I have tried to explain why I think it is so. It has everything to do with getting closer to the breath of life that creates music and nothing to do with loving distortions of various and sundry types that tube lovers are constantly accused of.
For those that have at least a rudimentary understanding of electronics, you are familiar with Ohm's Law. With regards to power output, Ohm's Law is simply stated as P=IxE. For those that don't know the terms of this equation, "P" is power measured in watts. "I" is current measured in amperes, and "E" is voltage measured in volts. You can see by the formula that "P" doesn't care what combination of current and voltage exists because "P" will always equal the current times the voltage. However, Ohm's Law can only state that P=IxE. Ohm's Law can't tell you how those watts will sound, only that the watts are equal from a current times voltage perspective. And, there is a reason why its called "Ohm's Law" and not "Ohm's Best Guess." Ohm's Law has stood the test of time and is the backbone of how electronics are designed. Again, what Ohm's Law can't tell you is that two power amps that have the same power rating will sound the same. And they don't.
Many people realize that tube amps make their power with high voltage and low current and that SS amps make their power from high current and low voltage. I proffer that although a SS amp and a tube amp can have equal power output (and they can and do), they will not sound the same because of how that power output is created. Watts created from high voltage and low current sound different than watts created from high current and low voltage. David Manley actually should get credit for pointing this out to people who cared to read about it. David Manley wrote a book called the Vacuum Tube Logic book and he discussed how tube amps made their power from high voltage and they sound like it and the effect of using high voltage was readily audible. I personally would describe the difference in sound between tubes and SS as tubes sounding more live (more 'charged' with the energy of life) and thus more real and involving. It's another step closer to the microphone and away from the reproduction chain so to speak.
People often talk about how tube amps sound twice as powerful for a given output power rating than a SS amp does. We know from Ohm's Law that for a given output power, a tube amp can't be twice as powerful as a SS amp with the same output power rating. I think what people are really hearing is the effect (and sound) of watts that are created from high voltage. I'm specifically not talking about driving either amp into clipping and how tube amps behave differently than SS amps do (tubes tend to compress the top of the waveform and SS tends to shear off the top of the waveform when overdriven). I'm talking about operating both amps at a level that is within their output power capability and not driving them into clipping.
In order to give credit where credit is due for SS amps, we need to talk about the bottom two octaves. Many people are aware that the majority of subwoofers and large woofers sound their best when driven by SS amps due to the high current and high dampening factors of SS amps compared to tube amps. If you want iron fisted control over your large cone woofers that results in deep, tight, and accurate bass, that is really only going to come from the output of a SS amp. Tube amps can have decent bass, but I have never heard one that has great bass that extends to the bottom octave. Tube amps simply lack the current drive of SS amps as well as the high dampening factor of SS amps that most woofers need in order to sound their best.
In summary, there is a reason why some people prefer the sound of vacuum tube electronics over SS and I have tried to explain why I think it is so. It has everything to do with getting closer to the breath of life that creates music and nothing to do with loving distortions of various and sundry types that tube lovers are constantly accused of.