I recently finished building my first EL34 single ende tube amp. I must say it sounds rather good. I dare to say it sounds really good. I have had many amps and speakers and also worked in a hifi store for several years. Last weekend I went to a friend of my friend's father who used to be a professional audio technician for several decades and has worked with several great artist along the way. So if one person knows sound, it must be him. He also builds speakers for a living.
When I took the amp to his place, he was very impressed with the sound. Ofcourse the low end lacks in comparison with a powerfull solid state, but he very much liked the openess, transparency and detail my amp produced. He also said how easy it is to listen to. Like no listening fatigue at all. Later in that day a friend of him als visited (also audiophile) and confirmed what he heard. He was also very impressed with my amp. My friend (also a musician) was there also and was very impressed by the sound and noted how clean and free of distortion it sounded. He said the music has a lot of body to it and the instrument seperation is stellar. He did not want to stop to listen to it. What had to be a 1 hour demonstration turned to a 3 hour listening session.
NOW HERE COMES THE CATCH:
Yesterday I wanted to measure my amps distortion and also measure some other things. I was baffled by the results. I attached my prongs to the speaker output posts with a real speaker load.
The square waves look absolutely awfull on the scope. They are something like the picture below. Note that this is not the actual screenshot of my scope. I have no picture of my own scope and am writing this post from outside of home. But the square wave looks like this across almost all of the frequency range. It is absolutely symmetrical. There is less ringing though in my case.
What the... &*^!!8768?!?!!?
Like how is this even possible? I would expect a ton of ringing and simple bad sound being produced by my amp. It should induce a ton of fatigue and distortion to the sound based on the measurements on my scope, yet it yields very good results while actully listening to it.
My theory is that we are measuring the amplifiers performance all wrong this whole time. Why? Because we are not measuring what our ears hear! Simple as that. We have to think of another way to properly measure what we as humans are actually hearing, and that is the pressurewave produced by the speaker, and not the voltage swings that are going into the speaker.
The wrong way to measure
Measuring the voltage swings on the speaker output posts either with an artifical load (resistor) or a real speaker load. We would only measure the voltage swing, but not the actual pressurewave we as humans perceive.
The right way to measure
Place a microphone in the room where your listening position is. Ideally the microphone would have the same characterisics as the human ear. A "perfect" micrphone would still yield unusable results as it would posess super human capabilitys and thus yieliding inacurate results as to simulate what our ears are hearing. We will capture the pressurewave and the actual way our ears perceive it and thus yielding an accurate representation of the amps and speaker's performance.
Why does the apparent overshoot sound good in real life?
My theory is that it has to do with the way we are converting energy. All energy in the universe transmutes. In our case we are transmuting electrical energy into kinetical energy by changing the magnetic flux in the speaker's magnet. Because the movement of a speaker includes a time to speed up and time to slow down, this already causes distortion in the sound. An ideal speaker would move in a instant. Ideally in planck time. But this is not possible in practice.
But what I think happens is that the oveshoot, which is a higher voltage, makes the speaker move faster on the initial movement therefore causing it to move more "accurate" thought the amp itself does not produce a correct signal.
I like to see it as follows: Whe we want to accelerate a car from 0 - 60 Mph we would need some engine power. Imagine my car is able to produce 100 Hp. If my goals were to be to reach the 60Mph as accurately as possible, in ideal circumstances I would only need to appy lets say 20% throttle to achieve it in 3 seconds. But because of air resistance and other factors I need to apply 100% of throttle to get there in 3 seconds and that go back to 20% to maintain. Though I have a "overshoot" of throttle, my real life performance would be close to a square wave than what my throttle input actually is.
Should we than throw the old way of measuring out?
No. Absolutely not as it will still provide valuable insight in the technical limitations of an amplifier. For example when it starts to really clip. And it will not make you deaf when you use an artificial load (resistor) ;)
So what do you think? Is thare any sense to my theory? Am I missing something? Or could I be onto something?
Let me know!
P.S. Any square wave above 10Khz ~ish is a sine anyway due to the fact use a DAC at 44Khz sampling rate..