Amp/Preamp Asylum: harmonic distortion does not get 'buried in the mix'. by Ralph Looking for a new Amp or Preamp? If you're after tubes, post over here.

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Posted by Ralph (M ) on July 4, 2012 at 11:13:05

In Reply to: RE: I think there are a few. posted by villastrangiato on July 3, 2012 at 20:31:27:

And the claimed differences in sound from one amp to the next are practically non existent compared to the differences between the speakers they're connected to. The diversion to your lp cutterhead "experiment" is just more subterfuge.

No, its not- its very real. I certainly concede that there are huge differences in speakers- I deal with that all the time in my work! But this thing with the mastering lathe? One of the speakers we heard that on was a set of boom box speakers . Even there, with nothing for tweeters, the difference could be heard. And just so we are clear, measurable too (unless you are trying to say that the measurements of odd ordered harmonics I was referring to earlier don't exist...). When it is measurable and audible I treat that as real.

By definition, an experiment is a scientific procedure undertaken to make a discovery, test a hypothesis, or demonstrate a known fact. Contrary to your "beliefs", listening to different recordings done with different amplifiers is not a scientific procedure. To be a "scientific procedure", data has to be collected and that set of data must be able to be duplicated under the same conditions by anyone else. Without the data, it's just another anecdotal flim flam. I know it's a shock to your system, but your personal subjective opinion is not science - it's just blather.

You are making a lot of assumptions here- the first being that I don't use instruments or something. I don't go on listening alone. I won't even start if the measurements indicate there is no point. I can also give the lathe cut to someone else and they can hear the same things on **any system**. That is pretty 'repeatable'. When we started the tests with the different amps, we didn't know what they would do but we found out pretty quick. Anyone could repeat the same tests, and I can also say that the distortion characteristics of each amp can be correlated by anyone. 'Repeatable' is in fact the name of the game- on this we agree.

Loudspeakers are nothing like lp cutterheads and similarly are not like moving coil cartridges. Yes, all three can use moving coils but this is essentially where the similarity begins and ends. The damping, energy storage, and losses associated with each system are vastly different and it is precisely these factors that determine the distortion signature of each. A near zero output impedance amp is most definitely going to have a different cutterhead system response than an amp with several ohms of impedance. If you actually intended to produce a meaningful conclusion from your "experiment", you should be presenting data that was collected - not total conjecture that "a few hundredths of a percent" of odd ordered harmonic from an amplifier are somehow going to be evident from sound produced by a loudspeaker that contains hundred's of times that amount of odd ordered harmonic as a result of loudspeaker generated distortion.

Sorry, on this matter its obvious to anyone with LP mastering experience you don't know what you are talking about. If I were you, I would spend some time around a cutterhead if you can, try some different amps and see if you still say that :) There is a very practical reason why amplifiers designed to drive speakers are also used to drive cutterheads. The results we recorded on the lathe cut can be duplicated on any loudspeaker.

Your assertions about audibility of odd ordered distortion generated by amplifiers are neither reasonable nor plausible. It is akin to detecting a pin dropping while a massive 10 car pileup is happening - the loudspeaker being the pileup and the amplifier generating the pin drop. Perhaps this explains why you decided to throw out the lp cutterhead non sense to prove a point that has no logic or truth.

I'm not the one that discovered the facts above that you want to refute; that work was done by General Electric in the 1960s. Maybe go talk to them. I just read the results of the study. There is more from it that I have not revealed in this thread as well- I recommend that you look it up (which, BTW, is a pain in the rear as it never got posted to the web, but its out there). However, since you are no 'audiophool', I will give you an exercise:

Get a sine/square generator, an amplifier, a speaker and a VU meter. The type of amp or speaker is not important but they should work properly. Run the amp into the speaker using the VU, set the sine wave output so the meter reads 0VU. Cover the meter, turn the volume of the generator down and switch to square wave. Run volume up until it *sounds* as loud as the sine wave did. Uncover the meter and observe the reading.

Now squarewaves are composed of odd-ordered harmonics. What GE learned is that the ear uses odd orders to determine how loud a sound is and you will see this in this experiment. Its apparent to me that you were not aware of this aspect of human hearing so you need to learn it first hand and this is a simple way. As you see from the test, the squarewave output will be a fraction of the original sine wave level.

So what I am talking about is this: that the **measurable** odd ordered harmonic distortions of very slight amounts are indeed also audible to the human ear because that is one of the things that to which it is the most sensitive . Much more so than human vocal ranges, image location, etc. It is arguably the most fundamental rule of human hearing. Don't believe me- then you didn't do the experiment above...

It also sounds to me like you are expecting the odd ordered distortions to be somehow 'buried in the mix'. Distortion does not work that way. The loudest sound in any recording will have this distortion on top of it. The idea that its buried is really just fantasy (just look at an oscilloscope...). If we go back to that sine wave, we already know it will be slightly distorted as a result of the generator, the amp, the speaker... so where do you suppose that distortion is? On top of the waveform or somewhere else??? Honestly, if you work on amps, preamps, speakers and do measurements on them we would not be having this conversation! Go do the test and see for yourself. The ear treats harmonic distortion of all types as tonality. Its something anyone can hear (its the source of the tube vs transistor debate for example), and yes, its quite measurable and repeatable too.

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