Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

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RE: Absolute Polarity, Asymmetric waveforms and clipping effects

Posted by Tony Lauck on March 11, 2016 at 11:46:27:
If you are doing any kind of listening test and making adjustments to input signals then you are not hearing the signal, you are hearing the amplifiers and speakers reaction to the signal. Thus, for example, if you have a signal with two sine waves at 25 kHz and 26 kHz and there is no distortion you will hear nothing. But if the amplifier distorts it will create a beat tone at 1 kHz which may be audible. (If you crank the volume up in a clean system you may create similar distortion in your own ears, if you don't smoke your equipment and damage your hearing.)

It is certainly possible for amplifiers to have asymmetric response and different clipping levels for positive and negative signals. This is sometimes easy to see with a sine wave signal and a scope as you increase the volume.

Correctly identifying the cause of small sonic deficiencies can be difficult. One has to have good hearing and training to recognize that something is wrong, but that's not enough to identify the cause. That requires additional knowledge or careful experimentation. In the case of the amplifier polarity scenario, one way to isolate whether the problem was with the amplifier would be to reverse the polarity of the input signal and the speaker wiring (both speakers) and compare the sound with the original input and speaker wiring. This will catch polarity effects with the amplifier, but not the speaker. If the speakers were perfectly symmetric dipoles then perhaps you could turn those around to check for the effects of asymmetric speaker distortion, but obviously this won't work for box speakers.