Recently I built the Nelson Pass H2 Harmonic Generator, a circuit that injects some 2nd harmonic distortion into the signal chain. Whilst I still need to get this boxed up to play with it properly, I’ve been mooching around and doing some reading on distortion.
As part of my meandering, I came across this website which provides a software method of distorting the audio signal. Why would you want to purposely distort your music? It’s all very well having measured parameters that show a certain piece of equipment has x amount of y distortion, but do you know what that distortion sounds like and can you hear it at certain levels? The author of the software offers certain questions that can be addressed, some of which are detailed below:
- Is SINAD of 110dB audible?
- Is THD below 1% audible?
- Do even harmonics sound better than odd?
- Do higher-order harmonics sound less pleasant?
- Does SET distortion really sound good?
- At what level does the noise floor or the mains frequency become audible?
- What kind of music is improved by lower THD? Even harmonics? Lower noise floor?
As a nice companion piece, Amir at Audio Science Review recently wrote a helpful post over at his site with a simple explanation of the testing he does for DACs. I imagine at some point, anybody with an interest in measured performance of audio gear will have come across this site and it’s suite of measurements and graphs. This is a good, introductory primer for those, like me, who are familiar with these measurements but do not completely understand them.
Archimago has initiated another Internet blind test, this time examining the audibility of harmonic distortion. The objective of most commercial and hobby builders of components is for increasingly lower Total Harmonic Distortion (THD) but Archimago is attempting to understand whether listeners can discern what would be considered relatively high THD. He has used the Distort software mentioned above to create a number of tracks with varying levels of distortion for you to try out and hopefully submit. Give it a go, you may be surprised.