Distortion

In this blog i will compare the use of digital and analog distortion and analyse the sonic characteristics of running a sine wave through them.

Digital Distortion 

I will be using logic stock distortion plug in sets and analyzing them over a spectral analyzer of Logics stock EQ plugin. I will use a basic sinewave that is playing at 400Hz which is being triggered by logics stock TestOsc.

Bitcrusher

By applying digital distortion to a sinewave such as a bitcrusher the wave can be seen to morph from a sinewave to a squarewave.

Screen Shot 2015-03-16 at 6.06.15 PM

Ive set the clip level so that once it reaches 0dbfs it will have a sharp cut at the top almost flattening the peaks and throughs. I have used this setting because it is the most common way of digital distortion since it will not play anything that is clipped at the 0dbfs threshold.

Looking from a post analyzer EQ, more frequencies and harmonics are added when a signal is distorted. However the fundamental frequency of 400Hz is still the same.

With no gain boost

Screen Shot 2015-03-16 at 6.09.00 PM

With 3.5 dB gain boost

Screen Shot 2015-03-16 at 6.09.37 PM

With 12 dB gain boost

Screen Shot 2015-03-16 at 6.09.12 PM

In terms of subjective analysis, the square tone is more harsher but also more brighter compared to the sine wave. There is also a difference in perceived loudness since the square tone emits a much more louder noise but dynamic metering would still read both tones capped at 0dBFs.

Limiter Distortion

Running a sinewave through a limiter such as logics Adlimit achieves the same results however, the percieve loudness is not as harsh as running it through a bitcrusher.

I ran the same sinewave through a 22dBfs gain inside a limiter.

Screen Shot 2015-03-16 at 6.22.21 PM

And here is one running at 44dBfs, double that of the first one.

Screen Shot 2015-03-16 at 6.22.30 PM

even though there is a 44dBfs boost, it is still not louder than the same wave boosted through a 12dBfs bitcrush distortion. One reason could be because the bitcrusher reduces the resolution of the audio as well as boosts the gain, and the more quantization you can hear, the more harsher it would sound, thus the more fundamental it creates, thus their is a perceived loudness.

The perceived loudness could also just just be due to the way logic’s coding works.

Analog Distortion

For these analog tests, i paired up with my peers Jordan Forrester, Jackson Martin and Joshua Graham. The assets were shared around Google Drive.

For our first analog distortion we played a 192 Hz Sine Wave, Inserting the JLM LA500A Compressor into the Channel and Increasing the Makeup Gain to point of sonic distortion.

Screen Shot 2015-03-16 at 6.46.57 PM

Towards the halfway point of the make up gain pot, it starts to distort and play its fundamentals.

Screen Shot 2015-03-16 at 6.47.00 PM

when it has reached the halfway point on the Makeup Gain it slowly loses its harmonics but, increases in buzz and noise from 5kHz to 20kHz, making for an undesirable effect.Screen Shot 2015-03-16 at 6.49.36 PM

Here is the video for the makeup gain overload on the outboard compressor.

https://drive.google.com/a/student.sae.edu.au/file/d/0B5kxHx5sAoxyX3pnN3NRSVhiLUU/view

Input Clipping

We also tested microphone clipping. We did not use a tone but we had used Jackson Martin’ scream and fed it through the outboard gear in different gain, one at -5dBfs and one at 0dBFs.
The mic used was an SM57.

Screen Shot 2015-03-16 at 7.07.38 PM

At low levels it was not noticeable but if enough gain was introduced, more crackle was heard. The noticeable difference is that when the gain was boosted more, lower frequencies and higher frequencies are introduced to the audio.

Screen Shot 2015-03-16 at 7.07.41 PM

The crackle could be due to the way the mic is built and how much air pressure the diagram could take but was not noticeable with a lower gain. It could also be due to the way the outboard processor could artificially create these extraneous sounds due to the electronics inside was manufactured.

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