Saturday, June 4, 2016

The joy of frequency shifting

Frequency shifting, or single sideband (SSB) modulation as it is also called, differs from the more well known ring modulation in that it produces less partials in the resulting spectrum. Whereas ring modulation is the same as the convolution of the carrier's spectrum with the input signal's spectrum, single sideband modulation just shifts the partials up or down in frequency. Harmonic tones become inharmonic, unless the amount of shift happens to equal the frequency of one of the harmonics.

SSB modulation can be carried out with analog as well as digital techniques. There has been much prejudice and heated debate about the advantages of analog vs. digital. In this comparison between an analog eurorack module and several DSP implementations of SSB, one can hear differences in their sound, but that is not to say that everyone will agree on what sounds better or which method would be preferred in a given situation.

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