Intermodulation Distortion

    • March 7, 2023 at 10:32 am #5113
      Ted Onyszczak

        So you go your whole mixing career as a former guitarist aware of distortion and the general pitfalls in digital processing. And aliasing distortion, cause your career started after the digital era and you didn’t work on analog tape until the 2000’s. Then once you basically retire you suddenly deep dive into distortion and come up with intermodulation distortion. You’d been vaguely aware of it all your career but never paid that much attention. But once you learn about it, it eats at your brain and cause late nights without sleep. Did I miss out on something critical all those years?

        So my actual question for the experts: does poor DSP programming cause more IMD than good? and does it cause more than the equivalent analog processor? Can it be reduced? Eliminated, like aliasing seeming can with good programming? Or is it all just part of the game?

        Should I be losing sleep over this? Someone let me know before I start recording all my distorted guitar chords one note at a time like Def Leppard on Hysteria (yes just the song, I am aware it was only one part of one song, and the clean part ironically too, so probably not an IMD issue)

      • March 8, 2023 at 10:36 am #5115
        Bob Katz

          I’ve seen intermodulation distortion issues in both analog and digital gear. Poor designs don’t seem to discriminate between analog or digital implementation. If you test with your analyzer using 19 and 20 kHz and there is significant difference product at 1 kHz it’s likely to add a fuzz or harshness. But if the first order difference product is fairly low in level and what’s left is just some extra stuff created in the high frequency region, the IM can be fairly innocuous.

          If you see lots of additional products in the midband other than 1 kHz, it is likely due to aliasing and that can cause harshness and fuzziness. I’ve seen that in a lot of analog-emulation plugins — and I don’t like its sound one bit.

          Keep in mind that if the device produces some “good” harmonic distortion, particularly second and third, and this is dominant, with relatively little stuff above 3rd harmonic, then the device’s residual IM may not be audibly significant.

          Also remember: If it sounds good, even if it measures bad, it is good!

        • March 8, 2023 at 11:50 am #5116
          Alexey Lukin

            Intermodulation always goes together with harmonic distortion. Whenever there is harmonic distortion, there’s also an intermodulation, as long as the signal contains more than one tone/pitch. True for both analog and digital.

            Aliasing (i.e., intermodulation with the samplng rate) is a separate issue that only exists in digital. However in analog there can also be intermodulation with tones not belonging to the signal, like electric hum or tape bias.

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