SV: Re: SV: Re: [sdiy] Nonlinearities in IR3109 filters

[JH.]

>I started to recognize that the
>VCA really did color the sound and effect the dynamics quite a bit!


Sure. And the real miracle is that the distortion of slightly overdriven
differential pairs (think OTA-VCAs, or VCAs built from diff pairs)
works "in reverse" for many sounds:

While it would add harmonics to a sine wave ( ... where THD measurements
are done), it actally *reduces* the level of harmonics on typical synth
waveforms with sharp corners (tri, saw, ...)

Just think for a moment, the very same overdriven ota structure is often
used
to form a crude sine wave from a triangle in synthesizer waveshapers .. .

And there is more. The compression effect from soft limiting / signal
rounding,
be it in VCFs or VCAs, helps to reduce the amplitude modulation that
occurs with two saw wave VCOs beating against each other, consequently
allowing a higher amount of detuning without sounding chopped.

JH.