The objective of SDO is to minimize the significance of noise in the outputs. Let's take a closer look. A familiar example of white noise is the sound of a jet engine running at full throttle. It is like a perfect reproduction of television sound when it's on a channel where no signal is being transmitted. Any active electronic circuit is characterized by a basic level of white noise present on its output, originated predominantly by the active devices in the circuit. Typically this noise is small compared to the relatively large signal values processed by the device, but the device's noise (of whatever spectral range it may have) establishes a floor at and below which any output signal is of questionable integrity, for at such a level the signal is no stronger than the circuit's own characteristic noise. This noise floor establishes an absolute minimum criterion for the amplitudes of usable signals coming from the device.
The circuit is ALSO characterized by a maximum usable output signal, for if the circuit is well designed, then the minimum and maximum DC potentials provided by its power supply (sometimes called its "supply rails") define the extreme output peaks potentials that the device can provide from its outputs. Any demand on the device to produce larger peak outputs causes excesses to be "clipped" at the values of those upper and lower supply potentials. This introduces harmonic distortion that is presumably not the intent of the equalizer.
The natural restriction of usable signal levels to a range between the noise floor and the peak-clipping level defines the "dynamic range" of the device. The band-level controls of conventional equalizers act strictly as band volume controls, simply increasing or decreasing the band's amplitude. Thus, when a band is set flat, then the EQ must have on reserve the capability of increasing its amplitude by as much as 12, 15 or 18 dB (that's up to 8 times the flat band's output voltage).
Collier equalizers achieve relatively large capabilities for band level boost (up to 20 dB), yet when in their low-boost states their supply rails restrict their peak outputs by no more than 6 dB below the clipping level, not 12 or 15 or 18 or 20 as found in conventional equalizers. Colliers' 2x3EQ Parametric Equalizer can produce up to 20 dB spectral boost in each band, not just by increasing the band's level, but by concurrently reducing the levels of all the external frequencies, which were comparatively excessive to begin with. Accordingly, the overall volume of the output remains relatively unchanged albeit redistributed, and the peak values of the signal can remain more nearly that of the max-output level established by the peak clipping constraint. Accordingly, the signal level in Collier Equalizers can remain typically at the optimum volume setting above the noise floor without ever having to readjust the channel volume control.
For reasons I hope to have clarified here, we at Collier Electronics think that Spectral Distribution Optimization is the way of the future for high-end equalizers in general, not just for parametric equalizers.
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