Parametric equalizer demonstration

Welcome to the prototype parametric equaliser control panel! This is a single-band stereo equaliser, which we are using to get the parametric controls set up right. Once that's done, we'll probably just make this into a four-band parametric, and try and add some sensible dynamic range limiting as well.

General information

As for the other audio IO demos, this application controls the Sun Audio device. By default, the Ptolemy universe that created it configures the device to run stereo at 44.1 kHz with 16-bit linear encoding.

There is a single band of parametric equalisation, with control over the band frequency, band width, and band gain. The frequency range is settable; in the future, it will also be possible to select low-pass, band-pass, or high-pass filtering as well.

Controls

Input and output selectors
The input and output selectors do the obvious thing. Or, at least, they would if they worked.
Rec
Controls the gain on the input. For CD source, this should really be down quite low to avoid clipping.
Bal
Controls the balance of the output signal. Negative numbers are left, positive are right.
Gain
Controls the output gain. Again, if it's too high or there's too much gain in a filter, you'll get nasty noises. This is why we need dynamic range control :-)
Freq
Controls the center frequency of the filter, in Hz. The two entry boxes at the top left of the filter set the range of adjustment. You may notice a couple of funnies of you use this -- we re working on logarithmic scaling for the slider, which should fix things.
BW
Controls the band-width of the filter, in octaves. This is measured at the half-gain (in dB) point. A typical ten-band graphic equaliser, for example, has a band-width of one active.
Gain
Controls the peak gain of the filter, in dB. At maximum gain, the filter sometimes craps out, which is a mystery. (Bill?)

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Last updated: 05/07/98, comments to: tycho@eecs.berkeley.edu