NASPA Systems (A Robert E. Weatherford D/B/A)
dynamic bandwidth reduction is a single ended
noise reduction system based on a variable lowpass filter that is controlled
by the amount of high frequency content of the source material.
When little or no high frequency information is present, the
filter’s cutoff moves to a low frequency, rolling off the background
noise. As high frequency
content increases, so does the cutoff frequency.
The design was based around the Signetics NE572 compander, configured
as a VCF, controlled by the source signal through a highpass filter.
Schematics were later input into OrCAD.
You can click on the images on the right to see a larger image.
The schematics for the dbr are available in PDF format