| 摘要 |
A tone control shelving equalizer providing low shelf (bass) boost and cut, and high shelf (treble) boost and cut is disclosed wherein the active filter stages provide sharpened (accelerated) amplitude versus frequency response characteristics at the band transitions to leave the center frequencies uncorrupted by out-of-band effects of the tone controls while maintaining circuit stability and avoiding dropouts due to excessive filter phase shifts. Each high and low end band filter network has multiple poles and offset zeros located at a frequency offset so as to restrict the maximum phase shift of the filter to within a safe level not greater than about 90 DEG .
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