Env Follow Filt - Kurzweil K2600 Musician’s Reference

KDFX Reference
KDFX Algorithm Specifications

900 Env Follow Filt

Envelope following stereo 2 pole resonant filter
PAUs: 2
The envelope following Þlter is a stereo resonant Þlter with the resonant frequency controlled by the
envelope of the input signal (the maximum of left or right). The Þlter type is selectable and may be one of
low pass (i), high pass (ii), band pass (iii), or notch (iv).
Figure 10-49
The resonant frequency of the Þlter will remain at the minimum frequency (Min Freq) as long as the signal
envelope is below the Threshold. The Freq Sweep parameter controls how much the frequency will change
with changes in envelope amplitude. The frequency range is 0 to 8372 Hz, though the minimum setting for
Min Freq is 58 Hz. Note that the term minimum frequency is a reference to the resonant frequency at the
minimum envelope level; with a negative Freq Sweep, the Þlter frequency will sweep below the Min Freq.
A meter is provided to show the current resonance frequency of the Þlter.
The Þlter Resonance level may be adjusted. The resonance is expressed in decibels (dB) of gain at the
resonant frequency. Since 50 dB of gain is available, you will have to be careful with your gain stages to
avoid clipping.
The attack and release rates of the envelope follower are adjustable. The rates are expressed in decibels per
second (dB/s). The envelope may be smoothed by a low pass Þlter which can extend the attack and release
times of the envelope follower. A level meter with a threshold marker is provided.
10-112
(i)
(iii)
Resonant Filters: (i) lowpass; (ii) highpass; (iii) bandpass; (iv) notch
(ii)
(iv)