The VM907A Fixed Filter Bank consists of eight bandpass filters that attenuate frequencies at 1/2-octave intervals as well as fixed corner-frequency lowpass and highpass filters. Its intended use is to create more realistic instrumental sounds by imparting a pattern of peaks and dips to the audio spectrum of synthesizer waveforms.
Inputs, Outputs, and Controls
Lowpass- A low pass filter allows frequencies below the cutoff frequency setting to pass through, but blocks frequencies above the cutoff frequency. This knob does not control the cutoff frequency; it controls the volume of frequencies below the fixed 175 Hz cutoff frequency.
Bandpass Filter volume knobs- Each of the eight main knobs corresponds to a medium-Q, four pole, dual stagger-tuned bandpass filter. The input signal is presented to all the filters and the knobs collectively behave like an output mixer. At zero, that channel is completely off. When everything is turned up, all filters are heard and the response is a bumpy spectrum with a peak at every center frequency and a dip in between.
Highpass- A high pass filter allows frequencies above the cutoff frequency setting to pass through, but blocks frequencies below the cutoff frequency. This knob does not control the cutoff frequency; it controls the volume of frequencies above the fixed 4000 Hz cutoff frequency.
Input jacks- Patch audio signals in here.
Output jacks- Summed output of the fixed filter bank.