The Minimoog Model D adapted some of the circuitry ( such as the filter section ) from earlier modular instruments, but designed other circuitry ( such as the oscillators and contour generators ) from scratch.
32.
:: An infinite number of low pass filter sections will give a perfect Gaussian pulse at the output when fed with a pulse of the correct width ( if you can wait for ever ).
33.
Both the T-section ( from ladder topology ) and the bridge-T ( from Zobel topology ) can be transformed into a lattice topology filter section but in both cases this results in high component count and complexity.
34.
Besides the OB " 12, 1983's OSC OSCar synthesizer is the only synth having this facility; in the OSCar this function is called " separation " and has a dedicated knob in the filter section, unlike the OB " 12, whose Delta parameter is inside filter's edit menu.
35.
Technically, this was easy to do within the filter as it could always be arranged that adjacent filter sections had matching image impedances ( one of the characteristics of m-type sections is that one side or the other of the m-type section will have an image impedance identical to the equivalent constant k section ).
36.
He was now using, in addition, m-type half sections at the ends of his composite filters to improve the impedance matching of the filter to the source and the load, The difficulty that he was trying to overcome was that the image impedance techniques being used to design filter sections only gave the mathematically predicted response if they were terminated in their respective image impedances.
37.
A feature of the filter section rarely available in an analog synthesizer is the ability to modulate the filter's cutoff frequency using the VCO signal, resulting in timbres ranging from a slightly growly character to sounds that can be similar to some of the metallic FM sounds typically produced by the Yamaha DX7, depending on the VCO waveform, the VCF cutoff frequency, and the amount of filter resonance.
