Q150 Transistor Ladder Filter

The cutoff frequency can be controlled manually and by control voltages from an envelope generator, oscillator, keyboard, etc. Frequency control signals can be attenuated and inverted without the need for utility modules. Resonance (Q) of the filter can be adjusted with the front panel control. The filter will self-oscillate and track a 1V/Octave keyboard control voltage. Both -12dB and -24dB slopes are available offering a wide range of sounds. One pole and three pole responses are jumper-selectable for even more possibilities. A convenient two-channel mixer is provided for incoming audio signals. A special feature of the Q150 is output leveling. In most ladder filters the output signal level is greatly reduced as the resonance is increased. This usually requires resetting input levels (sometimes many) when changing resonance settings and can become quite annoying. Special circuitry in the Q150 maintains constant output level at various resonance settings while keeping the harmonic content unchanged. This feature is jumper-selectable and can be deselected if identical behaviour to the Moog ladder filter is desired.