904A LOW PASS 44B

The 904A Low Pass Filter is a Modcan re-creation of the 4 pole 24db low-pass filter from the Moog Modular synthesizer. The 44A honors the Moog spec. with precision matched 2N3392 transistor pairs through out.

904A Demo sequence electropop.mp3
All sounds were created using the 904A

Another demo with bass line from the 904A moogbass.mp3

Range Switch
Retained from the original design, sets the frequency band over which the Fixed Volt knob operates in two ocatve steps.
1 -1Hz to 5kHz
2 -4Hz to 20kHz
3 -16Hz to 60kHz

Input Level
The filter input level is adjusted using the Level control attenuator.

1V/Oct Input
Exponential converters track linear voltage input at 1 volt per octave. This input is primarily used for keyboard tracking and pitch control of filter in self-oscillation mode.

CV Input 1
Control Voltage input with attenuator
to control the depth of frequency modulation.
Incorporates the standard Modcan inverting/non-inverting
sign changer circuitry.

CV Input 2
Secondary Control Voltage input with attenuator.

Regen Control
Knob varies the amplitude of the resonant peak at the cutoff frequency of the filter.

Fixed Voltage
Sets the cutoff frequency of the filter.

Specifications:
Wide-range low pass filter with variable-height
resonant peak at cutoff frequency.
4 pole response
24db/oct cutoff slope
Cutoff Frequency Range 1Hz-60kHz
Signal Input impedance: 10K
Control Input impedance 100K
Output impedance: 1K AC coupled
Control Sens: 1 volt per octave