AMSynths AM4023 Lowpass Filter (PCB)

Unpopulated PCB for SDIY'ers to create the classic AM4023 low pass filter.

The AM4023 is a clone of the ARP 4023 2-pole 12dB low pass filter in the ARP Odyssey. This filter has a smooth behavior and unlike many 4-pole filters, does not attenuate the low end with increased resonance settings. Also, with a shallower cutoff slope, it could be argued that the Odyssey had a brighter sound overall. The filter is good for bass and bright lead sounds, and with modern components it is not noisy. It will self-oscillate at high Q settings and it can shred speakers – so beware! With so many 4-pole filters around, it’s nice to have a 2-pole version for some contrast. 

The control inputs are calibrated to 1V/octave, and there are up to two CV inputs which have front panel attenuators. There is also an un-attenuated CV in for direct connection to a keyboard or 1V/Octave  input.

The filter frequency has two front panel controls; FREQ for coarse adjustment and FINE for fine adjustment, there is also an on-board trimmer to set the initial cut-off frequency. The filter has a frequency range of 1 Hz to over 20kHz.

The filter has a Q control (RESONANCE) to adjust the resonance of the filter. Higher settings of Q will take the filter into sine wave oscillation. The filter will oscillate from 16Hz to 20 kHz.