The A-105 is a 24dB/octave voltage-controlled low-pass filter, and is very similar to the A-122 that uses a CEM chip. In contrast to the A-122 the A-105 uses the legendary SSM filter chip - the SSM2044, as was used in the Korg Polysix & Mono/Poly, Fairlight CMI II, PPG Wave 2.2 & 2.3, Emu SP-1200, Siel DK600 & Opera 6. The first Sequential Prophets used the SSM2040 - the predecessor of the 2044 - that generates a very similar sound.
The special feature of the 4 pole low pass SSM2044 is the patented “true open loop design that delivers a characteristic fat sound not available from other devices”, as it does not lose any low frequency response with higher resonance settings.
The A-105 features voltage controlled resonance and a sensitive audio input to allow input cliping distortion - if so desired.