The A-105 is a 24dB low pass filter that bases on the SSM 2044 chip that
was used amongst others in following units: Korg Polysix, Korg
Mono/Poly, Fairlight II, PPG Wave 2.2 und 2.3, Emu SP-1200, Siel DK600,
Siel Opera 6. The first Prophets used the SSM2040 - the precedessor of
the 2044 - that generates a very similar sound. The filter convinces
with a very powerful sound. The resonance starts quite early to color
the signal and makes a big range of sounds possible up to
self-oscillation. The latter provides a very clean sine wave - no
wonder, because the SEM2044 chip wasn´t designed only as a filter core
but also as a sine wave oscillator.
