AM8328 The Mirage Filter

Based on the CEM3328 4-pole Low Pass Filter chip from 1984

This module is based around the CEM3328 4-pole Low Pass Filter chip that was released in 1984, as one of the last filter chips and with some great features. It has differential signal inputs, an accurate exponential scale over 14 octaves and voltage controlled resonance. It has a unique feature, the signal level is automatically increased as the resonance goes up, thereby avoiding the usual signal level dropping off as resonance comes in. The CEM3328 was late onto the analog stage, just before digital filters appeared, so it only made it into the BIT01 and Ensoniq Mirage (and a few drum machines).

So this chip has never really seen action, and was never under analog pot control, just lonely digital parameter access! In the Mirage it was not even allowed to oscillate…..We just love giving it a new lease of life in a new analog module!

http://www.amsynthstore.co.uk/AM8328_The_Mirage_Filter/p1461448_8637315.aspx