Dual Voltage Controlled Filter


The 40235 Dual Filter Module integrates the circuitry of two of the most popular voltage controlled lowpass filters, the ARP 4023 and 4035, onto a single board. The 4023 is the filter found in early Odyssey synthesizers (model 2800), a 2-pole (12 dB/oct) OTA-based biquad design. The 4035 is a 4-pole (24 dB/oct) design built around Moog's transistor ladder, and was originally installed into Odyssey models 2810-2812. This rather rare filter is similar to the 4012 filter which was used in early model 2600 synthesizers, although it uses IC transistor arrays instead of matched discrete transistor pairs.

The upgrade adds a front panel control for switching between 2-pole and 4-pole filter modes.

The 40235 is signal compatible with ARP 4035 and 4075 filters, and can be used as a direct replacement in the following instruments:

AXXE-2(models 2310 and higher)
ODYSSEY-2(models 2810 and higher)
AVATAR(all models)
OMNI(all models)
OMNI-2(all models)
QUADRA(all models)

40235 Revision History
REV: A1 (initial)DATE: 20-APR-1997

Downloadable Files
40235.PDF (128K) Portable Document File
40235.ZIP (129K) Archive containing the following files (GIF/Postscript):

40235S1.GIFSchematic (page 1)
40235S2.GIFSchematic (page 2)
40235TXT.PSInstructional document - includes assembly information and parts list
40235WD.PSWiring diagram
40235-T.PSTop side PCB layout (Postscript - recommended for artwork)
40235-B.PSBottom side PCB layout (Postscript - recommended for artwork)
40235-C.PSComponent placement

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Last Updated: April 24, 1997