Module description

A Voltage Controlled Filter based on the CEM 3320 chip.

Four types of filter configuration are available using the same PCB design. They are: 4-pole, 24dB/octave Low Pass (80-6L), Band Pass (80-6B), High Pass (80-6H) and Phase Shift with two deep notches (80-6P). Exponential voltage control (1V/octave) for good tracking with oscillators. Envelope generator sweep input and three signal inputs (two with attenuators). Manual and voltage control of resonance. Filters may be made to oscillate. All four filters cover the full audio range.

The original model 80-6 was replaced by an updated version (here referred to as 80-6A) incorporating minor improvements to the circuitry to reduce CV feed through.

Construction information

• ETI May 1980 for 80-6 (3.7MB pdf file)
• PCB foil diagram for 80-6 (34KB gif file)
• Digisound document for 80-6A (1.6MB pdf file)
• PCB foil diagram for 80-6A (34KB gif file)
• PCB size (mm) 160 x 69

Front panel designs

80-6L Low Pass Filter

• Original 9 x 3 inch (3KB fpd file)
• MOTM-format 5U x 2U (3KB fpd file)

80-6H High Pass Filter

• Original 9 x 3 inch (3KB fpd file)
• MOTM-format 5U x 2U (3KB fpd file)

80-6B Band Pass Filter

• Original 9 x 3 inch (3KB fpd file)
• MOTM-format 5U x 2U (3KB fpd file)

80-6P Phase Shift Filter

• Original 9 x 3 inch (3KB fpd file)
• MOTM-format 5U x 2U (3KB fpd file)

For more Digisound-related documents, please refer to the Other Digisound documents page.