AM8176 Triple Resonant Filter

14 HP | AM8176 Triple Resonant Filter | User Manual (PDF) | You Tube

OVERVIEW Roland never made an analog resonator circuit but Korg did with the triple bandpass resonator in the PS3100 of 1977. This module is a re-imagining of this filter for the 100M Eurorack format.

The AM8176 module has three vactrol filters which can be independently adjusted for frequency, resonance and modulation depth. The modulation inputs are usually driven by one or more LFO’s to create band pass sweeps.

DESCRIPTION The AM8176 has rotary potentiometers (with TR808 style knobs) at the top of the front panel are used to adjust the level of the individual filter outputs (CH-1 and CH-2). The CH-3 potentiometer pans between the input and output of channel 3. All three channel outputs are mixed together (at unity gain) and available at the MIX output.

The frequency and resonance of each channel is adjusted using slide potentiometers with subtle green LED lighting. The trimmer pots at the bottom of the panel control the level of frequency modulation from two inputs per channel, typically two LFO’s at different rates.

The signal inputs of CH-2 and CH-2 are normalised to CH-1 and both modulation inputs on CH-2 and CH-3 are normalised to CH-1. This makes parallel operation easy with minimal patching.

The output mix always has the outputs of CH-1 and CH-2 blended with a mix of the input and output of CH-3. This enables the input signal to be mixed with the outputs, or just the CH-2 output. 

The first two resonators can be patched manually into series operation, with the option of using the mix out as a blend of CH-1 and CH-2 and CH-3.

CONNECTIONS There are four jack sockets for each channel:

• Signal Input
• Signal Output (Mix Out on CH-3)
• Frequency modulation 1
• Frequency modulation 2

The module comes with a set of M3 mounting screws and washers, and a standard Doepfer power cable.

MODULE STATUS: LIMITED PRODUCTION

This module is built in small runs of five every few weeks because Vactrols are hard to locate and expensive. You can reserve an AM8176 by sending us an email (see contact page)

The Vactrols used in this module are RoHS compliant, please refer to this datasheet.