Based on the formant filter form the Trautonium the A-104 offers four resonant filter, switchable between low pass and band pass. Especially in band pass mode is good for creating static resonances, formats and vocal sounds.
The module has a common audio inupt with level control and a common audio output which emits the mix of the four filters.
Each filter has a slope of -12dB per octave and a frequency range of 50Hz to 5kHz which means it's rather heavy in the lows and mids. Each has individual controls for setting cutoff frequency, resonance and output level. The switch selects between the modes: low pas / off /band pass.
Due to the sensitive input it has a tendency to distort and has a rather gnarly, very wooden flavor. The resonance doesn't go very high and self oscillation is not possbile. Also filter ringing for creating percussive sounds is hardly possible but it's prety sweet for low-tuned woodblock sounds.
Audio input and audio output
3U Eurorack module, 20HP wide, 45mm deep
current draw 30mA