This 14HP module is a re-imagining of the ARP 1013 octave filter bank that was announced in 1970 by Tonus as part of the 2500 Synthesizer but it never made it into production. It consists of eight band pass filters with their cutoff frequency spaced one octave apart, from 63Hz to 8 KHz.
The filter is very useful for creating formant and vowel sounds. The individual outputs enable voltage control of the filter by using eight external VCA’s – for example the 1032 Mixer & Distributor module.
Description The AM1013 has Op Amp based band pass filters created by a 12dB high pass filter in series with a 12dB low pass filter. Both filters have a Q of 5. This design is similar to the EMS Eight Octave Filter Bank from April 1971. High quality WIMA polypropylene capacitors have been used to ensure a beautiful sounding filter.
The design uses more Op Amps than the Yusynth FFB and has a higher Q of 5.0 rather than 2.7. The Behringer FFB has a slightly higher Q at 7.0 but uses a mix of polyester and ceramic SMD capacitors. The AM1013 has a wider set of frequency bands form 64 Hz to 8kHz, which is more versatile than the Moog style range of 125 Hz to 5.6 KHz and there are individual band pass filter outputs.
The eight filter outputs are mixed into a single output with two jack sockets. Each filter is adjusted for level using the potentiometers with blue ARP 2500 style control knobs. The input and output levels can also be adjusted using the front panel potentiometers (with green coloured control knobs).
The filter has a bypass feature which is set by using the momentary push button switch which latches on/off (with green LED indicating bypass is active).
Use Cases The AM1013 pairs nicely with the AM 1032 Mix & Distributor module, where each band pass filter output can be patched into a VCA, enabling time domain mixing of the fixed filter sounds. Here are some more patch ideas:
- Add a feedback loop with an AM1042 channel providing variable attenuation, with the VCA output patched into the second AM1031 input.
- Buy two and process different sides of a stereo pair with different band pass setups.
- Process echo delay tails via the FFB.
- Patch individual outputs into a filter such as the AM1031.
Connections There are twelve 3.5 mm jack sockets on the anodised aluminium front panel:
- IN 1, IN 2 – audio signal inputs with level control
- OUT 1, OUT 2 – audio signal outputs with level control
- INDIVIDUAL OUTPUTS – eight direct outputs, one from each filter
There are high quality Alpha rotary potentiometers for adjusting the level of each octave filter into the final mix, and for adjusting both the input and output levels. The module comes with a set of M3 mounting screws and washers, and a standard 10 to 16-way Doepfer power cable.
Outcomes & Availability The AM1013 prototype was developed in the Spring of 2024 and worked amazing well. Production modules started shipping from August 2024, please check our webstore for stock.
For effect pedals it is generally accepted that when it is active, e.g. bypass is inactive, the associated LED is lit. This is just the other way round than the description of the AM1013 pedal. So i would recommend a jumper or bitswitch on the back to be able to change this functionality if so desired.
Otherwise i think the AM1013 module really is a must-have in a EuroRack modular ARP 2500 re-creation rack, and should be equally appreciated in any EuroRack.
Many thanks for the positive feedback and the second run will have LED lit when bypass is off. Best Regards Rob