Doepfer A-108

12

Low-Pass Filter 6 / 12 / 24 / 48 dB

Module A-108 is a completely new voltage-controlled low pass / band pass filter based on the well-known transistor ladder (Moog ladder). The module has an internal 8-stage low-pass filter with different slopes to select from: 6, 12, 18, 24, 30, 36, 42 and 48 dB per octave. Of these 8 available levels, only the outputs of levels 6, 12, 24 and 48 dB are routed to outputs. These appear to us to be the most useful setting arrangement, as the differences are clearly audible. For example, the difference between 24 dB and 32 dB, or between 42 dB and 48 dB is hardly audible. If, however, you need one of the other filter stages to be available as an output, this can be changed internally.

Note: Only 4 output stages are available, which are set in the manufacturing process to the filter levels 6, 12, 24 and 48 dB. By changing the internal connections (jump wires), each of the filter stages can be set to an output, but only four at any one time. A multiway switch could be used, but the preinstalled factory settings (6 / 12 / 24 / 48 dB) represent the best combination - For example: having as simultaneous outputs the slopes 36, 42, and 48 dB make little sense from a music standpoint.

The resonance (or emphasis) can be adjusted manually right up to self-oscillation, in which case the filter will behave like a sine wave oscillator. An external input (feedback) is available for the resonance, which is fed internally to the 48 dB output if no cable has been plugged into the feedback socket. Any other modules can be looped into the feedback path (e.g., a VCA for voltage-controlled resonance or phaser-/ frequency sliders for phase / frequency shift effects).

The frequency is manually controlled (frequency control), via 3 control voltages (CV1, CV2, CV3), whereby separate attenuators are available for CV2 and CV3.

The audio input is sensitive enough that distortion is possible even at normal A-100 levels (e.g., VCO output). In the case of excessive distortion levels and simultaneous self-oscillation (sine oscillator), the self-oscillation will start to decline. This can also be implemented for additional stylistic means.

In combination with the A-135 voltage-controlled mixer and the A-144 morph controller, a filter with a voltage-controlled slope of 6 ... 48 dB can be achieved.

  • Low-pass: 6 / 12 / 24 / 48 dB
  • Width: 12 HP / 60.6 mm
  • Depth: 75 mm (measured from the rear side of the front panel)
  • Power requirement: +40 mA (+ 12V) / -40 mA (-12V)
Available since July 2004
Item number 170862
Sales Unit 1 piece(s)
Width 12 TE / HP
2.111 kr
Including VAT; Excluding kr200 shipping
In stock
In stock

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12 Customer ratings

4.9 / 5

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6 Reviews

B
Doepfer A-108 Filter
Blair 12.11.2013
When I decided to expand my Doepfer Dark Energy mk1 and mk2 setup, the first modules I bought were two A-110 standard VCO's and the A-108 low pass filter.

This filter definitely imparts its own character onto whatever sound source you put through it. It is a transistor ladder design in the style of the minimoog, and having owned and used a minimoog for several years, in my view it captures the sound of that synth's filter, but it is also a great sounding filter in its own right. The A-108 offers 4 outputs that correspond to four filter 'slopes' from 6db, 12db, 24db and finally 48db. My favourite is the 24db output, but they all sound great. As with several of Doepfer's filters, the input stage can be overdriven, which results in a harmonically rich sound, a bit like running a synth through a valve guitar amp.

The filter can be forced into self oscillation if the emphasis ( resonance) is turned up high, and the filter can produce the full range of fat bass synth sounds up to squelchy acid-house stuff.

I really cannot fault this filter, especially at the price. I have other filters such as the multi-mode filter in my Doepfer Dark Energy mk2, and a Doepfer A-101-2 Vactrol low pass / gate module. These all sound good and very different from each other.

My only suggestion is that the A-108 would look great with black control knobs, like the ones fitted to the Dark Energy synths. That would be really cool.
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SD
Fat and Fabulous
Sean D. 24.05.2013
Lovely bread and butter module. Probably the most Moog-like filter Doepfer makes, though it doesn't sound exactly like the classic Moog ladder. By the time I finished my Euro modular I had only kept 3 filters, and this was one of them.
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HT
Good quality Filter
Harry Turner 02.11.2019
Straightforward multi-filter.
No frills
Sounds good but won't set the world alight.

Affordable
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Artificial Birdsong
colon 05.06.2017
I have had the module now for about a week and a half and i am having a great time with it. I used it both as an oscillator and a VCF.

Setting up volt/oct the VCF in self oscillation and modulating it with a Make Noise Maths i was able to create a convincing birdsong, which i have posted on my youtube channel here, used it in the creation of a Karplus Strong patch where it controlled the white noise that fed a delay line used.
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