Filters VIII: Doepfer A-106-5 SEM Filter

Yay... finally a new filter-module :-)
Last week i treated myself with an A-106-5 SEM Filter.
The A-106-5 is a 12dB multimode filter that is based on the filter circuit of the Oberheim SEM module (Synthesizer Expander Module), Oberheim's first official analog synthesizer that was produced from 1974 to 1979.

On the outside it looks quite like the A-124 Wasp filter, but sound-wise they are very different.
The filter is equipped with a band pass output and a combined low/notch/high pass output.
For this output a control knob defines the relation between low and high pass signal.
If both signals appear at the same level (i.e. middle position of the Mix knob) one obtains a notch filter. Otherwise the low or high pass signal predominates.
The module sadly does not feature self oscillation in contrast to most of the other filters of the A-100 system.

I had heard some good things about it, and it really sounds incredible.
I do have a slight preference for 12dB filters (like the A-121 Multimode Filter and the WASP filter - two of my favorites), and this one is another great sounding filter module.

The sound is hard to describe but i can say this one sounds fat enough for me (not very thin like most reviews say), and is already in my favorite filter-list.
It does not sound like any of the other filters that i own...
The only thing i miss in this filter module is an CV input to control the resonance, just like the A-121 Multimode Filter or the other Oberheim filter, the A-122 24 dB Lowpass filter VCF3 have.

Video: Doepfer A-106-5 Filter demo

" Short Doepfer A-106-5 Demo by NetPierre
Starts with a sequenced bassline, generated by my Doepfer MAQ16/3 and Doepfer VCO A-110 (saw wave)
Bandpass Mode first,  LP/HP later
A-118 Random voltages added to VC2 input somewhere in the middle.
Drums provided by an Elektron Machinedrum
More info on the A-100 and related stuff at http://PatchPierre.blogspot.com "

Also check out http://blog.andreaskrebs.de/2010/05/08/doepfer-a-106-5-sem-filter-example/ for sound examples and find more A-106-5 on YouTube

Filters II : A-121 VCF2 Multimode Filter

The first Doepfer filter that i ever bought was the A-121 Multimode Filter. It is a 12 dB/Octave filter, and has multiple simultaneous outputs available; a Low-Pass, Band-Pass, High-Pass and Notch (or Band Reject).
It also has 4 CV inputs, 2 for adjusting the cutoff frequency and 2 for resonance.

This is still one of my favorite filter modules, the multiple outputs are very useful, and i  like all the CV inputs. It just gives you so much more control over the filter, and that's what i like most in a module; maximum control.

Although it is 'only' a 12 dB filter it sounds very nice, from very smooth and warm up to quite rough, especially with the resonance turned up ( ...up to self-oscillation ).
Most of the times i patch an A-174-2 Wheels CV into FCV1, and a simple envelope CV to the (adjustable) FCV2. Works fine in most situations.
With some analog or digital noise added to QCV2 to give it a touch of unpredictable resonance you will quickly get a convincing fat bassline.

Together with an A-138 B (exp) Mixer you can easily make some pretty impressive stacked bass-sounds, all with just a single filter-module.

Find A-121 sound examples at Andreas Krebs Blog : HERE

As the special circuit CEM3320 used in this module is no longer available the module is discontinued. I believe there are still a few available, but they don't make new ones anymore. Doepfer advices modules like the A-106-6 ( with eight simultaneous outputs! ) or A-107 Multi-Type Morphing Filter as a replacement.