Tuesday, 14 December 2010

My favourite synth module - Doepfer A-156 Dual Quantizer

Taking a leaf out of PatchPierre's book I have decided to post an article about a really neat module: the Doepfer A-156 Dual Quantizer.

Firstly what does a quantizer do? Well it is a control voltage processor, it takes a voltage applied to its input and outputs a control voltage that only has certain discrete voltage levels. Normally a quantizer will be used between a step sequencer and a VCO to control its pitch. For instance a chromatic quantizer will only output voltages that are in 1/12th of a volt (83.3mV) or semitone steps. A diatonic quantizer will only output voltage steps that represent the notes of a major or minor scale.

I like the A-156 so much I have two of them.  So what makes it so special?

For a start it is two separate quantizers; In the last week I have heard two people say that Quantizer 1 is not as useful as Quantizer 2 because Quantizer 2 has major/minor scale and chord switches whereas Quantizer 1 is just chromatic. Tone's Top Tip #1: There is a jumper that can be set so that both quantizers use the switches (update 19th Dec: Check out PatchPierre's modification). This is great because now two VCOs can be controlled to give a two-part harmony or in my case with two quantizers and four VCOs, a four-part harmony. This works even if what you apply to the inputs is random e.g. LFO into one and S/H into the other. You only get pitches that sound good together (unless the switch is in the All position) and also first set up both VCOs to be in tune with no CV input applied. I usually tune my VCOs to D with the quantizers outputs set to 0V. With the switch set to major scale what comes out is all in D major.

Top Tip #1 Jumper setting
Tone's Top Tip #2: The Trig In jack means the quantizer can be used as a Sample and Hold (S/H). It will only output a new quantized note when it sees a trigger pulse. Ok so its quantized but it's useful.

Tone's Top Tip#3: The Trig Out only fires when it sees a change on the input that causes a new quantization level to be output - so it's a voltage change detector. The A-156 only operates on voltages that are between 0V and +10V so any negative voltage will not produce a trig output. This can be used to great rhythmic advantage. Try triggering the quantizer with one LFO whilst putting another into its CV input. Trig out only happens when there is a trigger in AND there is a positive CV input that is different to the previous CV input that was triggered. I do this with one LFO into both Trig Ins and another LFO into one CV In and a S/H into the other - use the Trig out's to fire ADSRs to control VCFs/VCAs and vary the rates of the LFOs and S/H to get great rhythmic patterns. 

Tone's Top Tip#4: Also try triggering both quantizers with a LFO and take X/Y outputs from the A-174 Joystick into the CV ins and use the CV outputs to control two VCOs - play nice two-part harmonies with just the joystick.

Tone's Top Tip #5: Try putting a VCO through the quantizer, it mangles the audio in a similar sort of way as a bit-crusher does. It works well at lower frequencies; you can use the CV out and the Trig out for very nasty audio distortion.


In this picture my two A-156s are in the top left next to the MFB SEQ-02. 

Rush out and buy one if you don't have one, better still buy two!



9 comments:

  1. Great post, highly informative and also one of my favorite modules.
    This module makes playing the ribbon controller and theremin more fun too, with an added A-170 Dual Slew Limiter.
    I hope to modify my A-156 soon, by wiring the internal jumpers to an extra switch on the frontside as described here:
    http://www.analoguehaven.com/usercomm/diy/
    Keep up the good work!

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  2. Thanks Pierre. I've been tempted to mod mine but am thinking of using a 4hp panel sat between my two A-156s with the switches on that and using 3-pin sockets to connect the switches to the jumpers.

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  3. I've wanted to pick one of these up for so long, its going to happen 2011 ;)

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  4. Just discovered your blog. It's fantastic.
    I started with eurorack and modular stuff a year ago and I can use the tips and tricks !

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  5. Hi Benjamin,

    Thanks a lot, nice of you to say so!!

    Lots of new bits and pieces coming out over the next month or two so keep an eye out for those. Are you totally a Doepfer user or do you have other manufacturers too? My Eurorack line-up is ever growing and now includes Doepfer, Analogue Systems, Analogue Solutions, TipTop, MFB, DinSync and my own Synovatron modules. I need more rack space!!!!!

    Have fun with your synth!

    Cheers
    Tony

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  6. The A-156 is the key element of the dopfer synth used in the Gusgus live set. There it is used with A-174 to create two quantized pitch benders directed to two of the three oscilators of the synth. Basically can change given baseline to solos with this. https://www.facebook.com/27595561729/photos/a.10150279728641730.356072.27595561729/10150279729246730/?type=3&theater Love BV.

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    1. Thanks for that BV, the live set up looks great. It's always interesting to see what gets used in a live setup - no padding, all grunt! The A-174 and A-156 work very well together; I use two of each. It's surprising how rhythmic and melodic harmonies can be derived from just two A-174 joy-sticks.

      Check out https://soundcloud.com/monakrome/magic-box-2 a bit odd but entirely played on Roland 100m VCOs, LFOs and VCFs using a Doepfer Joystick controlling Roland LFO levels with a pair of Doepfer linear VCAs via a Doepfer dual quantizer, tempo set by a LFO, The filters are controlled manually and also by long time constant ADSRs triggered by the quantizer.

      I will keep my eye on Gusgus!
      Cheers
      Tony

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  7. Ok I get some of it. Im very new to modular systems. Where does this go in the chain if the oscillators only have CV ins. This is probably a really stupid question but I'm confused sorry.

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    1. H Matthew,

      Sorry for the slow response, I have been maxed out on the day job for several weeks now and am just catching up with stuff. Firstly it's not a stupid question so don't be sorry. The quantizer takes a CV source (LFO, sequencer, joystick etc) as its input, its quantized output goes to the oscillator's CV input (preferably an input that is 1V/octave such as CV1 on aDoepfer A-110). There are a couple of good diagrams in the A-156 manual here http://www.doepfer.de/a100_man/A156_man.pdf

      Best
      Tony

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