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!

CV Tools Module prototype is fully working

The CV Tools Module has been prototyped and with a few minor tweaks is working very well.  

It's actually surprised me how much fun it is to use and how useful it is for getting those all important modulation adjustments right.  

It's very versatile in single, dual, triple and quad channel modes, adding, inverting, scaling and offsetting (or combinations of all). It works well enough as an audio mixer too.  The slew control is great for adding just that little bit of portamento to really slugging step changes. 

Here's a couple of photo's of it at work in my synth alongside Doepfer, MFB and TipTop modules.

Still considering a few changes such as polarity indication LEDs.  Any thoughts on features you might like to see? Oh and did I mention that there is a rear port so that one or two of these can be coupled up to a gate sequencer (next project) to give step sequencing similar to the function of the bottom half of the Doepfer sequencer (DC, modulation or audio sequences)?

The prototype used my Kit 1 and Kit 3 DIY boards too - here's a (slightly unfocused) photo:

Progress Update

Well, over the past few weeks Synovatron Electronic Music has been registered (the tax office now knows about me), the first batch of DIY kits are half sold and I have customers in UK, Sweden, France and Turkey. 

I have had a really nice write-up from a great synth enthusiast Pierre Serné.  Thanks for that Pierre! Please visit his blog.

I have added some new pages to the blog - Feedback, Modular Sounds and CV Tools Project. Feedback is a place to make any comments or suggestions (and a bit of shameless self-promotion). Modular Sounds is about the 'music', or you may prefer sounds, that I have made with my modulars. CV Tools Project is a blog-style, step-by-step, account of the design lifecycle of my CV Tools module which aims to be both educational and a subliminal sales ploy (_8-(|) doh!

First Eurorack DIY Prototyping kits and cables are now shipping

The first orders have been received and are now being shipped. 

Synovatron Electronic Music is underway!!

Eurorack synth prototyping products now available

Please check out the product and support pages on this blog. 

Kits and cables are also available through eBay; just search "Modular synth prototyping kit" or click here

Update on New Eurorack modular synth prototyping kits - Circuit boards have arrived

The new DIY prototyping circuit boards have arrived. They look good and the quality is very good.

The pots, pot brackets, headers, caps and jacks all fit which which is a huge relief.  To give you an idea of what they'll look like assembled checkout the preliminary piccies below of both types of board with some components assembled ready for prototyping to start. Note I have added some LEDS to one of the DIY2 boards too.

Time now to sort out the packaging, data pack, options and pricing - about another week before they become available.

Update on front panel artworks

Just thought I'd give a little more detail on front panel artworks as there is already some interest.

The picture below of my module currently in development shows the CAD drawing for a 12HP front panel in the top left. The adjacent front panel overlays show an evolution from a very simple, flat looking artwork to more 'sexy' metallic looking and coloured alternatives with some apparent depth.

 
Edit 08/07/11: The following graphics, based on ink-jet/laser printable vinyl overlays, was attempted on the first off batch of CV Tools modules but has been withdrawn in favour of a standard screen printed panel for two reasons. The first was that it was not liked that much by customers; people saw it as a cheap label. The second was that it was expensive and difficult to apply accurately. I will still use the overlays for prototypes.Please read the following but note it has all been superceded by events.

My task is to make this a service that is affordable by streamlining how I go about setting out the pot scaling, legends, functional grouping (separating lines or boxes). A good place to start from is if you use Schaeffer Front Panel Designer to get the panel made then I can use the DXF file generated to align the graphics to the holes; obviously with as much description from you as possible about what you actually want to see.

The one-off 2mm anodised panel from Schaeffer cost me 27 Euros (about 23GBP, $35US but it is beautifully machined!!); I anticipate the cost of an artworked plastic overlay would need to be less for that size panel to make it attractive, including my design effort (that's why I need to streamline the process - the slicker I get the more viable it'll be!).

The hardest part is lining up the overlay accurately on the panel as the overlay is self-adhesive. I'm getting quite adept at this now as I have prototyped several overlay types. You do get several chances and I may include a spare.

I am still developing the technology as it needs to have great graphics, be cheap to make whilst still having good wear and scratch resistance properties.  This balance is not easy and I will still need to explore better processes and techniques so initially this will be for smaller prototypes with some caviats on how much abuse it can handle. The artwork is great quality though and the durability is reasonable but could be better. The price will reflect this fact. Having said all that I'm going to use it in my system as it stands as I don't tend to abuse my hardware.

Any suggestions and comments would be most welcome.