Tuesday, 21 December 2010

Preview 2011 - the next module

Here's a sneak preview of the next module on the drawing board with a working title of "Diode". I'll leave you all to guess it's function - hopefully if I've done the front panel design right then that should be an easy task for you. Answers on a postcard.....

What's happening with CV Tools? Just having a last minute ponder and double-double-check before I commit to copper (and expense). I expect the first batch of production models to be available by the end of January.

Here's a question: The colourful high-res graphic front panel designs are cheap and easy enough for me to produce for prototypes but will be a more expensive for a production run. 
Does a nice front panel in a range of bright and colourful styles interest anyone or are we only interested in function?

I'd be grateful for any comments.

This will probably be my last post in 2010 so I just want to wish you all a happy, safe, fun and rewarding 2011. Keep those analogue modulars throbbing out amazing sounds.... Tony

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!

Tuesday, 7 December 2010

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: