Modular in a tool case

I had a day free on Saturday and set about putting a modular in a tool case. To be exact it is a Doepfer A-100 DIY kit #1 fitted to a Halfords engineers tool case. The point of this was to have an easily transportable demo system so I can take to shows, meets etc in order to show how lovely my CV Tools module is and to let people have a play.

In a follow-on to my cheap DIY store front panels post a few weeks back I used anodised aluminium angle strips in the construction from Homebase - the case is bigger than the 6U 84HP of the rack kit.
(Note to non-UK readers Halfords is a motor accessories store and Homebase is a DIY store)

Here's the case

Prep the case - remove separators, tool panel and unecessary fixings.

All done, ready to start serious modding

This will be powered by a 15VAC supply so a nice big hole for an XLR connector

XLR in place (EDIT: this is eventually replaced by a plug version as a power lead with exposed pins is bad karma)

A bit of judiscious foam cutting to neaten it up

Markout and drill the regulator boards fixing points - 4 x M3

Regulator screwed in place

I used M3 washers to spread the load - the case is just hardboard with a thin aluminium veneer

Position the bus boards and drill mounting holes - long M3 screws with tapped spacers fitted

All electrics now in place. Note this is temporary - there will be wiring to a front panel power switch on the next installment!

Next make the rack end pieces out of 10mm x 20mm anodised aluminium angle strip. These make the rack the perfect width to fit the case.

Similar to above I made top and bottom strips to fill the gap - I used 25mm x 25mm anodised angle, again an almost exact height fit - starting to look good.

Here's a view showing the fixings (ok I drilled a hole in the wrong place. Motto: measure twice, cut once!!!).

As I said a near perfect fit in the case. At this point just resting on the foam and not screwed in. That's in the next installment.

Loaded with modules and powered up. Take no notice of the modules selection, I've since changed it to a more coherent set.

Even a nifty scope showing VCOs, Synovatron DioDe and CV Tools in operation - now that's a waveform!

 Next installment will add a power switch and fixings to anchor the rack to the case. It will also make use of all that front panel space top and bottom for passive and buffered mults, bus access, simple LFOs, gate logic, 3.5mm to 6.25mm/RCA adaptors, etc etc (the thought of the lovely goodies that will get built in is going to keep me awake a night - so sad!!)

Here's a short clip of it working:-

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!