4-channel mixer and multiple

When mounting different modules in one of my cabinets I ended up with a small empty space, 3HP. The reason for this is that I mixed “standard” 8HP modules (DIY and Doepfer) with 5HP and 10HP modules (Eowave). Since the space is too small to add much controls on a front panel, I thought about adding a small blank panel covering the empty space. But, on the other hand, you’ll always need to be able to split and sum signals, why I built a small 4-channel mixer and multiple. The module mixes up to 4 signals without any level controls, and distributes the mix to 4 independent buffered outputs.


4-channel mixer and multiple

The module works fine for both audio and CV signals, and can easily be soldered on stripboard.

4-channel mixer and multiple

4-channel mixer and multiple soldered on two small stripboards


Mod wheels

I had two mod wheel from an old MIDI keyboard laying around, and thought it would be nice to have another control source in the modular, something that’s not that small that Eurorack tends to be… However, a mod wheel with only a volume control felt a bit boring, so I decided to add something else. One of the mod wheels had a spring making it return to the middle position and made it into Pitch bend wheel, with controls for the pitch bend range. I added three trim pots to adjust DC offset as well as range, it’s certainly not perfect but works good enough.


Pitch bend wheel

It turned out a rather nice module, not very sexy or exciting, but useful. The second mod wheel did not have a spring, but stayed at the set level.  To make it into something more exciting I added an internal clock source. There’s also an input for an external clock source for syncing the module with other modules. The clock signal in turn, controls a stepped triangle or ramp wave which is sent via the input to the wheel and then (buffered) to the output. If any signal is connected to the input, this will override the internal stepped wave, and then the module might be used as an buffered level control.The stepped output might be used as an arpeggiator where the mod wheel sets the range of the arpeggio. An external CV quantizer i highly recommended to get correct tones…


CV wheel with built in stepped LFO

Both these modules turned out nicely. They are useful, and fairly easy builds, in the way I enjoy to make music with my modular setup.


Doepfer A-156 Quantizer

Doepfer A-156 Dual Quantizer

The Doepfer A-156 Quantizer comes in bubble wrap with the mounting screws in a zip bag. As usual with Doepfer modules the manual is not included, but downloadable from Doepfer’s web site. At the first glance the module looks a bit dull, almost boring; nine jacks and three switches on an anodized aluminum face plate. However, the layout is easy to follow and makes patching a simple pleasure. As for all other Doepfer modules the A-156 feels sturdy enough, with good build quality.

The A-156 Quantizer is 8 HP and is easy to mount with the two supplied mounting screws. The module is divided in two parts: Quantizer 1 and Quantizer 2. Patching it up is easy, with four jacks for Quantizer 1 at the top, four jacks and three switches for Quantizer 2 below, and an additional transpose jack controlling both quantizers located at the bottom left corner.

By default Quantizer 1 is in chromatic scale (or All as Doepfer calls it). That means that Quantizer 1 will adjust all CVs to the nearest semitone according to the chromatic scale (i.e. voltage steps of 1/12 V). However, by moving a jumper (J1) on the circuit board Quantizer 1 can be controlled by the same three switches as Quantizer 2. The first of these three switches is the Scale switch: All (Chromatic), Major, or Minor. In the All setting all 12 semitones in the octave is used, in Major only the tones in the major scale is used, and in Minor the minor scale is used. This is really handy since it will help you set the right pitch CV for your track. If the Scale switch is set to All, the second and third switch have no function.

The second switch, Mode, selects the output mode: Scale, Chord, Fundamental & fifth. In the Scale mode the quantizer outputs all pitch CVs (tones) within the scale set by the Scale switch (major or minor), in the Chord mode the quantizer outputs only the three tones that build up the chord (major or minor depending on the scale switch, e.g. C E G for a C major chord, and C Eb G for a C minor chord), and in the Fundamental & fifth mode the quantizer outputs only the fundamental and the fifth tone (e.g. C and G, if the fundamental tone is a C). If the Mode switch is set to Scale the third switch has no function. The third switch, Sixth/Seventh enables the addition of a sixth or seventh tone to the output CV. In position “-” this function is disabled.

The trigger input sets when the quantizer should read and quantize an incoming CV. If no external trigger source is provided incoming CV will be quantized at the internal rate of 500Hz. The trigger out outputs a trigger pulse of 10ms every time a quantization takes place, i.e. every time the output CV changes. This trigger signal might be used to trigger other modules, e.g. an envelope generator, with every note change from the quantizer.

Transposing the quantized CV is easy to do by applying a CV at the Transpose CV in. The CV will be quantized to the nearest correct semitone and then both quantizers will be transposed. It might be worth mentioning that it is only possible to transpose upwards since you can only add a positive voltage, and up to maximum output CV of +10V. If you add +0.0833V you’ll transpose one semitone (1/12V), if you add +1.0V to the transpose input you’ll shift the quantizers one octave up. There are ways of working around the limitation of positive transpose voltages. You could, for example, start with adding +1.0V to the transpose CV input and tune your VCO to the right octave, if you then decrease the voltage at the transpose CV input you’ll transpose to a lower tone than the original one. So, if you would like to change chord from Bb major to C major this is easily done by adding +0.166V (two semitones) to the transpose input. However, if you then want to go to a G minor a transpose change is not enough but you need to switch Scale from major to minor as well. Then you need to switch back to Major and add another CV to the transpose to go to F major. After a while you’ll wish for CV control of the Scale, Mode, and Sixth/Seventh switches.

A small problem I’ve noticed is, if your pitch CV is too far away from a “real” note you’ll get some artifacts from the quantizer. It might be due to it is shifting very fast between two semitones or some kind of aliasing effects, resulting in a poor CV signal which creates a growling sound from the VCO. The VCO will be in tune but sound harsh. If this is the case you need to adjust your CV source to be closer to the correct voltage to avoid this.

To summarize, apart from the problem with the sometimes harsh CV output and the wish for more CV controllable options, the A-156 works very nicely, adjusting CVs from sequencers to warmed up tuned VCOs creating beautiful music.
Ratings (1 = poor, 5 = excellent)
Build quality: 4
Functionality: 3
Audio quality (if applicable): –
Ease of use: 3
Cost/Bang for your buck: 3

Comparison chart
Category: Utility
Controls: 1x Scale (3-position switch: Chromatic, Major, Minor), 1x Mode (3-position switch: Scale, Chord, Fundamental & Fifth), 1x Sixth/Seventh (3-position switch: None, Sixth, Seventh).
Inputs: 2x CV in, 2x Trigger in, 1x Transpose CV in.
Outputs: 2x CV out, 2x Trigger out.
Size: Width: 8 HP, Depth: 55 mm
Power consumption: +12 V = 50mA, -12 V = not specified, +5 V = not specified
Price: 120.00 € / $175.00

Pittsburgh Modular M3 – Audio and Control Voltage Signal Router

Pittsburgh Modular M3

The Pittsburgh Modular M3 is a very usable utility module. In every modular system there is need to be able to split as well as mix signals and CVs. The M3 consists of one multiple and two mixers/signal splitters. The multiple is passive, which means that any of the four jacks can act as input and the rest as outputs. There are some possible drawbacks with a passive multiple compared to a buffered multiple. For example, the setting in one module might backfire and affect the other modules in an undesirable way via the passive multiple. But with that said I do not mean that there is no use for a passive multiple, they are usually cheaper and any jack can act as input or output which might come in handy. The mixers have two inputs and two outputs and each can be used as a two-channel mixer input and a two output buffered multiple. If both mixers are patched in series you can achieve a three-channel mixer or a one input to three buffered outputs multiple. With the multiple and the two mixers patched together the M3 can perform a wide range of functions at once.

I have never been too excited about Pittsburgh Modular panel layouts, but the M3 is simple, concise and lucid. Strangely enough Pittsburgh Modular has marked the passive multiple with one input and three outputs, but since it is passive all jacks can work either as inputs or as outputs. There is no manual available, but I really doubt the need of a manual for this module. It is easy and intuitive to work with, despite the somewhat ambiguous panel markings.

To summarize, the M3 is a useful tool for every modular, even if Pittsburgh Modular have made some questionable panel layout choices.

Ratings (1 = poor, 5 = excellent)
Build quality: 3
Functionality: 3
Audio quality (if applicable): –
Ease of use: 5
Cost/Bang for your buck: 3

Comparison chart
Category: Utility
Controls: Not applicable.
Inputs: 1 passive multiple in, 2x mixer in x 2.
Outputs: 3x passive multiple out, 2x mixer out x 2.
Size: Width: 4 HP, Depth: 20 mm
Power consumption: +12 V = 20 mA, -12 V = not specified, +5 V = not specified
Price: 59.00 € / $59.00