What about … Dual Function Generators

Today we have a look at three modules that can be described as Dual Function Generators – the Make Noise Maths, Befaco Rampage  and the Serge Dual Universal Slope Generator (DUSG) by Random Source. Dual Function Generators follow the same core principal – they can do whatever you want them to do. What seems a bit of a stretch is of cause one, but it is closer to being true than you might expect. Because these circuits usually don’t just do one thing, but can be anything from a VCO, Slew Limiter, Envelope, Trigger Delay, Filter and so on. These multi-functional tools are very popular in modular synthesizers since the early days. There was the Envelope Shaper from the EMS System and the Dual Universal Slope Generator from the early Serge System for example – and the Serge module is now available for eurorack.

And why it is a great idea to put two function generators into one module is shown by Make Noise Maths and Befaco Rampage. Both take the signals from their two sides and process them independent from your regular output. Maths for example gives you a mixing stage with additional inputs, attenuverters and four outputs. Rampage takes the generated signals from both sides and compares them in an analog logic section. Both modules try to create as much useful information from its generators as possible. They do point in different directions, but are both useful additions for almost any system. Another nice aspect with having two function generators in one module is being able to modulate one side with the other. With voltage control of several parameters, mixing stages, trigger outputs and more, these modules are not just real all-rounders but also boosters for creativity.DFG_quer_groß

But first let’s have a look at the basic structure of these modules and one of the common use-cases: A dual function generator usually consist of two more or less identical sides (left/right) that can be used independently. A typical use for them is to work as envelopes or LFOs. Therefor the modules provide inputs that expect triggers or gates to start generating the rising and a falling CV of an envelope, both can be modulated with CV so that they can have variable lengths. Maths, Rampage and DUSG all provide a cycle switch that restarts the generated envelope as soon as the Rise and Fall stage are completed – now the module functions as a LFO. All three modules have Trigger/Gate inputs to start the Rise/Fall CV, voltage control of both of these parameters at the same time and individual voltage control of both parameters, variable envelope characteristics and END-OF-Something outputs. All three modules have an input jack and a dedicated Trigger input. While using the Trigger input the resulting envelope will always consist of only two stages – Rise and Fall. While using the other input to start the envelope it is possible to implement a Sustain stage to the envelope. The duration of the Sustain stage is just as long as the gate is high minus the time of the Rise section. With all these features it is possible to very precisely shape envelopes – way more complex and versatile than many other envelope generators. While losing the Decay stage of an ADSR, you get voltage control of the remaining stages and the possibility to precisely work on the shape of the envelope. the normal input jack is also the way to go f you would like to use the modules as slew limiters for example. But as we can not discuss all the possible functions here, let’s focus of what sets the modules apart from each other – for example their size: DUSG (26hp) > Maths (20hp) > Rampage (18hp). And there are more differences:

Befaco – Rampage

The unique part of the Rampage module is the central logic and comparator section that creates signals from the differences between both sides of the module. Using the Balance control you can determine the weight between the left and right function generator. MIN is an analog AND gate, which outputs only the minimum voltage. On the other side the MAX output only emits the currently highest voltage. B>A is a circuit comparing the amplitudes of both curves and generating a pulse when B higher is than A. Additionally there is a slope detector on both sides of the Rampage. This means the module outputs gates while the current slope is rising or falling. Depending which slope is given, either the rising out or the falling out emits a gate signal until the slope changes again. AND: The Rampage has a dedicated trigger button for both sides, so you can manually trigger the envelopes – very handy!

Random Source – Serge Dual Universal Slope Generator Mk2 (DSG)

The Serge DUSG is a direct successor of the original design in 4U format. The eurorack version has been slightly revised and optimised, for example the tracking when used as audio oscillator. Therefor both sides feature dedicated 1V/Oct input jacks. This is something that separates the DUSG from Maths and Rampage – these two do also work as audio oscillators but are not able to track the 1V/Oct standard reliably. In general the DUSG is pretty straight forward when it comes to usability and the user interface – if a clear layout and comfortable spacing is one of your main concerns when deciding on a module, this is the Dual Function Generator to go for. …and it sounds great as an audio oscillator!

Make Noise – Maths 2

The Make Noise Maths might be one of the most important eurorack modules of all time. It has been around for a long time and still is one of the most recommended modules when it comes to planning a new system. The envelopes that can be created with Maths are considered to be especially snappy and musical. What Maths brings to the table besides two envelopes/oscillators is a four channel mixer with individual and mixed outs, end of rise, end of cycle and logic outputs. This attenuverting mixer section doesn’t seem to be very exciting at first, but it is one of the most useful additions in “Dual-Function-Generator-Land” – with its ability to not only mix but also offset, attenuate and invert signals!

All in all these are three great modules that will all add something special to your system. You really cant go wrong with any of these modules and therefor it is a thing of personal taste, the little aspects described above that differ, or maybe size that can give the decisive momentum.


And as always:

This is by no means a complete overview of available modules nor a full review of the discussed modules. The what about… text are here to give you new ideas and maybe another perspective on things. All these modules offer more features than we have talked about in this post. For further information please click the provided links or – even better – visit the SchneidersLaden and ask our experts in the showroom.


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