333 Utility


ProAudio Sum and Distribution

333: three sections, each with three inputs and three outputs.




90,00  + VAT

In stock


The 333 is a summing and distribution module for Eurorack modular systems.

It is composed of three identical sections, red, yellow, and green, each of those featuring a three-input summing amplifier with three independently buffered outputs.

Derived directly from the CGM creative mixer series, the sum section is DC coupled, allowing the sum of control voltages as well as audio signals.

With an extremely low tolerance in both sum and output sections, it is also suitable for summing quantized voltages like the ones coming out from the quantized outputs of the SAPEL.

In case CVs or audio signals are particularly hot, the 6dB attenuator might be helpful to reduce exactly by 50% the incoming signals.

The red and yellow output are also normalled to the first jack socket of the yellow and green input: in this way, this module can also work as a 1-to-9 buffered multiple.

Key Features

The 333 architecture allows you to use it as a mixer, as a buffered multiple, or both.

You can use the three sections together for sending one signal to up to nine outputs, or you can use the three inputs of a section to mix as many sounds or CVS.

Each section’s output is semi-normalled to the following one’s input so that you can blend up to seven signals.

The 333 borrows some design choices from the CGM so that you can mix audio signals with an excellent summing stage and duplicate them.

The inputs are DC-coupled and allow you to precisely sum CVs as well.

All nine outputs are buffered to guarantee a high multiplication fidelity.

Your V/oct signals will be safer than ever!

If your audio signals are too hot, each section has a -6dB switch to halve the amplitude. If you patch CVs, they will be divided by two.

Since the three sections are connected, you can cascade the three switches and get -12 and -18 dB in the second and third sections, respectively.




Additional information

Weight 0,143 kg
Dimensions 15,6 × 6 × 6 cm



6 HP


38 mm

Current draw

48 mA @ +12 V

48 mA @ -12 V

Recommended warmup time

30 min

Input impedance

> 90 KΩ

Output impedance

< 50 Ω

CV tolerance

< 0.5%

Global CV offset per section

-20 to 20 mV

Frequency response

DC to 30 KHz

Harmonic distortion (THD+N)

< 0.01%

More details on the Manualone.


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A. Use

Our modules are packed with high-quality components that demand a proper power supply and can get sensibly warm.

That is its normal temperature and we can guarantee their performance.

The red led show positive signals while the yellow show negative signal. If you fed a section with a bipolar pulse signal, they would change their color from red to yellow according to the current signal polarity. If you feed a section with an audio rate signal, they will seem to be completely lit up, but they are actually oscillating between red and yellow as many times per second as the signal’s frequency.

You can achieve some results similar to the OR behavior when using trigs, but there might be some differences. If you patch, for example, two gate-on signals (say 5v each), a Boolean OR will output one gate (say 5V). If you patch the same two gates to the 333, it will output 10V (5V+5V).

B. Design

We have two main kinds of capacitors.

The first one is necessary to AC-couple the audio signal: they prevent any unwanted DC offset, and they offer protection against wrong connections. For this reason, you can patch nearly every input to every output, and the worst thing that can happen is some pops or some silence.

The second one is power filters to guarantee a cleaner current flow across the case. They might sound a bit over the top, but we must remember that a Eurorack system is not something that comes straight out of the factory. Instead, every Eurorack setup is unique and may change according to the musician’s need. For this reason, we want to add as much protection as we can, both to avoid issues with our modules and to ensure that even the other modules behave correctly. We use a wide mix of capacitors in our modules: ceramic, electrolytic, tantalum, and multilayer. They can be assembled thru-hole or SMD, according to what gives the best balance between result and space. For example, all the electrolytic capacitors are mounted thru-hole because they perform better according to our tests.

However, the capacitors have zero impact on the power draw, on which you can read in this other FAQ.

Power draw should always be related to what a module does.

Generally speaking, there are modules like SAPÈL that undoubtedly consume more than other random generators. However, SAPÈL is a double module, so a fair comparison would be between it and a pair of similar modules. The same can be said for FUMANA, the most power-demanding filter bank. However, it is also the only Eurorack filter bank with 32 analog bandpass filters, half of which have a 48 dB/oct slope. So, also in this case, a fairer comparison would be between FUMANA and TWO other 16-band filter banks, which leads to similar power consumptions.

More in detail, we engineer our modules to be safe to use. To protect both the modules and the rest of the case, we add a proper buffering stage to every input and output: even if a single buffer doesn’t draw that much power, all the ins and outs piled together can significantly impact the final power draw.

C. Shop

Yes! We opened our online store in October 2022. Check out the full catalog!

Our resellers receive our modules exclusively through our distributor, so we do not have access to the individual shops’ orders or stocks.

We restock every module at least once over a year: we focus on a module’s batch at a time, then we move on to the next one, and so on.

If you want an estimated delivery time for a specific module, drop us a line! We’ll be happy to answer you.

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