Tag Archives: #stepontothefuture

MOD Duo’s Hi-Fi Soundboard Unveiled

This is a testimonial from Rafael Guayer, our Hardware Design Engineer and Barbecue Manager.

It was a great challenge to develop a soundboard from scratch. After working with ultrasound frequencies, where the sampling frequencies reached 80MHz, I thought it would be easy, but it wasn’t that simple. Sampling and reproducing sound is not only about physics and engineering specifications. It has a subjective approach, for the nuances of sound are highly human-dependent. In these digital times we are looking back to some old analog concepts. It’s like the parallel between the CD and vinyl, and silicon amplifiers and tube ones.

The MOD audio processing is all digital. We wanted the most “analog-ish” sound conversion and we wanted the sound to be warm and colorful, but most of all we wanted to satisfy an “audiophile ear”. So we started digging into some concepts to reach the best balance between the digital and analog domains, and also to make an economically viable product. It wasn’t easy at all!

MOD’s Release Canditate 1 Audio Board with components

The first piece of the puzzle was the domains converter, the analog to digital (ADC) and the digital to analog (DAC) converters. We chose an external audio codec from the renowned manufacturer Cirrus Logic, which is known to produce great sound converters. Here we faced some challenges like poor documentation and support, and the fact that there was no driver available for the chosen codec.

Being a multi-purpose device, and thus, multi-instrument, the MOD needs an input circuit that adapts the different electrical characteristics of each instrument to match the ADC. Normally in this kind of equipment you see push buttons and other switches used to toggle different input impedances. But it is known that these mechanical devices can introduce sound artifacts and that their contacts don’t last forever .

An engineering and design task was in our hands - we had to develop a flexible impedance input with no mechanical components that was digitally controlled directly from the soundboard driver. The solution was an impedance bridging circuit based on internal switches that changes the resistor network directly connected to our input. Here we faced the dilemma of using modern switches that would make our life easier. But instead of using small and cheap CMOS switches, despite its great engineering specifications, we’ve chosen to use discrete JFET switches, which are less complicated silicon components and more suitable for audio.

Then we came into the black magic of passive components. How could capacitors and resistors with the exact same specifications sound so different? Here the sky was the limit, I mean, our pocket was the limit! At higher costs, we are using only components that are known for their sound quality. We use only metal film resistors, and metal film and special electrolytic capacitors. We don’t use any resonating surface mount component in the soundboard. And we are experimenting with many different brands to get the best trade-off between quality, availability and price. It’s a pleasant surprise to see how different these components sound.

We took extra care in choosing the operational amplifiers and their topologies. Even the sound decoupling voltage bias is an active filter, not only a voltage divider.

The layout of the printed circuit of our soundboard was treated like a baby. A bad layout can ruin a great project, so the small sound signal path was carefully routed, and we ended with a great quality sound device.

We’ve made a prototype that sounds great. We’re working now with the release candidate product and we are sure that it’ll sound even better. We are still experimenting some solutions but we already have the initial specifications of our soundboard:

MOD DUO’s Sound Board Initial Technical Specs


2 independent inputs 

- 1/4′ TS connectors
- Digital input impedance selector | line / microphone / instrument
- Programmable Gain Amplifier: ± 12 dB Gain, 0.5 dB step plus a 32 dB gain stage for microphone

2 independent outputs 

- 1/4′ TS connectors
- Volume Control: 0 to -127 dB, 0.5dB step

Headphone output

- 1/4′ stereo connector
- Digital volume control from +12dB to −33dB

Neutrik® connectors
True Bypass circuit


- Instrument: 500kΩ.
- Line: 75kΩ.
- Microphone: 3kΩ.


- Manufacturer: Cirrus Logic
- DAC: 104dB Dynamic Range. -90dB THD+N
- ADC: 104dB Dynamic Range. -95dB THD+N
- 24 bit / 48 kHz AD/DA


- Manufacturer: Texas Instruments
- Class AB Amplifier
- THD+N at 1kHz, 105mW continuous average output power into 16Ω: 0.1%
- THD+N at 1kHz, 70mW continuous average output power into 32Ω: 0.1%


- Dual Core ARM A7 1.0GHz
- Dual/Quad Core ARM A7 1.5GHz (Stretch Goal)
- 1GB RAM - 4GB Flash Storage


- 2 knobs with LCD screen
- 2 foot switches with color LEDs


- MIDI IN connector – DIN 5 pins – for musical instruments and controllers

- MIDI OUT connector – DIN 5 pins

- Control-Chain – RJ-45 – for additional controllers

- USB HOST - USB 2.0 Standard-A type
- USB Bluetooth
- USB Wifi

- USB DEVICE - USB 2.0 Standard-B type
- USB Ethernet Adaptor
- USB Audio 2.0 (Stretch Goal)

We are still improving the soundboard and we need your help with this crowd funding project so we can make the best sound quality available in MOD Duo.

MOD Duo - This week on Kickstarter

The MOD Duo crowdfunding campaign will be launched this week on Kickstarter.com

Stay tuned to buy the MOD Duo with a huge price discount.

We will also have stretch goals during the campaign in order to produce the MOD Duo with even better features, such as a 24 bits USB audio interface, an unibody aluminum casing and a 50% faster processor, so help us to spread the word!

The more people involved in the campaign the better MOD Duo will get.

Register your email at: portalmod.com and be informed 24h before the campaign starts!

We are counting on you to help us produce the Last Live Sound Processor You’ll Ever Need!

Thanks a lot!

The MOD Team


When a developer wants to create or port an effect for the MOD Duo, the first thing to understand is that our plataform relies in an open standard, the LV2. It’s similar in scope to VST, AU, LADSPA and others, with one great feature that makes the MOD concept possible: It can be freely extended, so new functionality can be added to LV2 by anyone, making distributed development of the plugin API itself possible. So, hundreds of LV2 plugins used in desktop systems can be installed in MOD Duo live sound processors without modifications. Besides that, there’s the possibility of creating a custom HTML5 interface for each plugin, using the MODGui LV2 extension and our SDK. Continue reading

Twisting the saxophone with the MOD

The saxophone player Marcelo Coelho is one of those few musicians that has the experience of many.
Besides teaching for years in different music schools, he released several authoral albums and has been playing with many influential musicians in small clubs, large concerts and orchestras.
He knew the MOD a few weeks ago and now he is back to our studio to try some different texture for his saxophone.
We recorded all this experience and you can see for yourself what an amazing musician can do with the endless possibilities of MOD.


Why Linux?

Many people that are not familiar with Linux have this idea that it is a “simpler” version of operating systems. I’ve heard friends of mine saying that they thought that Linux was a cheap version of Windows or Mac. This is a huge mistake. In fact, the reality is the opposite. Continue reading

The flutist and the DJ

A small video showing Laura Sobenes playing the flute and Bruno Gola, a DJ, using the same MOD.
With 2 audio inputs + MIDI input,  the MOD allows you to use up to 3 instruments simultaneously. Each one with it’s own effects chain controlled independently.
The possibilities are endless.



MOD Control Chain and Arduino Shield

Besides the well-known MIDI connection, MOD introduces the Control Chain, a new and enhanced way to connect external devices, that allows you to expand the possibilities on how to control the effects parameters. Control Chain was designed focused on LV2, the standard for audio plugins used by MOD. It’s flexible and ready to be upgraded if necessary. Continue reading

MOD Duo’s Hi-Fi Soundboard

For the MOD Duo, our Hardware Engineer, Rafael Guayer, designed a soundboard that follows audiophile concepts.

Making use of special operational amplifiers, audiophile passive components, a high definition CODEC and a carefully designed circuit layout, the MOD Duo provides a quality level for the audio interface that is seldom seen on a mass market digital sound processor.

Beautiful, isn’t it?