Emulight System Link

The Emulight System Link (or “Eurorack Serial Link”) is an advanced digital bus system to connect multiple modules within a Eurorack into one big system. The connection is bidirectional and half duplex and therefore only requires one cable between modules.

History

In the early days of electronic synthesizers, analog control voltages and gate signals were used to control oscillators, filters, and other parts of a synthesizer. A single voltage could control a single parameter. This was perfectly fine for monophonic synthesizers, but it is impractical for polyphonic synthesizers because every voice would require its own set of control voltages. In addition, interoperability between different synthesizers was limited due to the lack of standardization.

To solve all the shortcomings of the old analog approach, the digital MIDI protocol was specified in the 80s. It defines a physical protocol with 31250 Baud (3.125 kB/s) as well as a logical protocol with short packets to control a digital instrument which somewhat resembles a keyboard. Every decent synthesizer, sampler, and other kind of audio equipment supports MIDI until today. There were a few attempts to replace MIDI in the past, e.g., by replacing it with a faster RS232 connection, but only the original physical MIDI connection as well as the most recent standardized USB-MIDI is used today.

Although MIDI solves the problem, it also has a series of disadvantages which limit its application. Most importantly, the physical connection is slow with only 3.125 kB/s transfer speed and it requires two cables for a bidirectional connection. The slow data rate makes it infeasible to send large amounts of control data in real time and the requirement for two cables means a big central MIDI interface is necessary to connect multiple devices.

A Eurorack based modular synthesizer needs more flexibility and higher data rates than what is available with MIDI. Although many Eurorack devices still use control voltages, this does not solve the problem with polyphonic control signals. As a result, the ESL bus was developed: it provides higher data rates and only requires a single cable between the modules. It can be used to transfer data between modules, send MIDI commands, and even send lots of real time parameter changes without saturating the link.

Features