Conference Interpreter Unit

c3lingo.org is doing the great job of translating many talks of the Chaos Communication Congress and other CCC-related events to multiple languages. But the required hardware for simultaneous translation is quite expensive to rent, even if it's "just" a specialized analog audio mixer.

So the idea was born to design an easy to use hardware with the special requirements of our interpreters in mind.

Requirements

The hardware unit should deliver the native audio (stage/ hall mix) to the interpreter's headset and provide a sum of all interpreter's microphone to the input of the video streaming/ recording chain. Mixing of the final translated audio (ducking the native audio with the translation) will be done as part of the streaming/ recording chain, so the interpreter unit should just provide the sum of all microphones.

Normally just 2 interpreters will provide one translation, but demanding talks might require 3 people. So either 3 headphone inputs/ outputs should be provided or it must be possible to daisy-chain multiple units.

The user interface of the unit should be as simple, as possible to decrease the risk of mis-configuration. This means, that no compressor and equalizer will be added in the input group.

General requirements:

• Line input of stage/ hall mix (native language) (XLR/ 6.3 mm balanced jack combo connector)
• 3x Microphone input (XLR) (at first just dynamic microphones)
  • VU-Meter for each input channel. (Perhaps with special color scheme: too quiet, good, too loud, clipping)
  • Fader/ Potentiometer for gain control
  • Mute switch (on/ off position, with state LED)
  • Temporary mute button (momentary switch)
• 3x Headphone output (6.3 mm mono/ stereo (2x mono) jack)
  • Should output mix of native audio and own microphone
  • Potentiometer for output volume
  • Potentiometer for volume of own microphone in the mix
• Outputs:
  • Sum of all translators (XLR/ 6.3 mm balanced jack combo connector)

All inputs (besides the microphones) and outputs should:

• expect/ deliver a nominal level of +6dBu (german TV broadcast standard, 0 dBu = 0,775 Veff)
• be transformer balanced and galvanically isolated

Status

Requirements collection done, first research for circuit design, but no real progress yet.

Help is always appreciated!