Data Connections

The Atomic Pro is used to convert the position of the slider in a slider box into MIDI.

Each Atomic Pro has two female DB25 plugs which provide 5 volt power, ground, and 16 analog inputs. Each slider is connected in a voltage divider circuit, with +5 volts, ground, and analog output on the three pins of its XLR output.

Boîte de scène

Using a connection box called a "boîte de scène", 16 female XLR plugs are connected to a male DB25 connector at the end of a long cable in a circuit which provides 16 analog outputs to the Atomic Pro, as well as +5V and ground.

Schematic diagram of boîte de scène, including distorted caricature of the slider boxes. The female XLR connectors in the boîte de scène are not pictured.
Female XLR inputs 1 -- 12. Note the ID number on the top and the 30 meter cable with male DB25 connector at the end
Inputs 13 -- 16. The other eight connectors are not used.

There are 30 meters of cable between the boîte de scène and the DB25 connectors for the Atomic Pro. These are the cables intended to pass between the auditorium and the noisy machine room via some sort of acoustically isolated cable passage.

There being two DB25 analog input plugs on the Atomic Pro, there are two boîtes de scène per Atomic Pro. We use four Atomic Pros, thus 8 boîtes de scène, to be able to treat 128 slider boxes.

The boîtes de scène are laid out in the auditorium close to the passage to the machine room; the slider boxes are fixed to seats in the middle of the auditorium; so inevitably a whole lot of male-female XLR cable (such as microphone cable) is necessary to connect the slider boxes to the the boîtes de scène, as will be discussed in the section on Auditorium installation

The boîtes de scène were named by the technical people who concieved them. Literally, it means "stage box", but that phrase is so ambiguous it invites all kinds of inappropriate interpretations. We decided to keep the original name, barring objections, in order make the whole business seem real classy and sophistiqué, but, on the other hand, not to put it in italics. There are limits.

Boîte de scène -- Atomic Pro connections

The eight DB25 connectors from the boîtes de scène are connected according to the following table:

AtomicPro no. AtomicPro inputs
Analog in (1-16) Analog in (17-32)
1 1 2
2 3 4
3 5 6
4 7 8
boîte de scène no.

Atomic Pro -- Unitor 8 connections

The MIDI outputs of the Atomic Pros are connected to the inputs of the Unitor 8s. One MIDI output from each Atomic Pro is connected to each Unitor 8. The Atomic Pros are configured to send identical MIDI data on MIDI outputs 1 and 4 (and nothing at all on outputs 2 and 3: beware.)

Although it is of no importance which inputs are used on the Unitor 8 (once it's properly configured), by convention the connections are made in the following way:

Unitor 8 connections -- G4 connections

Each Unitor 8 is connected to its corresponding G4 with a USB B -- USB A cable, normally supplied with the Unitor 8. If everything is configured properly, the cables between the Unitor 8s and the G4s could be arbitrarily swapped, which could be useful during debugging (but not advisable during the experiment.)