Connectors

In the UK, the terms jack plug and jack socket are commonly used for the respective male and female connectors. In the US the more fixed connector is called a jack.

Patching
The jacks and plugs commonly used for creating synthesizer patches are the 1/4" (exactly 6.35mm), the 3.5mm (approx 1/8"), the 4mm banana and the 0.141" (3.58mm) Tini-Jax, these are all monophonic. The reliable and solid feeling 4.40mm Bantam or TT (tiny telephone) jacks, widely used in professional audio, are an option offered by Wiard and Hinton Instruments.

Banana plugs vs. other plugs
Banana are unshielded but CVs don't need shielding and because audio levels are usually high, this won't be a problem. When patching into external synths or other devices use a shielded cable with both ends of the shield connected to ground. Banana sockets are cheaper because they are mechanically simpler. They are also much more durable since there is less to go wrong. They are widely available and come in a range of colours.

Banana plugs are stackable i.e. one can plug into the end of another. Most banana synths are designed with stackable plugs in mind, whereas most 1/4" and 3.5mm jack systems include multiples.

On Buchla synthesizers the audio and contol paths and control are kept seperate. The control path uses banana connectors and swings between +/-15V, while the audio path is at 1.228V RMS, (+4dBu professional line level) and uses 0.141" Tini-Jax.

Regular jacks provide an extra switched connection enabling normalization (connections when there is no cable plugged in).

Midi
MIDI cables terminate in a five pin 180° DIN connector. Standard applications use only three of the five conductors: a ground wire, and a balanced pair of conductors that carry a +5 Volt signal. Some proprietary applications, such as phantom-powered footswitch controllers, use the spare pins for DC power. Opto-isolators keep MIDI devices electrically separated from their connectors, which prevents ground loops from occurring.

External DC connector
The coaxial power connector is the miniature power connector used for attaching extra-low voltage devices such as consumer electronics to external power supplies. Also known as barrel connectors, concentric barrel connectors or tip connectors, these small cylindrical connectors come in a variety of sizes.

3U
For internal power distribution, a Eurorack case typically has a distribution board with 10-pin IDC headers. The 16 pin IDC used by Doepfer includes +5 Volts, Gate and CV as used by a few modules to pass these signals between modules without needing extra patch cables. The power cable is typically a length of ribbon cable with a female 16-pin IDC connector on one end and a 10-pin on the other. Incorrectly connecting one of these connectors can damage the module. The stripe on the ribbon cable indicates the -12V side of the connectors.

See also Comparison of 3U module formats

5U
To distribute DC from the power supply to the modules MOTM and Oakley Sound Systems implement a star distribution with 4 way AMP MTA-156 headers or 4 way Molex KK 0.156" headers on a PCB. The CGS uses a power distribution bus.

Modcan and Cyndustries have the same type of connector as MOTM to distribute power to modules except they only use a 3 pin version which provides +/-15v only. Power is also distributed from the power supply via a bus board.

Synthesizers.com implements a DC star distribution via cable harness, connected to the power supply by a 4 pin .093 Molex connector while six pin keyed MTA-100 connectors on the harness connect to male headers on the modules, with +/-15V, +5V and a ground shared between these.

See also Comparison of 5U module formats

Other formats
Frac and Wiard 300 series use the same 4 way MTA-156 connectors as MOTM.

Power connectors

 * Power distribution thread at Muffwiggler forum
 * Supplier part numbers for MOTM 4 pin 0.156 MTA
 * Supplier part numbers for Synthesizers.com 6 pin .100 MTA
 * Oakley Sound Systems' Construction Guide has a comparison between MTA and Molex connectors.