# Making Hardware Clock Connections

The following instructions pertain to Symphony, Pro Tools HD and Standalone audio interface modes.

Symphony I/O provides several facilities for the connection of clock signals:

- Word Clock inputs and outputs - Use the word clock inputs and outputs for most clock connections to digital consoles, digital effects devices, or other digital audio devices equipped with standard word clock I/O.

- Loop Clock inputs and outputs - Use Loop clock inputs and outputs to lock together multiple Symphony I/Os in a computer-based digital audio workstation (DAW) such as Apogee's Symphony 64 PCI system. Symphony I/O's Loop clock is compatible with Avid Pro Tools Loop Sync, meaning that a Symphony I/O may be freely incorporated into a Pro Tools Loop Sync chain.

- Digital audio inputs and outputs - Use Symphony I/O's digital audio I/O to send and receive clock between Sympony I/O and digital devices that don't include work clock I/O. When using Symphony I/O in Standalone audio interface mode, the most convenient way to clock the connected digital device is through the digital audio input from Symphony I/O.

In Symphony audio interface mode, both loop and "star" clock configurations are possible, as described below.

## Locking External Devices to Symphony I/O (Loop or Star clock configuration)

To lock external clock devices to a single Symphony I/O:

> 1. Connect the rear panel WC OUT to the word clock input of the device, using a BNC cable. Set the external device's clock source to Word Clock.
> 2. When connecting digital devices to Symphony I/O’s AES, ADAT/SMUX or S/PDIF outputs, clock is transmitted with the digital connection, allowing the receiving device to simply clock to its digital input.

1 SIO WC out to device WC in, device set to WC clock

## Locking Symphony I/O to External Devices (Loop or Star clock configuration)

To lock a single Symphony I/O to external devices such as a Master clock:

> 1. Connect a BNC cable between the device's word clock output and Symphony I/O’s WC IN. When using multiple interfaces, connect to the master Symphony I/O's WC IN.

> 2. If no other devices are to be connected, press in the rear panel termination (WC Term) switch.

> 3. To lock Symphony I/O to a digital input, connect the source's digital output to Symphony I/O digital input.

1 SIO WC in to device WC out, SIO set to WC clock

> Once clock connections are made, see Setting the Clock Source to complete the process. Note that software settings may vary based on the audio interface mode.

## Locking multiple Symphony I/Os with Loop Clock

When multiple Symphony I/Os are used together in a digital audio system (for example with a Symphony 64 or Avid Pro Tools HD PCI card), use the rear panel Loop connections to lock the Symphony I/Os together, as described below:

Using a BNC cable, connect the Loop Out of unit 1 to the Loop In of unit 2. With additional BNC cables, connect the Loop Out of each unit to the Loop In of the next unit until all units are connected. Finally, connect the Loop Out of the last unit to the Loop In of the first unit. Please consult the diagram below for an example connection.

## Locking multiple Symphony I/Os to External Devices (Loop clock configuration)

To lock multiple Symphony I/Os to external devices such as a master clock, first connect Loop Clock as shown above. Then connect a BNC cable between the device's word clock output and one Symphony I/O’s WC In. Configure this Symphony I/O as the Loop Master as described in Setting the Clock Source.

## Locking multiple interfaces using a Star clock configuration

When using Symphony I/Os, 16X and Rosetta series interfaces in the same system, it's necessary to use a star clock configuration as shown below. Two options are shown below: 1) using the first interface as master and connecting slave interfaces using BNC "T" connectors; 2) using an external master clock such as Apogee's Big Ben as the master.