788T Linking with Multiple 7-Series Recorders
788T firmware revision 2.10 introduced the ability to link multiple 788T recorders for simultaneous, synchronous recording. It also allows linking the 788T with other Sound Devices 7-Series recorders including the 702, 702T, 722 and 744T. This is ideal for applications requiring higher track counts or synchronized backups. Important considerations for successful multi-unit linking include:
- 788T C. Link linking requires setting the 788T to Connect As Mass Storage in the Setup Menu option FireWire/USB: Connection [# 2] . C. Link serial communication is disabled when Wave Agent CTRL (USB Only) is selected in this menu, though word clock and time code are transmitted and received.
- Use a quality RJ-12 cable to connect to the C. Link ports. An intermittent connection can result in audio dropouts and other problems.
- Connect source device and sync device(s) via C. Link cables before powering. Power the source recorder before the sync devices. To ensure accurate synchronization after power up, allow the sync device(s) time to fill up buffers and fully lock to the source device before pressing record. 20 seconds should be more than adequate.
- When linking the 788T with 702, 702T, 722, and 744T recorders with digital inputs used, configure the 788T as the sync device and the other recorder as the source device.
- Ensure source and sync devices are set to the same sampling rate and time code frame rate.
- Ensure sync devices are set to Ext TC time code mode in the Time Code: Mode menu
- The 702, 702T, 722, and 744T recorders automatically lock to an incoming sync reference. An ‘L’ lock indicator is shown in the main display when locked.
- A 788T sync device must be manually set to sync to incoming word clock in the Rec: Sync Reference menu. A ‘W’ lock indicator is shown in the main display when locked. Ensure sync devices are correctly sync referenced:
- When changing sampling rates, power cycle both source and sync devices.
- When recording is stopped on the source device, wait for a few seconds before commencing a new recording. If the sync device is a 788T, wait until it’s ‘Media Notification: Writing to media. Please wait...’ message has disappeared.
- It is not necessary to set the pre-roll on sync devices. Sync devices automatically detect the source device’s pre-roll value and apply it accordingly.
Sample Accuracy of Linked Units
There are three machine linking scenarios, each behaves slightly differently:
- 788T-to-788T Linking When two or more 788T recorders are linked, all linked inputs are sample and phase-accurate. No compensation is required between units.
- Linking multiple 702/702T/722/744T Recorders When two or more of the 702, 702T, 722, or 744T recorders are linked, all linked inputs are sample and phase-accurate. No compensation is required between units.
- 788T Linked to a 702/702T/722/744T Linking the 788T with 702, 702T, 722, or 744T recorders is time code frame accurate but not sample accurate. The 788T recorders analog and digital input circuitry is different than that of the two- and four-channel recorders. This results in a short, predictable, and constant digital delay between the inputs of linked machines. Since the delay is constant, tracks are easy to align in a DAW. The chart below indicates the amount of delay the 788T has relative to the two- and four-channel recorders..
Chart of Delays
|Input Type||Sample Rate/kHz||788T Input Delay Relative to the 702, 702T, 722, 744T Recorders|
|All Analog||44.1||1.0 ms|
|All Digital||44.1||3.5 ms|
An input delay can be set in the two- and four-channel recorders (in the input delay menus) to align the inputs of the machines. Use the table above to set the delay value. Note: when daisy-chaining audio from the outputs of one recorder into the inputs of a linked recorder, there is no need to apply delay.