Specifications

HD I/O Guide18
High Sample Rates and Expanded Pro Tools|HD
Systems
With 176.4 kHz and 192 kHz sample rates, as
many as four Pro Tools|HD cards can be used.
Any additional cards (up the total system maxi-
mum of seven cards) will switch to Inactive
mode. The Pro Tools|HD cards and any attached
peripherals will become active again when the
sample rate is set to 96 kHz or lower (see the
Pro Tools Expanded Systems Guide for more infor-
mation).
Clock Source
The Pro Tools Hardware Setup dialog lets you set
the Clock Source for the system.
Internal If you are recording an analog signal di-
rectly into Pro Tools, you will usually use the
Pro Tools Internal clock source.
External If you are transferring material into
Pro Tools from an external digital device, or if
you utilize a common house clock signal, you
will need to synchronize Pro Tools to that digi-
tal device or common signal. Depending on
your audio interface configuration and the se-
lected sample rate, external options can include:
• S/PDIF [Encl] (at all sample rates)
• Optical (S/PDIF) [Encl] (up to 96 kHz)
• AES/EBU [Encl] (at all sample rates)
• AES/EBU 1–8 (Single Wire in stereo pairs at
all sample rates)
• AES/EBU 1–4 (Dual Wire) (in stereo pairs at
176.4 and 192 kHz)
• ADAT 1–8 (at 44.1 and 48 kHz)
• ADAT S/MUX 1–4 (at 88.2 and 96 kHz)
• ADAT S/MUX 1–2 (at 176.4 and 192 kHz)
• TDIF 1–8 (at 44.1 and 48 kHz)
• Optical ADAT [Encl] (at 44.1 and 48 kHz)
• Word Clock (at all sample rates)
To select the Clock Source:
1 Choose Setup > Hardware.
2 From the Clock Source pop-up menu, select
the clock source.
3 Click OK.
If you have an expanded system with five or
more Pro Tools|HD cards, any I/O con-
nected to any Pro Tools|HD cards beyond
the first four must be disconnected in order
to operate at sample rates higher than
96 kHz.
Selecting the Clock Source
Your digital input device must be connected
and powered on for Pro Tools to synchro-
nize to it. If your input device is not powered
on, leave the Clock Source set to Internal.