Using the 888/24 I/O
3
3. Sample Rate and 1–2 Format
Indicators
These LEDs indicate the sample rate of the
888/24 I/O internal crystal oscillator and
the digital format (AES/EBU or S/PDIF) of
the audio input signal to channels 1 and 2.
The choice of digital format for these two
channels is made in the Session Setup win-
dow or Hardware Setup dialog. Digital in-
put pairs 3–4, 5–6, and 7–8 of the
888/24 I/O are always AES/EBU. Sample
Rate is set in the Session Setup window or
Hardware dialog in Pro Tools.
The 888/24 I/O provides the following
sample rates:
48 kHz
This is a standard sampling rate of
many professional audio devices. It is rec-
ommended for use with devices that can-
not receive digital transfers at 44.1 kHz.
44.1 kHz
This is the compact disc standard
sampling rate and the Pro Tools default
sample rate. To avoid the need for sample
rate conversion, you should use this rate
when you are recording material that will
ultimately be published on a compact disc.
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When you are using an external digital
source such as a DAT recorder, the front panel
of the 888/24 I/O indicates only the internal
oscillator sample rate, not that of the external
digital source.
4. Level Meters
The 888/24 I/O level meters monitor the
channel outputs of Pro Tools. Input levels
are monitored on-screen in the Pro Tools
software.
The 888/24 I/O is factory calibrated so that
a meter reading of –18 dB corresponds to
the 888/24 I/O nominal operating level
(which can be set to 4 dBu or
–10 dBV). If you sent the output to an ana-
log device with a VU meter, this would cor-
respond to “0 VU” on the VU meter.
The red LED indicators on the Audio Inter-
face indicate both full-code (highest level
before clipping) and clipping of Pro Tools
output signals. The on-screen meters in
Pro Tools software indicate clipping when
at least three consecutive full-code samples
follow each other.
5. Input Level Trims
The 888/24 I/O analog inputs are factory
calibrated at a –18 dB nominal level, refer-
enced to a full code signal. This means at
the nominal reference input level (either
+4 dBu or –10 dBV), you have 18 dB of
headroom before clipping. The input level
trim pots allow adjustment of the
888/24 I/O input levels to match the oper-
ating level of your external equipment. Ad-
justments can be made with a Phillips
screwdriver.
6. Output Level Trims
The 888/24 I/O analog outputs are factory
calibrated at a –18 dB nominal level, refer-
enced to a full code signal. This means at
the nominal reference output level (either
+4 dBu or –10 dBV), you have 18 dB of
headroom before clipping. The output
level trim pots allow adjustment of the
888/24 I/O output levels to match the op-
erating level of your external equipment.
Adjustments can be made with a Phillips
screwdriver.
