Metric Halo Mobile I/O - Manual (Page 72)

ULN-2 Users Guide
72
• Trim Enable switch — This is a push-button switch which allows you to control whether the attenuator
trim pot is in the signal path or not. Push the switch IN to enable the trim pot. The attenuation range
of the trim pot is 0dB to -20dB.
• Mic/TRS switch — This is a push-button switch which selects the input stage. The ULN-2 has two
distinct input stages: The Mic Amp and the DI Amp.
• The Mic Amp is optimized for high gain and very low noise with low impedance sources like micro-
phones. This input is connected to the XLR portion of the Neutrik combo connector. Maximum gain
is 72 dB. Push the Mic/TRS switch IN to select the MIC input.
• The DI amp is optimized for high impedance sources like magnetic pick-ups. This input is connected
to the TRS portion of the Neutrik combo connector. Maximum gain is 63 dB. The Mic/TRS switch
should be in the OUT position to use this input.
• Trim Pot — The trim pot controls a passive attenuator. The attenuator is buffered between the return
receiver and the A/D converter so its operation is transparent with regard to sound quality. Push the the
trim enable switch IN to enable the trim pot. The attenuation range of the trim pot is 0dB to -20dB.
The front panel also provides ULN-2 system status at a glance:
• Sample Rate (nominal 44.1, 48, 88.2, or 96)
• The Sample Rate is determined from the currently selected clock source so it will accurately indicate
the current sample rate, even when the clock source is being provided by an external device.
• Clock source:
• Internal indicates that the system is internally clocked
• Wordclock indicates that system is being clocked from the wordclock input
• 256x WC indicates that the system is being clocked from a 256x clock at the wordclock input
• Digital In indicates that the system is being clocked from the selected digital input (AES or S/PDIF)
• Power — Indicates that the ULN-2 is receiving power.
• FireWire — Indicates that the ULN-2 has been successfully connected to a FireWire bus and has detected
the isochronous cycle required to transmit and receive audio.
• Locked — Indicates that the system clock recovery circuit is properly locked to the selected clock source.
If this light is not illuminated, the ULN-2 will not be locked to a clock and will revert to its failsafe
internal clock source. Even if the Locked light is not illuminated, the actual sample rate will still be
indicated on the front panel display.
• Digital I/O Section:
• The AES and S/PDIF lights are mutually exclusive and indicate which of the the two input ports are
feeding the Stereo Digital input of ULN-2. The Locked light indicates when the digital receiver is
locked to the incoming digital audio signal.
The ULN-2 hardware supports Persistent State Snapshots. There are 10 snapshot slots in the ULN-2 that are
recallable from the controls on the ULN-2 front panel. Each Persistent State Snapshot contains a complete
description of the state of the box, including Sample Rate, Clock Source, Digital input source, Sample Rate
Converter Enable, Mixer Configuration, Levels and +DSP configuration and routing. In other words, a snapshot
saves every aspect of the configuration of the ULN-2.
The first snapshot slot is special as it is used by the unit to configure the hardware and the routing when the
ULN-2 starts up. The other 9 slots are available for storing alternate configurations that can be selected “on
the fly” after the ULN-2 is up and running.
When a computer is attached to the ULN-2, the front-panel controls to select snapshots are locked-out since
the computer is actively controlling the configuration of the box.
If the computer is not attached, the two tact-switches on the left-side of the front-panel (between the status
indicators and the meters) may be used to select the snapshot that you want to use to configure the ULN-2.