ULN-2 Users Guide
146
Using the ULN-2 Hardware
ULN-2 Front Panel
Figure 7.3: ULN-2 Front Panel
The ULN-2 front panel provides ten-segment metering for the 2 analog inputs and the main outputs as
well as knobs and switches to control the input, monitor, and headphones sections. The meters are fast
VU meters with auto-resetting peak holds.
Each input channel has the following controls:
• Input gain knob — This is a 12 position gold-contact rotary switch which allows you to control the
gain of the selected input.
• Phantom Power enable switch — This is a push-button switch which enables/disables Phantom pow-
er. Push the switch IN to enable phantom power.
• 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 mi-
crophones. 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 con-
nected 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, 96, 176.2 or 192kHz)
• The Sample Rate is determined from the currently selected clock source so it will accurately indi-
cate the current sample rate, even when the clock source is being provided by an external device.
• 176.4kHz sample rate is indicated when both 44.1 and 48 are lit.
192kHz sample rate is indicated when both 88.2 and 96 are lit.
Note: A/D conversion is not available at 4x sample rates. Interestingly, the D/A converters operate
fine at 4x rates, even though they are 96kHz-specified chips.
• Clock source:
• Internal - indicates that the system is internally clocked
