From MH Wiki
Notes on the ULN-2
On the ULN-2, all monitor controller gain is in the analog domain, and you can adjust the maximum level via the front panel knob for the monitor outputs.
The first state is called the "Boot State" and is automatically loaded when the unit boots. To store the boot state to the hardware, open MIO Console App and select the following menu command
Menu Bar > Utilities >Save Boot State
The other states are Hardware configuration snapshot states. These can be recalled from the front panel up and down buttons. To store a snapshot state to the hardware, open MIO Console App and select the following menu command
Menu Bar > Utilities >Save Snapshot x State
(X= bootstate number corresponding to front panel button number)
To safety boot the ULN-2, hold the the 'up arrow' button (there is no mute button on the ULN-2). To bypass the boot-state hold the 'down arrow' button while booting the unit.
The AKM 5383 is a 108 kHz 24-bit ADC, used in both the ULN-2 and 2882
The AKM 4393 is a 96 kHz 24-bit sigma-delta DAC, used in both the ULN-2 and 2882
These are both stereo chips, so the ULN-2 has one for input and two for output, while the 2882 has four of each of them for the main analog I/O plus an additional DAC for the cans. The ULN-8 has 8 of each, plus a DAC for the cans.
depending upon the sample rate, these AKM converters run at 128x oversampling – which happens to be the same rate as SACD. The DACs also have an 8x digital filter inside.
SRC in the 2882 and ULN-2 use a Cirrus Logic CS8420 Digital Audio Sample Rate Converter which runs at 108 kHz and 24-bit for real-time SRC.
ULN-2 Analog Stages
Both the ULN-2 and 2882 use the Excalibur low-noise high-speed JFET-input op-ampsfrom Texas Instruments,
and the ULN-2 adds Burr-Brown OPA 2228 op- amps for high precision and low noise in high-gain situations.
The minimum pre-regulation voltage is 9V.
The Maximum preregulation voltage is 33V.
At 12 Volts the current demand is:
ULN-8 : 3-3.5A
2882 High Power Mode 1.5A
2882: Low Power Mode 1A
ULN-2 : 0.75A
A custom [jump boot] device can be be built with a pair of 9V batteries. It is used to power-on the MIO if the inrush current is too high for some macbooks to power the MIO properly.
the TRS on the Combo Jack is 200K, which is pretty Hi-Z and would be a good DI.