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Notes on the ULN-2

Monitor gain

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.


There are 9 additional alternative states that can be stored in the ULN-2 hardware, and 8 alternative boot states stored in the ULN-8 & LIO-8 hardware.

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)

Safe-Boot Mode

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.

ULN-2 Conversion

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.

Power Requirements

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.

Both the 2882 and ULN-2 can be bus powered, the ULN-8 will pass bus power, but does not provide it. (it also must be connected to a computer to power a MIO downstream)

DI Input

the TRS on the Combo Jack is 200K, which is pretty Hi-Z and would be a good DI.

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