MSB Technology Select DAC II User Manual page 6

Input Modules
About the 4 INPUT Module Slots
The SELECT has four input module slots. They are labeled A through D. There are two classes of input modules, Analog and Digital.
Analog modules must be placed adjacent to the Analog Output module. They can be either input or output modules. Digital modules
are only inputs and can be placed in any position.
Each module is completely self contained. It is recognized by the SELECT and identified on the display. When not selected the module
is turned off.
Analog Input Module (XLR or RCA)
The Analog Input module provides a second analog input. It is set up in the menu and can either be used with volume control or can
bypass the volume control. It must be placed adjacent to the Analog Output module. When installed and activated in the menu, 2nd
ANALOG INPUT will show up in the menu. It can either be Balanced or Single Ended.
Subwoofer Output Module (XLR or RCA)
The Subwoofer output module provides an isolated output suitable for connection to a powered subwoofer or class D amplifier.
Subwoofers need a lot of power and they are not sensitive to high frequency noise. So the speaker manufacturers like to match their
subwoofers up with some pretty low quality amplifiers, with switching power supplies and not much filtering. So what's the problem? The
subwoofers sound perfectly OK. The problem we found is that you have to hook that subwoofer up to your ultra clean, ultra precision,
perfect analog output from your DAC. The presence of this noisy subwoofer amplifier just being hooked up to your DAC creates
incredibly obvious noise in the DAC and thus distortion on your main amplifier and speakers. Its like serving fine wine in paper cups.
Its just intolerable. The concept of this output is that class D amplifiers found in subwoofers create a lot of electrical noise that can be
carried BACK to the DAC and can interfere with the DAC conversion and clocks. We aggressively block that noise with the Subwoofer
output module.
It must be installed adjacent to the Output Module or another Analog Module.
Digital Input Modules
There are a number of digital input modules shown below. Some have one input and others have more than one. New modules will be
added from time-to-time. In the case where a module contains more than one input, the DAC will recognize that and simply add another
input to the input list allowing you to select each input as if it was a separate module.
Digital Input Module - Optical and Coax with Word Sync Clock Output
This digital module is like two inputs in one. Both are industry standard S/PDIF inputs capable of accepting data streams up to 24 bits
and 384 kHz as well as DSD via DoP up to double rate. Note that some sources may not be able to output this high a rate on these format
connectors but at least the input can handle it.
It is very valuable to keep the source in sync
with the DAC so we provide a Word clock
output using a BNC connector that would
allow you to sync with the source. This sync
is primarily a feature for studio use, where
the ultra low jitter DAC clock can be used as
the master studio clock. This issue of clock
sync is not easy to understand. The quality
of the data being received is not changed by
syncing the source, but the noise associated
with recovering the data from a "different"
clock is substantially less.
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