LavryBlue 4496
Operation
1
LavryBlue 4496 System Overview
The LavryBlue System is a modular 1U high 19 inch rack unit, configurable to accommodate multiple
functions including Digital to Analog conversion, Analog to Digital conversion, and Microphone Pre-
amplification. The hardware is designed to operate at industry standard 44.1, 48, 88.2 and 96 kHz sampling
rates, with the additional flexibility in “Wide Mode” of operation from external clocks at non-standard or
variable sample rates in the ranges of 42 to 50 kHz and 84 to 100 kHz.
The Lavry Blue chassis contains a power supply equipped with additional output power noise filtering. The
modules are bolted in and connected to each other in a daisy chain manner, enabling power distribution
across the chassis. This interconnection also provides for communication between the units that in some
cases are user selectable. One of the advantages of this approach is the ability for AD converters to “share”
a common clock source- the M·SYNC- to minimize jitter and operate multiple channels in phase.
The chassis provides room for up to 4 “single width” modules. Most modules are single width 2-channel
units, so the chassis has space for up to eight channels of conversion or processing. The MicPre is also 2-
channel, but it takes up the space of two AD or DA modules, so one chassis can provide up to four channels
of microphone preamplification. Each module has a front panel and a rear panel that are directly in-line
with each other from front-to-back in the 4496 chassis.
This flexible design means that the Lavry Blue chassis can be configured to accommodate anything from a
single module for stereo AD or DA conversion, to a maximum of eight channels of conversion. The unit
may be configured for any mix of functions- for example: 2 channels of AD and 2 channels of DA, or 6
channels of AD plus 2 channels of DA. One popular configuration is 2-channels AD, 2-channels of DA and
2-channels of MicPre. Another advantage is that the LavryBlue can initially be purchased in a “minimal”
configuration and then later upgraded to add more channels or different functions, as the user’s needs
change. Please see “Opening the LavryBlue 4496” on page 20 for details.
All modules are added left-to-right. Because the M•SYNC provides the clock source for all A-to-D
conversion, the M•AD-824 A-to-D modules must be grouped together on the left side of the 4496 chassis.
M•DA-824 D-to-A converters are placed in the next available slots to the right of the A-to-D’s. The MicPre
would be furthest to the right in 4496 units with converter modules. The MicPre is a doublewide module,
and thus would occupy two “slots.”
Another aspect of the modular approach is that all analog audio and AES/SPDIF digital connections are
made externally. The only interconnecting signals internal to the 4496 are detailed below under “Shared
clocks and settings.” For example, this means that if you wanted to record the MicPre output using the
M•AD-824, you would need to connect XLR cables from the MicPre output to the M•AD-824 input. Or, if
you wanted to monitor the M•AD-824’s digital output through the M•DA-824, you would need to provide
an AES digital connection to the M•DA-824 from the M•AD-824 or the device the M•AD-824 is feeding.
Shared AD clocks and settings:
Operating multiple channels of Analog to Digital conversion with
independent clocks can creates timing or “phase-shift” differences that degrade sonic imaging. To avoid
this problem, a Master Sync unit (the “M•SYNC”) controls the clocks of all AD converters in the 4496
simultaneously. It takes the form of an additional printed circuit board that is controlled by the panel on the
left side of a LavryBlue equipped with AD converters. In multichannel systems, user settings such as word
length or dither are typically the same across all channels, so a selectable “Master-Slave” mode is available
on the M•AD-824 module. This allows the front panel parameters set on the Master module to be sent to
the Slave modules so that each module does not need to be set individually.
Stand alone DA modes:
The M•DA-824 digital to analog converter functions well as a stand-alone unit.
CrystalLock
jitter elimination enables the M•DA-824 to clock externally while virtually eliminating the
audible effects of source jitter. Independent operation also means multiple signals at different sample rates
can be converted asynchronously from digital to analog
in the same 4496 unit
equipped with multiple DA
modules. Although the DA’s operate independently, the CrystalLock™ and Narrow modes have a fixed
“propagation delay,” so the outputs from multiple DA’s clocked from a common source remain coherent.
