LavryBlue 4496
Operation
15
MICROPHONE PREAMP
A.) OPERATION
The LavryBlue Microphone Preamplifier is a dual channel “double width” unit. This means that a 4496
frame can hold a total of two MicPre’s or one MicPre and two other modules. One popular configuration is
the “2A2D2MicPre,” which has two channels each of A-to-D, D-to-A, and microphone preamplification.
Use of a digitally controlled ANALOG level control ensures the precision of gain adjustment as well as
consistently low noise and distortion across a gain range of 21to 70dB’s (or 11to 60dB’s of gain when
using the output “Gain Pad”). The transformerless input employs special circuitry for very high Common
Mode Rejection with extended frequency response. Impedance matching at the input stage optimizes the
response for Ribbon, Dynamic, and Condenser microphones.
Phantom power is enabled only in the “Condenser” setting which is indicated by the “decimal point”
illuminating on the right side of both channels’ Gain Display. Phantom power can be disabled for use with
vintage condenser microphones that have their own power supply, by changing an internal jumper setting
(see “settings” section, below).
The output is electronically balanced XLR +4dBu nominal level. The inputs and outputs are electronically
balanced, and configured for Pin 2 “+” (non-inverting) operation. There are internal jumpers to reconfigure
the output for unbalanced operation (see “settings” section, below). When the output
Gain Pad
switch is
set to the “on” position; the output level is reduced 10dB to allow connection to equipment not capable of
accepting full professional level signals. The input will “clip” at the same level for any given Gain setting;
whether the Gain Pad is “on” or “off.” The Gain display shows the total Gain- input to output; the Gain
display changes by 10 dB when the Pad is switched “on,”
but it does not change the level at which the input
will clip
. The
Gain Pad
is therefore not recommended for use with most professional audio equipment.
Looking at the back of the 4496, each MicPre module has two sets of two XLR connectors- two female
inputs and two male outputs. In each set, the LEFT CHANNEL is the
right
XLR and the RIGHT
CHANNEL is the
left
XLR connector.
This “mirror image” position of the XLR connectors is due to the straight-through construction of the
modules. Facing the front of the 4496, the Left channel is on the LEFT and the Right channel is on the
RIGHT side of each module’s PC board.
All audio connections to the MicPre are made with the four XLR connecters on the back panel. There are
no connections internal to the 4496 for these signals.
As a safety feature to prevent unwanted “pops” or “thumps,” the MicPre enters
Protected Mode
when
power is applied to the MicPre. This is indicated by the level display numerals “flashing.” In this mode,
they will indicate the last level that was set before power was removed as a convenient reminder,
but the
actual gain will be set to “Minimum.”
Each channel has its own Protected Mode.
To exit Protected Mode, you simply need to adjust the gain “up” or “down.” Even a quick activation of the
toggle switch will cause the display to stop flashing and set the MicPre to the indicated gain.
Please Note:
You should always exit Protected Mode on BOTH channels after powering the 4496 “On,”
even if you are not using one or both of the MicPre channels at that time.
