1. OVERVIEW.
1-2. INTRODUCTION.
The SR series integrated mixer/amplifiers have been
designed for easy setup and simple but versatile oper-
ation. Requiring only the addition of microphones and
speakers, the SR powered mixers are self-contained
sound reinforcement systems, with features and per-
formance generally found only in units costing much
more.
Each input preamp channel provides a balanced XLR
MICROPHONE input with switchable phantom power
for condenser microphones, a 1/4’’ phone jack LINE
input, MAIN level control, LOW, MID, and HIGH fre-
quency tone controls, MON. send control and an
EFF./REV. send control.
The master section features MAIN MASTER, MON.
MASTER, AUX. LEVEL, and DIGITAL REVERB and
EFFECTS level controls, a GRAPHIC EQUALIZER, and a
versatile patch bay.
The SR series mixers include DELTACOMP
TM
, an adap-
tive compression system. DELTACOMP
TM
is a high per-
formance power amp limiter that senses amplifier
error due to clipping, and automatically reduces the
gain until the distortion is minimized. A front panel
yellow PEAK LED indicates power amp input limiting.
To make setup as simple as possible, the mixer,
graphic equalizer, and power amplifier are pre-
patched in a standard configuration that requires
plugging in only the microphones and speakers to be
“on the air.” To make the system as versatile as possi-
ble, this “normalized” patch may be bypassed by
using the inputs and outputs of the patch bay. These
allow the individual components of the system to be
used in various combinations, and for external equip-
ment to be added into the system as the need arises.
The SR Series has been designed to meet the needs of
professionals, and can be counted on to provide reli-
able service in the most demanding situations.
1-1. BLOCK DIAGRAM. The block diagram illustrates
the typical signal path for the SR series.
2. FRONT PANEL CONTROLS, JACKS AND LEDs.
2-1-1. LINE INPUTS. The 1/4” phone jacks are
intended for high impedance balanced or unbalanced
inputs whose amplitude is under 8 VRMS. This would
include instrument and line level signals. When used
as a balanced input, the tip connection of the 1/4”
jack is the non-inverting (+) input and the ring con-
nection is the inverting (-) input.
2-1-2. MICROPHONE INPUTS. The three-pin audio
connectors (often called “XLR” or “Cannon” connec-
tors) on the front panel are intended for balanced
input signals from low impedance microphones. To
avoid clipping in the input stage, signal levels should
not exceed 0.8 VRMS. Higher amplitude signals, such
as balanced line levels signals, may also be patched
into these jacks if an input pad is used (see Section 4-
4). The XLR jack is wired according to the following
standard:
Pin 1 is ground.
Pin 2 is the non-inverting (+) input.
Pin 3 is the inverting (-) input.
Signals at the XLR jacks experience 20 dB more gain
than those at the 1/4” channel input jacks.
2-2. CHANNEL CONTROLS.
2-2-1. CHANNEL MAIN CONTROL. The channel’s
MAIN control determines how much of the channel’s
signal is sent to the Main mixing buss and to the
EFF./REV. control. For best signal to noise ratio, this
control should be set relatively high; usual settings are
around 2 o'clock, except when input signal levels are
great enough to cause clipping. See Section 4-1-2.
2-2-2. CHANNEL TONE CONTROLS. The LOW, MID,
and HIGH controls on each channel may be adjusted
to enhance the qualities of its particular audio signal
and to control excessive boominess or sibilance (“s”
sounds) by using the LOW, MID, and HIGH controls.
When these controls are at 0 (straight up), the channel
is “flat” (no frequencies cut or boosted). The most nat-
ural sound is achieved by avoiding extreme tone con-
trol settings.
2-2-3. EFF./REV. CONTROL. This control determines
how much signal from each channel goes onto the
Effects/Reverb buss. All signals on this buss are com-
bined in the master mixer section, and sent both to the
EFF. OUTPUT jack and to the internal reverb system.
The EFF./REV. control is wired post MAIN control and
post-EQ; thus, the level and tone of the EFF./REV. sig-
nal are altered by the settings of the MAIN, LOW,
MID, and HIGH controls.
2-2-4. MON. CONTROL. The MON. control deter-
mines how much of a channel’s signal is sent to the
Monitor buss. This allows a separate mix to be creat-
ed for stage monitoring. The control is wired pre-
MAIN control and pre-EQ; thus, the monitor signal is
independent of other channel controls.
2-3. MASTER SECTION CONTROLS.
2-3-1. MAIN MASTER LEVEL CONTROL. This is the
master level control for the main mix. It controls the
signal level present at the MAIN OUT jack, if nothing
is patched into the EQ. IN jack or the PWR. AMP
INPUT jack. The MAIN MASTER control also deter-
mines the graphic equalizer and power amplifier input
levels.
2-3-2. MONITOR MASTER LEVEL CONTROL. This is
the master level control for the monitor mix. It con-
trols the signal level present at the MONITOR OUTPUT
jack.
