Biamp SPM412E User Manual

SPM412e

Stereo Preamp/Mixer

Operation Manual

Biamp Systems | 9300 S.W. Gemini Drive | Beaverton, OR | 97008 | USA | +1.503.641.7287 | www.biamp.com

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Front Panel Features
Rear Panel Features
Modifications
Remote Control
Applications
Block Diagram
Specifications
Warranty

TABLE OF CONTENTS

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SPM412e

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INTRODUCTION

The SPM412e Stereo Preamp/Mixer provides four stereo line inputs, one mic/line input, and two independent outputs. With input sourc
selection, automatic page-over muting, and remote control functions, the SPM412e is ideally suited for applications such as restaurants,
bars, meeting rooms, aerobics studios, and school gymnasiums. The SPM412e is extremely versatile, yet cost-effective, and is eas
install and operate.

SPM412e features include:

♦ four stereo line inputs with trim controls & RCA connectors
♦ balanced mic/line input on plug-in barrier strip connector
♦ trim, pad, peak indicator, & level control on the mic/line input
♦ +24 volt phantom power switchable on the mic/line input
♦ balanced stereo main output on plug-in barrier strip connector
♦ balanced mono zone output on plug-in barrier strip connector
♦ front panel push-buttons select stereo inputs & adjust main level
♦ simultaneous selection of multiple stereo inputs from front panel
♦ front panel display shows stereo input selections & main level
♦ treble, bass, and balance controls for the stereo main output
♦ rear panel switch defeats treble & bass at stereo main output
♦ rear panel switch converts the stereo main output to mono
♦ limiter with threshold control for the stereo main output
♦ front panel rotary level control for the mono zone output
♦ automatic talkover muting when the mic/line input is in use
♦ internal jumpers assign mic/line input pre or post treble & bass
♦ internal jumpers assign mic/line input pre or post main level
♦ internal jumpers assign mic/line input to main and/or zone
♦ internal jumpers assign stereo line inputs to main and/or zone
♦ internal jumpers assign talkover muting to main and/or zone
♦ separate internal talkover mute adjustments for main and zone
♦ wall-mount, custom, or third-party remote controllers
♦ wall-mount ‘Controller’ overrides commands from front panel
♦ remote control affects stereo input selection & main level
♦ default settings can be defined & stored for recall at power-up
♦ incorporates AES recommended grounding practices

marked and UL / C-UL listed power source

♦
♦ covered by Biamp Systems' five-year warranty

1

FRONT PANEL FEATURES

(1) (2) (3) (4) (5) (6) (7)

(1) Mic Level: This rotary control adjusts the level of the Mic

Input signal sent to the Main Output and Zone Output sections.

Mic Input signal can be assigned to the Main and/or Zone Outputs
individually, plus it can be assigned to the Main Output as pre/post
Tone and pre/post Main Level (see Modifications on pgs. 4 & 5).

(2) Channel Select: These four momentary push-buttons select
which Stereo Line Input signal is sent to the Main Output and Zone
Output sections (see Stereo Input Assign on pg. 4). To select a
desired Stereo Line Input, press the corresponding push-button.
The adjacent LED indicator will light, indicating the selection. More

than one Stereo Line Input can be selected at a time by pressing
the corresponding front panel push-buttons simultaneously.
Whenever power to the SPM412e is turned off or interrupted,
Channel Select settings are retained in non-volatile memory for
recall when power is turned back on. However, default settings
can be defined and stored for recall at power-up (see Power
Switch below). NOTE: See Remote Control on page 6.

(3) Bass: This rotary control adjusts the low-frequency (Bass)
content of the Main Output signals. When this control is centered
(12 o’clock), Bass is normal (flat). When turned counter-clockwise,
Bass is decreased (-12dB @ 200Hz max.). When turned
clockwise, Bass is increased (+12dB @ 200Hz max.). A rear

panel switch allows the Bass & Treble controls to be bypassed
(see Tone on pg. 3).

(4) Treble: This rotary control adjusts the high-frequency (Treble)
content of the Main Output signals. When this control is centered
(12 o’clock), Treble is normal (flat). When turned counter­clockwise, Treble is decreased (-12dB @ 5kHz max.). When
turned clockwise, Treble is increased (+12dB @ 5kHz max.). A

rear panel switch allows the Bass & Treble controls to be bypassed
(see Tone on pg. 3).

(5) Balance: This rotary control adjusts the stereo balance of the
Main Output signals. When this control is centered (12 o’clock),
left and right signal levels are equal. When turned counter­clockwise, left signal level increases and right signal level
decreases. When turned clockwise, right signal level increases
and left signal level decreases. Use the Balance control to
compensate for uneven speaker coverage.

(6) Zone Level: This rotary control adjusts the overall level of
signals sent to the Zone Output (see Zone Output on pg. 3).

(7) Main Level: These three momentary push-buttons adjust the
overall level of signals sent to the Main Output (see Main Output
on pg. 3). The Down push-button decreases level and the Up
push-button increases level. As long as either push-button is
being pressed, signal level will continue to change until the
minimum or maximum level has been reached. It takes
approximately five seconds to adjust from one extreme to the
other. When the Mute push-button is pressed, the output is muted
(turned off). Pressing the Mute push-button again will gradually
un-mute the output. Pressing the Up push-button (while the output

is muted) will immediately un-mute the output and begin increasing
the level. However, Pressing the Down push-button (while the
output is muted) will cause there to be a decreased level when the
output is un-muted. Whenever power to the SPM412e is turned off
or interrupted, Main Level settings (except Mute) are retained in
non-volatile memory for recall when power is turned back on.
However, a default level setting can be defined and stored for
recall at power-up (see Power Switch below). The 9-segment LED

display indicates the relative level setting for the Main Output. The
display is not a signal level meter. The output has approximately
10dB of gain at ‘max’, 70dB of attenuation at ‘min’, and 0dB of gain
(unity) when seven of the nine LEDs are lit. When Main Output is
muted, only the ‘min’ LED will be lit. When Main Output is un­muted, the display will return to the current level setting. Pressing

the Down button (while the output is muted) will cause there to be
a decreased level when the output is un-muted
display will remain at ‘min’ until the output is actually un-muted.

NOTE: See Remote Control on page 6.

NOTE: Whenever power to the SPM412e is removed or
interrupted, Channel Select & Main Level settings (except Mute)
are retained in non-volatile memory for recall when power is
restored. Default Channel Select and Main Level settings can be
defined & stored for recall at power-up. To define & store default
settings: 1) Select the default Stereo Line Input(s). 2) Adjust
Main Level to the default setting. 3) Allow 3 seconds of inactivity
(settings are stored in non-volatile memory). 4) Turn unit off (un­plug from AC power). 5) Press and hold the Mute push-button
while restoring power. 6) Release the Mute push-button. 7)
Cycle power off & on again (confirms the default power-up settings
are stored). These Channel Select & Main Level settings are now
stored in non-volatile memory, and will be recalled whenever
power to the SPM412e is turned off & on (interrupted). NOTE:
This process can be reversed (so the SPM412e will again recall
the most recent settings at power up) by repeating steps 4~7.

, however, the

2

REAR PANEL FEATURES

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

(1) DC Power Supply: The included power supply module

provides 24 Volt DC power to the mixer. It is connected to the DC
Power Jack on the rear side of the mixer. To ensure compatibility,
only use a Biamp Systems’ supplied power supply.

(2) Remote: When the adjacent switch is released, the ‘IR2’,
‘IR3’, & ‘gnd’ terminals can be used for connection of optional
remote controls (see Remote Control on pg. 6). When the
adjacent switch is depressed, the ‘hi’, ‘lo’ & ‘gnd’ terminals can be
used as a ‘Translator’ input for remote control via third-party
controllers which utilize a carrier-stripped serial bit-stream (see
Translator on pg. 7).

(3) Zone Output: This balanced output carries a mono sum of
the selected Stereo Line Input signal, and the Mic/Line Input signal
(see Modifications on pg. 4). Zone Output provides 6dB of
additional gain when balanced. For unbalanced use, connect
signal to (+) and ground to (

d

), leaving (-) unconnected. When
Mic/Line Input signal is present, stereo input signal may be muted
automatically by up to 40dB (see Mic/Line Input on this page).

(4) Main Output: This balanced stereo output carries the
selected Stereo Line Input signal, and the Mic/Line Input signal
(see Modifications on pg. 4 & 5). Main Output provides 6dB of
additional gain when balanced. For unbalanced use, connect
signal to (+) and ground to (

d

), leaving (-) unconnected. When
Mic/Line Input signal is present, stereo input signal may be muted
automatically by up to 40dB (see Mic/Line Input on this page).

(5) Limit Threshold: This screwdriver adjustable control sets the
threshold level for the internal limiter. When Main Output signal
levels exceed this threshold, the limiter is activated and the
adjacent Limit indicator will light. Limit Threshold range is -4dBu to
+24dBu (balanced) or -10dBu to +18dBu (unbalanced). Use the
limiter to set maximum levels for sound system protection.

(6) Main (Stereo / Mono): When depressed, this switch
combines the stereo left & right Main Output signals into a mono
sum, which is then sent to both left & right Main Outputs. When

Main Output is set for mono operation, the front panel Balance
control still affects the relative level of the left & right Main Outputs.

(7) Tone (Bypass): When depressed, this switch bypasses the
front panel Bass & Treble controls. Tone Bypass defeats any tone

(8) Inputs 1~4: These RCA connectors provide the unbalanced
Stereo Line Inputs for line-level signals (-10dBu or +4dBu). Use

these inputs to accept signals from cassette, CD, VCR, tuner,
satellite, cable, computer, etc. Inputs 1~4 each have a screwdriver

adjustable control for setting level of the corresponding Stereo Line
Input signal. Use these controls to compensate for different input

signal levels. For best performance, reduce level only on inputs
which are higher than the others. These controls are factory set
fully clockwise for +10dB of gain. This is appropriate for most
inputs such as CD, cassette, tuner, etc. (-10dBu nominal levels).

(9) Mic / Line Input: This balanced input will accept either low­impedance microphone or line-level input signals. For unbalanced

d

use, connect signal to (+) and ground to both (

) & (-). Three
additional terminals are provided for ‘page-over’ muting of the
Stereo Line Input signals. By wiring ‘signal present’ to ‘mute’,
automatic muting of the currently selected Stereo Line Input will
occur whenever signal is present at the Mic/Line Input. Manual
muting of the currently selected Stereo Line Input is achieved by
wiring a switch or contact-closure between ‘mute’ and the adjacent
‘gnd’ terminal. From the factory, ‘page-over’ muting is set for

-40dB, and is assigned to both the Main Output and the Zone
Output (see Mute Assign & Mute Adjust on pg. 4).

(10) Pad: When depressed, this switch reduces the Mic/Line
Input signal level by 30dB (see Mic/Line Input above). Use this

switch when Mic/Line Input signal levels exceed the normal
operating range of the Trim control, or whenever a line-level input
signal is connected.

(11) Trim: This screwdriver adjustable control sets gain at the
Mic/Line Input (see Mic/Line Input above). Use this control to

compensate for different input signal levels. For best performance,
adjust Trim so the adjacent +10 indicator flashes only on
occasional peaks in signal level.

(12) Phantom Power: When depressed, this switch provides +24
Volt Phantom Power to the Mic/Line Input (see Mic/Line Input
above). Phantom Power is for powering condenser microphones.

CAUTION: Never turn Phantom Power on when line-level signal
devices are connected to the Mic/Line Input. Always turn power off
and Mic Level down before switching Phantom Power or making
connections to the Mic/Line Input.

adjustments made to the Main Output signals.

3

MODIFICATIONS

P4

P5

P6

P7

P8

P9

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TS

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To access internal modifications, first disconnect power to the unit. Then lay the unit on a flat surface with the front panel facing forward
and the top panel facing up. Remove the top panel (eight screws along the sides and rear; one screw centered behind the front panel).
Modifications are at the center of the circuit board, starting from the left side (see diagrams below). Modifications require no soldering.

MIC/LINE ASSIGN: Internal jumpers are provided to assign Mic/Line Input signal to the Main Output and the Zone Output, independently.
From the factory, Mic/Line Input signal is assigned to both the Main Output and the Zone Output. To un-assign Mic/Line Input signal from
the Main Output, move jumper P2 (‘MIC INPUT TO MAIN OUTPUT’) forward one pin to the ‘OUT’ position, using needle-nose pliers. To
un-assign Mic/Line Input signal from the Zone Output, move jumper P1 (‘MIC INPUT TO ZONE OUTPUT’) forward one pin to the ‘OUT’
position. If desired, Mic/Line Input signal may be un-assigned from both outputs. A jumper is also provided to assign Mic/Line Input signal
to the Main Output pre or post tone (Treble & Bass). From the factory, Mic/Line Input signal is assigned post-tone (not affected by Treble &
Bass). To assign Mic/Line Input signal pre-tone (affected by Treble & Bass), move jumper P3 (‘MIC INPUT TO MAIN OUTPUTS’) forward
one pin to the ‘PRE-TONE’ position, using needle-nose pliers. See also Mic Pre/Post VCA on page 5.

STEREO INPUT ASSIGN: Internal jumpers are provided to assign Stereo Line Input signals to the Main Output and the Zone Output,
independently. From the factory, Stereo Line Input signal is assigned to both the Main Output and the Zone Output. To un-assign Stereo
Line Input signal from the Main Output, move jumpers P4 & P6 (‘LEFT INPUT TO MAIN OUTPUT’ & ‘RIGHT INPUT TO MAIN OUTPUT’)
forward one pin to the ‘OUT’ position, using needle-nose pliers. If desired, left & right Stereo Line Input signals may be un-assigned from
the Main Output independently. To un-assign Stereo Line Input signal from the Zone Output, move jumper P8 (‘STEREO INPUTS TO
ZONE OUTPUT’) forward one pin to the ‘OUT’ position, using needle-nose pliers.

MUTE ASSIGN: Internal jumpers are provided to assign muting of Stereo Line Input signals at the Main Output and the Zone Output,
independently. From the factory, muting is assigned to both the Main Output and the Zone Output. To un-assign muting from the Main
Output, move jumpers P5 & P7 (‘LEFT INPUT MUTING’ & ‘RIGHT INPUT MUTING’) forward one pin to the ‘OFF’ position, using needle­nose pliers. If desired, muting may be un-assigned from left & right Main Outputs independently. To un-assign muting from the Zone
Output, move jumper P9 (‘STEREO TO ZONE MUTING’) forward one pin to the ‘OFF’ position, using needle-nose pliers. If desired,
muting may be un-assigned from both the Main Output and the Zone Output.

NOTE: Mic/Line Assign, Stereo Input Assign, and Mute Assign are totally independent of each other. Therefore, Mic/Line Input signal may
be un-assigned from either output, without un-assigning the muting function from that output. Likewise, the muting function may be un­assigned from either output, without un-assigning Mic/Line Input signal from that output. To un-assign both Mic/Line Input signal and the
muting function from a given output, both jumpers must be moved. Also, Mic/Line Input signal may be un-assigned from the Main Output
and Stereo Line Input signal may be un-assigned from the Zone Output, creating separate outputs for Stereo Line Input and mono Mic/Line
Input signals. This is useful when separate high-fidelity (music) and distributed (speech) speaker systems are desired.

MUTE ADJUST: Internal screwdriver adjustable controls are provided to adjust the amount of muting applied to Stereo Line Input signals.
From the factory, -40dB of muting is set for Stereo Line Input signals. To decrease the amount of muting at the Main Output, adjust
controls R75 & R76 (‘MUTE TRIM’) clockwise. To decrease the amount of muting at the Zone Output, adjust control R77 (‘MUTE TRIM’)
clockwise. These controls are totally independent. Therefore, different amounts of muting may be set for each output. However, muting is
usually set the same for left & right Main Outputs. The muting range is adjustable from -40dB (max.) to -4dB (min.).

IN
OUT

LEFT INPUT

TO MAIN OUTPULEFT INPUT

MUTING

P2 P3

IN
MIC INPUT TO MAIN OUTPUTS
OUT

P1

IN
MIC INPUT TO ZONE OUTPUT
OUT

ON
OFF

MUTE TRIM

(CCW = MAX)

R75 R76 R77

IN
OUT

RIGHT INPUT

TO MAIN OUTPURIGHT INPUT

ON
OFF

MUTING

POST-TONE (SEE VCA JUMPERS)
MIC INPUT TO MAIN OUTPUTS
PRE-TONE

MUTE TRIM

(CCW = MAX)

IN

ON

OUT

OFF

STEREO INPU

TO ZONE OUTPUSTEREO TO ZO

MUTING

MUTE TRIM

(CCW = MAX

4