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Introduction
Congratulations on purchasing the Samson PL 2404 four-bus line mixer! The
PL 2404 is optimized for use as a keyboard submixer in both live performance
and recording applications, and it can be used wherever there are a number of
stereo or mono line-level sources that need to mixed down to two or four
outputs. Although the PL 2404 is designed for easy operation, we suggest you
first take some time to go through these pages so you can fully understand how
we’ve implemented a number of unique features.
In this manual, we’ll provide you with an overview of PL 2404 features, followed
by a guided tour of its front and rear panels. Then we’ll describe how the
PL 2404 should be connected to your existing equipment (including wiring
diagrams) and talk about the important topics of gain structure and grounding
techniques. Next, we’ll cover a number of specific PL 2404 features (such as
busing, submixing, channel muting, as well as using balance, equalization,
auxiliary sends and returns, channel inserts, and PFL/AFL) in detail. Finally,
we’ll wrap things up with a series of applications notes describing a number of
ways to use the PL 2404 for both recording and live performance, plus reference
Appendices and full specifications. You’ll also find a warranty card enclosed—
please don’t forget to fill it out and mail it so that you can receive online technical
support and so we can send you updated information about other Samson
products in the future.
SPECIAL NOTE: Should your unit ever require servicing, a Return Authorization
number (RA) is necessary. Without this number, the unit will not be accepted.
Please call Samson at 1-800-372-6766 for a Return Authorization number prior
to shipping your unit. Please retain the original packing materials and, if
possible, return the unit in its original carton and packing materials.
PL 2404 Features
“PL” stands for “Program/Line” and the name describes the broad range of
signals which can be handled by this powerful four-bus mixer. In fact, the
compact design of the PL 2404 belies an extraordinary versatility. Add excellent
sound quality to the equation, and you’ve got a product which is equally useful in
live performance and for recording (you’ll find descriptions of each application at
the conclusion of this manual). Here are some of the PL 2404’s main features:
• Twenty-four input channels, which can be used as twelve stereo channels.
All channels provide electronically balanced line-level inputs, and are ideal
for line-level sources such as keyboards and MIDI tone modules; drum
machines; outboard signal processors; CD players; and tape or cassette
recorders. In addition, channels 1 and 3 provide electronically balanced XLR
mic inputs so that you can connect one or two microphones to the PL 2404.
• Four bus outputs (a “bus” is simply a pathway through which a signal can be
routed) and an electronically balanced main stereo output, with dedicated
front panel control. Any channel input can be routed to either of the two bus
pairs (1/2 or 3/4), and any of the buses can be routed to the Left/Right mix
output with the touch of a button. This flexible design allows you to easily
mute selected channels and/or to create submixes within your main mix.
1
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PL 2404 Features
• An independent electronically balanced Control Room output (with dedicated
level control) for connection to a power amplifier and studio monitors.
• Four Bus faders enable easy control of bus output levels.
• Input trims for the mic inputs of channels 1 and 3 are continuously adjustable
from +4 to -50 dB, making it possible to use the PL 2404 with a wide variety
of microphone types.
• Four auxiliary sends and four stereo auxiliary returns (which can be routed to
any of the four buses). All aux sends are post-fader and post-equalizer.
• Independent 3-band equalization for each channel, with 15 dB of cut or boost
for low (80 Hz), mid (1 kHz) and high (10 kHz) frequencies.
• Balance controls for each channel that allow you to blend the relative levels
of stereo inputs.
• Center detents for all Balance and EQ controls, making it easy to use the
PL 2404 even in low-light situations such as live performance.
• Selectable Pre Fade Listen (PFL) or After Fade Listen (AFL) soloing for each
channel. PFL allows headphone monitoring of individual channels, pre-fader
(but post-EQ), while AFL enables headphone monitoring of individual
channels, post-fader and post-EQ, with the channel in its proper stereo
position. Both types of solo function are non-mix-destructive in that they do
not affect the signal being output either by the Main, Bus, or Control Room
outputs.
• A flexible front panel metering system includes a ten-segment level meter
and allows you to view at a glance the levels of the main Left/Right output,
as well as power and PFL or AFL status.
• An independent front-panel headphone output with dedicated volume
control and Main/Solo switch for selective monitoring of either the Main
output or of channels that are soloed.
• Channel inserts are provided for channels 1 - 4, enabling you to use
outboard signal processors such as equalizers, compressor/ limiters, or
noise gates in a standard “effect loop.”
• Bus inserts allow external signals to be submixed into any or all of the four
buses and also enables linking of multiple mixers.
• The PL 2404 can be mounted in any standard 19" rack (taking four rack
spaces), making it easy to integrate into any existing system.
• Last but certainly not least, affordability. The PL 2404 has been designed
from the ground up to provide versatility and excellent sound quality at a
cost-conscious price.
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Guided Tour - Overview
The following illustration shows an overview of the front panel of the PL 2404:
AUX RETURNS
CH 1/2
CH 3/4
CH 5/6
CH 7/8
CH 9/10
CH 11/12
CH 13/14
CH 15/16
CH 17/18
CH 19/20
CH 21/22
CH 23/24
SAMSON
PL 2404 STEREO MIXER
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
HIGH
MID
0
HIGH
MID
0
HIGH
MID
HIGH
MID
0
HIGH
MID
HIGH
MID
HIGH
MID
HIGH
MID
HIGH
MID
HIGH
MID
HIGH
MID
HIGH
0
-15
-15
+15
+15
-15
-15
+15
+15
-15
0
+15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
-15
+15
+15
-15
+15
+15
∞
+10
-15
-15
AUX RET.1
0
0
0
0
MID
0
0
0
-18 -12 -9 -6 -3
0
0
+3 +6 +9 +12
LEFT
1/2
3/4
RIGHT
-15
-15
+15
-15
LOW
-18 -12 -9 -6 -3
PFL AFL
+3 +6 +9 +12
POWER
LOW
AUX
LOW
LOW
0
LOW
LOW
0
LOW
0
LOW
0
LOW
0
LOW
0
LOW
0
LOW
0
0
0
-15
+15
-15
+15
+15
+15
-15
+15
-15
+15
-15
+15
-15
+15
-15
+15
-15
+15
-15
+15
0
-15
+15
∞
∞
-15
+10
PFL
AFL
SOLO
MAIN
AUX RET.2
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R AUX
1L-2R
0
0
0
0
0
0
0
0
0
0
0
1/2
3/4
0
0
∞
∞
∞
+10
0
∞
∞
∞
∞
∞
∞
+10
0
∞
∞
∞
+10
0
∞
∞
∞
+10
0
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
∞
+10
0
∞
∞
∞
+10
0
∞
∞
∞
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
0
AUX
AUX
3L
AUX
3L
AUX
3L
AUX
3L
AUX
AUX
3L
AUX
3L
AUX
3L
AUX
3L
AUX
3L
AUX
3L
AUX
AUX
3L AUX
4R AUX
3L
∞
+10
MAIN LEVEL
∞
+10
+10
CONTROL ROOM
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
+10
0
AUX RET.3
4R AUX
4R AUX
4R AUX
4R
4R AUX
4R AUX
4R AUX
4R AUX
4R AUX
4R
4R
1/2
3/4
L
R
L
R
+10
+10
+10
+10
+10
+10
+10
+10
+10
+10
+10
+10
0
+10
dB
+10
dB
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
OFF
SOLO
ON OFF
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
∞
+10
AUX RET.4
0
MUTE
3/4
0
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
MUTE
3/4
1/2
3/4
0
0
+10
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
L
R
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
BALANCE
0
0
0
0
0
0
0
0
0
0
0
0
∞
∞
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
∞
+10
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
LEVEL
PHONES
BUS
1
BUS
2
BUS
3
BUS
4
CHANNELS
MAIN SECTION
3
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Guided Tour - Channels
1: Equalizer (violet) - These knobs determine the amount of boost or attenuation in each
of three frequency areas (up to 15 dB for each area). The mid frequency control (centered
at 1 kHz) utilizes a resonant (“bell”) peaking curve, while the high and low frequency
controls (centered at 10 kHz and 80 Hz, respectively) utilize shelving curves. The EQ
setting affects both the odd- and even-numbered channel inputs, although the signals
remain separate. A center detent in each knob (at the “0” position) indicates no boost or
attenuation (that is, flat response). As each knob is turned clockwise from the “0” position,
the frequency area is boosted; as it is turned counterclockwise from the “0” position, the
frequency area is attenuated. For more information on the application of EQ, see the
“Using Equalization” section on page 19.
CH 1/2
0
HIGH
MID
-15
-15
+15
+15
0
0
1
2
LOW
AUX
2: Auxiliary sends (blue) - These knobs (labeled “Aux 1L-2R,” “Aux 3L,” and “Aux 4R”)
allow you to route signal to any of the PL 2404’s four Auxiliary outputs. These are typically
used to route signal to outboard effects devices. When a pair of channel inputs (that is,
both odd-numbered and even-numbered) are connected, the odd-numbered (left) input
signal can only be routed to Aux 1L and Aux 3L, while the even-numbered (right) input can
only be routed to Aux 2R and Aux 4R. In this case, the Aux 1L-2R send acts as a stereo
auxiliary send, with the left side of the input signal routed to Aux 1L and the right side rout-
ed (at equal level) to Aux 2R. When only the even-numbered (right) input is connected, the
signal can only be routed to Aux 2R or Aux 4R. When only the odd-numbered (left) input is
connected, the signal can be routed to any of the four Aux sends. When an Aux send knob
is at the “0” (2 o’clock) position, the signal is routed with unity gain (that is, no boost or
attenuation). As each Aux send knob is turned clockwise towards the “+10” position, the
signal is boosted (by a maximum of 10 dB); as it is turned counterclockwise towards the
“∞” position, it is attenuated (at the very bottom, it is attenuated infinitely—in other words,
no signal is routed). All four Aux sends are post-fade; that is, the level of the signal is
determined by the position of the channel’s Level control, its EQ settings, the position of
the main Level control, and (in the case of channels 1 and 3) Trim control. For more
information, see the “Using Auxiliary Sends and Returns” section on page 20.
-15
+15
1L-2R
0
∞
∞
+10
0
AUX
AUX
3L
+10
0
4R
∞
+10
SOLO
OFF
3
4
ON
MUTE
3/4
5
6
L
R
BALANCE
3: Solo On/Off switch - When pressed in, the channel is soloed (in headphones only, and
only when the Solo/Main switch in the PL 2404 main section is in the Solo position).
Soloing will be in either PFL (Pre Fade Listen) or AFL (After Fade Listen) mode, depending
upon the setting of the PFL/AFL switch in the PL 2404 main section. See #7 and #8 on
page 7 and the “Using PFL/AFL” section on page 22 for more information.
0
∞
+10
LEVEL
4: Mute 3/4 switch - When up, the channel’s signal is routed to the Bus 1/2 faders and
then on to the Bus 1/2 and, optionally, Main and Control Room output jacks (if, as
described in #10 on page 7, the Bus “L/R” switches for those buses is pressed in). When
pressed in, the channel’s signal is instead routed to the Bus 3/4 faders and then on to the
Bus 3/4 and, optionally, Main and Control Room output jacks (if, as described in #10 on
page 7, the Bus “L/R” switches for those buses is pressed in). If you set the Bus 3/4 faders
all the way down (to their “∞” position), this switch can be used for channel muting. See
the “Busing, Submixing and Channel Muting” section on page 17 for more information.
5: Balance (brown) - When a pair of channel inputs (that is, both odd-numbered and
even-numbered) are connected, the odd-numbered (left) input signal is automatically
panned hard left and the even-numbered (right) input signal is automatically panned hard
right. In this case, the “Balance” knob controls the relative levels of the paired input
signals. When the knob is placed at its center detented position, both signals are at equal
strength. When moved left of center, the odd-numbered (left) input signal remains at the
same strength but the even-numbered (right) input signal is attenuated; when the knob is
moved right of center, the even-numbered (left) input signal remains at the same strength
but the odd-numbered (right) input signal is attenuated. When placed fully counterclock-
wise, only the odd-numbered (left) input signal is heard (panned hard left); when placed
4
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Guided Tour - Channels
fully clockwise, only the even-numbered (right) input signal is heard (panned
hard right). When only the odd-numbered (left) input is connected, the Balance
knob functions as a constant level Pan control, allowing you to continuously
place the incoming signal anywhere in the left-right stereo field. For more
information, see the “Using the Balance Control” section on page 18 in this
manual.
6: Level (white) - This knob (purposely made a little bigger than the others so
you can find it easily in low-light situations) simultaneously controls the volume
of both the odd- and even-numbered channel inputs (the relative volumes of the
two can be adjusted with the Balance knob, as described in #5 above). In
practice, you will use the Level controls to continuously adjust the loudnesses of
the various signals being blended together by the PL 2404. The “0” (2 o’clock)
position of the knob indicates unity gain (no level attenuation or boost). Moving
the knob counterclockwise from the “0” position (towards “∞”) causes the signal
to be attenuated (at the very bottom, it is attenuated infinitely—in other words,
there is no sound). Moving it clockwise from the “0” position (towards “+10”)
causes the signal to be boosted by as much as 10 dB.
For best signal-to-noise ratio, all Level controls for channels carrying signal
should generally be kept at or near the “0” position. Channels that are unused
should have their Level controls kept fully counterclockwise at their “∞”
(minimum) level. See the “Setting the Correct Gain Structure” section on page
13 in this manual for more information.
5
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Guided Tour - Main Section
AUX RETURNS
SAMSON
PL 2404 STEREO MIXER
0
∞
+10
AUX RET.1
-18 -12 -9 -6 -3
0
0
+3 +6 +9 +12
5
6
9
LEFT
1/2
3/4
RIGHT
-18 -12 -9 -6 -3
PFL AFL
+3 +6 +9 +12
POWER
0
∞
+10
8
7
PFL
AFL
SOLO
MAIN
AUX RET.2
1/2
3/4
1
2
0
0
0
10
∞
+10
MAIN LEVEL
∞
+10
∞
+10
CONTROL ROOM
AUX RET.3
1/2
3/4
L
R
L
R
11
0
+10
dB
+10
dB
∞
+10
AUX RET.4
0
0
1/2
3/4
0
3
4
0
+10
∞
∞
12
PHONES
BUS
1
BUS
2
BUS
3
BUS
4
1: Auxiliary Return Level (orange) - These knobs determine the input level of
signal arriving via the PL 2404’s four stereo Auxiliary returns. The “0” (2 o’clock)
position of each knob indicates unity gain (no level attenuation or boost). Moving
each knob counterclockwise from the “0” position (towards “∞”) causes the signal
to be attenuated (at the fully counterclockwise position, it is attenuated infinite-
ly—in other words, there is no sound). Moving each knob clockwise from the “0”
position (towards “+10”) causes the signal to be boosted by as much as 10 dB.
For information on how to properly set these, see the sections in this manual
entitled “Setting the Correct Gain Structure” and “Using the Aux Sends and
Returns” (pages 13 and 20).
2: Auxiliary Return Bus switch - These switches determine which of the two
pairs of stereo buses (1/2 or 3/4) the Aux return signal is routed to. When up,
the Return’s signal is routed to the Bus 1/2 faders and then on to the Bus 1/2
jacks as well as (if the Bus “L/R” switch is pressed in—see #10 on page 7) the
Main and Control Room output jacks. When pressed in, the channel’s signal is
instead routed to the Bus 3/4 faders and then on to the Bus 3/4 jacks as well as
(if the Bus “L/R” switch is pressed in) the Main and Control Room output jacks.
If you set the Bus 3/4 faders all the way down (to their “∞” position), this switch
can be used for selective muting of Aux returns. See the “Busing, Submixing
and Channel Muting” and “Using the Aux Sends and Returns” sections on page
17 and page 20 in this manual.
3: Headphone Level - This knob sets the level of the signal sent to the
headphone jack (see #4 below). WARNING: To avoid possible damage to con-
nected headphones (or, worse yet, to your ears!), always turn this all the way off
(to the fully counterclockwise “0” position) before plugging in a pair of head-
phones—then raise the level slowly while listening. The Headphone Level has
no effect on the final Main output level or on the Control Room output level.
4: Headphone jack - Connect any standard stereo headphones to this jack
(via a 1/4" TRS plug) for private monitoring of the Main output (including all
connected Aux returns). The built-in PL 2404 headphone preamp delivers
120 mw at 33 ohms.
6
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Guided Tour - Main Section
5: Meter - This ten-segment bar meter shows the continuous output level of the
Main left/right output. For optimum signal-to-noise ratio, try to adjust all levels so
that program material is usually at or around 0 VU, with occasional but not
steady excursions to the red “+” segments. See the “Setting the Correct Gain
Structure” section on page 13 in this manual for more information.
6: Meter LEDs - These show the status of various conditions within the
PL 2404. The leftmost LED (labeled “PFL”) lights steadily green when the
PL 2404 is in PFL mode (see #7 below). The center LED (labeled “AFL”) lights
steadily red when the PL 2404 is in AFL mode (see #7 below). The rightmost
LED (labeled “Power”) lights steadily red whenever the PL 2404 is powered on.
7: PFL/AFL switch - This determines whether the PL 2404 is in PFL mode
(switch up) or AFL mode (switch pressed in). For more information, see the
“Using PFL/AFL” section on page 22 in this manual.
8: Solo/Main switch - This switch affects headphone monitoring only. When
the switch is up (Solo mode), the headphones receive signal from only those
channels whose Solo switches are currently pressed in; when the switch is
pressed in (Main mode), the headphones always receive the Main output
regardless of the settings of any channel Solo switches. For more information,
see #3 on page 4 and the “Using PFL/AFL” section on page 22.
9: Main Level - This knob determines the final signal level of the rear panel
Main output—you can think of this as being the “master fader.” The 2 o’clock “0”
position of the knob indicates unity gain (no level attenuation or boost). Moving
the knob counterclockwise from the “0” position (towards “∞”) causes the signal
to be attenuated (at the very bottom, it is attenuated infinitely—in other words,
there is no sound). Moving it clockwise from the “0” position (towards “+10”)
causes the signal to be boosted by up to 10 dB. For more information, see the
“Setting The Correct Gain Structure” section on page 13 in this manual.
10: Control Room Level - This knob determines the signal level of the rear
panel Control Room output, allowing independent monitoring of the Main output
signal. The 2 o’clock “0” position of the knob indicates unity gain (no level
attenuation or boost). Moving the knob counterclockwise from the “0” position
(towards “∞”) causes the signal to be attenuated (at the very bottom, it is attenu-
ated infinitely—in other words, there is no sound). Moving it clockwise from the
“0” position (towards “+10”) causes the signal to be boosted by up to 10 dB.
11: Bus L/R switches - These switches allow you to route the output from any
of the four buses to the Main left/right output jacks and Control Room left/right
output jacks on the rear panel (see #5 and #6 on page 8). When up, the signal
from that bus is not routed to the main outputs and terminates at its Bus out jack
(see #4 on page 8). When pressed in, the signal from that bus is routed to the
main outputs as well as its Bus out jack.
12: Bus Faders (white with blue line) - These linear sliders determine the
relative level of the four bus outputs. The “0” position of each fader indicates
unity gain (no level boost or attenuation). Moving the fader below this position
(towards the “∞” position) causes the signal to be attenuated (at the very bottom,
it is attenuated infinitely—in other words, there is no sound). Moving it above
this position (towards the “+10 dB” position) causes the signal to be boosted by
up to 10 dB. For best signal-to-noise ratio, all Bus faders should generally be
kept at or near the 0 level. For more information, see the “Setting The Correct
Gain Structure” section on page 13 in this manual .
7
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Guided Tour - Rear Panel
4
7
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
1
2
1
TRS
TRS INSERT
XLR
TRS
BALANCED
STEREO INPUT
UNBALANCED
BALANCED
3
3
POWER
+4
−50
+4
−50
TIP = LEFT
TIP = RETURN
RING = SEND
SLEEVE = COM
3 = LO
2 = HI
TIP = HI
RING = RIGHT
SLEEVE = COM
RING = LO
1 = COM
SLEEVE = COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC 3
9
MIC 1
1
8
9
OFF
2
1
23
21
19
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
24
22
20
18
16
14
12
10
8
4
6
4
2
2
4
3
LINE INPUTS - BALANCED 10KΩ+4dBu
3
1
2
3
10
POWER
INSERT
115V - 60 Hz 25W
RATING
CAUTION
RISK OF ELECTRIC SHOCK
R
L
!
DO NOT OPEN
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
R
L
AUX SENDS
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
UNBALANCED <75Ω +4dBu
S/N
5
6
11
12
13
1: Power on-off switch - As you may have guessed, this is what you use to turn the
PL 2404 on and off. To avoid potential damage to your speakers, turn the PL 2404 on
before you turn on any connected power amps—and turn it off after the power amps are
turned off.
2. Fuse - Contains a 1 amp, 250 volt fuse.
3. AC input - Connect the supplied standard 3-pin “EEC” plug here.
4: Bus out (1 - 4) - These unbalanced outputs allow you to route signal from each of the
four discrete buses to external devices such as a multitrack digital or analog tape
recorder. The signal is post-bus fader but pre-Main control. See the “Busing,
Submixing, and Channel Muting” section in this manual for more information.
5: Main Out (L, R) - These are the PL 2404’s main outputs. In live performance
applications, you’ll usually use these to connect the PL 2404 to a power amp and
speakers; in recording applications, these will normally be connected to the inputs of a
two-track recorder. The Main out jacks are electronically balanced, so you should use
balanced three-conductor cabling and 1/4" TRS plugs wherever possible (unbalanced
two-conductor plugs can also be inserted into these outputs, but you’ll get better signal
quality and less outside noise and hum if you use balanced lines). See the “Connecting
the PL 2404” section on page 10 for more information.
6: Control Room Out (L, R) - In recording applications, these will normally be
connected to a power amplifier and loudspeakers. The Control Room out jacks are
electronically balanced, so you should use balanced three-conductor cabling and 1/4"
TRS plugs wherever possible (unbalanced two-conductor plugs can also be inserted into
these outputs, but you’ll get better signal quality and less outside noise and hum if you
use balanced lines). See the “Connecting the PL 2404” section on page 10 in this
manual for more information.
8
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Guided Tour - Rear Panel
7: Mic inputs (channels 1 and 3) - Use these electronically balanced XLR jacks
to connect a microphone to channel 1 and/or channel 3. These are intended to
accept signal from low-level, low-impedance mics but can also be used for signal
from other sources (such as direct injection boxes) if the channel’s Trim control
(see #8 below) is turned down. WARNING: Do not connect a channel’s micro-
phone input if you already have something connected to its line input (see #9
below); these channels are designed to accept only one source or the other.
8: Trim control (black) - This knob determines the input level of the mic signal
connected to channel 1 and/or channel 3. Continuously adjustable from +4 dB
to -50 dB, the trim control is at unity gain (no boost or cut) when set to the “0”
(9 o’clock) position. The input signal is boosted when the trim is turned to the
right of “0” and attenuated when turned to the left of “0.” For information on how
to properly set this, see the section on page 13 entitled “Setting The Correct
Gain Structure.”
9: Line inputs - Use these electronically balanced 1/4" jacks to connect line-
level sources such as synthesizers, drum machines, CD players, tape decks, or
effects processors to any of the PL 2404’s twenty-four channels. Use balanced
three-conductor cabling and Tip/Ring/Sleeve (TRS) plugs wherever possible
(unbalanced two-conductor plugs can also be inserted into these inputs, but
you’ll get better signal quality and less outside noise and hum if you use
balanced lines). When connecting monophonic (as opposed to stereo) signal
sources, use the left (odd-numbered) inputs; the Balance control for that channel
pair will then act as a constant level pan control—see the “Using the Balance
Control” section on page 18 for more information. The “Connecting the
PL 2404” section on page 10 provides more information on how best to use
channel inputs. WARNING: Do not connect the channel 1 or 3 line input if you
already have something connected to that channel’s microphone input (see #7
above); these channels are designed to accept only one source or the other.
10: Channel Inserts (1 - 4) - Use these to insert an external effects processor
(such as outboard equalizer, compressor/limiter or noise gate) into any of the
PL 2404’s channels 1 - 4 in an “effects loop” configuration. These jacks accept
1/4" TRS plugs, with the ring carrying the send signal and the tip carrying the
return signal. Normally, this will be connected to a Y-cord; see the “Connecting
The PL 2404” section on page 10 for more information and a wiring diagram.
11: Bus Inserts (1 - 4) - Connect the output from another device to these in
order to “submix” in their signal to the PL 2404 at unity gain. This can be used to
link multiple PL 2404s or to add the output from another mixer to the PL 2404
without taking up channel line inputs. The Bus Insert jacks accept unbalanced
1/4" plugs. See the “Linking the PL 2404” Application on page 26 for more
information.
12: Aux Returns (1 - 4) - These unbalanced 1/4" inputs allow you to route
signal from external devices such as effects processors to any of the four stereo
Aux Returns. These jacks accept 1/4" TRS plugs, with the tip carrying the left
signal and the ring carrying the right signal (sleeve is common ground). See the
“Using Aux Sends and Returns” section on page 20 for more information.
13: Aux Sends (1 - 4) - These unbalanced 1/4" outputs allow you to route
signal from any of the four discrete Aux Sends to external devices such as
effects processors. All four PL 2404 Aux sends are post-fade. See the “Using
Aux Sends and Returns” section on page 20 for more information.
9
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Connecting The PL 2404 - General Suggestions
The actual connections you’ll make to and from the PL 2404 will vary according
to the environment you use it in and the particular equipment you have. In the
“PL 2404 Applications” sections at the rear of this manual, you’ll find some
suggested setups. Here are a few basic rules concerning PL 2404 connections
that will apply in most situations:
• In general, it’s best to make all connections with the PL 2404 and any
connected power amplifiers turned off. If you must make connections with
the power on, make sure that the Main and Control Room Level knobs are
completely counterclockwise and that all four bus faders are completely
down (at their “∞” position). Whenever powering down, bring the Main and
Control Room Level knobs completely counterclockwise and set all four bus
faders completely down, turning off the main power amps first. Wait a few
seconds for their power supplies to discharge and then turn off all connected
equipment, turning the PL 2404 off last.
• Try to use balanced connectors and cabling wherever possible. These kind
of connections do a better job of rejecting extraneous noise and hum and
generally provide a cleaner signal. Although the PL 2404 will accept unbal-
anced connectors throughout, it specifically provides electronically balanced
inputs for all line inputs and for its Main and Control Room outputs. The
wiring diagram below shows how 1/4" TRS (Tip/Ring/Sleeve) connectors
should be wired for use with these inputs and outputs:
SLEEVE
RING
TIP +
TIP
GROUND
RING -
Unbalanced cables use standard 1/4" phone connectors, wired as follows:
+ SIGNAL
GROUND
+ SIGNAL
GROUND
• Make one connection at a time and then monitor the incoming signal. If you
hear a distinct hum or buzz, you may have a grounding problem with that
particular device. See the “Grounding Techniques” section on page 15 in
this manual for information on how to avoid grounding problems.
• When using channels 1 and 3, be sure not to connect both a microphone
and line level input simultaneously—use one or the other. The diagram
below shows how your mic connectors should be wired:
3 - SIGNAL
1 GROUND
2 + SIGNAL
TO MIXER
10
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Connecting The PL 2404 - General Suggestions
• Matched signals (i.e. the stereo left-right outputs of a keyboard, drum
machine, tone generator, effects processor, CD player, or tape recorder),
should always be connected to the PL 2404’s paired odd/even channels (i.e.
1L/2R, 3L/4R, etc.). The channel Balance control will allow you to adjust the
relative levels of the two inputs, and you can also equalize the stereo signal,
with the same EQ settings applied to both inputs.
• There are four more “hidden” (or at least not so obvious) stereo inputs to the
PL 2404; these are the Auxiliary returns. Use these whenever you want to
bring in stereo signals that will not need to be equalized.
• When connecting only one monophonic signal to a stereo channel, always
use the left (odd-numbered) input. When only the left input is connected, the
PL 2404 treats that channel as if it is a mono channel and the signal can
then be panned (using the Balance control) and routed to all four Aux sends.
See the “Using the Balance Control” and “Using Aux Sends And Returns”
sections in this manual (pages 18 and 20) for more information.
• Signals that are likely to require “in-line” processing (such as
compression/limiting or expansion/noise gating) should be connected to
channels 1 - 4, since these channels provide an insert connection. Insert
cables (sometimes called “Y-cords”) should terminate in standard 1/4" TRS
jacks (ring to send and tip to return), wired as follows:
SLEEVE
RING
TIP RETURN
GROUND
RING SEND
TIP
• The PL 2404 Aux return jacks are unbalanced stereo inputs, with the tip
carrying the left input signal and the ring carrying the right input signal (with
the sleeve carrying common ground), as shown below. Insertion of a mono-
phonic 1/4" jack into an Aux return will result in the incoming signal being
automatically routed to the left input only (and therefore panned hard left).
TIP (LEFT SIGNAL)
RING (RIGHT SIGNAL)
SLEEVE (COMMON GROUND)
11
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Setting Up and Using The PL 2404
Setting up your PL 2404 is a simple procedure which takes only a few minutes:
1. Remove all packing materials (save them in case of need for future service)
and decide where the unit is to be physically placed—it can be mounted in any
standard 19" rack, requiring four rack spaces, or used on a tabletop.
2. Before even plugging the unit into an AC socket, begin by connecting the
PL 2404 Main or Control Room outputs into a power amp and the amp into
loudspeakers (you’ll usually connect the Main output to a power amp in live
performance environments and the Control Room output to a power amp when
using the PL 2404 for recording). It is never a good idea to power up any
amplifier that is not connected to loudspeakers.
R
L
MAIN
BALANCED <75Ω+4dBu
SAMSON
SERVO - 240
3. Next, make the signal input connections to the mic or line inputs of the
various channels. WARNING: When using channel 1 or 3, do not connect its
microphone input and line input simultaneously; these channels are designed to
accept only one source or the other.
4. Turn all channel Level controls fully counterclockwise (to their “∞” setting),
bring all four bus faders completely down (to their “∞” setting), and set the Main
and Control Room Level controls fully counterclockwise (to their “∞” setting.
If you are using the channel 1 or 3 mic inputs, set their Trim controls fully
counterclockwise (to their “+4” setting). Then connect the EEC main power cord
and plug the PL 2404 into any grounded AC socket.
5. Turn on the rear panel Power switch—the “Power” LED in the main section
will light up.
12
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Setting the Correct Gain Structure
You’re now ready to establish the correct gain structure—the key to getting the
best performance from the PL 2404, or from any mixer, for that matter. This is a
simple procedure that ensures optimum input and output levels so that no
unnecessary noise (caused by too low a signal) or overload distortion (caused by
too high a signal) is created. Here’s a step-by-step description of how to do so:
a. With all connections made (as described above) but with the power amplifier
and PL 2404 off, start by setting the power amplifier volume to minimum. On
the PL 2404, turn all channel Level controls fully counterclockwise (to their “∞”
position) and set all four bus faders to their “∞” position. If the Main output jacks
are connected to a power amplifer and loudspeakers (as described in #2 on
page 12), set the Main Level knob to its 2 o’clock “0” position. If the Control
Room output jacks are connected to a power amplifer and loudspeakers (as
described in #2 on page 12), set the Control Room Level knob to its 2 o’clock “0”
position.
b. If you have a microphone connected to channel 1 and/or channel 3, set the
rear panel Trim knobs to their fully counterclockwise (+4) position.
c. Set all channel EQ and Balance knobs to their center detent “0” positions.
d. Set all channel Aux send knobs and all Aux return Level knobs to their fully
counterclockwise (“∞”) position.
e. Turn on all devices connected to channel line inputs and Aux returns and set
their output level controls to unity gain or, if there is no unity gain indicated on
their output control, to maximum. If you’ve got outboard effects processors con-
nected to Aux returns, make sure they are sending completely “wet” (processed)
signal, with no “dry” (unprocessed) signal mixed in.
f. Turn on the PL 2404’s rear-panel Power switch—the Power LED in the main
section will light up. Finally, turn on your power amplifier.
g. Play an instrument connected to one of the PL 2404’s line inputs* and, while
doing so, slowly raise the corresponding channel Level control to the 2 o’clock
“0” position. Then slowly raise the power amplifier volume until you reach the
level you want to hear. If the incoming signal sounds distorted, you may need to
lower the output level of the instrument, though this will rarely occur. Conversely,
if the signal is too low even with the output level of the instrument all the way up,
something’s definitely wrong: in all likelihood, the connecting audio cable is faulty
and should be replaced.
h. Repeat step (g) above for each instrument connected to the PL 2404 channel
line inputs.
** If you’re using an instrument such as electric guitar or bass, we recommend
that you connect it to the PL 2404 with a direct injection box to ensure correct
impedance.
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Setting the Correct Gain Structure
i. If you have a microphone connected to channel 1 or channel 3, the procedure
for setting optimum microphone levels is as follows: sing or speak into the mic at
the level you expect to use in performance while slowly raising the Level control
for that channel to its 2 o’clock “0” position. Again, slowly raise the power ampli-
fier volume until you reach the level you want to hear. Then raise the rear panel
Trim control for that channel to a point at which you get a strong, clear signal that
doesn’t distort even at the highest singing or speaking levels. For best signal-to-
noise ratio, always keep the Trim control as high as possible short of distortion.
j. If you have any outboard signal processors connected to the Aux send and
return jacks on the rear panel, follow this step. Because outboard effects
processors can sometimes be quite noisy, it’s particularly important to maximize
the amount of signal being sent to them via the PL 2404 Aux sends. The idea is
to drive these devices as hot as possible (short of overloading them) and then to
use the corresponding Aux return level to carefully adjust the amount of
processed signal being blended with the dry signal. To set optimum Aux send
levels, use a channel that has already had its gain structure adjusted in step (g)
or (i) above. Turn all Aux send knobs for that channel to their “0” (unity gain)
position (bear in mind that, when a pair of channel inputs are connected, the
odd-numbered [left] input signal can only be routed to Aux 1L and Aux 3L, while
the even-numbered [right] input can only be routed to Aux 2R and Aux 4R; when
only the odd-numbered [left] input is connected, the signal can be routed to any
of the four Aux sends). Then play the instrument (or sing into the microphone)
connected to that channel. Adjust the input levels of connected outboard effects
processors so that their meter shows incoming signal normally in the 0 vu range
(with only occasional higher excursions). Finally, optimize the Aux return levels:
While continuing to play your instrument (or continuing to sing into the micro-
phone), slowly raise each Aux return level control until you hear the desired
amount of processed signal added to the dry signal. For more information, see
the “Using Aux Sends and Returns” section on page 20.
k. At this point, if you want to route any channel or Aux return signal(s) to any of
the four bus outputs at optimum level, simply set the channel’s “Mute 3/4” or Aux
return’s Bus switch correctly and raise the corresponding bus fader to its “0”
(unity gain) position.
l. The gain structure is now correctly set—you’ve optimized the level of all
signals coming into and out of the PL 2404, and the end result will be minimum
noise and distortion and maximum clean sound. You’ll now find that the majority
of your mixes can be accomplished with the Main or Control Room Level knobs
and with most channel Level controls at or near their 2 o’clock “0” (unity gain)
position. If you need to make adjustments to the overall level, use the level
control of your power amplifier.
If you encounter difficulty with any aspect of setting up or using your PL 2404,
you can call Samson Technical Support (1-800-372-6766) between 9 AM and
5 PM EST.
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Grounding Techniques
Hum and buzz are the biggest enemies you face when interconnecting a large
number of different pieces of equipment to a central audio mixer. This is
because each piece of equipment may operate at a marginally different voltage
(this difference is called potential) and, when two devices at slightly different
potential are physically connected with audio cabling, the end result can be
nasty, extraneous noise (mind you, connecting two devices at very different
potential can result in a major electrical shock!).
However, there are several steps you can take to avoid grounding problems.
First, assuming you have an isolated electrical circuit that can handle the
electrical demands of your mixer and all connected audio equipment (these
needs will usually be modest), you should always plug your mixer and all
connected equipment into the same circuit. If possible, nothing else but this
equipment should be connected to that circuit. If you can’t do this, at least avoid
plugging your mixer and audio equipment into the same circuit that is already
powering things like heavy machinery, air conditioners, heaters, refrigerators,
washing machines, neon signs or fluorescent light fixtures. One particular culprit
that will almost certainly create problems is the standard light dimmer (the kind
that uses silicon controlled rectifiers). Where low-level lighting is desired, use
incandescent fixtures with autotransformer-type dimmers (sometimes called
Variacs) instead—these cost considerably more than the standard dimmer you’ll
find at your local hardware store, but are well worth the extra expense.
Three-prong plugs (such as the one used by the PL 2404) should always be
used as is; don’t use adapters to lift the ground (unless you’re using a “star
ground network”—see below). If you hear hum or buzz from a device that uses
a two-prong plug (or an external two-prong AC/DC adapter), you can try revers-
ing the plug in the socket. If that doesn’t work, you may need to physically
ground that device’s chassis by connecting a wire (called a strap) from it to a
grounded piece of metal such as rack ears. Some pieces of equipment have a
screw-type ground post to which the strap can be connected; if not, you can
attach some kind of metallic binding post to the case itself. If you are using rack-
mounted audio devices and are experiencing hum or buzz, there’s a simple test
to determine the source of the problem: while keeping all devices powered on
and connected with audio cabling, physically remove each device, one by one,
from the rack. If the hum disappears when a particular device is removed, you’ll
know that device is the culprit.
We also recommend that you use balanced audio cabling and connectors
wherever possible. The PL 2404 provides electronically balanced inputs for all
line channel inputs and for its Main outputs. The wiring diagram in the
“Connecting The PL 2404” section of this manual (page 10) shows how 1/4" TRS
(Tip/Ring/Sleeve) connectors should be wired for use with these inputs and
outputs.
In addition, you can minimize possible interference by planning your audio,
electrical, and computer cable runs so that they are as far apart from one
another as possible and so they don’t run parallel to one another. If they have to
cross, try to ensure that they do so at a 90° angle (that is, perpendicular to one
another). In particular, try to keep audio cabling away from external AC/DC
adapters.
15
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Grounding Techniques
If you’re using the PL 2404 in a fixed location such as a recording studio, you
may want to invest the time and money into creating a star ground network. This
is by far the best technique for avoiding grounding problems. It involves using a
formidable ground source such as a cold water pipe or a copper spike driven into
the earth. A thick grounding cable is connected to that source and then brought
to a central distribution point; from there, individual cables are connected to each
piece of equipment. This setup also requires that you lift the ground plug of all
three-prong AC connectors, so there is the possibility of danger if it is done incor-
rectly. We strongly recommend that you contract with a qualified professional to
carry out this or any kind of electrical work.
Another, less common problem you may encounter is that of oscillation (a ringing
tone), which, apart from being annoying, is potentially dangerous to your
speakers. This is generally caused either by poor outside wiring or by returning
a signal out of phase (most commonly from an outboard signal processor). If
audible oscillation occurs, try isolating each input signal by turning down all other
inputs. If one signal alone is causing the problem, you should be able to elimi-
nate the oscillation by reversing that signal’s phase (many signal processors
have a switch that allows you to do this).
16
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Busing, Submixing and Channel Muting
As we’ve seen, the PL 2404 uses a system of four buses—pathways through
which signal can be routed. The four PL 2404 bus faders control the overall
level of the signal being output through the four buses. When the “L/R” switches
above each bus fader are pressed in, the signal from that bus is also routed to
the Main and Control Room outputs. In the case, buses 1 and 3 are automatical-
ly routed to the left side of the Main and Control Room outputs and buses 2 and
4 are automatically routed to the right side of the Main and Control Room
outputs. This four-bus system (which can eventually mix down to a single stereo
output) gives you a great deal of flexibility in terms of signal flow.
+10
dB
+10
dB
0
0
For example, you may want to connect the PL 2404 to a four-track cassette or
open-reel tape recorder. One good way to do this is to route each of the four
individual bus outputs to a tape input, and to bring each of the four tape outputs
back to individual channels. With this setup, to record onto track 1, you’d route
one or more instrument or microphone channels to bus 1 (via the channel “Mute
3/4” switch); to record onto track 3, you’d route them to bus 3, etc. To connect
the PL 2404 to an eight-track digital recorder (such as the Alesis ADAT™ or
Tascam DA88™ system), simply use signal splitters or patchbay mults to
combine the signal from buses so that bus 1 is routed to tape inputs 1 and 5;
bus 2 to tape inputs 2 and 6; bus 3 to tape inputs 3 and 7; and bus 4 to tape
inputs 4 and 8. See the “Applications” section at the conclusion of this manual
for more information on using the PL 2404 as a recording mixer.
∞
∞
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
2
1
Another important plus is that you can use each bus to set up a submix within
your overall mix. For example, let’s suppose that you’re using the PL 2404 to do
live sound and you have eight microphones on the drum kit—separate mics for
the bass and snare drums as well as for the hi-hat, another mic for each of three
tom-toms, and an overhead pair for picking up cymbals. To get all this signal
into the PL 2404, you’re going to have to use eight mono channels. During a
sound check, you’ll usually start with the drums, working to get the blend of the
eight different drum mics just right. After that’s done, the next step is typically to
start bringing in the other instruments. During the gig, however, you may need
to raise or lower the overall level of the drums, but you surely won’t want to upset
the blend you so carefully set up. This won’t be easy to do if you have to move
eight faders at once! The solution is to use the busing system provided by the
PL 2404—route the eight drum channels to one pair of buses and all other
instruments to the other pair. Now you can adjust the overall level of the entire
drum mix by moving just two bus faders!
4
3
+10
dB
+10
dB
0
0
You can also use the PL 2404 bus switches to mute particular channels (that is,
remove them temporarily from the overall mix without having to change their
fader position). To do this, keep bus faders 3 and 4 down at their “∞” position
(no signal) and use buses 1 and 2 for your overall mix. Then, to mute a signal,
all you have to do is press that channel’s “Mute 3/4” switch; the signal will be
rerouted to buses 3 and 4 (which are off) and will be removed from the mix you
hear. To restore the signal (that is, unmute it), all you have to do is press that
channel’s “Mute 3/4” switch again—since its fader hasn’t been moved, the sound
will come back at the same level as before.
∞
∞
3/4
1/2
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Using the Balance Control
The final Main output of the PL 2404 is stereo—that is, there are two discrete
Main output jacks (and two discrete Control Room output jacks), labeled “left”
and “right,” which will normally be routed to two discrete speakers.* Because of
this, you will usually be working with a stereo field that ranges from hard left to
hard right. The PL 2404 provides twenty-four stereo channels, each with two
inputs—an odd-numbered (left) input and an even-numbered (right) input. When
only the odd-numbered (left) input is connected, the Balance control in that
stereo channel acts like a panning control, allowing you to place each individual
sound at any point within this left-right field, while keeping the overall level con-
stant.
L
R
BALANCE
You can use stereo panning creatively in a variety of ways: For example, you
might want to have guitars coming from one speaker and keyboards from
another, or you might use panning to “spread” the signal from a piano miked with
two microphones—one over the bass notes (panned left) and the other over the
treble notes (panned right). In live performance, you may want to resist the
temptation to pan anything completely hard left or right, since some members of
the audience not seated in the center of the venue may miss some signal alto-
gether. In these circumstances, you’re best to use modest panning, with signals
routed no further than the 9 o’clock and 3 o’clock positions.
In channels where both the odd-numbered (left) and even-numbered (right)
inputs are connected, the odd-numbered (left) input signal is automatically
panned hard left and the even-numbered (right) input signal is automatically
panned hard right. The Balance knob in these channels then controls the
relative levels of the two input signals. When the knob is placed at its center
(detented) position, both the odd-numbered (left) and even-numbered (right)
input signals are at equal strength. When moved left of center, the signal of the
odd-numbered (left) input remains the same but the signal of the even-numbered
(right) input is attenuated; when the knob is moved right of center, the the signal
of the even-numbered (right) input remains the same but the signal of the odd-
numbered (left) input is attenuated. When placed fully counterclockwise, only
the odd-numbered (left) input is heard; when placed fully clockwise, only the
even-numbered (right) input is heard.
* You can, of course, also use the PL 2404 monophonically—simply route the
same signal to both the left and right outputs.
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Using Equalization
One of the most exciting aspects of using a mixer such as the PL 2404 is the
ability to shape a sound, using a process called equalization. But there are few
areas of sound engineering more misunderstood than equalization, and, just as
good EQ can really help a sound, bad EQ can really hurt it, so read on...
0
0
HIGH
MID
Every naturally occurring sound consists of a broad range of pitches, or
frequencies, combined together in a unique way. This blend is what gives every
sound its distinctive tonal color. The EQ section in a mixer allows you to alter a
sound by boosting or attenuating specific frequency areas. The PL 2404
provides independent three-band equalization controls for each of its channels
(the same equalization is applied to both the odd-numbered [left] input and the
even-numbered [right] input). Each EQ knob is labeled with the maximum
amount of cut or boost provided ( 15 dB). The Mid frequency control utilizes
a resonant (“bell”) peaking curve, while the Low and High frequency controls
utilize shelving curves. This means that, in the case of the Mid EQ control,
frequencies around 1 kHz are affected; in the case of the Low EQ control,
frequencies around or below 80 Hz are affected; and, in the case of the High
EQ control, frequencies around or above 10 kHz are affected. We provided
these particular frequency areas because they have maximum impact on
musical signals—that’s why they are sometimes known as “sweet spots.”
-15
-15
+15
+15
LOW
0
-15
+15
When an EQ knob is in its center detented position (“0”), it is having no effect.
When it is moved right of center, the frequency area is being boosted; when it is
moved left of center, the frequency area is being attenuated. In all channels,
the EQ setting always affects both the odd- and even-numbered inputs the same
way, although the two signals remain separate.
In most instances, the best way to approach equalization is to think in terms of
which frequency areas you need to attenuate, as opposed to which ones you
need to boost (boosting a frequency area also has the effect of boosting the
overall signal; too much EQ boost can actually cause overload). Be aware of the
phenomenon of masking, where loud sounds in one frequency range obscure
softer sounds in the same range; by cutting EQ “notches” in a loud signal, you
can actually make room for a softer one to shine through. And try not to think of
EQ as a miracle worker—no amount of equalization can put a singer in tune or
remove the distortion from an overloaded input signal! The key is to get the
signal right in the first place, by using correct gain structure and mic placement.
Although the specific EQ you will apply to a signal is very much a matter of
personal taste, here are a few general suggestions: Boosting the low frequency
of instruments such as bass drums or bass guitar will add warmth and make the
sound “fatter”; conversely, you may want to attenuate the low frequency
component of instruments such as cymbals, high-hats, and shakers so as to
“thin” them out. Boosting Mid frequencies can be used to help bring out vocals
or guitars, while attenuating them can help to reduce “boxiness.” Be careful not
to boost high frequencies too much or you risk adding hiss to the signal, though
just a touch can help add “shimmer” to an acoustic guitar, ride cymbal, or
high-hat. Finally, because the PL 2404 High and Low EQ utilize shelving curves,
attenuated High settings can be used to reduce hiss (which is composed almost
exclusively of high frequencies) or attenuated Low frequencies can be used to
reduce rumble (which is composed almost exclusively of low frequencies).
19
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Using Aux Sends and Returns
The PL 2404’s four Auxiliary sends allow you to combine the signal from multiple
1L-2R
AUX
channels and send the resulting mix to external devices such as effects proces-
sors. When an Aux send knob is at its 2 o’clock “0” position, the signal is routed
with unity gain (that is, no boost or attenuation). As it is turned clockwise from
the 0 position, the signal is boosted; as it is turned counterclockwise from the 0
position, it is attenuated. All Aux sends are post-fade; that is, the level of the
signal is affected by the channel Level control and equalizer settings, as well as
(in the case of channels 1 and 3), the mic Trim control.
0
∞
∞
∞
+10
0
AUX
AUX
3L
+10
0
4R
The PL 2404 can accommodate up to twenty-four stereo channels, so we’ve
designed the Aux sends so that, when a “matched” pair of consecutive channel
inputs (that is, both odd-numbered and even-numbered) are connected, the odd-
numbered (left) input signal can only be routed to Aux 1L and Aux 3L, while the
even-numbered (right) input can only be routed to Aux 2R and Aux 4R. In this
case, the Aux 1L/2R control acts as a true stereo Aux send, simultaneously
setting the level of both sends equally. When only the even-numbered (right)
input is connected to a channel, the signal can only be routed to Aux 2R and 4R.
When only the odd-numbered (left) input is connected to a channel (the recom-
mended way to connect monophonic devices to the PL 2404), the signal can be
routed to any of the Aux sends.
+10
0
∞
+10
AUX RET.1
The PL 2404 also provides four stereo Auxiliary returns. These allow you to
return signal from outboard devices in stereo pairs. In practice, you’ll probably
want to use the Auxiliary returns to bring in signal from connected effects
processors. Signal arriving at the left input is automatically panned hard left and
signal arriving at the right input is automatically panned hard right. The PL 2404
Aux return jacks are unbalanced stereo inputs, with the tip carrying the left input
signal and the ring carrying the right input signal (the sleeve carries common
ground), as shown in the wiring diagram on page 11 of this manual. Insertion of
a monophonic 1/4" jack into an Aux return will result in the incoming signal being
automatically routed to the left input only (and therefore panned hard left). Each
of the stereo Auxiliary returns is somewhat similar to a stereo channel, except
that a signal being brought into to a channel can be equalized if necessary and
optionally sent on to other outboard devices (via Aux sends or channel inserts).
1/2
3/4
0
∞
+10
AUX RET.2
3/4
1/2
0
∞
+10
The signal arriving at each of the four stereo Aux returns can be routed to either
of the two bus pairs (1/2 or 3/4) with the use of the associated Aux Return bus
switch (as described in #2 on page 6). The signal can then be routed to the
Master and Control Room outputs by pressing in the associated bus L/R switch
(as described in #10 on page 7). Note that signal arriving via the PL2404 Aux
returns can be monitored over headphones only when the Solo/Main switch is
set to “Main” (Aux Returns cannot be soloed). See the “Using PFL/AFL” section
on page 22 in this manual for more details.
AUX RET.3
3/4
1/2
0
∞
+10
AUX RET.4
3/4
1/2
20
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Using Channel Inserts
In addition to using Auxiliary sends and returns to access outboard devices, the
PL 2404 also provides channel inserts for the first four input channels. These
should be used when you want to affect just one input signal, as opposed to
signal from several inputs—most often, this will be for dynamic processing
purposes (such as outboard equalization, compression/limiting, or noise gating).
You can also use the channel insert sends as post-eq (but pre-fade) direct
outputs, if you need to route a single monophonic signal to an external device
such as a tape deck.
4
3
2
1
INSERT
The channel insert jacks on the rear panel accept 1/4" TRS plugs, with the ring
carrying the send signal and the tip carrying the return signal; this will normally
be connected to a Y-cord (see the “Connecting The PL 2404” section on page 10
in this manual for a wiring diagram). This configuration is sometimes known as
an “effects loop,” since the signal is sent and returned over the same cable.
If nothing is plugged into the channel insert jacks, they have no effect—but if you
connect them to a passive device like a patchbay, you’ll need to normal (perma-
nently connect) or half-normal (connection is made unless overriden by a patch
cord) the send to the return. The insert signal is returned just before the channel
Gain control. For this reason, you’ll have to be careful to set the output of exter-
nal devices connected this way to unity gain.
21
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Using PFL/AFL
The PL 2404 provides two options for soloing input signals in headphones
connected to the front panel headphone jack—Pre Fade Listen (PFL) and
After-Fade Listen (AFL). The PFL/AFL switch in the main section allows you to
choose between these two modes of operation. Although they may at first
glance appear similar (and both are non-mix-destructive), there are in fact
several significant differences between the two.
PFL
AFL
SOLO
MAIN
The main function of PFL is to allow you to check that a signal is actually arriving
at a particular input. When the PL 2404 is in PFL mode and a channel Solo
switch is pressed in, the pre-fader (but post-EQ) signal of that channel alone is
routed to the headphone output if the Solo/Main switch is up (set to Solo mode).*
The Bus outputs, Main outputs, and Control Room outputs are not interrupted
during a PFL solo, so you can press any channel Solo switch even during
recording or live performance without affecting the main signal flow. This also
makes it possible for you to correctly cue up a tape or CD before bringing it into
the main mix.
SOLO
OFF
ON
The main drawback to using PFL mode, however, is that it does not allow you to
hear a signal in context. For one thing, because the PFL soloed signal is
monitored pre-fader, it may sound considerably louder or softer than it actually is
in the main mix (depending upon the current position of the channel Level control
and, for channels 1 - 3, the mic Trim control). Also, the Balance control has no
effect during a PFL solo—if the soloed channel has both its odd- and even-
numbered inputs connected, you’ll hear both inputs, panned hard left and right; if
only the odd-numbered input is connected, you’ll hear the signal monophonically.
Therefore, you may in some circumstances prefer to use AFL mode, which
provides in-context soloing. When the PL 2404 is in AFL mode and a channel
Solo switch is pressed in, the post-fader, post-EQ signal of that channel alone is
routed to the headphone output if the Solo/Main switch is up (set to Solo mode).*
Like PFL, AFL is non-destructive to your mix—the Bus outputs, Main outputs,
and Control Room outputs are not interrupted during an AFL solo. However,
over the headphones, you’ll hear the AFL soloed signal at its current level and in
its current pan position (if only the odd-numbered input is connected) or with the
correct relative levels of its two inputs as set by the Balance control (if both the
odd- and even-numbered inputs are connected). By pressing the Solo/Main
switch during an AFL solo, you can quickly compare the soloed signal on its own
with its impact on the overall mix.
In both PFL and AFL modes, you’ll hear the soloed channel with its EQ settings
and (if the soloed channel is one of channels 1 - 4) all effects being applied and
returned via the channel insert. Note that there is no provision for soloing signal
arriving via the PL2404 Aux returns.
LEDs in the meter section allow you to see at a glance which mode the PL 2404
is in. The leftmost LED (labeled “PFL”) lights steadily green when the mixer is in
PFL mode, while the center LED (labeled “AFL”) lights steadily red when the
mixer is in AFL mode.
* If the Solo/Main switch is pressed in (Main mode), connected headphones
will always receive the complete Main mix (including signal from the Aux
Returns) whether or not any channel Solo switches are pressed in.
22
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Applications
Here are four suggested applications for the PL 2404; bear in mind that your particular circumstance may dictate
changes in these suggested signal connections and routings.
Application 1 - Using The PL 2404 As A Recording Mixer
The PL 2404 is optimized for use as a recording mixer with multitrack digital or analog recorders. As shown in the
illustration below, microphones and line level signals are connected to various channel inputs. Signal processors are
connected to Aux sends and returns and to channel inserts as required. The Control Room outputs are connected to a
power amplifier driving studio monitors. The Main outputs are connected to the inputs of a two-track or DAT recorder,
with the outputs of the two-track or DAT recorder connected to a PL 2404 stereo channel. The four Bus outputs are
connected to the inputs of a multitrack recorder, with the multitrack outputs connected to two PL 2404 stereo channels.
During mixdown, those channels carrying the multitrack outputs are routed to bus 1/2 (via their channel “Mute 3/4”
switches), with buses 1 and 2 routed to the Main L/R outputs (by pressing in their Bus “L/R” switches). To listen back to
the mix, the channel carrying the two-track outputs is routed to bus 3/4 (via its channel “Mute 3/4” switch); then simply
connect buses 3 and 4 to the Control Room outputs by pressing in their Bus “L/R” switches.
L
R
MIDI TONE GENERATOR
MIDI KEYBOARD
R
L
DRUM MACHINE
MULTITRACK
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
1
2
TRS
TRS
BALANCED
TRS INSERT
UNBALANCED
XLR
BALANCED
STEREO INPUT
3
3
POWER
+4
−50
+4
−50
TIP
=
LEFT
RIGHT
COM
TIP
=
HI
TIP
=
RETURN
3
2
1
=
=
=
LO
RING
=
RING LO
=
RING SEND
=
HI
SLEEVE
=
SLEEVE
=
COM
19
SLEEVE
=
COM
COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC
9
3
MIC
1
OFF
2
1
23
21
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
24
22
20
18
16
LINE INPUTS
14
12
10
8
4
6
4
2
2
4
3
-
BALANCED 10KΩ+4dBu
3
1
POWER
RATING
INSERT
115V - 60 Hz 25W
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
R
L
!
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
Ring
SIGNAL PROCESSOR
Tip
R
L
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX SENDS
UNBALANCED <75Ω +4dBu
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
S/N
SAMSON
-
+
1
1
5
5
d
d
b
b
+
-1
1
5
5
d
db
b
0
0
-15db
+15db
-15db
+15db
0
0
CASSETTE or DAT
R
L
SIGNAL PROCESSOR
SAMSON
SERVO - 240
23
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Applications
Application 2 - Using The PL 2404 As A Main Live Mixer
Here, the PL 2404’s Main output is connected to the input of a power amplifier, and, from there, to PA speakers.
Microphones are connected to channels 1 and 3, while line level signals are connected to other channel inputs (stereo
signals are routed to “matched” consecutive odd- and even-numbered inputs). A two-track tape deck is connected to
stereo Aux return 1, while a signal processor is connected to Aux return 2, with signal being sent to that signal processor
from Aux send 2. Another signal processor is connected to channel insert 1 so as to affect the signal coming from the
mic connected to channel 1.
MIDI KEYBOARD
L
R
MIDI TONE GENERATOR
R
L
DRUM MACHINE
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
2
1
TRS
TRS
BALANCED
TRS INSERT
UNBALANCED
XLR
BALANCED
STEREO INPUT
3
3
POWER
+4
−50
+4
−50
TIP
=
LEFT
RIGHT
COM
TIP
=
HI
TIP
=
RETURN
3
2
1
=
=
=
LO
RING
=
RING LO
=
RING SEND
=
HI
SLEEVE
=
SLEEVE
=
COM
19
SLEEVE
=
COM
COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC
9
3
MIC
1
OFF
2
1
23
21
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
24
22
20
18
16
LINE INPUTS
14
12
10
8
4
6
4
2
2
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
4
3
-
BALANCED 10KΩ+4dBu
3
1
POWER
RATING
INSERT
115V - 60 Hz 25W
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
R
L
!
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
Ring
SIGNAL PROCESSOR
Tip
R
L
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX SENDS
UNBALANCED <75Ω +4dBu
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
S/N
SAMSON
-
+
1
1
5
5
d
d
b
b
+
-1
1
5
5
d
db
b
0
0
-15db
+15db
-15db
+15db
0
0
R
L
CASSETTE or DAT
R
L
SIGNAL PROCESSOR
SAMSON
SERVO - 240
24
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Applications
Application 3 - Using The PL 2404 As A Keyboard Submixer
Here, various keyboards and MIDI tone generators are connected to the channel line inputs of the PL 2404, with stereo
signals routed to “matched” consecutive odd- and even-numbered inputs. Signal processors are connected to Aux sends
and returns and to channel inserts as required. The Main output can then be routed to a stereo input channel of a live
performance or recording mixing console, with the performer having complete control over the blend of signals being
provided to the sound engineer.
R
L
MIDI TONE GENERATOR
R
L
MIDI KEYBOARD
L
R
MIDI TONE GENERATOR
MIDI KEYBOARD
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
1
2
1
TRS
STEREO INPUT
TRS
BALANCED
TRS INSERT
UNBALANCED
XLR
BALANCED
3
3
POWER
+4
−50
+4
−50
TIP
=
LEFT
TIP
=
HI
TIP
=
RETURN
3
2
1
=
=
=
LO
RING RIGHT
=
RING LO
=
RING SEND
=
HI
SLEEVE
=
COM
SLEEVE
=
COM
19
SLEEVE
=
COM
COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC
9
3
MIC
1
OFF
2
1
23
21
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
24
22
20
18
16
LINE INPUTS
14
12
10
8
4
6
4
2
2
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
4
3
-
BALANCED 10KΩ+4dBu
3
1
POWER
RATING
INSERT
115V - 60 Hz 25W
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
R
L
!
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
R
L
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX SENDS
UNBALANCED <75Ω +4dBu
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
S/N
Ring
SIGNAL PROCESSOR
Tip
IN
R
L
SIGNAL PROCESSOR
SAMSON
MPL2242
MPL2242
25
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Applications
Application 4 - Linking The PL 2404 With Other Mixers
The provision of four rear-panel Bus Inserts makes it easy to link multiple PL 2404s or to link the PL 2404 with other
mixers, without the need to use up channel line inputs. As shown in this illustration, simply connect the main output of
another mixer to the PL 2404 Bus Inserts. The signal from that mixer will then be “submixed” in at unity gain; you can
then use the main output faders of the secondary mixer to blend its relative level with that of the PL 2404.
SECONDARY MIXER
SAMSON
MPL2242
MPL2242
SECONDARY MIXER
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
1
2
1
TRS
STEREO INPUT
TRS
BALANCED
TRS INSERT
UNBALANCED
XLR
BALANCED
3
3
POWER
+4
−50
+4
−50
TIP
=
LEFT
TIP
=
HI
TIP
=
RETURN
3
2
1
=
=
=
LO
RING RIGHT
=
RING LO
=
RING SEND
=
HI
SLEEVE
=
COM
SLEEVE
=
COM
19
SLEEVE
=
COM
COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC
9
3
MIC
1
OFF
2
1
23
21
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
24
22
20
18
16
LINE INPUTS
14
12
10
8
4
6
4
2
2
4
3
-
BALANCED 10KΩ+4dBu
3
1
POWER
RATING
INSERT
115V - 60 Hz 25W
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
R
L
!
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
R
L
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX SENDS
UNBALANCED <75Ω +4dBu
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
S/N
MAIN OUT
R
L
PL 2404 24 CHANNEL PROGRAM STEREO / LINE MIXER
SAMSON
0
-10
0
-10
2
1
2
1
TRS
TRS
TRS INSERT
UNBALANCED
XLR
BALANCED
STEREO INPUT
BALANCED
=
3
3
POWER
+4
−50
+4
−50
TIP
=
LEFT
RIGHT
COM
TIP
RING
SLEEVE
HI
TIP
=
RETURN
3
2
1
=
=
=
LO
RING
=
=
LO
RING SEND
=
HI
SLEEVE
=
=
COM
19
SLEEVE
=
COM
COM
ON
BUS OUTPUTS
UNBALANCED
<75Ω+4dBu
MIC
9
3
MIC
1
OFF
2
1
23
21
17
15
13
11
7
5
3
1
LEFT / MONO
RIGHT
AVIS:
RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
FUSE
1A/250V
DO NOT EXPOSE THIS EQUIPMENT
TO RAIN OR MOISTURE
24
22
20
18
16
LINE INPUTS
14
12
10
8
4
6
4
2
2
4
3
-
BALANCED 10KΩ+4dBu
3
1
POWER
RATING
INSERT
115V - 60 Hz 25W
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
R
L
!
MAIN
BALANCED <75Ω+4dBu
4
3
2
1
4
3
2
1
4
3
2
1
~AC INPUT
115V, 60Hz
25W
R
L
BUS INSERTS
UNBALANCED <75Ω +4dBu
MIXER LINKING
AUX SENDS
UNBALANCED <75Ω +4dBu
AUX RETURNS
STEREO INPUTS
UNBALANCED 10KΩ+4dBu
CONTROL ROOM
BALANCED <75Ω+4dBu
S/N
MASTER MIXER
26
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Appendix A: Block Diagram
27
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Specifications
1. Frequency Response (unity gain, line input 0 dB)
Mic in to Main out
20 Hz to 30 kHz 1 dB
15 Hz to 70 kHz 3 dB
15 Hz to 70 kHz 3 dB
20 Hz to 30 kHz 1 dB
15 Hz to 70 kHz 3 dB
Line in to Main out
Aux return to Main out
Mic in to Control Room out
Line in to Control Room out
2. THD+N (unity gain, line input 0 dB, with 30 kHz LPF)
Line in to Main out
Less than 0.02 %
Less than 0.02 %
Less than 0.02 %
Line in to Aux send
Line in to Control Room out
3. Maximum Gain
Mic in to Main out
75 dB
85 dB
35 dB
35 dB
24 dB
Line in to Main out
Line in to Control Room out
Aux return to Main out
Line in to Aux send
4. Crosstalk (Ch - to - Ch, 1 kHz, with 30 kHz LPF)
-70 dB
5. Residual Noise (with 30 kHz LPF, all faders down)
Main out
Aux send
Control Room
-96 dB
-87 dB
-96 dB
6. Headphone Output Level
120 mW (33 Ω loaded)
7. Equalizer
High
10 kHz 15 dB
1 kHz 12 dB
80 Hz 15 dB
Mid
Low
8. Dimensions
19 in (w) x 7.9 (d) x 7 (h)
482 mm (w) x 200 (d) x 177 (h)
9. Weight
16.5 lbs • 7.5 kg
28
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Produced by On The Right Wavelength for Samson Technologies Corp.
Copyright 1996, Samson Technologies Corp.
Printed March 1996
Samson Technologies Corp.
575 Underhill Blvd.
P.O. Box 9031
Syosset, NY 11791-9031
Phone: 1-800-3-SAMSON (1-800-372-6766)
Fax: 516-364-3888
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