DUAL 31 BAND EQUALIZER
Table of Contents
Introduction
2
3
System Features
Controls and Functions
Front Panel
4
5
Rear Panel
Setting Up and Using the S curve 231
System Configurations
About Equalization
6 - 7
8 - 10
11
Grounding Techniques
Using a Patchbay
12
12
Using the S curve 231 with an RTA
Using the S curve 231 to Remove Feedback
S curve 231 Wiring Guide
Specifications
13
14
15
16
Pass-Band Graphs
16
Block Diagram
17
Copyright 2003, Samson Technologies Corp.
Printed Oct., 2003
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
Introduction
Congratulations on purchasing the Samson S curve 231 dual channel,1/3 Octave, 31 Band Constant Q
Graphic Equalizer! Although this product is designed for easy operation, we suggest you take some
time out first to go through these pages so you can fully understand how we’ve implemented a number
of unique features.
The S curve 231 is a professional quality signal processor that gives you precise tonal control over a
stereo, or two mono audio signals. Center detented sliders with LED illumination allow you to selec-
tively cut or boost selected frequency areas by as much as 24 dB. Front panel controls include output
level sliders, a variable Lowcut filter, as well as Cut Only, Range and Bypass switches. The rear panel
provides electronically balanced inputs and outputs on 1/4-inch and XLR connectors. Thanks to low
noise circuitry, the S curve 231 can be used in a wide variety of applications, including live performance
(in conjunction with either Front Of House or monitor mixers), in broadcast environments, or for record-
ing.
In this manual, you’ll find a more detailed description of the features of the S curve 231, as well as a
guided tour through the front and rear panels, step-by-step instructions for using the unit, suggested
applications for use with a patch bay, a Real Time Analyzer (RTA) or for ringing out monitor systems.
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
plete information about our full product line.
With proper care and adequate air circulation, your S curve 231 will operate trouble free for many
years. We recommend you record your serial number in the space provided below for future reference.
Serial number:
Date of purchase:
Should your unit ever require servicing, a Return Authorization number (RA) must be obtained before
shipping your unit to Samson. Without this number, the unit will not be accepted. Please call Samson at
1-800-3SAMSON (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 the original carton and
packing materials.
2
S curve 231 Features
The Samson S curve 231 Graphic Equalizer utilizes state-of-the-art, Constant Q filtering technology for
precise tonal control. Here are some of it’s main features:
•
•
The S curve 231 is a two channel equalizer and each channel provides 31 bands of equaliza-
tion, with each frequency band representing 1/3 of an octave in the 20 Hz to 20 kHz range.
Constant Q circuitry ensures that the bandwidth of the selected frequency area stays the same
even when approaching maximum boost or attenuation. As a result, phase shifting and inter-
modulation distortion is greatly reduced, making for pristine sound.
•
•
The S curve 231 can be set for either 6 or 12 dB of gain and attenuation for each of the fre-
quency bands.
For monitor applications, the S curve 231 can be set for CUT ONLY mode providing up to 12dB
of attenuation with full slider range.
•
•
•
•
Ultra-low noise circuity ensures superb audio fidelity.
Variable Low Cut Filter for removing rumble and floor noise can be adjusted from 15 to 200 Hz.
Electronically balanced XLR and TRS inputs and outputs.
Front panel, hard-wired, relay controlled Bypass switches (with dedicated Bypass LEDs) allow
the equalization circuitry and output level control to be activated or deactivated.
•
Main Level control enables output signal to be attenuated or boosted for optimum signal-to
noise ratio.
•
•
•
•
LED faders and 8 segment LED bar VU meters.
Relay power-on circuitry prevents speaker “thumps” when the unit is turned on.
Internal power supply ensures reliability and trouble-free operation.
Standard 19", 2 rack-space design for easy integration into any traveling or fixed installation
audio system.
•
•
•
Optional security cover kit prevents EQ settings from accidentally being altered.
All-steel chassis makes the S curve 231 eminently road-worthy.
Three year extended warranty.
3
Controls and Functions
FRONT PANEL LAYOUT
1
Equalizer level sliders - Independent Equalizer sliders are provided for each frequency area (The S
curve 231 provides 31 frequency areas).Calibration markings on either side of each Equalizer slider
allow you to cut or boost each frequency area. As described below, the exact action of the Equalizer
sliders depends upon the setting of the Range switch as well as the setting of the Cut Only switch (see
#3 and #5).
When the Cut Only switch is not pressed in: When an equalizer slider is at its center detented 0 position, the
frequency area is unaffected (that is, there is no boost or cut). When moved all the way up (to the +12
dB) position, the frequency area is boosted by 12 dB (if the corresponding Range switch is notpressed
in) or 6 dB (if the corresponding Range switch is pressed in). When moved all the way down (to the -12
dB position), the frequency area is attenuated by 12 dB (if the corresponding Range switch is not
pressed in) or 6 dB (if the corresponding Range switch is pressed in).
When the Cut Only switch is pressed in: When an equalizer slider is at its top-most position, the frequency
area is unaffected (that is, there is no boost or cut). As the Equalizer slider is moved down, the frequen-
cy area is attenuated. When moved all the way down, the frequency area is attenuated by 6 dB (if the
corresponding Range switch is pressed in) or 12 dB (if the corresponding Range switch is not pressed
in).
2
Main Output level slider - Use this to adjust the output level of signal leaving the S curve 231 via its
rear-panel output connectors (see D on page 5 for more information). When the main slider is at its
center detented 0 position, the corresponding output signal is at unity gain (that is, there is no level cut
or boost). When the main slider is moved all the way up (to the +6 dB) position, the output signal is
boosted by 6 dB. When a Level slider is moved all the way down (to the ∞ position), the output signal is
infinitely attenuated (that is, there is no signal). Note that the Main level slider is deactivated when the
S curve 231 is in Bypass mode (see #7).
3
4
Frequency control - When the Low Cut switch is pressed in, the variable low cut control is active. You
can adjust the point at which the low frequencies begin to roll off with a frequency range of from 15 to
200 Hz.
Low Cut switch - When pressed in, the LED in the switch lights yellow and the variable highpass filter is
applied to the signal. Using the Low Cut can be highly effective in removing rumble and other low fre-
quencies.
4
Controls and Functions
5
CUT ONLY switch - When pressed in, the LED switch lights and all the Equalizer sliders serve to attenuate
their frequency areas only (there is no boost) by up to 6 or 12 dB, depending upon the setting of the
RANGE switch (see #7 below). The Cut Only switch should be used when you need to notch out certain
frequencies in order to reduce feedback or “ring out” a room. See the “Using the S curve 231 to remove
feedback” section in this manual (page 14) for more information.
6
LEVEL METER - This eight segment LED bar VU meter displays the Input Level from –30dB to +18dB.
7
Range switch - When pressed in, the LED in the switch lights and the Equalizer sliders cut or boost each
frequency area by up to 6 dB, allowing fine frequency curves to be set. When out (in the up position), the
Equalizer sliders cut or boost each frequency area by up to 12 dB, allowing coarse control. The setting of
the switch also affects how Cut Only operates—see #1 on the previous page for more information.
8
Equalizer switch - When not pressed in, the equalization circuitry is made inactive so that the signal
passes through unaffected, regardless of the settings of the Equalizer or Level sliders. When pressed in,
the LED in the switch and the sliders light green and the equalization circuitry affects the signal as per the
setting of the front panel Equalizer and Level sliders (see #1 and #2).
9
Power switch - Use this to turn the power on and off.
10
Channel 2 - Same functions and controls and Channel 1.
REAR PANEL LAYOUT
A
B
AC input fuseholder - Connect the supplied
heavy gauge 3-pin “IEC” power cable here.
F
G
H
I
CH1 Balanced XLR jack input -
Electronically balanced XLR jack input.
Wiring is as follows: pin 2 hot, pin 3 cold,
and pin 1 ground.
CH2 Balanced XLR jack input - Electronically
balanced XLR jack input. Wiring is as follows: pin
2 hot, pin 3 cold, and pin 1 ground.
CH1 Balanced 1/4" TRS jack input -
Electronically balanced 1/4" TRS jack input.
Wiring is as follows: tip hot, ring cold, and
sleeve ground.
C
D
E
CH2 Balanced 1/4" TRS jack input -
Electronically balanced 1/4" TRS jack input. Wiring
is as follows: tip hot, ring cold, and sleeve ground.
CH1 Balanced XLR jack output -
Electronically balanced XLR jack output.
Wiring is as follows: pin 2 hot, pin 3 cold,
and pin 1 ground.
CH2 Balanced XLR jack output - Electronically
balanced XLR jack output. Wiring is as follows:
pin 2 hot, pin 3 cold, and pin 1 ground.
CH2 Balanced 1/4" TRS jack output -
Electronically balanced 1/4" TRS jack output.
Wiring is as follows: tip hot, ring cold, and sleeve
ground.
CH1 Balanced 1/4" TRS jack output -
Electronically balanced 1/4" TRS jack out-
put. Wiring is as follows: tip hot, ring cold,
and sleeve ground.
SETTING UP THE S curve 231
SETTING UP THE S curve 231
Setting up your S curve 231 Graphic Equalizer 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 used free-standing or mounted in a standard 19" rack.
2. Make sure the power to all mixers and amplifiers in your audio system is off. On the front panel of the S curve
231, place the Bypass switch to it’s out (off) position and set the Main Level slider to it’s bottom-most “OFF”
setting.
3. Set all Equalizer sliders to their flat (“0”) center detented position.
4. The S curve 231 can be used either as an “in-line” device, as an insert device (in conjunction with
mixer insert points), or in an effects send-return loop. The illustrations on pages 8-10 show each of
these typical configurations. Choose the configuration that is best for your application and then
begin by making the S curve 231 input connections, using either the XLR or 1/4" TRS connectors
on the rear panel. WARNING: Both the XLR and 1/4" TRS inputs should not be connected
simultaneously, or loading problems may result.
5. Next, make the S curve 231 output connections, using the XLR or 1/4" TRS connectors on the rear
panel. If required, connections can be made simultaneously to both.
6. Plug in the supplied AC connector and connect it to any standard AC socket. Because of the spe-
cial relay power-on circuitry built into the S curve 231, you can even plug it into the same power
strip that other audio devices (such as a mixing console) are connected to. You can then turn on all
devices at once with the single power strip on-off switch, without generating speaker “thumps”.
6
SETTING UP THE S curve 231
7. Press the front panel Power switch to turn on the S curve 231. Press the Equalizer switches in to
activate the equalizer. Note that audio signal will be muted for approximately five seconds until the
relay power-on circuitry is activated (at which time you’ll hear a click and the audio signal will be unmut-
ed).
8. Apply an input signal to the S curve 231 (if sending signal from a mixer output bus, drive the mixer’s
output meters at approximately 0 VU). While the input signal is present, slowly raise the front panel
main level slider to it’s center detented “0” point. For best signal-to-noise ratio, the main level slider
should be at or near the “0” point during normal operation. However, if the input signal is weak, use the
main level slider to slightly boost the volume (to a maximum of 6 dB). Conversely, if the signal causes
the front panel +18 LEDs to light, use the main level slider to attenuate volume as necessary. In nor-
mal operation, the +18 LED should not light at all; if they do, use the main level slider to lower the vol-
ume of the output signal so that it does not light at all (clipping not only sounds awful, it can also dam-
age speakers!).
9. Experiment by moving each of the Equalizer sliders up and down, carefully listening to the audible
result on the audio signal. Bear in mind that the very lowest and highest frequency areas may have lit-
tle or no effect on some signals. If there is significant low frequency noise (rumble) in the signal,
engage the Low Cut switch. Starting with the Low Cut frequency control fully counter-clockwise, adjust
the control so that the rumble is eliminated but the bass content of the signal still remains. Some exper-
imenting with this control may be necessary to acheive a satisfying result. As you work with the various
front panel controls, press the front panel Equalizer switch in and out from time to time in order to com-
pare the effect of the equalization curve you are creating with the original input signal.
10. Once you’ve created the frequency curve required for your particular application (see the “About
Equalization” section on the following pages for more information), an optional locking security cover
(available from your local Samson dealer) can be placed over the front panel to make sure that your
settings are not inadvertently altered.
If you have followed all the steps above and are experiencing difficulties with any aspect of setting up
or using your S curve 231, you can call Samson Technical Support (1-800-372-6766) between 9 AM
and 5 PM EST, or contact your local distributor.
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