Pendulum Audio SPS-1 User manual

SPS-1 Stereo Preamp System
For Acoustic Instruments
OPERATING MANUAL
Pendulum Audio, Inc. Serial No: SPS ___________
P.O. Box 339 • Gillette, NJ 07933 • [phone]

2
Channel 1
1. Input Level: The Input control sets the operating level. Set the
input level so the signal level stays between the limits set by the
Signal and Peak LEDs. The unity gain setting is 12:00.
2. Peak/Signal LEDs: The green 'Sig' LED indicates that the signal
level at the input stage is above -20 dbu, the lower limit for proper
operation. Set the Input level so this LED stays on most of the time.
The red 'Peak' LED indicates that the signal level is near the upper
limit for normal operation, +14 dbu, at one of the following places
in the signal path: Preamp Module output, Input stage, EQ input and
output, or Channel output. Set the Input Level control so that this
LED flashes only occasionally.
3. EQ In/Out Switch: Pressing the EQ button illuminates the red
'on' LED and puts the 3 band Parametric EQ into the signal path.
4. Three Band Parametric EQ: Each of the three bands (LO, MID,
HI) of the EQ has three controls:
Frequency: This control sets the center frequency for EQ. The ranges
are: LO: 35 - 880 Hz MID: 180Hz - 4.2KHz HI: 840Hz -19KHz
Bandwidth: The bandwidth control sets how wide ( ) or narrow
( ) a range of frequencies around the center frequency are affected.
The range of adjustment is:
LO: 0.1 - 1.0 octave MID, HI: 0.33 - 1.0 octave
Level: The level control sets the amount of boost or cut (±15 db
maximum) that is applied at the center frequency.
Channel 2
5. The operation of Channel 2 is identical to Channel 1. See 1-4
above.
Master Output
6. Pan: The pan controls determine the left (ccw) and right (cw) position in the stereo
mix for Channel 1 (top) and Channel 2 (bottom).
7. Master Level: This control sets the level for the Left and Right balanced outputs
on the rear panel. The unity gain setting is 2 o'clock.
8. Phase Rev: Press this switch to reverse the overall phase of the Master Outputs.
This can be useful for feedback control.
9. On/Loop: These two LEDs indicate the status of the mute and effects foot switches.
The 'On' LED (top) indicates that the master, monitor and channel outputs are active.
The 'Loop' LED indicates that the stereo effect loop in the master output section is
active. When the footswitch is not used, the 'On' LED is always lit, and the 'Loop'
LED ligjhts when an effect device is plugged into the stereo effects returns.
Monitor Output
10. Monitor Level: This control sets the level for the Left and Right 1/4"
unbalanced outputs on the rear panel. The unity gain setting is 2 o'clock.
11. Phase Rev: Press this switch to reverse the overall phase of the Monitor
Outputs. This can be useful for feedback control.
12. Monitor Source Switch: The Monitor outputs are normally fed the master
stereo mix (MIX), which is identical to the Master outputs. Press this switch to feed
Channel 1 directly to the monitors. This can be useful for controlling feedback in
pickup/mic applications, by feeding the pickup-only signal from channel 1 to the
stage monitors.
13. Phones: This is a separate output stage for driving a set of stereo headphones.
The output level is determined by the Monitor Level control.
14. Power: The yellow LED lights when ac power cord is plugged in, and the power
switch on the back panel is turned on.

3
POWER
MASTER OUTPUT
LEFT RIGHT
GND LIFT
L RETURN R
L SEND R
REPLACE
L
R
120V ON
Pendulum Audio, Inc.
MON. OUT TUNER
FT. SW.
OUTPUT INSERT LINE IN
CHANNEL 1
TRS BALANCED
+48V MIC
INPUT
PHASE
REV
1
1/2
OUTPUT INSERT LINE IN
CHANNEL 2
TRS BALANCED
+48V MIC PHASE
REV
INPUT
SPS-1 Condensed Operating Instructions - Rear Panel
256371 8
11
9
13
15
14
16
17
18 12 10 4
Channel 1
1. Input: An XLR-type balanced input used to connect the Preamp Module or an
External Mic to Channel 1.
2. Input Mode Switch: This switch is used to split the 'Ring' signals from a dual
pickup preamp module to Channel 2. With the switch 'out', the two signals (e.g.
pickup/internal mic or pickup 1/pickup 2) are blended together into Channel 1. By
pressing this switch, the two signals are separated, and the 'ring' signal (e.g. the
internal mic or pickup 2) is now processed by Channel 2. Use this mode when
processing a two pickup instrument in stereo.
3. Phase Rev: Press this switch to reverse the phase of Channel 1 only. This
allows you to switch the phase of Channel 1 relative to Channel 2. In this way,
you can listen to a pickup/mic or pickup1/2 combination in or out of phase
with one another. The two combinations will sound very different, and one
usually sounds a lot better.
4. Mic Switch/Mic Gain Trim: Press this switch only when using Channel
1 with an External Mic. Leave this switch 'out' when using a Preamp Module, or
when the XLR input is not in use. The trimpot directly above the Mic switch
adjusts the gain for the mic preamp. Turn counter-clockwise for less gain (a
vocal mic), and clockwise for more gain (acoustic guitar mic). Set this level so
the 'peak' LED flashes occasionally.
5. +48V: Press this switch to supply phantom power to an external condenser
mic, when using Channel 1 as a mic preamp.
6. Line In: An unbalanced 1/4" pre -EQ input for using Channel 1 with line
level signals, such as a wireless receiver, a cassette or CD player, etc. The Line
input remains active even when using the XLR input.
7. Insert: A mono effects loop for patching an effects device or volume pedal
directly into Channel 1. Tip = Send, Ring = Return.
8. Channel Output A TRS balanced direct channel output for sending the
output of Channel 1 directly to the board, a tape machine, a monitor amp, etc.
Channel 2
9. The operation of Channel 2 is identical to Channel 1. The Input Mode switch,
however, is unique to Channel 1. See 1-8 above.
Stereo Effects Interface
10. Replace Switch: With the switch 'out' (the MIX mode) the stereo
effects returns are blended with the dry signal in the preamp. Use this mode
when using reverb or other effects you wish to run 'wet only' and combine with
the unprocessed signal in the preamp. When the switch is pressed (REPLACE
mode), the dry signal is turned off and only the signal passing through the
effects loop is heard. Use this mode with a multi-effects chain, compressor, or
other effects meant to replace the 'dry' sound.
11. Effect Send A post-pan, line-level stereo send used to drive a reverb,
chorus, or other true stereo effects device.
12. Effect Return: A post-pan, line-level stereo input for returning the
effect output to the preamp. These inputs can also be used as post-EQ stereo
inputs for combining a CD or tape player, drum machine, or synth with
Channel 1 and 2.
13. Tuner Output: A channel 1 only signal for driving a tuner. This output
remains active even when the preamp is muted by the footswitch, for tuning
quietly.
14. Foot Switch: This jack accepts the stereo plug from the footswitch.
Closing either the tip or ring to ground causes the 'On' or 'Loop' LEDs to be
activated.
Monitor Output
15. Mon. Out: 1/4" unbalanced Left and Right outputs for driving a stereo
monitor amp or stage amp. Can be assigned to the stereo mix or Channel 1
only.
Master Output
16. Master Output: XLR-type balanced stereo outputs for connecting to a
snake, mixing board, tape machine, or other balanced input. Pin 2 is hot.
17. Gnd Lift: By pressing this switch, pin 1 of the XLR output connectors
is lifted from preamp ground. Use this to avoid ground loop hum when
connecting to a balanced input.
18. Power: On/off rocker switch and ac input. Wired for 120V/60 Hz unless
otherwise specified.

4
SPS-1 Condensed Operating Instructions -
Two Pickup Preamp Modules
Types: Pickup/Mic and Pickup 1/Pickup 2
Specifications
Pickup Input: Tip or Ring connection on the 1/4" stereo input plug.
Input Impedance: Piezo: 10 MΩ, unbalanced. Magnetic: 1MΩ, unbalanced.
Gain Adj: Unity to +20 db
Mic Input: Ring connection on the 1/4" stereo input plug.
Input Impedance: 15kΩ, unbalanced, +9 Vdc power to the mic.
Gain Adj: Off to +20 db
Controls: Balance (Pickup/Mic or Pickup 1/Pickup 2)
Master Volume
Hookup
The Dual Pickup Preamp Modules are designed to work on instruments equipped
with a 1/4" stereo Endpin jack. The Piezo or Magnetic pickup is wired to the 'Tip'
and the Mini-mic or Pickup 2 is wired to the 'Ring' connection. The mic is used in
the 'pigtail' configuration (without the mic's external electronics) and connected
in a two-wire configuration: see the attached hookup diagram. Connect the
Preamp Module to the Input of Channel 1 on the SPS-1 Main Preamp Unit. Press
the Input Mode (1/2) switch to send the 'tip' signal (pickup or pickup 1) to
Channel 1, and the 'ring' signal (internal mic or pickup 2) to Channel 2. Make
sure the Mic switch is 'out' on both channels.
Setting the Gain Adjustment Trimpots
The two trimpots on the top of the module allow you to set the gain of each
channel to match the pickups and mic you're using, and set the optimum balance
of the two.
• Turn the 'Input' controls for Channels 1 and 2 on the Main Preamp Unit to 10:00.
• Turn the Balance control counterclockwise to hear only the pickup signal, and
the Volume control all the way up. Strum your guitar as loud as the loudest you'll
be playing. Set the pickup gain adjustment trimpot on the left-hand side so that
the green 'signal' LED is on and the red 'peak' LED for Channel 1 of the Main
Preamp Unit does not flash. Some low level pickups may not have sufficient
output to cause the overload LED to go on. This is okay - just set it all the way
up.
0 10
Balance
Volume
Pickup Mic
0 10
Balance
Volume
Pickup 1 Pickup 2
Gain Adjust
Pickup 1 Pickup 2
Gain Adjust
Pickup Mic
• Set the balance control on the module to the center position (12:00). Set the mic
(or pickup 2) adjustment trimpot (on the right-hand side) for what you feel is the
best mix of the pickup and mic (or pickup 2). If for some reason you can't get the
mic or pickup 2 loud enough, just turn down the pickup (or pickup 1) gain.
• Set the Volume on the module to about 2:00, and turn up the Input levels on the
Channels 1 and 2 of the Main Preamp Unit so the green 'signal' LED remains lit
while you play, and the 'peak' LED does not flash. Adjust the input controls for
the proper balance of the two signal, and the Pan controls on the Main Preamp
Unit for the stereo image you prefer. Use the Phase Rev switch on Channel 1 or
Channel 2 (rear panel) to compare in and out of phase operation. To blend both
pickups in mono, set the Input Mode switch 'out' (1).
Note: Setting the gain in this manner conveniently locates the ideal mix of pickup
and mic or pickup 1/pickup 2 at the center position of the balance knob. From this
position you can easily make changes in the blend by turning the balance control
toward either the 'pickup' (pickup 1) or 'mic' (pickup 2) ends of the control.

5
SPS-1 Condensed Operating Instructions -
Single Pickup Preamp Module
Types: Pickup (Piezo ro Magnetic)
Specifications
Pickup Input: Tip connection on the 1/4" mono input plug.
Input Impedance: Piezo: 10 MΩ, unbalanced. Magnetic: 1MΩ, unbalanced.
Gain Adj: Unity to +20 db
Controls: Balance (Pickup/Mic or Pickup 1/Pickup 2)
Master Volume
Hookup
The Single Pickup Preamp Modules is designed to work on instruments equipped
with a 1/4" mono Endpin jack. The Piezo or Magnetic pickup is wired to the 'Tip'
connection of the endpin jack. Connect the Preamp Module to the Input of
Channel 1 on the SPS-1 Main Preamp Unit. Make sure the Input Mode (1/2)
switch is in the ‘out’ position. Make sure the Mic switch for Channel 1 is 'out'
Setting the Gain Adjustment Trimpots
The trimpot on the top of the module allows you to set the gain of the module to
match the pickup you're using, and set the optimum level sent the the Main
Preamp Unit
• Turn the 'Input' controls for Channel 1 to 10:00.
• Turn Volume control all the way up. Strum your guitar as loud as the loudest
you'll be playing. Set the pickup gain adjustment trimpot so that the green
'signal' LED is on and the red 'peak' LED for Channel 1 of the Main Preamp Unit
does not flash. Some low level pickups may not have sufficient output to cause
the overload LED to go on. This is okay - just set it all the way up.
Set the input control on Channel 1 to 12:00. The adjustment is complete.
Gain Adjust
Pendulum

6
Introduction
Congratulations! You have purchased the finest preamp system for
acoustic instruments available today. But you already know that, so we
won't bore you with the details. Suffice it to say the sound quality and
versatility of the SPS-1 are unmatched, both on stage and in the studio.
Since most of you would rather plunge right in and give it a listen, rather
than read a novel, we've taken a different approach to explain how to use the
SPS-1. If you're already technically savvy, you can head back to the
Condensed Operating Instructions that precede this introduction. It is a
capsule description of the main features of the SPS-1, and describes what all
the buttons and knobs and jacks do in their simplest form. It should get you
up and running immediately. If you need more information, or would like to
learn about some of the less obvious things you can do with the SPS-1,
read on.
Pickup Combinations - A Primer
Since we've been in the business of putting together preamp systems
for acoustic instruments longer than anyone else, we've come across most of
the configurations that players would like to use with their instruments. The
bottom line is that nearly everyone wants something different, and needs a
different approach to achieving it. For that reason, we've tried to incorporate
as many features as you're likely to need both now and in the future. Since
most players find that one pickup can't do the entire job, the SPS-1 is
designed specifically for blending a pickup with something else, be it
another pickup, an internal mic, or an external mic. What combination you
choose depends a lot on your playing style - flatpicking or fingerpicking,
playing solo instrumental music, accompanying vocals, or playing with
other instruments at high sound pressure levels. Even whether you play in
small clubs or with a concert sound system. The choices you make also
depend on whether you're playing live or in the studio. Here are a few of the
most popular combinations, and why people use them.
Two External Mics
The faint of heart need not apply! If you're a purist, and you're playing
solo guitar in a studio environment, this is the combination you're most
likely to use. However, it requires a pair of high quality condenser mics, and
a great sounding room. Since the SPS-1 has two studio-quality mic
preamps, parametric EQ and stereo output, it's the ideal preamp for going
directly to DAT or digital multitrack. Perfect for recording you solo record
yourself. No one would think of using this combination live, however, and
expect to be heard. Unless, of course, you're doing a classical concert in a
great European hall.
Pickup + External Mic
This is probably the ideal combination for solo acoustic
performance, when you're looking for a good representation of the sound of
your instrument but want some control over how 'woody' your guitar will
sound. In most cases the pickup will be some sort of string-sensitive device,
either a saddle or under the saddle piezo (that's pee-ay-zo folks, not pee-zo or
pie-zo) transducer or a magnetic soundhole pickup. Some work better than
others, some are easier to install, and some are just awful! The idea here is to
use the pickup to provide the direct 'in-your-face' sound of the vibrating
string, and combine it with the ambient sound of the wood vibration the
external mic gives you. By varying the blend between the direct and ambient
sound, you can get a very reasonable representation of your instrument. You
can use more pickup in a very lively room, and more mic in a dead room. By
using a single pickup or two pickup Preamp Module in one channel of the
SPS-1, and an external mic in the other, you can have complete control over
this blend on stage. Many players find that piezo transducers flatter light
fingerstyle playing, but are harsh when the strings are hit hard. The best
magnetic pickups, on the other hand, don't fold up when played hard, but are
too 'round' sounding for players who prefer that 'brash' piezo sound. The
choice is up to you.
In addition, most studio recording of acoustic instruments also relies
on using these two sound sources. During mixdown you can establish the
blend of pickup and mic that gets the guitar to cut through the mix.
The downside is that you have to have to stay glued to one position
for the mic to be effective. And, you can't use this setup with high stage
levels or in a band situation, since both feedback - and more important -
leakage of other instruments into the mic, will present major problems. Mic
selection and placement will often help solve some of these problems, but
not in all cases, or even in all rooms.
Pickup + Internal Mic
This is currently a hot combination, since it gives you the benefits
of an external mic, and you can move around. There is a price to be paid,
however, since a mic inside a guitar will never sound as good as a mic out in
front of your guitar. It may come pretty close, and in many cases it works
very well, but it's still a compromise. After all, it's is a mic in a box. All
that said, it works quite well in many applications, particularly for solo
players or groups where the stage levels are low. The problems encountered
with external mics, namely feedback and leakage, are also problems here.
Feedback problems can usually be cured by keeping the mic out of the stage
monitors, which the SPS-1's monitor output allows you to do. Leakage,
however is another matter. The mic is in a resonant box with a hole in it,
which acts as a 'magnet' for low frequency sound, particularly

7
drums and bass. You can roll off all the low end on the mic, but isn't that
what you wanted the mic for in the first place?
A word about soundhole covers: You may think that by blocking the
sound hole, you're blocking external sounds from reaching the internal mic.
This is true, but you're also preventing air from moving inside the
instrument. If the air doesn't move, neither does the diaphragm of the mic.
Consequently, the output of the mic drops dramatically, and sounds pretty
dreadful. Venting the cover by putting a few holes in it sometimes works,
but often the results are less than satisfactory. Sometimes you see a gauze
pad over a soundhole, which lets the guitar 'breathe'. It only attenuates high
frequency leakage though, not kick drum and bass.
Mic placement is another matter. The two most popular positions are at
the 2:00 or 5:00 position (neck is 12:00, bridge is 6:00), tucked inside the
soundhole about 1-2", 1" below the top, and aimed out at the strings. At
certain positions inside the instrument there are 'nodes' where the low end
boominess is less severe. Hunt around until you find a position that sounds
best without EQ. Some mics are less boomy to start with, particularly
hypercardioid capsules. Sometimes, pointing the capsule up directly at the
top, as close to the top as possible without touching (sort of a PZM
configuration), works well with large-body instruments. A little time
searching for the best position will pay off in the long run.
To sum up: internal mics work well when stage levels are low, the mic
is kept out of the monitors, and you've invested some time in hunting for a
sweet spot inside the guitar.
Two Pickups
If you're playing in a band, and it's loud, you can rule out any type of
mic. In this case, there are a couple of options. You can get a 'woodier'
sound by blending a string-sensitive pickup with a contact piezo transducer
mounted to the top. Although the contact pickup can feed back, the feedback
occurs at the cavity resonance of the instrument, which can easily be
notched out with parametric EQ on the SPS-1. The advantage, of course is
that leakage is no longer a problem. You won't get the sound of the pick or
your fingers hitting the strings, but at high sound levels this isn't a great
sacrifice. You will get some body noise, though - the sound of your shirt
sleeve scraping against the top, or your perspiring forearm peeling off the
top.
Another alternative is to blend two string-sensitive pickups. A common
combination is a saddle piezo pickup blended with a magnetic soundhole
pickup. Here, you're getting two different tonal colors which you can blend
to your liking. The piezo transducer is great for that brash, 'in your face'
sound, and a biting attack. The magnetic pickup is ideal for getting
harmonics out of your instrument (especially for tapping), and does very
nice things for slide playing. It definitely opens a lot of possibilities.
Setting up the SPS-1
In this section we'll highlight the operation for SPS-1 and describe
some of the many things you can do with it. Refer back to the Condensed
Operating Instructions for the front and rear panel layouts.
Standard Set-up with a Two Pickup Preamp Module
• Start off by plugging the Two Pickup Preamp Module into the XLR input
of Channel 1. Make sure all the pushbuttons on the front and rear panel
are in the 'out' position.
• Plug the Preamp Module into your instrument. Set the Balance control on
the Preamp Module to the left (Pickup or Pickup 1), and the Volume
control to 0.
• Plug a set of headphones into the 'phones' jack on the front of the SPS-1.
• Set the Monitor level to 10:00. Set the Input and Master level controls to
12:00. Turn the Pan controls to the center (12:00).
• Plug the SPS-1 into an ac outlet and turn on the power switch on the rear
panel.
• Turn up the Volume control on the preamp module to 2:00. Strum your
instrument. You should now hear the pickup in the headphones, and see
the green LED on Channel 1 flash as you play.
• Set the Balance on the Preamp Module to the right (Mic or Pickup 2).
• Strum your instrument. You should now hear the internal Mic or Pickup 2
in the headphones, and see the green LED on Channel 1 flash as you play.
• Set the Balance control on the Preamp Module to the center .
• Strum your instrument. You should now hear both pickups blended
together in Channel 1. If one pickup is considerably louder than the other,
you can use the balance control to alter the blend. To set the module up
for the optimum blend at the center position on the balance control, you'll
have to reset the gain adjustment trimpots on the top of the module.
Please refer to the condensed operating instructions for more details.
• Press the Input Mode switch (labeled 1 / 1/2), located next to the
XLR input on channel 1 When in the up position (1), the module output
feeds Channel 1 only. That is, both pickups are blended to mono into
Channel 1. By pressing this switch (1/2), the two signals split to
individual channels; that is, the Tip pickup now feeds Channel 1 only,
and the Ring pickup feeds Channel 2.
• Adjust the Pan controls for a stereo spread between the two pickups. Set
Ch. 1 to 10:00, Ch. 2 to 2:00. You should now hear your guitar in
stereo.
• Press the Phase Rev switch for Channel 1, on the rear panel next to the
Input Mode switch.
• Strum your instrument. You should hear a different character to the
combined sound, especially on the low frequencies. Choose the
combination which sounds the best to you.

8
Set-up for a Pickup and an External Mic
It's easy to blend one or two pickups in Channel 1 with an external mic
in Channel 2. You can use the mic on your instrument, or as a vocal mic
blended with your guitar sound.
• Set the Input level controls for Channel 1 and Channel 2 to 0.
• Plug the Single Pickup or Two Pickup Preamp Module into the XLR
input of Channel 1. Make sure all the pushbuttons on the front and rear
panel are in the 'out' position.
• Press the MIC button to use Channel 2 as a mic preamp.
• Plug an external Mic into Channel 2's XLR input connector.
• If you're using a condenser mic with phantom power, press the 48V button
for Channel 2.
• Turn up the Input level control for Channel 2 to set the proper level for
the external mic. If you're using the mic preamp with a vocal mic, it may
be necessary to adjust the Mic Gain Trim control above the MIC switch.
• Set the input level control for Channel 1 to 12:00.
• If you're using a two pickup module with a single pickup instrument, turn
the balance control to the Pickup or Pickup 1 only. If you want to blend
two pickups or a pickup and internal mic in mono in Channel 1 with an
external mic, set the balance control for the blend you'd like.
• Turn up the Volume control on the single or two pickup module to about
2:00.
• You should now hear a blend of Channel 1 and the external mic. Set the
Input controls on the SPS-1 for the blend of the two channels that you
desire. Be sure to keep the signal level between the limits set by the Sig
and Peak LEDs on the front panel.
• For a stereo blend, adjust the Pan controls of Channel 1 and 2.
• Press the Phase Rev switch for Channel 1, on the rear panel next to the
Input Mode switch.
• You should hear a different character to the combined sound, especially in
the low end. Choose the phase setting which sounds the best to you.
Set-up for Two External Mics
• Set the Input level controls for Channel 1 and Channel 2 to 0.
• Press the MIC buttons on Channel 1 and 2.
• Plug the external Mics into the XLR input connectors on Ch. 1 and 2.
• If you're using condenser mics with phantom power on one or both
channels, press the 48V button for those channels.
• Make sure the Input Mode switch for Ch. 1 is 'out' ( 1).
• Turn up the Input level controls both channels to set the proper level. Be
sure to keep the the signal level between the limits set by the Sig and
Peak LEDS on the front panel.
• For a stereo blend, set the Pan controls of Channel 1 and 2 for the stereo
spread you desire.
Set-up for Two Instruments
The SPS-1 can also be used with two single pickup or two dual
pickup instruments connected simultaneously. Each instrument is connected
to its own input channel, and EQed individually. The two pickups of any one
instrument are blended to mono in each input channel.
• Set the Input level controls for Channel 1 and Channel 2 to 0.
• Plug one Single Pickup or Two Pickup Preamp Module into the XLR
input of Channel 1. Make sure all the pushbuttons for Channel 1 are out.
• Plug another Single Pickup or Two Pickup Preamp Module into the XLR
input of Channel 2. Make sure all the pushbuttons for Channel 2 are out.
• Turn up the Input level controls for both channels to set the proper level.
Be sure to keep the the signal level between the limits set by the Sig and
Peak LEDS on the front panel.
• To run the two instruments in stereo, set the Pan controls for the desired
stereo spread.
Set-up for Instruments with On-Board Active Electronics.
The SPS-1 can also be used with instruments with active
electronics, with or without the preamp module. When used with the preamp
module, set up as above. For use without the preamp module:
• Set the Input level controls for the Channel inputs to 0.
• Plug the instrument into 1/4" LINE IN for either Channel 1 or 2.
• If present, turn the volume knob up on the instrument, and run the any EQ
controls flat.
• Turn up the Input level controls for that channel to set the proper level. Be
sure to keep the the signal level between the limits set by the Sig and Peak
LEDS on the front panel.
Set-up for Use with a Wireless System.
Although the best sound quality is achieved using a Preamp Module
and a connecting cable, the SPS-1 can also be used with a wireless system:
• Set the Input level controls for the Channel input to 0.
• Plug the wireless receiver into 1/4" LINE IN for either Channel 1 or 2.
• Turn the output knob of the wireless receiver all the way up.
• If your instrument has on-board electronics, connect your instrument
directly to the wireless transmitter pack.
• If not, you'll need some sort of battery-powered buffer preamp to prevent
pickup loading and boost the signal level to the transmitter. We
recommend our SmartCord preamp module, for single pickup instruments.
• Turn up the Channel level control to set the proper level. Be sure to keep
the the signal level between the limits set by the Sig and Peak LEDs on
the front panel.

9
Features of Channels 1 and 2
In this section we'll detail the input, output and control features of the
individual channel inputs.
Rear Panel
Line Input
The LINE IN is an unbalanced 1/4" phone jack input for line level
signals such as a wireless receiver, CD or cassette player, or for use as an
outboard EQ during mixdown in the studio. The line input remains active
even when using the XLR input with a Preamp Module or an external mic.
Channel Insert
The INSERT is a mono effects loop for patching an effects device,
compressor or volume pedal into an individual channel. Use a 1/4" stereo
plug wired to two 1/4" mono plugs. The 'tip' is the send (to the effect
input), and the 'ring' is the return (from the effect output).
Channel Output
The OUTPUT is a TRS (tip - ring - sleeve) balanced direct output jack
for sending the channel output directly to a tape machine, mixing board, or
monitor amp. This output is also switched on and off under the control of
the foot switch. In order to connect this output into a 3 pin XLR-type
input, use a 1/4" stereo to 3 pin XLR adapter. Or you can make your own
adapter cable by wiring the tip to Pin 2, ring to Pin 3, and ground to Pin 1.
For unbalanced operation, use a 1/4" mono phone plug.
Input Mode Switch ( 1 , 1/2)
This switch is used to split the 'Ring' signal from a dual pickup preamp
module to Channel 2. With the switch 'out', the two signals (e.g.
pickup/internal mic or pickup 1/pickup 2) are blended together into Channel
1. By pressing this switch, the two signals are separated, and the 'ring'
signal (e.g. the internal mic or pickup 2) is now processed by Channel 2.
Phase Rev
Press this switch to reverse the phase of each channel individually.
This allows you to switch the phase of Channel 1 relative to Channel 2, and
vice-versa. In this way, you can listen to a pickup/mic or pickup1/2
combination in or out of phase with one another. The two combinations
will sound very different, and one usually sounds a lot better.
Mic Switch/ Mic Gain Trim
When this switch is 'in', the channel input is turned into a mic preamp.
Use this mode only when using an External Mic. Leave this switch 'out'
when using a Preamp Module, or using the Line Input. The Mic Gain Trim
(located directly above the MIC switch) is a screwdriver-adjustable control
for optimizing the gain of the mic preamp. Turn it counter-clockwise for
less gain, e.g. when using a vocal mic. It is set at the factory in the
clockwise position, the setting you'll use for micing an acoustic instrument.
Set the gain so the 'Peak' LED flashes rarely.
+48V (Phantom Power)
Press this switch to supply phantom power to an external condenser
mic, when using Channel 1 or Channel 2 as a mic preamp. This switch is
only active when the MIC switch is 'in' - that is, the channel is used as a
mic preamp.
Front Panel
Input Level
The Input control sets the operating level, from off to +20 db of gain
(module and Line input), or off to +50 db of gain (mic preamp). Set the
input level so the signal level stays between the limits set by the Signal and
Peak LEDs. The unity gain setting is 12:00 for the line input.
Peak/Signal LEDs
The green 'Sig' LED indicates that the signal level at the input stage is
above -20 dbu, the lower limit for proper operation. Set the Input level so
this LED stays on most of the time. The red 'Peak' LED indicates that the
signal level is near the upper limit for normal operation, +14 dbu, at one of
the following places in the signal path: Preamp Module output, Input stage,
EQ input and output, or Channel output. Set the Input Level control (and
the Mic Gain Trim, if required) so that this LED flashes only occasionally.
EQ In/Out Switch
Pressing the EQ button illuminates the red 'on' LED and puts the 3
band Parametric EQ into the signal path. Otherwise, the EQ is bypassed
entirely.
Three Band Parametric EQ
Why have we chosen to use a parametric EQ in the SPS-1? Well,
regardless of where a pickup or mic is positioned (though some locations are
much better than others), certain overtones will be exaggerated at the
expense of others. Only a parametric equalizer has the flexibility that is
essential for restoring the natural harmonic balance of your acoustic guitar.

10
You'll find that the SPS-1's three band parametric EQ, with its overlapping
frequency bands and variable bandwidth, gives you enough freedom to
accurately tailor the equalizer's response to the unique needs of your
instrument/pickup combination. Each of the three bands (LO, MID, HI) of
the EQ has three controls, which from left to right are:
Frequency: This control sets the center frequency for EQ. The ranges are:
LO: 35 - 880 Hz MID: 180Hz - 4.2KHz HI: 840Hz - 19KHz
Bandwidth:The bandwidth control sets how wide ( ) or narrow
( ) a range of frequencies around the center frequency are affected.
The range of adjustment is:
LO: 0.1 - 1.0 octave MID, HI: 0.33 - 1.0 octave
Level: The level control sets the amount of boost or cut
(±15 db maximum) that is applied at the center frequency.
There are two things to note; first, the three frequency bands have
considerable range (about 4 1/2 octaves) and overlap - that is, the MID band
can also be used in the middle range of the LO band, and so on for the other
bands. This gives you added versatility, e.g. if one band is dedicated to
removing a objectionable band of frequencies, another band may be applied
to access other frequencies nearby. Also note that the LO band is capable of
a narrower bandwidth (larger 'Q') than the others; this is important for using
the LO band to 'notch' out any objectionable low frequency resonances or
feedback, particularly the instrument's cavity resonance.
To put the equalizer into the signal path, press the 'EQ' pushbutton
to the right of the Input control - the red LED above it indicates the EQ is
on. With the level controls centered, the equalizer is inactive and you
guitar should sound no different than with the EQ off. Rotating the LEVEL
control to either side of the center position will boost or cut in the range
selected by the frequency and bandwidth controls. Choosing a wider
bandwidth ( ) will encompass more frequencies, causing a more audible
effect on your guitar's sound - more like that observed with with one band of
a graphic equalizer or a tone control with a 'peaking' response. With a
narrower bandwidth ( ), fewer frequencies are affected, so more boost or cut
has to be applied to notice a large difference in your guitar's sound.
However, the narrower bandwidth lets you be more selective about the
frequency range you want to target - giving you an extremely effective way
of eliminating unpleasant resonances without affecting other areas of the
frequency spectrum.
We'll have a few more things to say about EQing your instrument on
page 7.
Master and Monitor Outputs
In this section we'll discuss the outputs available on the SPS-1, and
which features you'll be most likely to use.
Master Output Section
PanThe pan controls determine the left (ccw) and right (cw) position in the
master stereo mix for Channel 1 (top) and Channel 2 (bottom). To obtain a
mono blend of the two channels, set both pan controls to the center
position.
Master Level
This control sets the level for the Left and Right balanced outputs on
the rear panel. Set the level for the mixing board, amplifier, or tape machine
you're using. The unity gain setting (+4 dbu) is 2:00.
Phase Rev
When this switch is 'in', the overall phase of the Master Outputs is
reversed. Reversing the phase can be useful for feedback control.
On/Loop LEDs
These two LEDs indicate the status of the mute and effects foot
switches. The 'On' LED (top) indicates that the master, monitor and channel
outputs are active. The 'Loop' LED indicates that the stereo effect loop in
the master output section is active. When the footswitch is not used, the
'On' LED is always lit, and the 'Loop' LED goes on when an effect device is
plugged into the stereo effects returns.
Master Outputs
The two XLR-type balanced stereo outputs are used for connecting to a
snake, mixing board, tape machine, or other balanced input. This is the
output you'll normally use to feed the 'house' sound system. Pin 2 is hot.
To connect up to an unbalanced input, use an XLR to 1/4" adapter. Or, you
can make your own adapter cable by wiring pin 2 to the 'tip' of a 1/4" phone
plug, and pin 1 to the sleeve.
Gnd Lift
By pressing this switch, the ground connection (pin 1) of the XLR
output connectors is lifted from preamp ground. Use this to avoid ground
loop hum when connecting to a balanced input. When using the master
outputs with an unbalanced input, make sure this switch is 'out'.

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Monitor Output Section
Monitor Level
This control sets the level for the Left and Right unbalanced
outputs on the rear panel. Set the level for the stage monitor, monitor
amplifier, tape machine or other system you're using. The unity gain setting
(+4 dbu) is 2:00. The monitor level also controls the signal level sent to the
headphone jack on the front panel.
Phase Rev
When this switch is 'in', the overall phase of the Monitor Outputs
is reversed. Reversing the phase can be useful for feedback control onstage.
Try it both ways and use the position that works best. The best setting will
depend on the position of your guitar relative to the monitor speakers. So, it
may change from night to night.
Monitor Source Switch ( MIX / CH 1 )
The Monitor outputs are normally fed the master stereo mix
(MIX), which is identical to the Master outputs. Press this switch (CH 1) to
feed only Channel 1 directly to the monitors. This can be useful for
controlling feedback in pickup/mic applications, by feeding the pickup-only
signal from Channel 1 to the stage monitors. The Channel 1 signal is
mono, post-EQ, post-Insert, but pre-stereo effects loop. It is turned on and
off by the foot switch.
Monitor Outputs
The two 1/4" unbalanced stereo outputs are used for connecting to a
stage monitor, monitor amplifier, tape machine or other unbalanced input.
This is the output you'll normally use to feed your onstage amp or 'monitor'
sound system. The output is assigned to the stereo mix or channel 1 via the
monitor source switch.
Phones This is a separate low impedance output stage for driving a set of
stereo headphones. The output level is set by the Monitor Level control, and
the feed is controlled by the monitor source switch. The phones output is
not affected by the monitor or master Phase Rev switches. We've given the
headphone amp extra level and drive capability to work with all types of
headphones. The 1/4" stereo jack is wired according the industry-accepted
standard: Tip = left, Ring = right.
Stereo Effects Interface
The Stereo Effects interface is used to insert true stereo effects into the
stereo mix of the Master and Monitor Output sections. Rather than just a
simple effects loop, the SPS-1's stereo effects interface allows you to
distinguish between effects that you want to mix with the unprocessed
guitar sound (e.g. reverb), or those you want to replace the unprocessed
signal (e.g. compressor or multi-effects processor).
Send Outputs and Return Inputs
Interfacing to the stereo effects mixer easy. Just connect the L and R
inputs from your stereo effects device to the L and R send output jacks on
the rear panel of the SPS-1. These are unbalanced, low impedance outputs
that are capable of driving any effects device.
Next, connect the L and R outputs from your stereo effects device to the
L and R return input jacks. The Return inputs are also unbalanced. The
'Loop' LED on the front panel will light, indicating the effects returns are
active.
The effects returns can also be used as a post-EQ auxiliary input. It's a
convenient way to combine a drum machine, synth, or to play along with
your favorite CD or cassette!
Replace Switch
With the switch 'out' (the MIX mode) the stereo effects returns are
blended with the dry, unprocessed signal in the preamp. In other words, the
loop is combined in parallel with the unprocessed sound. Use this mode for
combining reverb with the unprocessed guitar signal. - set the 'mix' control
on the reverb unit to return 'wet' or 'reverb-only' signal to the SPS-1. This
way, the dry signal is not degraded by the effects device.
When the switch is pressed (the REPLACE mode), the unprocessed
signal is turned off and only the signal passing through the effects loop is
heard. Use this mode with a compressor, stereo chorus, delay, or multi-
effects processor. The blend of the 'dry' and 'wet' signals is determined by the
effects device.
Foot Switch
The Foot Switch jack is used to turn your instrument on and activates
the stereo effect loop. The 'On' and 'Loop' LEDs on the front panel indicate
that the 'On' and 'Effects' switched on the Foot Switch are activated.
Tuner
This output is a Channel 1 only signal used to drive an instrument
tuner. Using Channel 1 only, which is usually a pickup signal, gives the
tuner greater accuracy. This output remains active when the instrument is
muted, for tuning quietly.

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Equalizing your Acoustic Guitar
Comments
Before you start to equalize your instrument's sound, it's probably a
good idea to:
• Listen carefully to your instrument unamplified. Try to decide what
it is you like about the way it sounds, and target any potential problem
areas you feel might need fixing. This will give you a clearer sense of what
you want the equalization to achieve.
• Try to get the best sound that you can from your pickup or mic
before applying any EQ. This includes (if possible) trying different
pickups, mics or mic placement, to get the most balanced sound possible.
Remember, it's best to use only as much EQ as necessary; when less is
needed to fix major problems, more is available to accent the good points.
It's also a good idea to perform the initial EQing by listening
through a pair of high quality headphones or in a quiet, controlled
environment (like your home studio). This is the best way to judge the
effect that various control setting are having on your sound. If you're
planning to use the SPS-1 onstage with a sound reinforcement system,
setting up this way first is important: it will help you distinguish problems
with the sound from your guitar and pickup from deficiencies in the sound
system.
Main Problem Areas
Since the requirements of each instrument and pickup system are
unique, it's difficult to pinpoint specific EQ setting that will work for
everyone. However, we have found that most of the problems fall into one
of four main categories. Here are a few hints on how to use each of the the
four bands you have available to handle them:
•Too Much 'Boominess'
Tuning the LO band to the instrument's body resonance
(typically in the range of 70-140 HZ) is an extremely effective way of
taming an overpowering low end 'boominess', especially with a
mini-mic in the body of a guitar. To do this, set the bandwidth control
fairly narrow (around 3:00) and add 12-15 db of boost. Then, lightly tap a
finger on the top of the guitar behind the bridge while tuning the frequency
control in the range given above (the larger the guitar's body, the lower the
resonant frequency). At a certain point, the tapping will turn into a deep
'thud' as you zero in on the body resonance. (If you listen closely, you'll
actually hear a series of harmonically-related resonances - tune in on the
lowest frequency one.)
Now, cut about 12 db, play a few chords and adjust the bandwidth and
level to your liking, while using the EQ in/out switch for comparison. Cut
the level and adjust the bandwidth to remove as much of this frequency range
as necessary. You should be able to find a setting that effectively removes
the problem without affecting the rest of the bottom end. The improvement
is usually dramatic.
• Lack of 'Clarity'
Often, because of the pickup's response or placement, the guitar's lower
midrange overtones get exaggerated. This causes your guitar to sound
'muddy' and lack definition. Use the LO or MID band (with a fairly wide
bandwidth) to cut a few db in the 400-1000 Hz frequency range.
• Lack of 'Presence'
Using the MID or HI band to add a few db in the 3-6 kHz range will
help your guitar stand out. Be careful though, since adding too much or
centering on the wrong frequency can make your guitar sound harsh. On the
other hand, some pickups tend to overemphasize frequencies in this range so
you may need cut back in this region.
• Lack of 'Brilliance'
Compared to the hyped-up high end we're used to hearing on recordings,
an acoustic instrument can often sounds too 'mellow' to the modern ear. A
broad boost of the HI band above 10 kHz will give you a 'crisper', 'brighter'
tone. Applied in moderation, it can bring life to a dull-sounding instrument.
Remember, EQ is largely a matter of personal taste and the
specific needs of your instrument may be quite different from these
general guidelines. Don't be afraid to experiment to find what sounds the
best to you.
Technical Extras
In case you were wondering, here are a few of the reasons why the
SPS-1 sounds so good!
• The latest in high speed/low noise circuitry is used throughout.
• All inputs and outputs are electronically balanced: there are no
transformers in the signal path.
• We use audiophile-quality components: metal film resistors,
polypropylene capacitors, conductive plastic potentiometers, and a
minimum number of electrolytic capacitors in the signal path.
• A toroidal power transformer is used for minimum hum.
• Single circuit board construction of the Main Preamp Unit and Preamp
Module are used for high reliability.
• Each unit is handcrafted entirely in the USA.

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SPS-1 Specifications
Preamp Modules
Input(Piezo or Magnetic): 10 MΩ, unbalanced
Input(mini-mic): 15 kΩ, unbalanced, +9 Vdc power to mic.
Maximum Input Level: +15.5 dbu (4.6 Vrms)
Input Noise: EIN less than -113 dbu, input shorted.
Frequency Response: +0/-1 db, 20 - 20,000 Hz
Distortion: THD less than 0.01% at 0 dbu
Gain: 0 to +30 db, adjustable
Output: Balanced, 3-pin mini-connector
Main Preamp Unit
Inputs: Module/Mic: 3-pin XLR, balanced
Line in: 1/4" phone jack, unbalanced, 10KΩ.
Insert: 1/4" stereo jack, tip=send, ring=return.
Mic Preamp: EIN less than -128 dbu, 50db gain.
Frequency Response: +0/-1 db, 20 - 20,000 Hz
Distortion: THD less than 0.007% at 0 dbu
Output Noise: EQ out, unity gain: less than - 93 dbu
EQ in, set flat: less than - 88 dbu
Maximum Output: +21 dbu, unbalanced
+27 dbu, balanced
Channel Outputs: 1/4" phone jack, TRS balanced, 600Ω.
Master Outputs: XLR, balanced, pin 2 in phase, 600Ω.
Monitor Outputs: 1/4" phone jack, unbalanced, 600Ω.
Effects Sends: 1/4" phone jack, unbalanced, 600Ω.
Effect Returns: 1/4" phone jack, unbalanced, 10KΩ.
Tuner Output: 1/4" phone jack, unbalanced, 10KΩ.
Phones: 1/4" stereo phone jack, 100Ω.
Metering: Signal (green): -20 dbu; Peak(red): +14 dbu
Equalizer: Three band fully parametric, ±15 db boost/cut
Lo: 35 - 880Hz, 0.1 to 1.0 octave (Q=10 to 1)
Mid: 180Hz - 4.2kHz, 0.3 to 1.0 oct. (Q=3 to 1)
Hi : 0.84 to 19kHz, 0.3 to 1.0 octave (Q=3 to 1)
Phantom Power: +48 Vdc applied to pins 2 and 3
Foot Switch: 1/4" TRS phone jack, 10 mA current loop.
Power: 120 VAC, 10 Watts
Dimensions
Preamp Module: 1.1" x 2.2" x 1.0", excluding input plug.
Main Preamp Unit: 1.75" x 19" x 8" (one standard rack space), 6 lbs.
Foot Switch: 4.3" x 2.3" x 1.2"
Notes: 0 dbu = 0.775 Vrms.
All noise measurements are unweighted, 20 - 20,000 Hz bandwidth.
All specifications are subject to change without notice.
Limited Warranty
Pendulum Audio, Inc. warrants to the first purchaser of a new
Pendulum SPS-1 Stereo Preamp System that the unit is free of
manufacturing defects in materials and workmanship for a period of one (1)
year from the date of purchase. Pendulum Audio, Inc.'s sole obligation
under this warranty shall be to provide, without charge, parts and labor
necessary to remedy defects, if any, which appear within one (1) year from
the date of purchase. All warranties expressed or implied made by Pendulum
Audio, Inc., including warranties of merchantability and fitness, are limited
to the period of this warranty. Pendulum Audio, Inc. is not responsible for
indirect, incidental or consequential damages arising from the use or failure
of this product, including injury to persons or property.
This warranty does not cover damage due to: misuse, abuse,
modification, accident or negligence. The warranty does not apply if the
unit is repaired or altered by persons unauthorized by Pendulum Audio, Inc.
in such a manner as to injure, in Pendulum's sole judgment, the
performance, stability or reliability of the unit. The warranty does not apply
if the unit is connected, installed or used otherwise than in accordance with
the instructions furnished by Pendulum Audio, Inc.
If the equipment requires warranty repair, return authorization must be
obtained from Pendulum Audio, Inc. prior to shipment. Equipment should
not be shipped to Pendulum Audio, Inc. until return authorization and the
proper shipping address is obtained from us. The equipment (with all its
components parts and connecting cables) must be suitably packaged,
including a note with the owner's name, address, telephone number and a
description of the reason for return. You pay two-way shipping (we
recommend UPS), and we suggest you insure your shipment.
This limited warranty is in lieu of all other warranties, expressed or
implied, and no representative or person is authorized to represent or assume
for us any liability in connection with the sale of our products than set forth
herein. This limited warranty gives you specific legal rights, and you may
also have other rights which vary from state to state.

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Pendulum Audio, Inc. P.O. Box 339 • Gillette, NJ 07933 • [phone] www.pendulumaudio.com