zapco ST-X DSP 2021 User manual

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Before operating the unit, p ease read this manua through y and retain it for future reference.
ST-X DSP 2021
Owner’s Manua

MISSION STATEMENT
Committed to Excellence
ZAPCO is dedicated to the pursuit o audio idelity. Our prime objectives are to
design and manu acture audio products o unsurpassed quality, to provide
unparalleled support and service or these products and to conduct business
in a manner that will enhance the quality o li e or all involved.
Experience
(Knowled e from doin )
There is absolutely no substitute or experience; that is a simple act o li e.
Another simple act is that ZAPCO has, or over orty years, been the leader in
de ining quality standards or the car audio industry.
These years o experience have led to a thorough understanding o the
challenges that are unique to the world o car audio. ZAPCO's relentless quest
or sonic purity consistently yields imaginative designs that utilize the most
innovative technologies. The resulting products set the criteria by which all
others in the industry are judged.

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Table of Contents
A new level o Sound Quality ......................................................................... 4
History o the Studio Series .................................................................... 4
The Studio-X DSP ampli iers ................................................................... 5
Main eatures o the Studio-X DSP ampli iers ........................................ 5
What’s new or 2021 .............................................................................. 5
Be ore you start your installation ................................................................... 6
Upgrading a Factory Stereo .................................................................... 6
Planning your power connections .................................................................. 7
Wire size ................................................................................................. 8
Mounting your Studio-X DSP ampli ier ........................................................... 9
Inputs and Controls ......................................................................................... 10
ST-4X DSP 2021 Input Ends ..................................................................... 10
ST-6X DSP 2021 Input Ends ..................................................................... 11
Speaker Wiring o the Studio-X DSP Ampli iers .............................................. 12
The ST-X DSP GUI Program ............................................................................. 13
Loading the GUI ..................................................................................... 13
Channel Setup ........................................................................................ 14
Delay ...................................................................................................... 15
Ch. Selection and Crossover ................................................................... 18
Phase/Level ............................................................................................ 19
Equalizer ................................................................................................ 20
System Phasing ...................................................................................... 22
Tuning - The Simple Rules .............................................................................. 24
Technical Speci ications .................................................................................. 26

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A new level of Sound Quality
Zapco has a reputation or sound quality that is unsurpassed. It is our dedication
to sonic purity and out passion or per ormance that built that reputation.
With all the new ampli iers coming into the market, none has been any threat
to Zapco's standing as the premiere amp and processor company or pure
sound quality.
Just check out the audio competition scene. The pros know what to use to win.
Competition amps however, do not come cheap, and not everyone wants to
compete. The challenge then, was to put Zapco's 40 plus years o experience
to use in the development o an ampli ier that would bring Zapco sound a line
o products or every-day use and that everyone could a ord. And the studio
line is just that ampli ier. In the time it has been out it has built a reputation as
the best sounding amp in the class.
O course, not everyone buys strictly by sound (although they should). Maybe
it's the wrong color, maybe it's too big... or too small. But one thing is constant.
Everyone who hears the studio amps agrees; it sounds better than any other
product in the class.
History of the Studio Series
Per ection cannot be achieved. But that does not make its pursuit less valuable.
Zapco is committed to making every product we make better than the last.
We introduced the ST-X amps in 2013. In 2015 we improved the PCB design
and upgraded components to make the sonically improved ST-X II.
For 2018 we developed o the Studio X SQ ampli ier to take a ordable sound
quality to a new level. We added the proprietary RCA connectors rom the Z-LX
ampli iers, changed the capacitors to a higher end audio cap, and made a ew
other small changes. All this takes take the Studio sound to a new level o sonic
per ormance or an a ordable ampli ier.
For 2019, we brought digital processing to the studio line in DSP/AMPs that can
be controlled by PC or by iOS or Android mobile apps.
For 2021 we have upgraded the ST-DSP with new eatures and unctions to
improve your listening experience. And developed a new an cooled aluminum
heat sink or improved e iciency and reliability under extreme temperature
and hard play.

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The Studio-X DSP Amplifiers
With the new Studio-X DSP amps you get the sound quality that other companies
o er only in their big competition amps (and better than many o them) in a
compact chassis with 65W RMS/Channel @ 4Ω (ST-4X DSP) 100W/Ch. @ 4Ω
(ST-6X DSP) plus the tuning power o the ST Digital Processing System. The
on-board DSP provides a wide variety o digital Crossovers, Parametric EQ at
each channel as well as Signal Delay, Polarity, and gain or each channel.
As or analog per ormance, the Studio X DSP amps give you more than power.
These amps have 0.2% THD+noise, over 90dB signal to noise, over 60dB
separation, and produce power rom 15 Hz to 30 KHz.
Main features of the Studio-X DSP amplifiers
• 4-Ch or 6-Ch Full Range, Class A/B Ampli ier
• On-Board, Full Function, 8-Ch Digital Signal Processing
• High-pass and low-pass ilters
• Signal Delay
• Phase (Polarity) control
• 15 channels o parametric equalization on each channel
• Optional BT Streaming (Bluetooth Port or external APTX HD Module)
• And o course, Zapco sound quality
New for 2021
• Analog input level controls with 2-stage clip indicators or accurate, distortion
ree gain settings
• Toslink Optical input or both the models
• 6-Channel speaker level input connections
• New high e iciency inned heat sink with an cooling
• Both models have 8-Ch digital processor to provide processed outputs or
external ampli iers

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Before you start your installation
ZAPCO highly recommends that a use or circuit breaker be placed within 18"
o the battery. Although you will add a use or use block near the ampli ier it
is still a possibility that a pinched power wire between the component use
and the battery could result in a short, or even a ire. The protection device
should be placed where it can be accessed easily and all wiring should be
routed sa ely and correctly according to the ollowing guidelines:
Do not run wiring close to hot or spinning objects.
Always use wire grommets when routing wire through the irewall or any
other metal panels.
Make sure that the potential or pinched wiring is avoided by routing all wires
away rom moving hinges and seats. This also includes brake, gas and clutch
pedals, hood and trunk hinges, etc.
Continuous exposure to excessive sound pressure levels may cause permanent
hearing loss. ZAPCO strongly advises that you use common sense when setting
volume levels. I you experience ringing in the ears, it could cause permanent
hearing damage!
When connecting our ampli iers to pre-wired stock speakers, care must be
taken that there are no common connections between le t and right speaker
wires, i.e. two or more speakers using the same ground connection (very
common in pre-85 cars), as this will cause the ampli ier to go into immediate
protection or may cause damage to the ampli ier. Output connections are not
common chassis ground. Please ollow the hookup instructions in this owner's
manual. Any questions should be directed to your local ZAPCO dealer.
Up radin a Factory Stereo
I you are upgrading a actory stereo the ST-X DSP amps have a separate speaker
level input plug that senses current, so you do not need to run a turn-on wire.
However, auto-on is not use ul in all cars as the ampli ier can come on when
you do not want it on, because o the car's electrical system. The ST-X DSP
amps have a switch that allows you to de eat the auto-on i you ind you do
not want to use that unction.

Plannin your power connections
The power end plates o the Zapco ST-X DSP amplifiers carry the power connecons
and the speaker connecons and vary somewhat by the number o channels.
For example, the power end o the ST-4X DSP below has (o course) speaker
connecons or our channels. The ST-X DSP amps all have on-board uses and
the use rang as printed above the uses. The main 12-volt power input, the
12-volt turn-on wire, and the main Ground connecon are common to both
models.
• The large connecon at the interior o the end plate is the main power
input. This must be connected the vehicle baery's posive (+) terminal,
and a main system use should be placed close to the baery
• The large connecon at the outside o the end plate is the main ground
or negave connecon. This must be securely aached to bare metal at
the vehicle rame, or other heavy chassis component with a direct
connecon to the rame
Note: Seat bolts and seat belt bolts are NOT ood round points
• The small terminal between the main power and ground is the +12
turn-on input and can be connected to the head unit turn-on output wire.
I none is available it can be connected to an accessory (ACC) terminal.
You should avoid using any ignition-on (IGN) wire, as they can be noisy
Note: The ST-X DSP amplifiers have terminals that do not require connectors. You simply insert
a bare portion of wire and ti hten the connection with the supplied Hex tool. As the wire
conforms to the connector the connection can loosen. You should re-ti hten the connection
after about a week.
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Turn-on tri er wire
Ground to chassis +12 volt at Baery posive terminal

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Some words about Power and Ground
Note: The second most common cause of underperformin amplifiers is insufficient power
current or a pour power connection. The most common cause of underperformin amplifiers is
insufficient round current or a bad round connection.
12-volt current: Battery Power works only i it travels in a complete circuit rom
the battery positive terminal to the battery negative terminal. Main power
input, o course, is attached to the battery positive terminal. Ground current is
returned to the battery through the chassis to the to the point where the battery
is grounded.
The current available or your ampli ier to use to produce power will be
restricted by the smallest gauge o wire in the circuit and by the weakest physical
connection in the circuit.
Wire Size
It's o ten surprising how many people will obsess about signal wire but routinely
provide the ampli ier with only a raction o the current it needs to do its job.
The most common wire gauge used in car audio is 10-gauge, and the most
common location or ampli iers is in the trunk.
Wire Sizin Chart
4 t 7 t 10 t 13 t 16 t 19 t 22 t 28 t
0-20 amps 14 12 12 10 10 888
20-35 amps 12 10 886664
35-50 amps 10 8866444
50-60 amps 88644442
65-85 amps 66442220
85 -105amps 66422220
105-125 amps 44422000
125-150 amps 22220000
Let's look at a airly small system. I you use a 50 watt/ch amp (25 amps)
or the highs and a 100 watt/ch amp (40 amps) or the woo ers, you need at
least a 4-gauge and maybe a 2-Guage wire to provide 65 amps at the trunk.
Anything less and your car won't go boom. It'll just go Blap!
Len th of Run

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Note: It takes lots of current to make lots of power!
Remember! An electrical circuit is just that... a complete circuit. For current to
travel, you must complete the circuit rom the positive terminal to the negative
terminal (which is connected to the vehicle rame). So what ever Gauge wire
you use or power (B+) you must also use or ground (B-).
Note: A 4- au e power wire needs 4- au e round wire!
Use the Wire Sizing Chart! Add up the use values on the ampli ier(s) then
choose the proper size wire based on the distance rom the car battery to the
ampli ier location. Again, always use the same gauge wire or the main ground
as you do or the main power. Always make your ground as short as possible
and secure it to a clean solid sur ace, pre erably the vehicle rame.
Mountin your ST-X DSP amplifier
Mounting your Zapco ampli ier is easy. Just keep in mind a ew guidelines:
• The ampli ier can be mounted in any direction, on wood, metal, or carpet
• The metal chassis o the amp can be grounded or le t isolated
• The ampli ier requires adequate ventilation. Creating power creates heat,
and cooling requires air. Position the ampli ier with su icient surrounding
area or air supply and keep the end plates clear or uture access
• Keep the ampli ier out o the engine compartment or other locations
that may cause excessive heat or moisture
• Do not mount the ampli ier to a subwoo er box or other place that may
have excessive vibration
Settin Input Gains: Gain pots are not volume controls. Be ore you irst turn on
your system, you should make sure all gain controls are set to minimum (counter
clockwise). A ter the system is installed and all components are connected; play
a loud track with your head unit at 3/4 to 7/8 volume. While watching the 2-
stage clip LEDs... turn the input gain controls up on the channels you are using
or input until the channel's LED indicators turn rom green to red, then back
o just slightly. I you reach a volume that you consider too loud be ore you see
the red LED, that's OK too. Leave the controls at that level. A ter you have set
the controls just watch them or through the rest o the song to be sure the red
clip lights don't come back on.

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ST-4X DSP Input/Controls Ends
The ST-4X DSP is a 4-Channel ampli ier with on-board Digital processing. The input
unctions are described below:
1• 4 Channels (1/2 and 3/4) o RCA level inputs or the internal ampli ier
2• 4 Channels (5/6 and 7/8) o processed RCA outputs or external ampli iers
3• High-level OEM input plug 4• USB Port or PC control connection 5• Auto
turn-on Switch to turn the system on by signal sensing 6• Toslink Port or digital
input 7• Comm Port or expansion 8• Analog input gain controls with clip
indicators
OEM Speaker level Input plu
INPUT GAIN
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Front Le -
Front Le +
Rear Le +
Rear Le -
Front Ri ht -
Front Ri ht +
Rear Ri ht +
Rear Ri ht -
4 5

INPUT GAIN
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ST-6X DSP Input/Controls Ends
The ST-6X DSP is a 6-Channel ampli ier with on-board Digital processing. The input
unctions are described below:
1• The ST-6X DSP has RCA inputs or 6-channels 2• The processed RCA out-
puts let you run an active 3-way system and still have an output or a sub amp
3• The 6X DSP has 6 channels o high-level input 4• USB port or PC control
connection 5• Auto-on Switch to turn the system on by signal sensing
6• The Toslink connector provides an SPDIF digital input 7• Comm Port or
expansion 8• Analog input level (gain) controls with 2-stage Clipping indicators
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1
7
6
4 5

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Speaker Wirin of the ST-X DSP Amplifiers
The Very Basics
• No speaker wires can be shorted to, or touching either ground or each other.
This will put the amp into protect and may damage the ampli ier
• When bridging the le t and right channels o any ST-X DSP ampli ier, you
use the le t channel (Ch1) positive and the right channel (Ch2) negative, as
indicated on the chassis by the speaker terminals
NOTE: If you brid e channels be sure to make all adjustments identical between brid ed
channels

The ST-X DSP GUI Pro ram
Before be innin the setup be sure all si nal sources are turned fully down so
there is no volume until after the crossovers are set.
The control program (GUI) or the ST-X DSP ampli iers is the same unctionally
or both the 4-Ch ST-4X DSP and the 6-Ch ST-6X DSP except or the number o
channels. Both will have a de ault system in the channel designation column
but since you have complete control over all unctions, you can use all channels
as they best suit your individual system.
Loadin the GUI
Download the GUI (Graphic User Inter ace) rom www.zapco.com > Downloads,
i you have not already done that, and load the GUI rom the .exe ile.
Connecting the PC: Connect the PC to the ST-X DSP amp using the supplied
USB cable. NOTE: The ST-X DSP GUI is very orgiving about PC Screen resolution.
However the ideal resolution 1600 x 900 optimal on most PC’s.
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Workin with the GUI
Navi ation bar: At the very top o the Screen you will ind the Navigation bar.
At the le t is the connection indicator. When you open the program while you
are connected to the DSP it will automatically link so you can use the GUI.
I connection is lost it will show Not Linked so you can check the connections.
Next is Channel Setup, which is where you will tell the program what inputs and
outputs you are using.
To begin you need to de ine your system. Fixed 2-Ch inputs (Toslink and Digital
BT) will apply le t channel in ormation to all odd number output channels and
right channel in ormation to all even numbered output channels. The analog
input is or A termarket head units and OEM ( actory) head unit adaptions.
These can be 2-Ch, 4-Ch, or 6-Ch RCA inputs. There are also 4-Ch o speaker
level inputs or OEM Integration. The SUM button will combine highs and lows
rom a 2-way actory system to make a single ull range signal or processing.
The Custom/Sum lets you determine your con iguration. A ter you have chosen
your input you can move on using the GUI.

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Save, lets you save to a ile on the PC or to a preset in the Processor. A ter you
spend valuable time setting up and tuning the system, you won’t want to lose
the setup, so you always want save your setup to one o the available presets.
And or a backup and to keep extra presets you should save all your setup and
tunes to a ile on your PC.
When you Save to File you will be taken to a older on the PC so you can choose
a name or the tune and click Save.
Load, o course, works just the opposite. Click load rom ile and you will go to
the same older, pick the desired preset, and click Open.
At the right side o the Navigation bar is the setting button. This will only be
used i there is a irmware upgrade at some uture point in time.

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The Main GUI Screen
The main screen has upper and lower sections. The upper section is where all
the original system setup will take place, while the lower section contains the
equalization controls and the requency graph.
Delay: At the le t o the main GUI Screen is the Delay section. Since you can not
sit directly in the center o the car, the program can delay the arrival time o
near speakers so it will sound as though you are right in the middle o the car.
Setting delay is quite straight orward. The purpose is to make every speaker the
same distance rom you, so you are in the middle.
a. Measure the distance between each speaker and where your ears will be in
the actual listening position.
b. Identi y the arthest speaker.
c. Add distance to each o the other speaker so that ALL speakers have the
same distance. You do this by subtracting each o the shorter speaker distances
rom the longest (see example below).

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In this example, the longer speaker distance is 70” so we subtract each o the
other speakers rom 70 and enter the results in the Delay chart.
A ter you have entered the distances in cm or inch you can click ms to see the
delay in milliseconds.

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The next section holds the Channel Selection and Crossover.
You can select a channel to tune by clicking on the desired speaker in the car
diagram/Delay section or by clicking on its box in the DSP Channel column. You
can pick channels on at a time or you can pick them by pair. Double clicking the
dot between a pair o channels links that pair. Similarly, i one channel is already
chosen and active, then clicking on the dot will pair them.
This is important as you should always set crossovers by channel pair so the le t
and right speakers will be the same. It is also easiest to do initial equalization by
channel pair.
Each channel has a High Pass (HP) and a Low Pass (LP) ilter. You can control the
requencies o the ilters by highlighting the FREQ box and typing in a value or
by using the keyboard up/down arrows. You can choose the Shape o the
crossover rom Butterworth, Linkwitz-Riley, or Bessel and the Slope using the
drop-down menus. The de ault crossovers are all 24dB/Octave Linkwitz-Riley.
The best source or in ormation on the proper crossovers or your own speakers
is the speaker maker. He can tell you what crossover to use and also how much
power the speakers can handle at di erent slopes and requencies.

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Phase/Level: The next section is or adjusting levels and checking Polarity to be
sure all speakers are in phase with each other.
There are a number o systems or checking System Phase. I the systems
speakers are not all in phase there will be issues you can not ix by tuning. You
can see the section on System Phasing to see one method o Phase checking.
The MUTE buttons allow you to turn o any speakers that you do not want to
hear while you are tuning other speakers.
You will also ind a master level control here and a system MUTE button.

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Equalizer: The lower section o the GUI is devoted to equalization.
Here are 15 bands o parametric equalization or each output channel and you
can vary Frequency, Gain, and Q (the shape o the adjustment) or each band in
several ways.
Frequency: Each band is numbered. You can simply click onto a band button
and drag it to where you want it. When you click onto a band there is a
“Heads-up display” o the requency, gain, and Q o the band. Any band that has
been adjusted rom 0dB is highlighted by the green dot under the band’s slider.
Band # shows in Red, as do the Gain, You can click into the Gain or Q value
Freq, and Q. The green squares show box o any band and adjust using the
the width (Q) o the ilter. up/down arrow keys.