zapco ST-2X SQ User manual

1
ST-2X/4X/6X SQ
Ow er’s Ma ual
Before operati g the u it, please read this ma ual throughly a d retai it for future refere ce.

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
(Knowledge from doing)
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 ......................................................................... 2
History o the Studio Series .................................................................... 2
The Studio-X SQ ampli iers ..................................................................... 3
Main eatures o the Studio-X SQ ampli iers .......................................... 3
Be ore you start your installation ................................................................... 4
Upgrading a Factory Stereo .................................................................... 4
Planning your power connections .................................................................. 5
Wire size ................................................................................................. 6
Mounting your Studio-X SQ ampli ier ............................................................. 7
Inputs and Controls ......................................................................................... 8
ST-2X SQ Input Ends ................................................................................ 8
ST-4X SQ Input Ends ................................................................................ 9
ST-6X SQ Input Ends ................................................................................ 10
Speaker Wiring o the Studio-X SQ Ampli iers ................................................ 11
ST-2X SQ Speaker Wiring ........................................................................ 11
ST-4X SQ Speaker Wiring ........................................................................ 13
ST-6X SQ Speaker Wiring ........................................................................ 15

2
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.
Last year we began development 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.

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The Studio-X SQ Amplifiers
With the new Studio X SQ 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 and 95W RMS/channel @ 2Ω
(100W/Ch. @ 4Ω and 150W/Ch. @ 2Ω or the ST-6X SQ). You also get plenty o
eatures, like 12dB/octave multi- unction crossovers, bass boost, variable gain
and even pass-through RCA outputs so you can daisy chain amps.
As or per ormance, the Studio X SQ give you more than power. These amps
have 0.2% THD+noise, over 90dB signal to noise, over 60dB separation, and
produce power rom 15Hz to 30kHz.
Main features of the Studio-X SQ amplifiers
Tiffany style Panel Mount RCA SQ Upgrades: Op-amps, Caps, Etc.
• Full Range, Class A/B
• SQ Upgrades: Op-amps, Caps, Etc.
• Ti any style Panel Mount RCA
• RCA and Speaker Level Inputs
• Variable input gain control
• Variable electronic crossover
• Auto-on with Speaker level inputs
• Variable bass boost control
• THD @ Rated Power < 0.5%
• Signal to Noise Ratio > 90dB
• Channel Separation > 60dB
• 65 watts/Ch. 4Ω (100 watts, ST-6X SQ)
• 95 watts/Ch. 2Ω (150 watts, ST-6X SQ)
• Frequency Response 15Hz to 30KHz ±1dB
• ST-2X SQ Dimensions:
Chassis 160(W) x 52(H) x 154(L)
Overall 160(W) x 52(H) x 180(L)
• ST-4X SQ Dimensions:
Chassis 160(W) x 52(H) x 282(L)
Overall 160(W) x 52(H) x 320(L)
• ST-6X SQ Dimensions:
Chassis 160(W) x 52(H) x 452(L)
Overall 160(W) x 52(H) x 488(L)

4
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.
Upgrading a Factory Stereo
I you are upgrading a actory stereo the ST-X SQ 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 SQ amps
have a switch that allows you to de eat the auto-on i you ind you do not
want to use that unction.

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Planning your power connections
The power end plates o the Zapco ST-X SQ 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 SQ below has (o course) speaker
connecons or our channels. The ST-X SQ 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 good ground 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 SQ amplifiers have terminals that do not require connectors. You simply insert
a bare portion of wire and tighten the connection with the supplied Hex tool. As the wire
conforms to the connector the connection can loosen. You should re-tighten the connection
after about a week.
Turn-on trigger 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 underperforming amplifiers is insufficient power
current or a pour power connection. The most common cause of underperforming amplifiers is
insufficient ground current or a bad ground 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 Sizing 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!
Length 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-gauge power wire needs 4-gauge ground 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.
Mounting your ST-X SQ 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
Setting 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. Gain
controls should be used only i absolutely necessary. Turning up gain controls
causes increased noise, makes distortion more likely and reduces the dynamic
range o your system. I you head unit does not have su icient output, you will
get much better results by investing in a line driver to provide more signal to
the ampli ier.

ST-2X SQ Input/Controls Ends
The Input ends o the ST-X SQ ampli iers is where you ind the signal input
connectors,the pass through outputs, the crossover controls, bass boost control.
For High Level (speaker level) you also ind the port or the input plug and
auto-on switch.
OEM Speaker level Input plug
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1• Pass through RCA output allows "daisy
chaining" ampli iers
2• RCA inputs rom an a ter-market head unit
3• Variable gain control (set to minimum
be ore initial turn-on)
4• Bass boost switch or 0, 6dB, or 12dB
5• Low Pass requency selector or the bass
crossover
6• Crossover selector or low pass, ull range,
or high pass
7• High pass ilter or the mids/highs
8• Auto-on switch or OEM integration
9• Green power-on LED and red protect LED
10• Speaker level input plug or OEM hookup.
Note that black ground wire must be grounded,
pre erably the actory head unit or ampli ier
(Green) Le +
(Green/stripe) Le -
Black: ground to factory head unit or factory ampli er
(Gray) Right +
(Gray/stripe) Right -
1 2
3 8
5 9
4
10
6
7

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ST-4X SQ Input/Controls Ends
The ST-4X SQ has similar unctions as the ST-2X SQ but the 4 channel layout puts
the controls in di erent positions.
* See explanations of OEM Input plug on the previous section 2-Channel amp
2 3 4
11 12 13
5 7 810
1
69
14 15
1• Green power-on LED and red protect LED
2• Rear High Pass requency control
3• Auto-on switch or OEM integration
4• Rear Low Pass requency control
5• Rear speaker level input plug or OEM
hookup (See #10 o ST-2X SQ)*
6• Rear channels variable gain control
7• Rear channels RCA inputs
8• Pass through RCA output (rear channels
can eed another amp)
9• Front channels RCA inputs
10• Front speaker level input plug or OEM
hookup (See #10 o ST-2X SQ)*
11• Rear crossover unction switch or high
pass, ull range, or low pass
12• Rear channels Bass Boost switch or 0, 6dB,
or 12dB
13• Front channels variable gain control
14• Front crossover unction selector or ull
range o high pass
15• Front High Pass requency control

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ST-6X SQ Input/Controls Ends
The ST-6X SQ has similar unctions as the other ST-X SQ amps but the 6 channel
layout puts the controls in di erent positions. Plus the ST-6X SQ has a 2, 4, or 6ch.
input mode selector and a remote control port.
* See explanations of OEM Input plug on the previous section 2-Channel amp
1 5 6
34 10
7 9 13 15
2
814
11 12
1• RCA inputs
2• Ch.1/2 variable gain control
3• Ch.1/2 crossover unction selector or ull
range o high pass
4• Ch.1/2 High Pass requency control
5• Ch.3/4 variable gain control
6• Ch.3/4 crossover unction switch or high
pass, ull range, or low pass/band pass
7• Ch.3/4 High Pass requency control
8• Ch.3/4 Low Pass requency control
9• Ch.5/6 variable gain control
10• Ch.5/6 crossover unction selector or low
pass or ull range
11• Ch.5/6 Bass Boost switch or 0, 6dB, or 12dB
12• Ch.1/4 speaker level input plug or OEM
hookup (See #10 o ST-2X SQ)*
13• 2/4/6 Ch. input mode selector
14• Remote control port
15• Green power-on LED and red protect LED

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Speaker Wiring of the ST-X SQ 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 SQ 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
ST-2X SQ Speaker Wiring
2Ch Stereo Mode
A simple 2 speaker hookup or a right and le t stereo pair.
Note the basics above or speaker wiring and assure that + and - are connected
correctly. A use should be added near the battery.
Single Channel Mode
This method is used most o ten to drive a mono woo er but can also be used to run
separate ampli iers or the right and le t channel.
• The ST-X ampli iers are stable to 2Ω stereo and 4Ω Mono so the single bridged
speaker must be o 4Ω minimum impedance

3Ch Mode
It is possible to run the 2Ch amps in “3-Channel” mode by running a pair o
speakers or the mids and highs on le t and right channels, and at the same time
run a woo er bridged between the L+ and R- terminals as shown. However, since
each channel will see 1/2 the impedance o the woo er you must use a woo er o
no less than 4Ω. The ampli ier sees impedance by requency, so you can have two
2Ω loads but you must use a passive crossover on each speaker in the three chan-
nel mode. With the crossovers in the line, the ampli ier will always see a minimum
load o 2Ω on each channel at all requencies.
• Main speakers can be 2Ω~4Ω. Woo er can be 4Ω~8Ω but cannot be less than
4Ω (as in any bridged situation)
• The active amp crossovers are not used in this system
A 3-Way hookup requires a coil on the
woofer and capacitors on the highs to
act as a crossover and maintain correct
impedance. Consult the speaker
manufacturer for correct cap and coil
values.
2Ω Min
12
4Ω Min

All speakers 2Ω Min
Bridged 4Ω Min
13
Bridged 4Ω Min
ST-4X SQ Speaker Wiring
4Ch Mode
If using coaxial speakers, consider using
the HP filters at the lowest setting to keep
deep bass from damaging the speakers as
a crossover and maintain correct.
High Power 2Ch Mode
Similar to bridging a stereo amp to a mono woo er, you can use the 4-Ch amp in a
dual mono mode to create (in this case) a stereo amp with 190 watts RMS/ch.
As with any bridged setup the speakers must be a minimum o 4Ω impedance.
I you are using the active crossovers you should be sure that they are set to the
same requency
High power stereo using dual mono bridge
hookups requires that the speakers be a
minimun of 4 Ohms impedance each.

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2-way Active System
Using the built-in active crossovers o the ST-4X SQ, you can easily create an active
2-way system with mid/highs on the ront channels and bass on the rear channels.
Below is an active system with a bridged subwoo er on the rear channels.
5Ch System
The 5-speakers system requires a passive crossover between the ront highs and
the mono woo er, with capacitors on the ront highs positives and a coil on the
woo er positive. All ampli iers channels are ull range.
Highs 2Ω Min
Mono Bass 4Ω Min
Highs 2Ω Min
Bass 4Ω Min

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ST-6X SQ Speaker Wiring
2-way Active System
Below is a 2-way active system with a high power ront stage. It gives 300 watts or
each le t and right ront speaker plus 300 watts or the woo er or a high power
center channel.
• Since all the channels are bridged, the speakers must all be 4Ω Minimum
• Ch1/2 and 3/4 will high passed just above the lowest recommended
requency or that speaker
• Ch 5/6 will be low passed ( or a woo er) at the same requency that 1/2
and 3/4 are high passed
5Ch System
The most popular system or a six channel ampli ier is right/le t ront, right/le t
rear, and a mono sub.
Note the hookup especially o the sub as Ch5+ and Ch6-. This give the sub the
combined power o the 2 channels. Note that since the sub is a bridged hookup
the sub must be 4Ω minimum.
4Ω / 8Ω
4Ω / 8Ω
4Ω / 8Ω

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4Ω / 8Ω
2Ω / 4Ω
2Ω / 4Ω
6Ch System
Below is a standard six speaker hookup or 3 pairs o right and le t stereo speakers
Since each channel has one speaker so each speaker can be 2Ω Minimum. Note the
basics o speaker hookup and assure that + and - are connected correctly.
All speakers 2Ω / 4Ω

1
Modesto, Califor ia USA
Si ce 1974
zapco.com