ZAPCO ST-204D SQ III 4 Ch. Class D SQ Amplifier Owner’s Manual

ZAPCO ST-204D SQ III 4 Ch. Class D SQ Amplifier

A new level of Sound Quality

Zapco has a reputation for sound quality that is unsurpassed. It is our dedication to sonic purity and our passion for performance that built that reputation. With all the new amplifiers coming into the market, none has been any threat to Zapco’s standing as the premiere amp and processor company for 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 of experience to use in the development of an amplifier that would bring Zapco sound a line of products for everyday use and that everyone could afford. And the studio line is just that amplifier. In the time it has been out it has built a reputation as the best-sounding amp in the class. Of 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

Perfection 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. Three years ago we introduced the Studio SQ amplifier to take affordable sound quality to a new level. We added the proprietary RCA connectors from the Z-LX amplifiers, changed the capacitors to a higher-end audio cap, and made a few other small changes. All this takes took the Studio sound to a new level of sonic performance for an affordable amplifier.

This year we bring you the Studio-SQ III series with a new high-efficiency finned chassis and temperature-controlled fans to assure that your amplifier plays all day long with no problems of overheating, even when you get that urge to really boogie. And with the new chassis, we even made a few tweaks to the internal components to take the sound quality up another notch. Your new ST-204D SQ III is the first of the Studio-D Series with all the Series III upgrades.

The Studio-204D SQ III Amplifier

With the new Studio-204D SQ III, you get the sound quality that other companies offer only in their big competition amps (and better than many of them) in a compact chassis. This is a full range, Class D amplifier with less than 0.5% total distortion, and nearly 90dB signal to noise and low noise. And you get all that sound quality with over 90% efficient class D power. How much class D power? The compact chassis ST-204D SQ III can put out over 1,000 Watts of top sound quality power. You can bridge this amplifier to 580 Watts RMS at a 4-ohm load. That’s over 1,100 Watts in a compact chassis! And with the new Finned Aluminum chassis and only-when-needed internal fan you won’t have to worry about overheating if you like it both Clean and Loud.

• Tiffany style Panel Mount RCA
• SQ Upgrades: Op-amps, Caps, Etc.

Temperature controlled keeps air moving but only when really needed. New finned aluminum Chassis helps move heat off the output devices.

Before you start your installation

ZAPCO highly recommends that a fuse or circuit breaker be placed within 18″ of the battery. Although you will add a fuse or fuse block near the amplifier it is still a possibility that a pinched power wire between the component fuse and the battery could result in a short, or even a fire. The protection device should be placed where it can be accessed easily and all wiring should be routed safely and correctly according to the following guidelines:

• Do not run wiring close to hot or spinning objects.
• Always use wire grommets when routing wire through the firewall or any other metal panels.
• Make sure that the potential for pinched wiring is avoided by routing all wires away from moving objects, including brake, gas and clutch pedals, etc.

When connecting our amplifiers to pre-wired stock speakers, care must be taken that there are no common connections between left 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 amplifier to go into immediate protection or may cause damage to the amplifier. Output connections are not common chassis ground. Please follow the hookup instructions in this owner’s manual. Any questions should be directed to your local ZAPCO dealer.

All Wire is not created equal

Please do not use CCA wire with Zapco amplifiers
It is easy to think of wire as just wire but the fact is there are major differences between the types of wires being offered today. The price of copper has gone up quite a bit lately, but you will notice that you can still buy heavy primary wire at very reasonable prices. How can this be? Simple… That lower price wire is not all copper, it is CCA wire.
CCA stands for Copper Clad, Aluminum. That means it is aluminum wire with a thin coating of copper around the outside of the wire. Does it look like copper wire? Absolutely. But does it conduct electrical current like copper? Absolutely NOT!

If the wire does not say OFC Copper wire or Solid Copper wire do not use it

Two things can and likely will happen:

• Because CCA wire can not conduct DC electrical current like copper wire can, your amp will not get the current it needs to produce its rated power. That means you get less power and more distortion. It also taxes the amplifier that is trying to make its power, shortening the life of the amp.
• CCA wire corrodes quickly and causes terminals that used to be tight to become loose. This causes arcing when electrons to fly around all the open space lookin for more copper. This causes heat that damages connections and can even eventually melt the terminal blocks on your amplifier.

In short: While CCA wire is excellent for high-frequency AC current (like tweeter voice coils), it is absolutely bad for high current 12V DC like power and ground for a car audio amplifier. We have seen CCA wire become a major cause of amplifier failures as buyers are offered CCA as a low-cost alternative to pure copper wire. So always look at the description of the contents of wire that you purchase. When someone offers to save you some money with CCA wire just say “No, thank you”. Protect your investment with real copper wire.

Planning your power connections

The power end plates of the Zapco ST-D III amplifiers carry the power connections and the speaker connections and vary somewhat by the number of channels. The main 12-volt power input, the 12-volt turn-on wire, and the main Ground connection are common to both models.

• The large connection at the interior of the end plate is the main power input. This must be connected the vehicle battery’s positive (+) terminal, and the main system fuse should be placed close to the battery
• The large connection at the outside of the end plate is the main ground or negative connection. This must be securely attached to bare metal at the vehicle frame, or another heavy chassis component with a direct connection to the frame

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. If 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-D III 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.

Some words about Power and Ground
The second most common cause of underperforming amplifiers is insufficient to power current or a poor 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 if it travels in a complete circuit from the battery positive terminal to the battery negative terminal. The main power input, of course, is attached to the battery-positive terminal. Ground current is returned to the battery through the chassis to the point where the battery is grounded. The current available for your amplifier to use to produce power will be restricted by the smallest gauge of wire in the circuit and by the weakest physical connection in the circuit.

Wire Size

It’s often surprising how many people will obsess about signal wire but routinely provide the amplifier with only a fraction of 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 for amplifiers is in the trunk.

Wire Sizing Chart

| Length of Run
---|---
4 ft   7 ft   10 ft 13 ft 16 ft 19 ft 22 ft 28 ft
0-20 amps| 14    12    12    10    10     8      8      8
20-35 amps| 12    10     8      8      6      6      6      4
35-50 amps| 10     8      8      6      6      4      4      4
50-60 amps| 8      8      6      4      4      4      4      2
65-85 amps| 6      6      4      4      2      2      2      0
85 -105amps| 6      6      4      2      2      2      2      0
105-125 amps| 4      4      4      2      2      0      0      0
125-150 amps| 2      2      2      2      0      0      0      0

Let’s look at a fairly small system. If you use a 50 watt/ch amp (25 amps) for the highs and a 100 watt/ch amp (40 amps) for the woofers, you need at least a 4-gauge and maybe a 2-Guage wire to provide 65 amps at the trunk. Use the Wire Sizing Chart. Add up the fuse values on the amplifier(s) then choose the proper size wire based on the distance from the car battery to the amplifier location. Always use the same gauge wire for the main ground as you do for the main power. Always make your ground as short as possible and secure it to a clean solid surface, preferably the vehicle frame.

Mounting your amplifier

Mounting your Zapco amplifier is easy. Just keep in mind a few guidelines:

• The amplifier can be mounted in any direction, on wood, metal, or carpet
• The metal chassis of the amp can be grounded or left isolated
• The amplifier requires adequate ventilation. Creating power creates heat, and cooling requires air. Position the amplifier with sufficient surrounding area for air supply and keep the end plates clear for future access
• Keep the amplifier out of the engine compartment or other locations that may cause excessive heat or moisture
• Do not mount the amplifier to a subwoofer box or other place that may have excessive vibration

Setting Gains:
Gain pots are not volume controls. Before you first turn on your system, you should make sure all gain controls are set to a minimum. Gain controls should be used only if absolutely necessary. Turning up gain controls causes increased noise, makes distortion more likely and reduces the dynamic range of your system. If your head unit does not have sufficient output, you will get much better results by investing in a line driver to provide more signal to the amplifier.

ST-204D SQ III Input/Controls

1. Front crossover function selector for full range of high pass
2. Input selector for 2-Ch. or 4-Ch. mode
3. Front channels RCA inputs
4. Rear channels RCA inputs
5. Pass through RCA output (rear channels can feed another amp)
6. Rear channels Variable Bass Boost
7. Rear crossover function switch for high pass, full range, or low pass
8. Green power-on LED and red protect LED
9. Front High Pass frequency control
10. Front channel variable gain control
11. Rear channels variable gain control
12. Rear Low Pass frequency control
13. Rear High Pass frequency control
14. Speaker level input plug for OEM hookup

Speaker Wiring

The Very Basics
No speaker wires can be shorted to, or touch either ground or each other. This will put the amp under protection and may damage the amplifier. When bridging the left and right channels of any ST-D SQ III amplifier, you use the left channel (Ch1) positive and the right channel (Ch2) negative, as indicated on the chassis by the speaker terminals.

4-Ch. Amplifier – Stereo Mode
A simple 4 channels hookup for a right and left stereo pair.

4-Ch. Amplifier – High Power 2-Ch. Mode
Similar to bridging a stereo amp to a mono woofer, 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 of 4Ω impedance. If you are using the active crossovers you should be sure that they are set to the same frequency.

4-Ch. Amplifier – 5-Ch. Mode
A 3-way system with front stage, rear stage, and subwoofer in mixed mono configuration. The 5-speakers system requires a passive crossover between the front highs and the mono woofer, with capacitors on the front highs positives and a coil on the woofer positive. All amplifiers channels are full range .

Technical Specifications

Continuous exposure to excessive sound pressure levels may cause permanent hearing loss. ZAPCO strongly advises that you use common sense when setting volume levels. Everything written in this manual is for the proper use of the products. Some features or specifications could be modified during production to improve the product performance. The technical specifications and functionalities stated here are current as of the time of publication. General instructions and safety warnings are intended in any case to be always effective for this type of product. The latest manual with any updates is always available at www.zapco.com/download.

References

• ZAPCO - The Driving Force

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