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ST-204D SQ III - 4-Channel Class D Sound Quality 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.
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 wont have to worry about over heating if you like it both Clean and Loud
Features
- 4-Channel, Full Range, Class D
- RCA and Speaker Level inputs
- Variable input gain control
- Variable electronic crossover
- Variable bass boost control
Explore the full range in Zapco Amplifiers.
Specification
| Power @ 4Ω | 4 x 200 watts RMS |
|---|---|
| THD @ Rated Power | < 0.5%THD |
| Power @ 2Ω | 4 x 290 watts RMS |
| Power Bridged @ 4Ω | 2 x 580 W RMS |
| Signal to Noise Ratio | > 90dB |
| THD + Noise | < 0.1% |
| Frequency Response | 15Hz to 30KHz ±1dB |
| Input Sensitivity | .25v to 5v |
| Net Dimensions (mm) | 160(W) x 58(H) x 300(L) |
| Overall Dimensions (mm) | 160(W) x 58(H) x 325(L) |
What's Included
- Zapco ST-204D SQ III
Zapco
About the Zapco ST-204D SQ III
From our tech experts at CEN
The Zapco ST-204D SQ III is a 4-channel, full-range Class D car amplifier rated at 4 x 200W RMS at 4Ω, rising to 2 x 580W RMS when bridged at 4Ω. THD is under 0.5% and the signal-to-noise ratio is 90dB. It accepts both RCA and speaker-level inputs and includes variable gain, crossover and bass boost controls.
Who it suits
This amp suits anyone wanting clean, accurate sound from a compact, efficient Class D design — a solid choice for a full speaker upgrade in most vehicles. If you also need a dedicated subwoofer channel, the Zapco ST-5B five-channel amplifier is worth considering.
Our tech experts advise
At 160 x 325 mm overall, the ST-204D SQ III fits most boot installations. Speaker-level inputs allow it to work directly with a factory head unit, so no separate line output converter is needed. The finned aluminium chassis includes an internal fan that activates only when required, guarding against overheating at higher output levels. Installation pricing varies by vehicle — see our car audio installation page for details.
Explore the full Zapco range at CEN, with fast UK dispatch and expert advice from our Nottingham team. Shop all Zapco
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Have it Fitted By Our Team
Our team fits car audio, stereos, dash cams and vehicle security at our workshop in Beeston, Nottingham. Tell us your vehicle and we'll confirm the parts and a fitted price.
- 1
Tell us your vehicle
Make, model and year, and what you'd like fitted.
- 2
We confirm the parts
Fascia, wiring and interfaces checked for your car, with a fitted price.
- 3
Fitted at our workshop
Bring it to our Beeston workshop and we do the rest.
Unit 25 Technology Drive, Beeston, Nottingham NG9 1LA
More from Zapco Amplifiers
More options from the same range, in stock and ready to go
Zapco ST-750D Amp Mono 1-Channel Class D Compact Subwoofer Amplifier 400w RMS
£279.00
View product
Zapco HB 154D II Amp 4 Channel Class D Bridgeable Amplifier 4x150w RMS
£249.00
Zapco REF 150.4 Amp 4 Channel Class AB Bridgeable Amplifier 4x150w RMS
RRP £1,379.00Save 5%£1,299.00
Zapco ST-104D SQ MINI Amp 4 Channel Class D Bridgeable Mini Car Amplifier
£349.00
Zapco ST-5B Amp 5 Channel Class AB Full Range Amplifier 4x70w + 1x250 RMS
£189.00
Frequently Asked Questions
Q: How do I choose the right amplifier for my speakers or subwoofer?
A: Match the amplifier's RMS output per channel to the RMS handling of your speakers or subwoofer at the same impedance. The Specification tab lists the power figures. If in doubt, contact CEN with your setup and we will recommend a match.
Q: What wiring do I need to install this amplifier?
A: You will need an amplifier wiring kit sized to the amplifier's power draw, typically including power and earth cable, a fuse, RCA leads and a remote wire. CEN stocks complete wiring kits, and the amplifier's fuse rating is the guide to the cable gauge required.
Q: What class of amplifier is this and does it matter?
A: Class D amplifiers are compact and efficient, ideal for subwoofers and modern installs. Class AB designs are traditionally favoured for outright sound quality on mid and high frequencies. The class is listed in the Specification tab where provided.
Q: Will an amplifier work with my factory head unit?
A: Yes, in most cases. If your head unit has no RCA outputs you will need a line output converter to feed the amplifier a clean signal. CEN stocks line output converters and can advise the right one for your vehicle.
Q: Can CEN install this amplifier?
A: Yes. CEN offers professional amplifier installation from our Nottingham premises, including secure mounting, wiring and setup. Contact us to book.
Q: Can the ST-104D SQ III connect to a factory head unit?
A: Yes. It has both RCA and speaker level inputs, so it can take a signal from a factory head unit without RCA outputs.
Q: How much power does the ST-104D SQ III produce?
A: It is rated at 4 x 100 watts RMS at 4 ohms, 4 x 150 watts RMS at 2 ohms, or 2 x 300 watts RMS bridged at 4 ohms.
Q: How big is the ST-104D SQ III?
A: The net dimensions are 124mm wide, 50mm high and 213mm long, or 254mm long overall.
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