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Short answer: the amplifier class used for subwoofers is Class D in nearly every powered design built today between roughly 200 W and 3 kW. Class AB still makes sense below about 150 W and in some hi-fi and automotive subwoofers, while Class H holds a place in high-power professional subwoofer channels. The class is a heat, size and cost decision before it is a sound-quality label. Sourcing a powered subwoofer, a plate amplifier or an OEM amplifier module usually starts with a power target and a cabinet drawing. The class decision then shows up in the heatsink, the power supply, the chassis depth and the bill of materials — and only later in the marketing copy. The sections below explain why Class D took over the low-frequency channel, where the linear classes still win, and which measurements actually tell you whether a subwoofer amplifier module will survive production. Why Class D Became the Default Amplifier Class for Subwoofers A 1,000 W subwoofer channel is unremarkable today, so the useful question is what the amplifier does with the power it never delivers to the driver. At about 60% efficiency — realistic for a Class AB stage driven hard — roughly 670 W of every 1,000 W leaves as heat. A Class D stage running at 90% leaves about 110 W. That ratio decides heatsink mass, fan noise, chassis depth, and whether the rear of the cabinet has to be vented at all. The frequency band suits the topology as well. A subwoofer crossed over at 80–120 Hz never asks the amplifier to reproduce switching residue in the audible midrange, and modern modulator designs close a feedback loop around the output filter, so the low-frequency distortion penalty that early Class D modules carried is now largely a historical problem. Typical full-power efficiency by amplifier class 25% 50% 75% 100% Class A ~25% Class AB ~60% Class H ~75% Class D ~90% Typical ranges quoted in amplifier design literature and manufacturers' datasheets; real values depend on load impedance and drive level. This is why a Class D subwoofer power amplifier module rated 650 W into 8Ω can sit on a rear plate without forced cooling, while a comparable linear design needs a heatsink several times larger and a heavier transformer behind it. EON180S+2092: LP 650W/8Ohm Pro Audio BTL Subwoofer Power Amplifier ModuleWe have a strong R & D team that can develop and produce products according to drawings or samples provided by customers.View Product → Class AB, Class D and Class H Compared for Subwoofer Duty The table compares the four classes that genuinely reach subwoofer products. Efficiency ranges are typical figures quoted in amplifier design literature and manufacturers' datasheets; real values move with load impedance, rail voltage and how hard the amplifier is driven. Typical efficiency by amplifier class and the heat each one produces for 1,000 W of subwoofer output. Heat figures are derived from the efficiency ranges shown. Class Typical efficiency Heat per 1,000 W out Where it still appears Main trade-off Class A 20–30% 2,300–4,000 W Niche hi-fi and studio subwoofers Very low distortion, very large heatsink Class AB 50–70% 430–1,000 W Sub-150 W systems, automotive, some studio subs Simple and EMI-quiet, but heavy and warm Class H 70–80% 250–430 W High-power professional subwoofer channels Cooler than AB, still needs a large transformer Class D 80–95% 50–250 W Default for powered subs, line array subs, portable Highest efficiency, layout and EMI care needed Heat generated per 1,000 W of output (watts) 750 W 1,500 W 2,250 W 3,000 W Class A ~3,000 W Class AB ~670 W Class H ~330 W Class D ~110 W Derived from the efficiency ranges above: heat = (100 / efficiency − 1) × output power. The Specs That Decide the Class in a Real Project Class is only the first filter. These are the numbers that separate a workable module from a datasheet that falls apart in production. Power at the real load. A module rated 650 W into 8Ω and one rated 650 W into 4Ω are different products. Ask for continuous power at the impedance the driver actually presents, not a peak figure. Damping factor at low frequency. Output impedance at 50 Hz controls how tightly a subwoofer cone starts and stops. It matters more below 100 Hz than any number measured above 1 kHz. THD+N below 100 Hz. Request the curve, not a single value at 1 kHz. The subwoofer band is where a class claim is genuinely tested. Thermal behaviour at continuous output. Heat is the reason Class D won. A module that meets its rating for a few seconds is not the same product as one rated for continuous use. Protection that matches real faults. Over-current, over-temperature, DC offset and short-circuit behaviour at the output should be defined, not implied by the word "protected". Idle and standby consumption. Retail channels in Europe and North America increasingly ask for standby figures, and they are cheapest to design in from the start. Inside a Powered Subwoofer Amplifier Module A subwoofer amplifier module is usually two or three boards stacked on standoffs: a power stage on an aluminium base, an output PCB carrying the devices, and a control or DSP board on top. That stack explains most of the thermal and layout constraints an integrator will face. DSP and control IC Amplifier output PCB Aluminium heatsink and power stage Layer stack of a typical powered subwoofer amplifier: heatsink base, output PCB on standoffs, and a control or DSP board on top. Where the heatsink sits, how much air the chassis allows and how far the DSP board is from the switching stage all change with the class. A linear Class AB stage usually needs vertical fins and an aluminium rear panel; a Class D module can often use the rear plate itself as the heatsink. Integrators who need a specific board outline, connector set or rail voltage can frequently adapt a standard module instead of starting from a blank PCB — that is what a customization service is for. How DSP and the Power Supply Shape the Class Result The amplifier class decides how much heat the output stage makes; the DSP and the power supply decide how well that output can be used. A limiter, crossover and EQ implemented in DSP let the power stage run closer to its ceiling without clipping the driver, which is why so many subwoofer modules pair a Class D stage with an ADAU1701-based DSP board and preset EQ modes. The supply matters just as much. A resonant LLC stage with power factor correction keeps efficiency high and holds the rails steady when heavy bass demands current in short bursts — the behaviour behind LLC resonant supplies in subwoofer systems that OEM buyers now treat as standard. DSP2405SUB Powered Subwoofer Amplifier with LLC Supply and BluetoothFor high-power subwoofer builds, this 1200W Class D amplifier pairs LLC resonant supply with DSP, Bluetooth TWS, and 1000W 8-ohm sub output.View Product → Where Class AB and Class H Still Earn Their Place Class D is not universal, and pretending otherwise leads to over-engineered products. Below roughly 150 W, a small Class AB design is often cheaper to build, needs no output filter and produces no switching EMI — which matters in compact enclosures with sensitive wireless circuitry nearby. Class H sits between the two. It keeps a linear output stage but steps the supply rails with the signal, so it wastes far less heat than Class AB at high power while avoiding switching noise altogether. In professional subwoofer channels where the platform is already linear, a Class H module such as an 800 W linear-transformer design remains a sensible choice. AMP800H Class H Subwoofer Amplifier Module with Linear TransformerFor linear subwoofer systems needing lower heat without switching noise, this 800W-transformer Class H module delivers 600W into 4-ohm loads.View Product → Frequently Asked Questions What amplifier class is best for a subwoofer? Class D above roughly 200 W — it runs cooler, weighs less and costs less per watt than Class AB at the same output. Below about 150 W, a small Class AB build can still be the cheaper option. Is Class D good for subwoofers, or does it sound worse? In the subwoofer band, a correctly designed Class D module is not audibly worse. What decides the result is damping factor at low frequency, THD+N below 100 Hz and how the supply behaves under load. Why do subwoofer amplifiers use Class D instead of Class AB? Heat. A 1,000 W channel at 60% efficiency wastes about 670 W as heat, while a 90% Class D stage wastes roughly 110 W. That gap sets heatsink size, chassis depth and fan requirements. What is the difference between Class D and Class H subwoofer amplifiers? Class D switches the output devices on and off; Class H keeps a linear output stage but steps the supply rails with the signal. Class H runs cooler than Class AB but still needs a larger transformer. How much power does a subwoofer amplifier module need? Match continuous power to the driver's RMS rating at its real impedance — 8Ω or 4Ω, not the peak figure on the carton. For a 15-inch to 18-inch professional sub, 600–1,500 W RMS is a common range. Do Class D subwoofer amplifiers need a special power supply? Not special, but well matched. Most designs pair the Class D stage with a switching supply using PFC and LLC resonance, which keeps efficiency high and output steady when heavy bass pulls the rails down. Choosing the amplifier class of a subwoofer comes down to three numbers: how much continuous power the design needs, how much heat the enclosure can shed, and how much the bill of materials allows. Class D answers all three for most modern subwoofers, while Class AB and Class H stay relevant at the low-power and professional ends of the market, where their specific strengths still pay for themselves. .article-section{color:#24292f;line-height:1.65;} .article-section h2{font-size:22px;font-weight:bold;text-align:left;margin-bottom:12px!important;} .article-section h3{font-size:16px;font-weight:bold;text-align:left;margin-bottom:12px;} .article-section p{font-size:16px!important;margin-bottom:12px;} .article-section ul{margin-bottom:12px;list-style-type:disc;list-style-position:inside;} .article-section ol{margin-bottom:12px;list-style-type:decimal;list-style-position:inside;padding-left:0;} .article-section li{list-style:inherit;font-size:16px;margin-bottom:6px;} .article-section table{display: table!important;border-collapse:collapse;width:100%;margin-bottom:16px;} .article-section thead{display: table-header-group!important;} .article-section tbody{display: table-row-group!important;} .article-section tr{display: table-row!important;} .article-section th{display: table-cell!important;} .article-section td{display: table-cell!important;} .article-section caption{caption-side:bottom;font-size:16px;margin-bottom:12px;font-style:italic;color:#808080;} .article-section th{font-weight:bold;border:1px solid #cccccc;padding:8px;} .article-section td{border:1px solid #cccccc;padding:8px;} .article-section .answer-box{background:#f2f7fd;border-left:4px solid #2f6fb3;border-radius:4px;padding:14px 16px;margin-bottom:16px;} .article-section .chart-wrap{width:440px;margin:0 auto 10px;} .article-section .chart-wrap svg{display:block;width:440px;height:auto;} .article-section .chart-note{font-size:13px;line-height:1.5;color:#6b7280;text-align:center;margin-bottom:18px;} .article-section .faq-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;margin-bottom:12px;} .article-section .faq-item{background:#f4faf6;border:1px solid #dcebe2;border-top:3px solid #2f8f63;border-radius:6px;padding:12px 14px;} .article-section .faq-item:nth-child(even){background:#fdf8f2;border-color:#f0e2cd;border-top-color:#d08a34;} .article-section .faq-item h3{color:#1d6b47;margin-bottom:8px;} .article-section .faq-item:nth-child(even) h3{color:#9a5a18;} @media (max-width:640px){ .article-section .chart-wrap{width:100%;} .article-section .chart-wrap svg{width:100%;height:auto;} .article-section .faq-grid{grid-template-columns:1fr;} } .product-card{display:block;margin:20px 0;border:1px solid #e5e7eb;border-radius:10px;overflow:hidden;font-style:normal;background:#fff;box-shadow:0 0 5px rgba(31,41,55,.08)} .pc-inner{display:flex;text-decoration:none;color:inherit;align-items:center;min-height:148px} .product-card .pc-img{width:auto!important;min-width:0!important;max-width:min(36%,240px)!important;height:auto!important;min-height:0!important;max-height:148px!important;aspect-ratio:auto!important;object-fit:contain!important;flex:0 0 auto;display:block;align-self:center} .pc-body{padding:12px 16px;flex:1;min-width:0;display:flex;flex-direction:column;align-self:stretch;justify-content:center} .pc-title{display:block;font-size:15px;font-weight:600;color:#111;margin:0 0 6px;line-height:1.4} .pc-desc{display:-webkit-box;font-size:13px;color:#6b7280;margin:0 0 8px;line-height:1.5;overflow:hidden;-webkit-line-clamp:2;line-clamp:2;-webkit-box-orient:vertical} .pc-cta{display:block;font-size:13px;font-weight:600;color:#11700F;margin-top:auto} .pc-inner:hover .pc-title{text-decoration:underline} .article-section a:not(.pc-inner),article a:not(.pc-inner){color:#11700F}.pc-cta{color:#11700F!important}
Putting a 500-watt subwoofer into a cabinet forces one specification decision before anything else: which amplifier class will drive the output stage. That single choice determines heat sink mass, power supply weight, enclosure volume, and how much headroom remains before distortion becomes audible. The practical conclusion for system builders: Class D dominates new professional audio module designs because it converts 85-95 percent of supply power into signal. Class AB remains the analog reference for transparent sound and predictable servicing. Class G and Class H deliver a middle path for high-power linear stages that need less heat. Class A and Class B matter mainly as concepts today, but their conduction-angle behavior explains every class that followed. What Defines an Amplifier Class? Every amplifier class is defined by the conduction angle of its output devices - the portion of each input cycle during which the transistors pass current. A device that conducts for 360 degrees stays on continuously; a device that conducts for 180 degrees handles only half of the waveform. The conduction angle sets a theoretical efficiency ceiling, because a conducting device that is not contributing signal still dissipates power. It also predicts the distortion signature of the stage. The classes below cover everything an audio system designer will encounter. Class C appears for reference only: operating below 180 degrees raises efficiency above 70 percent, but flattens the output so badly that it is restricted to radio-frequency transmitters rather than audio. Efficiency values are practical ranges cited in established electronics references and module datasheets; exact numbers depend on supply voltage, load, and operating level. Amplifier class conduction angle and practical efficiency in audio designs. Class Conduction angle Typical efficiency (audio) Main trade-off Class A 360 degrees 20-30 percent Lowest distortion, highest heat Class B 180 degrees 55-65 percent Crossover distortion without bias Class AB 180 to 360 degrees 50-65 percent Balance of linearity and heat Class C Under 180 degrees Above 70 percent (RF) Not usable for audio quality Class D PWM switching 85-95 percent Filter and EMC design needed Class G Switched supply rails 65-80 percent Multi-rail supply complexity Class H Modulated supply rail 65-80 percent Tracking supply cost Class A up to ~30% Class B ~60% Class AB 50-65% Class D 85-95% Class G ~72% Class H 65-75% 0% 25% 50% 75% 100% Class D delivers roughly three times the efficiency of the linear classes, which changes heat sink and power supply choices completely. Class A: Linearity at a High Operating Cost Class A output stages conduct for the full 360 degrees. A single device, or a pair running in single-ended mode, stays in its active region even when no input signal is present. That makes Class A the most linear topology of the analog families: there is no handoff between devices, so crossover distortion is absent by definition. The price is enormous idle dissipation. Practical single-ended Class A efficiency sits between 20 and 30 percent, so a 100-watt amplifier discards 200 to 300 watts as heat. Heat sinks grow, transformers grow, and running costs become permanent. In professional audio modules, full Class A output stages exist only at preamp level; within power amplifiers, Class A survives as the small-signal bias region of a Class AB input stage. Class B: The Push-Pull Origin Class B splits the waveform into two halves: one transistor pushes the positive half-cycle and the other pulls the negative half-cycle, so each device conducts for exactly 180 degrees. Theoretical efficiency rises to 78.5 percent, but the transition at the zero crossing introduces crossover distortion when neither device is fully in control. No serious audio output stage runs in pure Class B because the discontinuity is audible at low signal levels. Designers add a small bias current so both devices stay slightly on at the zero crossing, and that adjustment is what defines Class AB. Class AB: The Analog Workhorse Class AB adds controlled quiescent bias to the push-pull structure. Both output devices conduct a little at the zero crossing, eliminating the crossover notch, then step back toward cutoff as the signal grows. Efficiency settles between 50 and 65 percent in practical audio designs. A 600-watt Class AB module still throws off 200 to 300 watts when driven hard, so heat sinks with deep fins and sometimes forced air remain part of the design. Engineers choose Class AB when tonal behavior is the priority and enclosure size is permissive. The relationship between bias current, distortion, and thermal load is so delicate that manufacturers calibrate it over years of production refinement. That is also why engineers spend as much time on the output stage as on the drivers, because the amplifier module's contribution to sound quality is easier to hear than to measure. Class D: Switching for Efficiency Class D abandons the conduction-angle model completely. The output transistors alternate between full saturation and full cutoff at a carrier frequency well above the audio band, usually 400 kHz to 1 MHz, and the audio signal rides on the duty cycle of the resulting pulse-width-modulated waveform. An LC filter reconstructs the audio band at the output. Because a saturated switch drops almost no voltage and a cutoff switch passes almost no current, theoretical efficiency approaches 100 percent; real modules deliver 85 to 95 percent. The consequences for loudspeaker design are immediate. A 500-watt Class D stage keeps heat sinks small enough for a die-cast chassis, while an equivalent Class AB stage needs a heavy extruded profile and a larger transformer. Modern post-filter feedback corrects the distortion mechanisms of early switching designs, and well-implemented Class D modules pass blind listening comparisons against good analog amplifiers. The real engineering effort sits in the output filter, the EMI behavior, and the dead-time management of the switching stage. Suppliers who specialize in this area typically pair the switching core with a resonant or power-factor-corrected front end instead of treating the filter as an afterthought. EON522SUB Active Subwoofer Amplifier Module with LLC Resonant SupplyThis 500W Class D subwoofer module pairs an LLC resonant 800W supply with overload, short-circuit, and thermal protection, making it a practical fit for high-efficiency bass applications discussed in the surrounding text.View Product → Class G and Class H: Smarter Supply Rails Class G and Class H keep the linear output stage of an AB amplifier but feed it with a supply rail that adapts to the signal. Class G maintains two or more fixed rails, switching to the higher one only when signal peaks require it. Class H modulates the rail voltage continuously, tracking the signal envelope with a few volts of headroom. Output devices remain linear in both cases, so the distortion profile resembles Class AB, but the average voltage across the devices is lower. That reduces waste heat and pushes efficiency into the 65-80 percent range. The cost moves into the power supply: multi-rail transformers with switch-over logic for Class G, or fast tracking regulators for Class H. These classes suit subwoofer and line-array modules, where music with a high crest factor means the higher rail is active only for short peaks. The H-class approach is a common choice for bi-amplified enclosures with a linear transformer supply, which is why module suppliers list this combination as a standard configuration. Comparing Amplifier Classes in Real Modules The class decision is never made in isolation; it interacts with the power supply, the enclosure, and the duty cycle of the music program. The chart below shows why Class D is so attractive in portable and compact systems. 0% 25% 50% 75% 100% 0% 25% 50% 75% 100% Class D Class AB Efficiency versus output level for Class AB and Class D modules. Class D holds high efficiency far deeper into the operating range. Class D maintains high efficiency over most of its output range, while Class AB efficiency collapses at low listening levels. A 50-watt average output from a 500-watt Class AB module may sit at about 25-30 percent efficiency; the same condition keeps a Class D module above 75 percent. Over a touring season, that difference shows up in electricity cost, rack heat, and how often thermal protection triggers. Class recommendation matrix for common powered loudspeaker applications. Application Preferred class Reason Battery-powered portable speaker D Efficiency extends runtime and shrinks heat sink Mid-power PA monitor AB Predictable analog tone and simple supply Multi-channel line array D Low heat and compact PFC/LLC front end Subwoofer with heavy bass program D or H D for power density, H for linear feel Fixed installation AB, H, or D Depends on service familiarity and rail cost Understanding what an active power amplifier module contains helps buyers apply this matrix correctly. The class letter describes only the power stage; the supply design, feedback topology, and protection circuits determine real-world reliability. A subwoofer module, for example, combines a high-voltage rail with output limiting to survive continuous bass program, so the class choice and the protective features must be evaluated as one system. EON180S+2092 BTL Subwoofer Amplifier Module for Professional AudioFeaturing a 650W Class D BTL output and 800W switching supply, this subwoofer module includes protective circuits suited for continuous bass duty, aligning with the amplifier-class considerations described above.View Product → Anatomy of a Power Amplifier Module The cross-section of a modern module shows how the class interacts with everything around it. The input stage accepts balanced or DSP-processed signals, the driver stage shapes the switching or linear control, the output stage follows the chosen class, and the power supply sets the efficiency ceiling. The isometric diagram below shows the typical arrangement of these blocks in a self-contained module. Input / DSP Output filter Heatsink Power stage Typical block arrangement of a professional power amplifier module: input/DSP processing, switching or linear power stage, output filter, and heat sink. Frequently Asked Questions about Amplifier Classes Which amplifier class is best for professional audio? Class D offers the best balance of efficiency, weight, and heat for most pro audio modules. Class AB remains the analog-first choice, and Class H fits high-power linear stages. What is the difference between Class AB and Class D amplifiers? Class AB runs output transistors in the linear region, producing low distortion but wasting 30-50 percent of power as heat. Class D switches the transistors fully on and off, reaching 85-95 percent efficiency with an output filter. Are Class D amplifiers good for live sound? Yes. Modern Class D modules with LLC or PFC power supplies are widely used in line arrays and subwoofers; they handle high crest-factor program, stay cool, and reduce cabinet weight. Which amplifier class is the most efficient? Class D is the most efficient class used in audio, delivering 85-95 percent of input power to the load. Class C reaches even higher efficiency but is not usable for audio. Do Class D amplifiers sound as good as Class AB amplifiers? A well-implemented Class D module can sound very close to a well-implemented Class AB module. Output filter design, feedback loop, and power supply quality matter more than the class letter. What does amplifier class mean for speaker design? The class sets the conduction angle and efficiency of the output stage. 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You've saved up for a decent car audio upgrade, and the choice has come down to two four-channel amplifiers with nearly identical power ratings. One is a compact Class D unit. The other is a heavier Class AB design with a slightly lower price and a reputation for smooth, natural sound. Which one actually belongs in your trunk? This is one of the most common debates in car audio. Class AB amplifiers powered aftermarket systems for decades, but Class D has taken over most retail shelves in recent years. The engineering difference is real, and so are the trade-offs. This guide explains what the class label means in practical terms, what bench tests reveal about quality, and how to decide based on your speakers, your electrical system, and your listening habits. What Does "Class AB" Actually Mean in a Car Amplifier? Amplifier classes describe how the output transistors are biased and switched. In a pure Class A circuit, output devices conduct current all the time, which produces extremely linear sound but wastes most of the energy as heat. In Class B, each half of the audio waveform is handled by a separate transistor, which improves efficiency but creates crossover distortion where the two halves meet. Class AB is the middle path that became the car audio standard. A small idle bias keeps both output transistors slightly on around the zero-crossing point, so music at low and moderate levels is reproduced in a nearly Class A fashion. Vocals sound present, cymbals stay clean, and the transition between waveform halves does not add an audible notch. This is the technical reason behind the "warmth" so often attributed to Class AB. Power Supply Signal Input Bias & Driver Class AB Output To Speaker In a typical automotive Class AB amplifier, the signal path runs through an input buffer, a voltage amplifier, and a biased output stage before reaching the speaker. The power supply must keep the rail voltages clean under dynamic load, which is why good Class AB designs use either a generously sized linear transformer or a well-regulated switching supply. Class AB vs. Class D: Reading the Trade-Offs Correctly Class D amplifiers switch their output transistors on and off at frequencies above 100 kHz, then filter the result to recover the audio signal. The switching approach cuts power loss dramatically, which is why Class D amps are smaller, cooler, and easier on the alternator. The catch is that sound quality depends heavily on the quality of the filter, the feedback loop, and the power supply. A cheap Class D amp can sound harsh; a well-designed one can be nearly transparent. The numbers are typical values from manufacturer specifications and independent bench measurements. Actual performance varies with supply voltage and load impedance. Parameter Class AB Class D Typical efficiency 50–65% 75–90% Idle current draw Higher, continuous bias Much lower Heat output High Low Sound character Warm, natural midrange Transparent if well filtered Size and weight Larger, heavier Compact, lightweight Best use Component speakers, full range Subwoofers, tight installs The table is a starting point, not a verdict. A premium Class D amplifier with a clean output filter and robust power supply can measure better than a budget Class AB in distortion and noise. What Class AB gives you is a predictable, musically linear output stage that is hard to get badly wrong. What Bench Tests Reveal About Sound Quality An independent bench comparison published by BestCarAudio showed the efficiency gap in practice. The entry-level Class AB amp in that test drew just over 105 amperes and produced 793 watts during the dynamic power run. The premium Class D amplifier it was paired against produced about 80% more power with the same current draw, because it converted far less input energy into heat. Typical Efficiency at Moderate Output 0 25% 50% 75% 100% Class A ~25% Class AB ~55% Class D ~80% Representative values, not measurements of a particular model. The efficiency difference is not just a laboratory curiosity. The heat generated by a Class AB amp has to go somewhere: into the heatsink, the air behind a dashboard, or the interior of a sealed enclosure. This is what installers mean when they call Class AB "current hungry." Sound quality benefits are real, but they carry an electrical and thermal price. Total harmonic distortion (THD) and signal-to-noise ratio (SNR) also matter when you compare amplifiers. A well-executed Class AB amp commonly measures below 0.05% THD at moderate output. Budget Class D units sometimes show higher distortion at low levels because of switching noise. Take a familiar music track to your local shop and listen before you buy. Installation Realities: Heat, Fuses, and Wire Gauge Sizing the electrical path is part of any Class AB installation. At full output, a 400W RMS amp draws roughly 53A from a 13.8V system (about 400W divided by 13.8V and the 0.55–0.65 efficiency range). Under heavy bass, that load is sustained, not momentary. Use wiring and fuses rated for continuous operation. Recommendations assume a 13.8V electrical system and premium copper cable. Use the next heavier gauge if the cable run exceeds 5 meters. System RMS Power Class AB Current Draw Fuse Rating Wire Gauge 200W ≈27A 30A 8 AWG 400W ≈53A 60A 4 AWG 800W ≈105A 110A 2 AWG Treat the table as a floor, not a ceiling. In hot climates or enclosed trunks, a 12V cooling fan is an inexpensive upgrade for anything above 400W. The heatsink fin area of a Class AB amp should always be mounted with open airflow; never trap it against carpet or trim. Module-Level Options for Builders, Repair Shops, and OEM Integrators Custom fabrication shops, OEM audio brands, and technicians who rebuild factory sound systems often start with amplifier modules instead of finished chassis amps. A module provides a tested circuit layout, a mechanical footprint, and a documented power rating so you can design an enclosure around it. This shortens development time and reduces component-level debugging. For example, the amp300h-7294 module uses a Bi-Class H output stage and a linear transformer power supply. Its bias behavior resembles a Class AB amplifier, while the switched rail keeps heat production below a conventional AB design. That makes it a practical starting point when you need roughly 300W of low-frequency plus 50W of high-frequency output. When the build demands more headroom, a 400W plus 100W module with a U-shaped aluminum heat sink demonstrates how thermal design is solved at the board level. The radiator on the amp400h-7294 is already sized for sustained operation, so you do not have to guess at heatsink volume or airflow. AMP400H+7294 Class H Power Amplifier Module with U-shaped Aluminum RadiatorThis module combines a 400W Class H bass section with a 100W Class AB high-frequency stage, featuring a U-shaped heatsink and built-in protections for reliable, sustained car audio performance.View Product → Module-level sourcing is common because it shortens the path to production. Car audio builds that emphasize deep bass often combine a full-range module for the mid and treble channels with a dedicated subwoofer amplifier stage, which reduces development work and keeps the final assembly compact. Class AB Car Amplifier FAQ Is a Class AB amplifier good for car audio? Yes, especially for full-range speakers. The linear bias keeps vocals and instruments natural, and the midrange often feels more present than on an equal-cost Class D design. Just budget for the extra current draw and heat dissipation. What is the difference between Class AB and Class D car amplifiers? Class AB uses a biased linear output stage, which sounds smooth but generates heat. Class D switches its output transistors on and off and filters the result, which is more efficient and compact. Sound quality in both depends heavily on build quality and the power supply. Do Class AB amplifiers sound better than Class D? Most listeners find entry-level and mid-priced Class AB amplifiers sound warmer and less fatiguing than budget Class D designs. At the premium end, the gap narrows sharply, and many people cannot consistently tell them apart in blind listening tests. Can you use a Class AB amplifier for a subwoofer? Yes. Class AB bass tends to be tight and well controlled, and many subwoofer amplifiers still use a Class AB output stage. For custom builds, a dedicated subwoofer amplifier module is a good option when space is flexible. How many watts RMS do I need for a Class AB car amplifier? For component speakers, 50 to 100 watts RMS per channel is common. For subwoofers, plan on 300 to 600 watts RMS if your alternator can sustain it. Use RMS power at 4 ohms as the reference, because max power numbers are largely meaningless. Do Class AB amplifiers draw more current at idle? Yes. The bias current runs whenever the amp is on, typically 1 to 3 amperes depending on the design. Class D amplifiers idle at a fraction of that. 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