Class D Car Amplifiers

How Class D Actually Works

A Class D amplifier does not amplify the way Class A or Class AB does. Instead of holding output transistors partially conducting through the signal, it switches them hard between fully on and fully off, far above the audible range, and encodes the audio in the width of those pulses. A low-pass filter on the output strips the switching carrier back off and what reaches the speaker is the audio.

The efficiency comes straight out of that. A transistor that is fully on or fully off dissipates almost nothing. Dissipation happens in the partially conducting state, which is exactly where a Class AB output stage lives. Remove that state and you remove most of the heat, which is not a tuning trick a Class AB design can engineer its way around.

In a car that means the amp makes its rated power while pulling less current and shedding less heat than a Class AB amp of the same output. A 500W RMS Class D monoblock draws roughly 50 amps at full tilt. The Class AB equivalent is closer to 80 or 90, and needs the heatsink to match.

Class D or Class AB

Not a good-versus-bad question. Different trades, and plenty of good systems run both: Class D on the sub, Class AB on the front stage.

On a subwoofer, Class D is settled. Modern Class D from a good manufacturer is transparent full range too, which is why it is the practical answer for most builds. Where Class AB still gets reached for is the reference front stage: see Class AB amplifiers, Class A amplifiers, or the full amplifier lineup.

What to Check Before You Buy

Two things decide whether a Class D amp does what the box says: the impedance you wire it to, and whether the car can feed it.

Reading the Spec Sheet

Class D power ratings are among the most abused numbers in consumer electronics. They get quoted at impedances nobody wires to, under test conditions nobody drives in, and as burst figures rather than sustained output. Two numbers actually matter, and they are not the same number.

If you are running a dual voice coil subwoofer wired in parallel, confirm the minimum stable impedance before you buy. Two 2-ohm coils in parallel present 1 ohm. Two 4-ohm coils in parallel present 2 ohms. Check the driver first in car subwoofers.

Electrical System, Because Efficiency Is Not Magic

Class D efficiency shrinks the electrical problem. It does not delete it. A 2000W RMS Class D monoblock at 90% still pulls roughly 185 amps at full output, which is past what essentially any factory alternator sustains.

Over about 1000W RMS total system power, the Big 3 upgrade is the baseline: heavier gauge on both grounds and the alternator positive, to cut resistance and voltage drop under load. Past 2000W you are into high-output alternator and supplemental battery territory.

Voltage drop is what actually costs you output. Most Class D amps regulate power against supply voltage, so an amp rated at 12V makes proportionally less at 11V and may drop into protection. Building the electrical side properly is what lets the amp deliver what it says on the box.

Catalog by Tier

Compact and Multichannel, $225 to $470

Prodigy NBM100.4, 600W 4-channel ($225.99, from $270.99). Prodigy NBM1200.1, 1200W monoblock ($272.99, from $326.99). Wavtech link300.4mini, 4-channel ($329.99), and link500.4mini ($449.99, from $499.99), both compact-chassis for installs with no room. Prodigy NB300.4, 1200W 4-channel ($416.99, from $500.99, last one). Image Dynamics SQ800.4, 800W full-range 4-channel ($469.99), tuned around the brand's own drivers. See 4-channel amps.

Monoblocks, $329 to $1,249

The deepest part of this catalog, and where Class D is least arguable. US Acoustics Mike at 1500W ($329.99), Big Ben at 3500W ($599.99), Tony at 6000W ($999.99), and Phil at 8000W ($1,249.99) run the high-output line end to end. Image Dynamics SQ600.1D ($399.99) and SQ1200.1D ($504.99) are the SQ-tuned pair. Wavtech link1000.1mini ($399.99) and Link1500.1plus ($699.99) are the compact answers. Prodigy NB2800.1 at 2800W ($527.99, from $635.99, last one). Arc Audio X2 650.1 ($568.00). Crescendo Revolution 3A1 ($569.99) is 1000W RMS at 1 ohm on the IRS2092S chipset, and the only Class D in Crescendo's otherwise Class AB Revolution line. See monoblock amplifiers.

5-Channel and 8-Channel, $387 to $999

Prodigy NBM1000.5, 1000W 5-channel ($387.99, from $464.99), and Wavtech link1000.5plus ($649.99, from $749.99): a whole system on one chassis, front stage plus sub. Wavtech link1400.8plus, 1400W across 8 channels ($999.99), is the one to look at for a full active build where every driver wants its own channel. See 6-channel amps for the active three-way options.

2-Channel

Arc Audio Nighthawk, 800W ($699.99). The Class D option for a front stage where alternator headroom or mounting space rules out a Class AB chassis. See 2-channel amps and Arc Audio.

Brand lineups in full: US Acoustics, Wavtech, Prodigy, Image Dynamics, Crescendo. If you are tuning an active system, the DSP lineup is the other half of the chain, and gain is what protects all of it: how we set amplifier gain.