4 Channel Amplifiers

How to Choose the Right 4-Channel Amplifier

There are more 4-channel car amplifiers on the market than any other amplifier type, and the spec sheets are designed to confuse rather than inform. Peak power ratings, inflated channel counts, and vague efficiency claims make it genuinely difficult to compare products across brands without understanding what the numbers actually mean. Here's what to focus on.

RMS Power: The Only Number That Matters

Ignore peak power. It's a marketing figure with no relationship to real-world performance. RMS power (also called continuous power) is the amount of power the amplifier can deliver cleanly and continuously without distortion or thermal shutdown. This is the number you match to your speakers' RMS power handling.

Most quality 4-channel amplifiers in this collection are rated between 50W and 150W RMS per channel at 4 ohms. Most aftermarket component speakers have RMS ratings in the 75-150W range, which means a 4-channel amp delivering 75-150W RMS per channel is the correct match for the majority of front-stage builds. More power than the speaker can handle is a problem. Less power than the speaker needs causes clipping. The goal is a clean match, not the biggest number on the box.

Amplifier Class: Class D vs Class AB for Full-Range Speakers

This is where 4-channel amplifier selection gets more nuanced than monoblock selection. For subwoofer duty, Class D is universally accepted and sonically transparent because subwoofers reproduce a narrow frequency range where amplifier distortion characteristics matter less. For full-range speaker amplification (covering everything from 80Hz up through 20kHz including the critical midrange and high frequencies where the ear is most sensitive), amplifier class has a more audible effect.

Modern Class D 4-channel designs from quality manufacturers like Crescendo (REVOLUTION series), Image Dynamics (SQ800.4), Wavtech (link.4 series), and Prodigy (NB300.4) are genuinely transparent at full-range frequencies and appropriate for demanding speaker systems. Class D efficiency makes these the practical choice for compact installs and high-power builds.

Class AB 4-channel amplifiers like the Tru Technology Tungsten T4, Tru Technology Tungsten Grande, and US Acoustics Class AB lineup operate at lower efficiency and generate more heat, but maintain a bias current that eliminates crossover distortion entirely. For listeners building around absolute sound quality (high-end component speakers, active crossover systems, competition SQ builds), Class AB remains the reference standard for full-range amplification. The larger physical footprint and higher current draw are the tradeoffs.

Bridging: Running 3 Channels from a 4-Channel Amp

Most 4-channel amplifiers support bridged operation, which combines two channels into one for higher mono output. The most common application is running the front two channels in stereo for front speakers while bridging the rear two channels to drive a subwoofer. This gives you a complete system from a single amplifier (front stage and bass) without requiring a separate monoblock.

The limitation is impedance. Bridging two channels effectively halves the load each channel sees, so a 4-channel amplifier that's stable at 2 ohms per channel becomes stable at 4 ohms bridged. Most subwoofers present a 2-ohm load when wired for maximum power output from a monoblock, but a 4-ohm load works fine with many single subwoofer configurations. Before bridging, confirm the amplifier's bridged minimum impedance rating and make sure your subwoofer's wiring configuration matches.

Brands in This Collection

Tru Technology: Tungsten T4 (TS-4 HV v2.5) at $1,399.99 and Tungsten Grande T4 (TG-RS4 HV v2) at $2,399.99. US-built reference-grade Class AB 4-channel amplification for SQ-focused builds. The audiophile tier in this collection.

Crescendo: REVOLUTION 3A4 ($499.00), REVOLUTION 5A4 ($779.99), and REVOLUTION 7A4 ($1,699.99) Class D 4-channel amplifiers. Built for high-resolution car audio with output ratings and distortion specs that compete with amplifiers at significantly higher price points.

Arc Audio: Moto 720 Class AB 4-channel amplifier at $606.40. Arc Audio brings a long heritage of car audio engineering to a 4-channel design that splits the difference between SQ purity and daily-driver efficiency.

US Acoustics: Lisa (4x50W Class AB at $159.99) and Barbara Ann (4x100W Class AB at $399.99). The accessible Class AB tier for daily-driver builds where SQ matters but the price point is reasonable.

Image Dynamics: SQ800.4 (800W full-range Class D at $469.99). Engineered specifically for SQ-focused builds with Image Dynamics' own driver lineup.

Wavtech: link300.4mini ($329.99) and link500.4mini ($449.99). Compact-chassis Class D for installs where physical size matters as much as power output.

Prodigy Audio: NBM100.4 (600W at $225.99) and NB300.4 (1200W at $416.99). Value-tier Class D with strong power-to-price ratios.

Rainbow: SL-M4 micro 4-channel on closeout pricing at $199.99 (regularly $425). Compact for tight installs.