Ruthless Audio 400.4 Micro 4 Channel Amplifier
Description
Description
The Ruthless Audio 400.4 Micro 4-Channel Amplifier packs a ruthless 400 watts of total RMS power into one of the most compact amp footprints in the game — measuring just 7.25" in overall length. Engineered for serious enthusiasts who refuse to compromise on output or install flexibility, the 400.4 delivers clean, dynamic power across all four channels with the clarity, punch, and authority your system demands. Whether you're building a stealth OEM upgrade, a motorcycle audio system, a powersports rig, or a tight custom install, this micro amp fits where full-size amps simply can't.
Under the hood, the 400.4 runs a high-efficiency Class-D topology that minimizes heat and maximizes power delivery — rated at 100W x 4 @ 2 ohms and 60W x 4 @ 4 ohms at 14.4V. The signal-to-noise ratio of 95dB keeps your music clean and distortion-free, while the onboard high-pass (20Hz–8kHz) and low-pass (50Hz–8kHz) filters give you precise crossover control without external processors. A 60A fuse rating and 9–16V operating voltage range ensure reliable performance across a wide range of vehicle electrical systems.
The 400.4's bridgeable 4-channel design gives you serious flexibility: run all four channels to power a full front and rear speaker stage, or bridge channels in pairs for a 2-channel configuration with higher per-channel output to drive component midranges or a small subwoofer. At just 4.7" wide and 2.2" tall, it disappears under seats, behind panels, or inside custom enclosures — making it the go-to choice for builders who want maximum power with minimum footprint.
Why Choose the Ruthless Audio 400.4 Micro Amplifier?
- Ultra-Compact Micro Form Factor — 7.25" overall length fits in installs where traditional amps won't, including motorcycles, powersports, and stealth OEM builds.
- 400W Total RMS Power — 100W x 4 @ 2Ω delivers real, usable power — not inflated peak ratings.
- High-Efficiency Class-D Design — Runs cool and clean, maximizing power transfer while minimizing thermal load on your vehicle's electrical system.
- Bridgeable 4-Channel Configuration — Bridge channels in pairs for a 2-channel setup with higher output, giving you full system flexibility from one amp.
- Onboard High & Low Pass Filters — 20Hz–8kHz HPF and 50Hz–8kHz LPF let you dial in crossover points without additional signal processors.
- 95dB Signal-to-Noise Ratio — Exceptionally quiet background noise floor for crystal-clear audio reproduction at any volume.
- Wide Operating Voltage Range — 9–16V compatibility handles everything from stock alternators to high-output charging systems without issue.
- Premium Component Build Quality — High-efficiency circuitry and premium internal components engineered for long-term reliability in demanding environments.
Amplifier & Wiring Recommendations
The Ruthless Audio 400.4 is an ideal match for a set of component speakers or coaxial drivers in the 60–100W RMS range per channel. Pair it with a quality 4-channel RCA signal from your head unit or DSP processor for best results. For wiring, a 4-gauge power and ground kit is recommended to support the 60A fuse rating and ensure clean, stable power delivery. If bridging to 2 channels, verify your speakers can handle the increased output and are rated for 4 ohms bridged minimum. Keep power and ground runs as short as possible, and route RCA cables away from power wiring to eliminate noise.
For motorcycle and powersports installs, weatherproofing your connections and securing the amp to a vibration-dampened surface will maximize longevity. The compact heatsink (6.375") dissipates heat efficiently, but ensure at least 1–2" of airflow clearance around the unit in enclosed installs.
Full Specifications
| Specification | Value |
|---|---|
| RMS Power (2Ω) | 100W x 4 @ 14.4V |
| RMS Power (4Ω) | 60W x 4 @ 14.4V |
| Total RMS Power | 400W |
| Amplifier Class | Class-D |
| Channels | 4 (Bridgeable to 2) |
| Frequency Response | 20Hz – 8kHz |
| High Pass Filter | 20Hz – 8kHz |
| Low Pass Filter | 50Hz – 8kHz |
| Signal-to-Noise Ratio | 95dB |
| Fuse Rating | 60A |
| Operating Voltage | 9–16V |
| Overall Length | 7.25" |
| Heatsink Length | 6.375" |
| Width | 4.7" |
| Height | 2.2" |
| Warranty | 1 Year Standard / 2 Year Extended Available |
Frequently Asked Questions
Q: What size wiring kit do I need for the Ruthless Audio 400.4?
A: A 4-gauge power and ground wiring kit is recommended to properly support the 60A fuse rating and deliver clean, stable power to the amplifier.
Q: Can I bridge the 400.4 down to 2 channels?
A: Yes — the 400.4 is fully bridgeable. Bridge channels 1+2 and 3+4 for a 2-channel configuration with higher per-channel output. Ensure your speakers are rated for the bridged impedance load (minimum 4Ω bridged).
Q: Is this amp suitable for a motorcycle or powersports install?
A: Absolutely. The ultra-compact 7.25" footprint and wide 9–16V operating voltage range make the 400.4 one of the best choices for motorcycle, ATV, UTV, and marine audio builds where space is at a premium.
Q: Does the 400.4 include a bass boost or subsonic filter?
A: The 400.4 features onboard HPF and LPF crossover filters. For dedicated subwoofer control with bass boost and subsonic filtering, pair it with a DSP or line driver for maximum tuning flexibility.
