Ruthless Audio 400.4 Micro 4 Channel Amplifier
Need four channels of power without giving up precious installation space? The Ruthless Audio 400.4 Micro 4-Channel Amplifier delivers a combined 400W RMS in a chassis measuring just 7.25" long. Its small footprint makes it a practical choice for an OEM-style upgrade, motorcycle or powersports system, or custom build where a conventional amplifier is hard to fit.
This Class-D amplifier is rated at 100W x 4 @ 2 ohms or 60W x 4 @ 4 ohms at 14.4V. A 95dB signal-to-noise rating, adjustable high-pass filter (20Hz–8kHz), and low-pass filter (50Hz–8kHz) give you useful tools for powering and tuning your speakers. Its listed fuse rating is 60A, and its operating voltage range is 9–16V. Match the installation and vehicle electrical system to those requirements.
Use all four channels for front and rear speakers, or bridge channel pairs when your setup calls for two higher-output channels. The 4.7" width and 2.2" height open up placement options under a seat, behind a panel, or in a carefully ventilated custom enclosure. It is compact enough to tuck away, but versatile enough to anchor a thoughtfully planned system.
Why Choose the Ruthless Audio 400.4 Micro Amplifier?
- Compact Micro Chassis — Its 7.25" overall length helps it fit in space-limited motorcycle, powersports, and discreet vehicle installations.
- 400W Total RMS Rating — Four channels rated at 100W each into 2Ω at 14.4V, or 60W each into 4Ω at 14.4V.
- Class-D Design — A compact, efficient amplifier layout suited to installs where space and heat management matter.
- Bridgeable Channels — Run four separate speaker channels or bridge them in pairs for a two-channel configuration, subject to the proper load.
- Built-In High-Pass and Low-Pass Filters — Adjust HPF from 20Hz–8kHz and LPF from 50Hz–8kHz to suit your speaker setup.
- 95dB Signal-to-Noise Rating — A published specification to consider when comparing amplifier options.
- 9–16V Operating Range — Check your vehicle's electrical setup against the amp's stated voltage range.
- Flexible Installation Footprint — At 7.25" long, 4.7" wide, and 2.2" high, it offers more mounting possibilities than a larger chassis.
Amplifier & Wiring Recommendations
Consider the 400.4 for component speakers or coaxials with suitable impedance and power handling in the 60–100W RMS-per-channel range. Feed it a quality four-channel RCA signal from a compatible head unit or DSP. A 4-gauge power and ground kit is recommended in this listing for the 60A fuse rating; confirm final wire size and fuse placement for the length of your run and installation. If bridging channels 1+2 and 3+4, check speaker power handling and keep the bridged load at 4Ω minimum. Route signal cables away from power wiring where practical to reduce noise.
For motorcycle or powersports use, protect connections from the elements and mount the amp securely against vibration. The heatsink is 6.375" long; allow approximately 1–2" of clearance for airflow when installing it in an enclosure. Confirm the mounting area and environmental exposure are appropriate before installation.
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: This listing recommends a 4-gauge power and ground kit for the 60A fuse rating. Select wire and protective fusing for the actual run and installation.
Q: Can I bridge the 400.4 down to 2 channels?
A: Yes. Bridge channels 1+2 and 3+4 for two higher-output channels. Use speakers appropriate for the resulting power and maintain a minimum 4Ω bridged load.
Q: Is this amp suitable for a motorcycle or powersports install?
A: Its 7.25" length makes it worth considering for motorcycle, ATV, or UTV builds with limited room. Plan for secure mounting, ventilation, and protected connections; don't assume the amplifier itself is weatherproof.
Q: Does the 400.4 include a bass boost or subsonic filter?
A: The listed onboard controls are high-pass and low-pass filters. If your subwoofer setup needs additional bass or subsonic control, plan for an appropriately configured DSP or other compatible processing.
