Rockford Fosgate T400-4 400W 4-Channel Amplifier

The Rockford Fosgate Power T400-4 is a four-channel car amplifier designed to add dedicated power to front and rear speakers in an aftermarket audio system. It delivers 60 watts RMS to each of four channels at 4 ohms, helping compatible speakers play with more headroom than a typical factory radio amplifier. Its four-channel layout supports conventional front/rear speaker systems and can also be configured for bridged operation.

This amplifier suits listeners building a balanced full-range system with component speakers, coaxials, or a combination of speakers and small subwoofer channels. It can run four speakers at 2 or 4 ohms, or bridge its channels into two higher-output channels. The 2/4-channel input selector can simplify integration when a source unit has only one pair of RCA outputs.

The T400-4 uses a Class A/B circuit topology with MOSFET power-supply and output stages. Its rated frequency response is 20 Hz to 20 kHz, allowing it to cover the full audible range for appropriately configured speakers. Differential RCA inputs are designed to help reject induced noise in the signal path.

Adjustable front and rear crossover sections let the amplifier be tuned for the speakers connected to each channel pair. Each section provides selectable high-pass or low-pass filtering from 50 to 500 Hz with a 24 dB-per-octave Butterworth slope. Separate Punch EQ controls provide bass adjustment at 45 Hz and treble adjustment at 12 kHz.

The compact chassis is intended for installations where amplifier space is limited, including many under-seat or trunk locations with adequate ventilation. Dynamic Thermal Management and protection circuitry support dependable operation when the amplifier is installed and wired correctly. Pair it with compatible speakers, RCA signal cables, suitable power wiring, and an externally fused power connection for a complete upgrade path.

Key Features

• Four-Channel Output: Powers front and rear speakers from one amplifier.
• Bridged Capability: Combines channel pairs for higher-output two-channel configurations.
• Class A/B Topology: Provides full-range amplification with rated 20 Hz–20 kHz response.
• 24 dB Crossovers: Separately tune front and rear speaker frequency ranges.
• Differential RCA Inputs: Helps reduce noise entering through signal cables.
• Punch EQ Controls: Adjusts bass and treble response for system tuning.

Design & Installation

The T400-4 combines MOSFET power and output stages with a focused-mass die-cast heatsink design. Its Dynamic Thermal Management and NOMAD protection circuitry are intended to monitor operating conditions and protect the amplifier from overload-related faults. Power, thermal, and protect indicators provide basic operating-status feedback.

Use the amplifier with 2- or 4-ohm speaker loads per channel, or bridge channel pairs as specified for the installation. The amplifier accepts RCA-level input through front and rear RCA pairs and provides a 2/4-channel input selector; it does not provide signal outputs. Install an external 100-amp fuse in the power wiring, use correctly sized power and speaker cable, make a solid chassis ground connection, and leave room around the heatsink for convection cooling.