JL Audio HD600/4 HD Series 4 Channel Class D Full Range Amp Amplifier 600w RMS

The JL Audio HD600/4 is a 4-channel Class D full-range amplifier from the HD Series, rated at 600W RMS total — 150W RMS x 4 into 1.5–4 ohms, or 300W RMS x 2 bridged into 4–8 ohms.

Pair it with the JL Audio HD750/1 monoblock to power a subwoofer, and add the optional HD-RLC remote level control for level adjustment from the driver's seat.

Key specifications

• Channels: 4, Class D full-range
• Power: 150W RMS x 4 @ 1.5–4 ohm (14.4V and 12.5V)
• Bridged: 300W RMS x 2 @ 4–8 ohm
• Frequency response: 6 Hz – 30 kHz (+0, -1 dB)
• S/N ratio: >110 dB (referred to rated power)
• THD+N: <0.03% at rated power
• Filters: low-pass or high-pass, 12/24 dB/octave, 50–500 Hz
• Fuse: 50A, minimum 4 AWG power and ground
• Dimensions: 273 mm W x 211 mm D x 49 mm H
• Finish: brushed aluminium with black powder-coated cast alloy heat sinks and bottom panel

HD600/4 4-Channel Class D Full-Range Amplifier, 600W (150W x 4 @ 1.5–4 Ω)

This compact amplifier uses JL Audio's Single-Cycle Control switching design and R.I.P.S. technology to deliver 150W x 4 or 300W x 2. Tight power supply regulation keeps distortion low and maximises sound quality.

Paired with the HD750/1 or HD1200/1, it works as an ideal satellite amplifier for a full system. It can also run standalone as a 3-channel system — 150W x 2 to front or rear speakers and 300W x 1 bridged to a subwoofer.

The amplifier features a brushed aluminium finish with black powder-coated cast alloy heat sinks and bottom panel. A black powder-coated, gasketed cover is included to protect the controls.

R.I.P.S. – Regulated, Intelligent Power Supply

R.I.P.S. (Regulated, Intelligent Power Supply) is a core feature of JL Audio's HD and 'Slash' amplifiers, ensuring consistent power delivery across a wide range of battery voltages and load impedances.

Regulated: The power supply adjusts its operation to maintain rated output and low distortion across vehicle voltages from 11V to 14.5V. Conventional unregulated supplies allow rail voltages to sag as battery voltage drops — even briefly — causing audible distortion. With R.I.P.S., rail voltage and clean power output remain completely stable.

Intelligent: A monitoring circuit tracks output current to optimise power delivery across load impedances from 1.5 ohm to 4 ohm per channel. Conventional amplifiers are tuned to one impedance and lose power when the load changes — for example, halving from 2 ohm to 4 ohm. R.I.P.S. detects the actual impedance being driven and adjusts automatically, delivering consistent output whether powering satellite speakers or a wide range of subwoofer configurations. It also works from the real system impedance, not a speaker's rated impedance.

The result: optimum power at any impedance between 1.5 ohm and 4 ohm per channel, at any vehicle voltage between 11V and 14.5V.

Advanced Rollback Protection

JL Audio's Advanced Rollback Protection monitors the amplifier's thermal condition and prevents unwanted shut-down events. If the amplifier reaches an unsafe operating temperature, the circuit rolls back peak power output — without changing gain — until it cools to a safe level. This is indicated by a red Thermal or Status LED. Once the amplifier cools, full peak power is restored and the indicator returns to its normal state. In most cases the rollback is inaudible, keeping music playing even under demanding conditions.

RealSink™

RealSink™ heat sinks use vertically oriented, cast alloy fins to dissipate heat through convection and radiation — no noisy fan cooling required. The fin geometry was refined using extensive finite-element analysis, keeping the amplifier cool under sustained heavy use.