Gravity GR-HL4 4-Channel High-to-Low RCA Line Converter

The Gravity GR-HL4 is a four-channel line output converter for adding an aftermarket amplifier to a vehicle audio system that does not provide RCA preamp outputs. It accepts speaker-level audio from a factory or aftermarket radio and converts it to low-level RCA signal. This allows an amplifier to be connected while retaining the existing head unit.

This converter is intended for installers and vehicle owners upgrading factory audio systems with amplified speakers, an external amplifier, or a subwoofer amplifier. Its four-channel design supports connection from multiple speaker outputs rather than limiting the system to a single stereo pair. RCA outputs provide a conventional signal connection for compatible aftermarket amplifiers.

The GR-HL4 is designed to provide a controlled signal handoff between a radio's speaker wiring and an amplifier's RCA inputs. Adjustable input signal sensitivity helps match the converter's output level to the connected amplifier. Proper level adjustment can help create a balanced system setup without unnecessarily overdriving the amplifier input.

A built-in 12-volt remote turn-on output is included for amplifier activation in installations where the radio may not provide a dedicated remote lead. The converter also incorporates a ground loop isolator intended to help reduce unwanted electrical noise in the audio signal path. These integrated functions can reduce the number of separate interface components needed for a basic amplifier integration.

The compact GR-HL4 is suited to installations where a factory radio is being retained and an amplifier is added downstream. It operates from a 12-volt negative-ground vehicle electrical system and accepts up to 100 watts of input per channel. Use it as part of a properly fused amplifier installation with suitable RCA cables, speaker-wire connections, and amplifier power wiring.

Key Features

• Four-Channel Conversion: Converts four speaker-level channels to RCA-level audio outputs.
• RCA Line Outputs: Connects compatible aftermarket amplifiers using standard RCA signal cables.
• Adjustable Sensitivity: Lets the installer set signal level for the connected amplifier.
• Remote Turn-On Output: Provides a 12-volt trigger output for amplifier activation.
• Ground Loop Isolator: Helps reduce electrical noise transferred through the signal path.
• Wide Frequency Response: Supports audio signals from 10 Hz to 50 kHz.

Design & Installation

The GR-HL4 uses a compact enclosed design intended for integration into vehicle audio wiring. Its RCA interface, level adjustment control, and integrated remote-output function place the primary connection and setup functions in one converter module. The design is made for negative-ground automotive electrical systems operating between 11 and 15 volts DC.

Install the converter between the radio's speaker-level outputs and the RCA inputs of a compatible amplifier, following the wiring diagram supplied on the package. Connect the amplifier's remote terminal to the converter's remote turn-on output when applicable, then set input sensitivity conservatively before final system tuning. Confirm speaker-wire polarity, secure all wiring, and keep signal wiring routed appropriately for the vehicle installation.