metra line output converter wiring diagram
This is a free printable metra line output converter wiring diagram: download the diagram as SVG or open it and print to paper or PDF.
Diagram checks and scope
- Components
- 6
- Wired connections
- 11
- Automated check
- Automated pin, route, source, and topology checks passed; this is not a safety certification.
A Metra Line Output Converter Wiring Diagram wiring diagram provides comprehensive guidance for electrical installation and troubleshooting in automotive and industrial applications. This specialized diagram illustrates the proper connections, wire gauges, component placement, and safety procedures required for correct system operation. Understanding this wiring is essential for technicians, electricians, and professionals working with electrical systems. The diagram shows all connections with color coding, amperage ratings, and grounding requirements to ensure safe and reliable operation. Proper installation following this diagram prevents electrical hazards, system failures, and compliance issues. The schematic includes detailed information about terminals, connections, and circuit protection measures. Professional implementation of this diagram ensures optimal system performance, equipment longevity, and electrical safety for all users and equipment.
How to wire metra line output converter wiring diagram
- Locate factory speaker outputs for LOC tap Identify the two speaker wires (positive and negative) for the channel you are converting. Rear full-range speakers are most commonly used — they carry the full-range audio signal needed for subwoofer and amplifier feeds.
- Strip and splice LOC input wires in parallel The LOC input wires connect in parallel across the existing speaker, not in series. Connect red and white input wires to speaker positive, black and grey to speaker negative. The factory speaker continues to function.
- Do not cut or interrupt the speaker circuit LOC inputs are high impedance and draw negligible current. The factory speaker circuit must remain intact — cutting and inserting the LOC in series causes signal loss and can damage the factory amplifier.
- Set the LOC input level control at minimum first Turn the adjustment pot fully counter-clockwise before connecting anything downstream. Playing audio with the gain wide open immediately clips the output and can damage the external amplifier on first power-up.
- Connect RCA outputs to the amplifier inputs Red RCA to right channel amplifier input, white to left. Keep RCA cables under 5 metres to avoid signal degradation. Route away from speaker cables and power leads to minimise noise pickup.
- Set gain with a test tone and oscilloscope or DMM Play a 0dB test tone at 80% head unit volume. Increase the LOC gain pot until the RCA output is at the amplifier's rated input sensitivity, typically 200mV–2V. Avoid clipping — look for flat-topping on the waveform.
- Test for alternator whine with engine running Start the vehicle and listen for a whine that rises with engine RPM. If present, check earth connections on both the LOC and amplifier chassis. A ground loop isolator may be needed if earth points differ.
Frequently asked questions
What does a line output converter do?
A line output converter (LOC) takes a speaker-level signal from a factory head unit and converts it to a low-level RCA preamp signal. This allows you to connect an aftermarket amplifier to a factory radio without RCA preamp outputs.
Where do I connect the Metra LOC input wires?
Connect the LOC input wires directly to the speaker output wires at the back of the factory head unit or at the speaker terminals. Use whichever is easier to access. Do not connect to door speaker wires if you can tap closer to the radio — keeps the signal cleaner.
How do I set the correct input level on the Metra LOC?
Turn the radio to about 75% volume and adjust the LOC gain trimmer until the amplifier receives a clean signal without distortion. Setting it with the radio at full volume clips the signal before it even reaches the amplifier and causes permanent tweeter damage.
Will a Metra LOC work with a Bose or Harman Kardon factory system?
Factory premium audio systems use signal processing and non-standard impedance outputs. A basic LOC often produces poor results with these systems. Metra and PAC make vehicle-specific signal processors designed for premium factory audio — use those instead.
Do I need a remote turn-on wire with a Metra LOC?
Many Metra LOC units include an automatic signal sensing function that generates a remote turn-on output when it detects audio signal. This eliminates the need to splice into the ignition circuit for the amplifier remote wire — a useful feature on factory radio installs.
Sources and verification
Review status: Not independently reviewed. Automated topology checks confirm stored terminals and routes, not the correctness of manufacturer pin assignments, ratings, regional codes, or installation decisions. Verify those claims against the current primary documentation before use.
- IEC 61082-1:2014 — Rules for electrotechnical documents — International Electrotechnical Commission. Supports: General diagram, drawing, table, and reference-designation presentation conventions. Checked 2026-07-15.
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