Earphone Diagram: Internal Wiring, TRRS Plug Pinouts, and Driver Circuits
This is a free printable earphone diagram: download the diagram as SVG or open it and print to paper or PDF.
Understand earphone internal wiring, TRRS jack pinouts, driver connections, and common repair circuits with this accurate reference guide for audio electronics.
An earphone — also called an earbud or in-ear monitor depending on form factor — converts an electrical audio signal into acoustic pressure waves using one or more electrodynamic or balanced-armature drivers. Understanding the wiring and circuit topology is essential for anyone repairing cables, building custom in-ear monitors, or diagnosing audio faults.
The standard consumer earphone uses a 3.5 mm stereo jack plug with three conductors: Tip (left channel), Ring (right channel), and Sleeve (common ground). When a microphone and in-line remote are added, the plug grows to four conductors — this is the TRRS (Tip, Ring, Ring, Sleeve) configuration. Two competing pinout standards exist for TRRS: the CTIA/AHJ standard (used by most modern smartphones) places the microphone signal on the second ring and ground on the sleeve, while the OMTP standard (older Android devices, common in some markets) swaps microphone and ground. Wiring a CTIA cable to an OMTP device produces no microphone function and a loud hum on playback, which is a common source of confusion.
Inside the earphone body, each driver unit has two terminals: positive (typically marked with a red dot, red wire, or '+') and negative (unmarked or marked with a blue/black wire). The left driver's positive terminal connects to the Tip conductor; the right driver's positive terminal connects to the Ring conductor. Both drivers share a common negative return wire that runs to the Sleeve ground. In earphones with a Y-split cable, the ground wires from both driver housings join at the splitter and continue as a single wire to the sleeve.
Balanced-armature drivers, used in professional in-ear monitors, have the same terminal polarity convention but much higher impedance (typically 8 Ω to 32 Ω per driver) and often require passive crossover networks when multiple drivers cover different frequency ranges within the same housing.
Cable colours follow a loose convention — red for right channel positive, green or blue for left channel positive, copper or uninsulated for common ground — but this is not universal. Always verify with a multimeter before soldering.
How to wire earphone diagram
- Identify the plug type and pinout standard Examine the plug under good light. Count the conductor bands (black rings) — one ring means TRS (stereo, no mic), two rings means TRRS (stereo plus mic/remote). If the device using the earphone is a modern smartphone, assume CTIA/AHJ pinout: Tip = Left, Ring 1 = Right, Ring 2 = Microphone, Sleeve = Ground. Confirm with the device manufacturer's documentation if available.
- Open the earphone housing carefully Most earphone housings are either glued or press-fitted. Insert a thin spudger into the seam and work around the perimeter with gentle, even pressure to separate the shell halves without damaging the driver or strain relief. Avoid using sharp tools that can puncture the driver diaphragm.
- Identify the driver terminals Locate the two solder pads on the driver unit. The positive terminal is often marked with a red dot, a '+' symbol, or a red wire in the factory assembly. If there is no marking, note which terminal the red or marked factory wire connects to. Photograph the assembly before desoldering any wires for reference.
- Strip and tin the replacement cable conductors Strip 3–4 mm of outer insulation from each conductor using a sharp blade or dedicated wire stripper. Many earphone cables use enamelled (lacquered) copper wire that does not strip mechanically — hold the conductor over a flame very briefly to burn off the enamel, then tin immediately with rosin-core solder. Do not use acid-flux solder on audio connections.
- Solder conductors to driver terminals Apply a small amount of solder to each driver terminal pad (pre-tin). Place the tinned conductor on the pad and apply the iron briefly — earphone driver pads are small and the voice coil wires are delicate. Excessive heat can detach the factory voice-coil leads from the driver pad. Aim for a shiny, smooth joint completed in under 2 seconds of iron contact.
- Test continuity and audio before closing Before reassembling the housing, connect the plug to a source and play audio to confirm both channels are present, balanced in level, and free of distortion or crackling. Then use a multimeter in continuity mode to verify there is no short circuit between the Tip and Ring conductors (left channel short) or between any signal conductor and ground (common short).
- Reassemble and strain-relief the cable Route the cable through the housing's strain relief boot before closing the shell. Ensure no bare conductor is pinched in the seam. Close the housing with adhesive if required. Tug the cable gently at the housing entry point to confirm the strain relief is carrying the mechanical load, not the solder joints.
Specifications
| Standard consumer earphone impedance | 16 Ω to 32 Ω at 1 kHz (typical) |
|---|---|
| Typical frequency response range | 20 Hz to 20 000 Hz (full audible range) |
| TRRS plug Tip assignment (CTIA/AHJ) | Left channel audio signal |
| TRRS plug Ring 1 assignment (CTIA/AHJ) | Right channel audio signal |
| TRRS plug Ring 2 assignment (CTIA/AHJ) | Microphone signal |
| TRRS plug Sleeve assignment (CTIA/AHJ) | Common ground (audio return + microphone return) |
| Typical audio signal voltage at earphone | Under 2 V peak from portable source at maximum volume |
Safety warnings
- Earphone circuits operate at safe low voltages (typically under 2 V peak from a portable audio source) and present no shock hazard in normal use. However, driving earphones at excessively high volume levels over extended periods causes irreversible noise-induced hearing loss. Do not use earphones at volumes that prevent you from hearing a conversation at arm's length.
- When working on earphone driver units, avoid touching the diaphragm surface. Natural skin oils contaminate the diaphragm material and electrostatic charge from your fingers can warp or puncture the thin diaphragm membrane, permanently damaging the driver.
- Do not use acid-flux solder on earphone connections. Acid flux residue is corrosive and will attack the thin copper conductors and driver pads over time, causing intermittent faults that are difficult to trace.
- Balanced-armature drivers are fragile. Excessive heat during soldering will destroy the voice coil or damage the armature. Use a temperature-controlled soldering iron, work quickly, and use the minimum amount of solder necessary.
Tools needed
- Temperature-controlled soldering iron (suggested tip temperature 300–320 °C for lead solder)
- Digital multimeter (continuity and resistance modes)
- Fine-tip spudger or plastic pry tool for housing separation
- Wire strippers or sharp blade for outer jacket
- Helping-hands workstation or PCB vise for holding small components
- Heat gun for heat-shrink insulation
- Magnifying glass or loupe for inspecting small solder pads
Common mistakes
- Confusing CTIA and OMTP TRRS pinouts when building or repairing a headset cable, resulting in swapped microphone and ground conductors and no microphone function.
- Applying heat to enamelled wire conductors for too long when burning off the enamel insulation, which anneals the copper and makes it brittle at the point of stripping.
- Over-heating the driver solder pads, which detaches the factory voice-coil lead wires from inside the driver unit — a non-repairable failure on most consumer drivers.
- Assembling the plug shell and strain relief boot onto the cable after soldering rather than before, making it impossible to install without desoldering the plug.
- Not testing audio and continuity before closing the earphone housing, requiring the housing to be reopened to fix a fault that would have been trivial to correct before reassembly.
Troubleshooting
- No audio in one earphone channel
- Cause: Broken conductor inside the cable (most commonly at a flex point near the plug or housing entry), open solder joint at the driver pad, or broken voice-coil lead inside the driver Fix: Flex the cable along its full length while playing audio to identify a break by the audio cutting in and out. Use a multimeter in continuity mode to trace each conductor from plug to driver pad. If continuity is present at all points but the driver still produces no sound, the driver voice coil is broken and the driver must be replaced.
- Crackling or intermittent audio in one channel
- Cause: Partial conductor break inside the cable, intermittent contact at a solder joint, or a contaminated driver diaphragm Fix: Flex and tug the cable while listening for changes in the crackling. If the fault is movement-dependent, replace the cable. If the fault is constant, inspect all solder joints under magnification and reflow any dull or fractured joints.
- Microphone not recognised by smartphone (headset cable)
- Cause: CTIA/OMTP pinout mismatch between the cable and the device, open circuit on the microphone conductor, or the plug is a TRS type that lacks the microphone conductor entirely Fix: Confirm the device uses CTIA/AHJ pinout (most smartphones post-2014). If the cable was sourced for a different market, it may use OMTP. A CTIA-to-OMTP adapter can resolve the mismatch without re-cabling.
Frequently asked questions
What is the difference between TRS and TRRS earphone plugs?
TRS (Tip, Ring, Sleeve) has three conductors and carries stereo audio: Tip is left channel, Ring is right channel, Sleeve is common ground. TRRS (Tip, Ring, Ring, Sleeve) adds a fourth conductor for a microphone signal or remote button input. The extra conductor allows the earphone to function as a headset with a built-in microphone.
Why does my replacement earphone cable have no sound in one ear?
The most common causes are a cold or broken solder joint at the driver terminal inside the earphone housing, a broken conductor inside the cable at a flex point (usually near the plug or the Y-split), or a mismatched CTIA/OMTP pinout. Use a multimeter in continuity mode to trace each conductor from the plug tip to the driver terminal.
How do I identify left and right earphone wires without colour coding?
Connect the plug to an audio source playing a stereo test tone that alternates channels. Touch each wire briefly to the driver terminals. The driver that produces sound when the Tip conductor is connected is the left channel driver. Alternatively, use a multimeter in continuity mode to confirm which plug conductor each wire connects to.
What impedance do typical consumer earphones have?
Most consumer earphones designed for direct connection to smartphones have a rated impedance of 16 Ω to 32 Ω at 1 kHz. Lower impedance earphones are easier to drive from portable devices. High-impedance earphones (150 Ω to 600 Ω) are designed for use with dedicated headphone amplifiers or professional audio equipment.
Can I use a balanced earphone cable with an unbalanced 3.5 mm source?
Not without an adapter. A balanced earphone cable carries separate positive and negative signal conductors for each channel (four signal conductors plus sometimes a ground), terminating in a 2.5 mm TRRS or 4.4 mm Pentaconn plug. Using such a cable with a standard 3.5 mm TRS output requires a balanced-to-unbalanced adapter that correctly bridges the conductors.