Quick answer: The red and white RCA plugs carry unbalanced line-level audio: white is the left channel, red is the right. Both are referenced to the shield, which is the outer ring. They carry about 0.5 to 2 V into an input of 10 kohm or more, which is why a cheap shielded cable works, and why the same plugs cannot drive a speaker or feed a turntable input. Match the colours at both ends and keep the run under about 5 m.
RCA is one of the oldest connectors still in daily use, and the colour convention is the only thing that keeps stereo wiring straight. The electrical rules are simple: signal on the centre pin, shield on the ring, no twisting of the pair, and no expectation of balanced noise rejection.
What the two channels are
Line level, not speaker level
A line output sits around 1 V with a source impedance of a few hundred ohm. Connecting it to a speaker produces almost no sound and risks nothing, but connecting a speaker output to a line input can destroy the input stage. The plugs are identical, which is exactly why the mistake happens.
Not a phono input
A turntable needs a phono stage with RIAA equalisation and much higher gain. Plugging a CD player into a phono input overloads it and sounds distorted; plugging a turntable into a line input gives almost no level and no bass. Both faults are common when a receiver’s inputs are not labelled clearly.
Cable choices
| Run | Cable | Result |
|---|
| Under 1 m | Any shielded twin RCA | No audible difference |
| 1 to 3 m | Foil or braid shield | Quiet if routed away from mains |
| 3 to 5 m | Low capacitance, good shield | Slight treble loss possible |
| Over 5 m unbalanced | Not recommended | Hum likely |
Connecting to other formats
To a 3.5 mm input, a twin RCA to stereo jack cable is the standard part; the wiring is tip to white, ring to red and sleeve to both shields. To a coaxial digital input, do not use an analogue RCA lead for a long run: the S/PDIF signal at 6 MHz needs a 75 ohm cable, and a thin twisted lead produces dropouts rather than obvious distortion.
Where the source is a computer without a jack, a USB audio adapter or a USB-C to 3.5 mm audio dongle provides the line output, and a RCA to 3.5 mm cable carries it to the amplifier. For a digital feed, the digital coaxial cable page covers the 75 ohm requirement.
Practical scenarios
- CD player into an amplifier: white to left, red to right at both ends, and check that the amplifier input is labelled CD or AUX rather than PHONO.
- TV headphone output into a hi-fi: a 3.5 mm to twin RCA cable, with the TV volume fixed at about 80 percent and the amplifier controlling level.
- Long run to a second room: convert to balanced or use a wireless link rather than 10 m of unbalanced RCA, which will hum.
- Subwoofer feed: a single RCA lead carries the LFE channel; the colour convention does not apply, so label it instead.
FAQ
Does red or white matter?
Red is right, white is left, and consistency at both ends is what matters. If the channels are swapped, the stereo image inverts but nothing is damaged. Check with a test track that announces the channel, or with a mono recording that should come from the centre.
Can I use a red and white cable for video?
The yellow plug is composite video and uses the same 75 ohm cable, so a red or white lead will carry video if the cable is coaxial. It will not be colour-coded, and thin audio leads lose sharpness, but it works for a short temporary run.
Why is there hum when the TV is connected?
Two grounded devices joined by an unbalanced cable form a loop, and the shield carries the current. Try a ground loop isolator on the RCA lead, or move both devices to the same outlet strip. Replacing the cable rarely fixes a loop.
