Quick answer: A record player outputs a very low phono level, about 3 to 5 mV, and needs a moving magnet stage before any line input. The cable itself is a short twin RCA, usually 1 m or less, plus a separate ground wire from the turntable chassis to the phono stage. Most hum complaints are a missing or looped ground, not a faulty cable.
Turntables are the only common consumer source where the cable, the ground and the gain stage all matter at once. Getting the cable right is easy; getting the ground right is where most setups fail.
Phono level against line level
A CD player outputs about 2 V. A moving magnet cartridge outputs 3 to 5 mV, roughly 500 times less, and the signal also carries the RIAA equalisation curve. Plugging a turntable into a line input produces almost nothing audible, and the hiss you hear is the gain being applied somewhere else.
Where the phono stage lives
Either inside the amplifier, selected by a phono input, or in a separate preamp box. Some turntables include a switchable preamp and output line level on the same RCA sockets, which is why the manual matters more than the cable.
Moving coil cartridges
Moving coil outputs are ten times lower again and need a step up transformer or a dedicated stage. Cable capacitance matters slightly here, but the dominant issue remains grounding.
Cable and ground requirements
| Item | Requirement | Typical failure | Fix |
|---|
| Twin RCA cable | 1 m or less, shielded | Long unshielded lead picks up hum | Shorten the run |
| Ground wire | Separate conductor, both ends bonded | Wire missing or loose | Connect chassis to phono ground post |
| Cartridge wiring | Correct colour code, snug clips | One channel silent or reversed | Reseat clips, check colour order |
| Phono stage input | 47 kohm moving magnet load | Line input used by mistake | Use phono input or preamp |
| Mains earthing | One ground reference | Ground loop with powered speakers | Same outlet group, or isolate |
Diagnosing hum in the right order
Disconnect the source
With the phono stage powered and the turntable unplugged, listen. If the hum remains, it is the stage or the amplifier. If it disappears, the turntable or its cable is the source.
Ground wire first
Connect the turntable chassis to the ground post on the phono stage with the thinnest practical wire. If the hum changes when you touch the wire, the ground path is the issue. Never disconnect a mains earth to solve hum; that is a safety risk.
Then cable position
Move the RCA leads away from power supplies and speaker cables. Phono level is 60 dB below line level, so a cable running beside a mains lead picks up audible noise that would be inaudible in any other part of the system.
Upgrading the cable sensibly
A turntable with captive leads cannot be recabled without soldering inside the plinth. Where the leads plug into the plinth, a short shielded pair with moulded plugs is enough; the capacitance of a 1 m cable is a few tens of picofarads, which is within the range most moving magnet cartridges expect.
Long runs are the case that justifies a phono stage near the turntable and a line level cable to the amplifier. Sending phono level 5 m through an unbalanced cable invites noise that no cable construction fully solves.
Practical scenarios
- Turntable beside an integrated amplifier: 1 m twin RCA plus the ground wire, both plugged into the phono input, hum gone once the ground is tight.
- Turntable across the room: compact phono preamp behind the turntable, then a normal line level RCA run to the amplifier.
- Turntable into powered speakers: built in preamp switched on, line output to the speakers, hum traced to a ground loop between two mains outlets.
- Vintage deck with captive leads: original leads retained, plugs cleaned, ground wire replaced with a new spade connector.
FAQ
Can I use any RCA cable for a turntable?
For a short run, a shielded twin RCA is fine. The ground wire matters more than the cable brand, and long unshielded leads cause audible hum.
Why is the sound very quiet?
The turntable is feeding a line input without a phono stage. Phono level is roughly 500 times lower than line level.
Do I need a special ground wire?
No. A thin insulated wire with a spade or bare end works. What matters is a solid connection at both ends.
Next step
Fix the ground before buying a cable. The RCA connector guide covers plug types and colour codes, the RCA patch cables page covers short shielded pairs, and the audio adapter guide explains how to convert between RCA and other connectors without adding noise.
