Hardware & signal path
Phono input
A phono input accepts the tiny signal a turntable cartridge produces and applies RIAA equalisation to it, boosting the level by around 40 dB and restoring the bass that was deliberately cut when the record was pressed.
In practice
Thin and quiet means a turntable on line. Deafening and distorted means a line source on phono. Check the switch first.
Set the switch before you plug anything in, and set it back when the deck changes. On a DJM the choice is a rear panel toggle per channel; on a battle mixer it is often per channel on the front. If you are using timecode vinyl, the input still has to be on phono — a control record is a normal record carrying a tone, and the cartridge in front of it produces exactly the same tiny signal any other record would.
~40 dB
Gain a phono stage adds
RIAA
The curve it undoes
Ground
The wire only vinyl needs
Where these come from: The RIAA standard and typical moving-magnet phono-stage gain — published specifications, not catalog figures. For what we can measure, see why the earth wire matters.
Why it matters
The switch beside it is the single most common cause of "my turntable is silent" and "my CDJ is deafening and distorted". A line source into a phono input is amplified forty decibels too far; a turntable into a line input is thin, quiet and bass-light because nothing has undone the RIAA curve.
It also explains why turntables need a grounding post and CDJs do not. The signal is so small that mains hum induced in an unearthed chassis is loud relative to the music, which is why the earth wire matters on vinyl and is simply absent on digital gear.
Frequently asked
Can I plug a CDJ into a phono input?+
You can, and it will be unusable — massively over-amplified and tonally wrong. Switch the channel to line, which is what every digital source expects.
Why does my turntable hum?+
Most often the ground wire is not connected to the mixer’s earth post. The phono stage amplifies everything by around forty decibels, including hum the chassis picks up when it is not earthed.
Does timecode vinyl need phono or line?+
Phono. The control record is read by an ordinary cartridge, so it produces an ordinary cartridge-level signal that still needs the phono stage before anything can decode it.
Related terms
Turntable
A turntable spins a record at a constant speed while a stylus tracks its groove. A DJ turntable adds a pitch fader, high torque so it reaches speed instantly, and a platter you can hold and release.
Cartridge
A cartridge converts the stylus’s movement in the groove into an electrical signal. It mounts to the tonearm, holds the replaceable stylus, and its design decides how securely a record tracks under handling.
Ground loop
A ground loop is a hum caused by two pieces of connected equipment being earthed at different points, so current flows through the audio cable's shield. It sounds like a steady low buzz at mains frequency.
DVS vs timecode vinyl
DVS is the whole system — software, an interface and control records — that lets a turntable play digital files. Timecode vinyl is one component of it: the record carrying the tone the software reads.
Explore: Beginner mixing guide · Ground loop · Timecode vinyl · All DJ terms