By NaJade · DJ in Bangkok · Published November 10, 2026
This guide is part of DJ mixers: the complete guide.
Your turntable isn’t broken. It’s probably just plugged into the wrong kind of input.
Every DJ mixer channel with a turntable socket has a little switch or a pair of sockets marked PHONO and LINE. Get it wrong and the deck is either whisper-quiet and thin, or loud, distorted and humming. The difference is about signal strength and one specific EQ curve — and once you understand it, you can connect any turntable, CDJ or laptop to any mixer without guessing.
Phono is the tiny, specially equalised signal that comes straight off a turntable cartridge; it needs a phono preamp to boost it and correct the tone. Line is the much stronger, ready-to-use level from CDJs, controllers and laptops. Turntables without a built-in preamp go into phono, with the ground wire attached. Everything else goes into line.
What Phono and Line Actually Mean
A turntable cartridge generates its signal by moving a tiny magnet and coil, so the output is very small — usually a few thousandths of a volt. On top of that, records are cut with the bass turned down and the treble boosted, so more music fits in the groove and surface noise is lower. Playback has to reverse that with the RIAA equalisation curve.
A phono input does both jobs: it amplifies the signal and applies the RIAA curve. A line input does neither, because it expects a source — a CDJ, a media player, an audio interface — that is already at full strength with a flat frequency response. Rane’s support team has a clear summary in their article on phono and line-level signals.
| Phono | Line | |
|---|---|---|
| Typical sources | Turntables with no built-in preamp | CDJs, media players, controllers, laptops, interfaces, turntables with the preamp switched on |
| Signal strength | Very low (millivolts) | Much higher, ready to mix |
| RIAA EQ applied? | Yes, inside the mixer | No |
| Ground wire needed? | Usually yes | No |
| Wrong-input symptom | Line source here: very loud, distorted, can risk damage | Phono source here: very quiet, thin, no bass |
Which Input Should You Use?
- Classic DJ turntables such as the Technics SL-1200 have no built-in preamp. They go into a phono input, every time.
- Turntables with a PHONO/LINE switch on the back — many newer and budget models — have a preamp built in. Set the switch to LINE to plug into a line input or powered speakers; set it to PHONO to use the mixer’s preamp. Never use both preamps at once.
- CDJs, controllers and laptops always go into line.
- DVS and timecode vinyl follow the same rule: the turntable output goes to phono on your audio interface or mixer. More in the timecode vinyl and DVS guide.
Most club mixers let you choose per channel. On the back you’ll find a pair of phono sockets next to a pair of line sockets, plus an input selector on top of the channel. Digital DJ Tips has a useful diagram-led overview of DJ mixer inputs and outputs if your mixer looks unfamiliar.
The Ground Wire and Why Decks Hum
A turntable’s tonearm and chassis need a common electrical reference with the mixer. That’s the job of the thin extra wire with a U-shaped spade on the end. Without it, you get a constant low hum that rises when you turn up the channel.
- Loosen the GND / SIGNAL GND screw on the back of the mixer.
- Slide the spade under it and tighten firmly.
- Do this for every turntable — several ground wires can share one post.
- Still humming? Check the RCA plugs are fully seated, move power cables away from signal cables, and test a different channel to rule out the cable.
Line sources don’t need a ground wire. If a CDJ hums, the cause is usually a cable or a mains issue, not grounding. For more on cable types and what goes where, see DJ cables explained.
Common Problems and Quick Fixes
| Symptom | Likely cause | Fix |
|---|---|---|
| Turntable very quiet, no bass | Plugged into line with no preamp | Move to phono, or switch the deck’s preamp on |
| Turntable loud and harsh | Double preamp: deck set to LINE into a phono input | Set the deck to PHONO, or use the line input |
| Low hum that follows the fader | Ground wire missing or loose | Attach it firmly to the GND post |
| CDJ distorting on one channel | Line source in a phono input, or gain too high | Use line, then reset gain |
| One side of the stereo missing | Loose RCA plug or worn cartridge contacts | Reseat plugs; check the cartridge and its clips |
Once the right input is selected, set levels properly with the trim knob so every deck hits the same meter level. That’s covered in gain staging for DJs.
A Note From NaJade
The first time I set up turntables at a Bangkok bar, I spent twenty minutes convinced one of the decks was broken. It sounded tiny and tinny no matter what I did with the EQ. The bar owner walked over, flicked the input selector on the mixer from LINE to PHONO, and walked away without a word. It’s a small switch, but it’s the first thing I check now on any setup that isn’t mine — along with the ground wire, because a lot of booths here have had that screw loosened and forgotten. If something sounds wrong with a deck, go back to the signal path before you blame the gear. Nine times out of ten, the fix takes ten seconds.
Related: DJ turntables: the complete guide, how to DJ with vinyl, connecting a controller to speakers, and choosing a DJ audio interface.
Frequently Asked Questions
What is the difference between phono and line?
Can I plug a turntable into a line input?
What happens if I plug a CDJ into a phono input?
Do I need a phono preamp for DJing?
Why does my turntable hum through the mixer?
Should my turntable switch be set to phono or line?
About the Author
NaJade is a Bangkok-based DJ playing progressive house, melodic EDM, pop, and Thai music across clubs, rooftops, and weddings in Thailand. He teaches beatmatching and mixing to beginners both in person in Bangkok and online over Zoom. When he’s not behind the decks, he’s documenting the journey on YouTube, Instagram, and TikTok.