Turntable hum or buzz: earth wire, phono vs line and other causes

You turn the channel up and there it is: a low hum under the music, or a buzz that's there even when nothing is playing. Sometimes it's only one deck. Sometimes it builds and builds as you push the volume until the whole room is droning.

The good news is that turntable hum is nearly always about how things are plugged in, not a broken deck. The Technics manuals all say the same three things: connect the earth lead, keep mains leads away from the phono cable, and keep the headshell contacts clean. This guide goes through the checks in the order we'd do them, from the free ones to the ones that need a repair.

Quick fix

• Connect the deck's earth wire to the GND or SIGNAL GND post on your mixer and screw it down tight.
• Check the deck is plugged into a PHONO input and the channel selector is on PHONO, not LINE.
• Pull each channel fader down in turn. If the hum stops, it's coming from that source.
• Move mains leads, power adaptors and any phono preamp away from the phono cable.
• Take the headshell off, wipe its contacts with a dry cloth and refit it tightly.
• If the hum grows and grows as you turn up, it's feedback. Move the speakers off the table the decks sit on.

First, work out which noise you've got

Different noises point to different causes, so listen for a minute before you start unplugging things.

• A steady low hum when the turntable channel is up. The classic missing or loose earth.
• A hum or rumble that grows as you turn up, and keeps growing. That's acoustic feedback: the speakers are shaking the deck and the stylus is picking it up.
• A buzz or whine on every channel, turntables or not. Usually a ground loop elsewhere in the rig: a laptop charger, a shared power strip or a house system.
• Hum or crackle that changes when you move the cable. A worn phono lead or earth wire.

Pull the channel fader down on the deck you suspect. If the hum goes, it's coming from that channel. If it stays with every fader down, look at the rest of the rig before you blame the turntable.

1. Connect the earth wire properly

Turntables have a separate earth wire, also called a ground wire, with a small spade on the end. It needs to be clamped under the GND or SIGNAL GND post on the back of the mixer. The SL-1200MK2 manual is blunt about it: if the ground isn't connected, or is loose, you get mains hum. Pioneer's DJM manuals say connecting the turntable's ground wire to SIGNAL GND helps reduce noise.

• Undo the thumb nut, sit the spade under it and tighten it down firmly. Resting it against the post isn't enough.
• Follow the earth wire back to the deck and check it is still attached. Second-hand decks sometimes turn up with it ripped off.

When someone on Reddit asks about turntable hum, the replies usually start with the earth wire, and several agree: with a hum, check the ground first.

MK7 and G series: there's an earth terminal on the deck too

The SL-1200MK7, SL-1210MK7 and the G and GR models have a detachable phono cable. The earth lead screws to a PHONO earth terminal on the back of the deck as well as to the mixer. Technics say to tighten that terminal with a Phillips screwdriver and to use only the supplied phono cable, earth lead and mains lead. If an MK7 hums with brand new cables, check the earth is fitted at both ends.

Broken earth post on the mixer

We've seen mixers come in with the SIGNAL GND post snapped off, or with its thumb nut missing and the earth wire taped to the bare stud. Tape slips and the hum comes back. If the threaded stud is still there, a matching nut is a far better stopgap than tape. If the post itself has gone, that's a repair.

2. Phono vs line: plug into the right input

A Technics SL-1200 or SL-1210 puts out a tiny phono-level signal. It needs a PHONO input: the phono channel on a DJ mixer, the PHONO terminals on an amp, or a separate phono preamp. Panasonic's own Technics support page says not to connect it to an input labelled anything other than PHONO.

Plug a Technics into a LINE or AUX input, or leave the mixer's channel switch on LINE, and you get a weak, thin sound. You then crank the gain to hear it, and the hum comes up with it. So if your deck sounds quiet and hummy, check this before anything else.

• Set the input selector above the channel to PHONO.
• Check you've used the sockets marked PHONO on the back of the mixer, not LINE or CD.
• No phono input on your speakers or interface? You need a phono preamp between the deck and them.

Decks with a PHONO/LINE switch

Some turntables, like the Pioneer PLX-500 and the Audio-Technica AT-LP120, have a built-in preamp and a PHONO/LINE switch on the back. Get it the wrong way round and the sound goes wrong in a different way. LINE into a phono input sounds loud and distorted, because it overdrives the mixer's phono stage. PHONO into a line input sounds very quiet. Match the switch to the socket you're using, and connect the earth lead either way.

Unused phono inputs

Pioneer DJM mixers such as the DJM-900NXS2, DJM-A9 and DJM-V10 come with small short-circuit pin plugs for the PHONO sockets. If you still have them, fit them in any phono inputs you're not using. Open phono sockets can pick up noise.

3. Keep mains leads away from audio leads

The MK7 troubleshooting table lists "humming is heard during play" with two checks: are other appliances or their mains leads near the audio cable, and is the earth lead connected.

• Route power leads and adaptors away from the phono cables.
• Move any external phono preamp away from power supplies and other boxes. One SL-1200 owner on r/turntables cured a rough, buzzy sound by reseating a lead and moving the preamp and an audio switcher to opposite sides of the desk.
• Unplug LED lights and chargers on the same power strip, one at a time. A DJM-250MK2 owner on Reddit traced a buzz to an LED light bar plugged into the mixer's power strip.
• A PLX-500 owner traced a high whine to network cables running alongside the speaker leads. Unplugging them stopped it.

4. Clean the headshell contacts

The MK2 manual says dirt on the headshell terminals can cause increased hum or intermittent sound, and tells you to wipe them with a soft, dry cloth. Take the headshell off, wipe the four pins, then refit it and tighten the locking collar fully. A loose headshell can hum and cut out.

While it's off, check the four small wires from the headshell to the cartridge are pushed fully onto their pins.

5. Hum that builds as you turn up: feedback

If the noise is a low rumble or howl that keeps getting louder as you raise the volume, it isn't an earth problem. The speakers are vibrating the surface the deck stands on, the stylus reads that vibration, and the speakers play it back even louder.

Technics manuals say to put the deck on a level surface protected from vibration, as far as possible from the speakers. To check:

• Turn the master and booth down and listen on headphones only. If the noise goes, it's feedback, not wiring.
• Get the speakers off the table the decks are on, and off any stand that touches it.
• Check all four feet are there and none is crushed. On Technics they are adjustable insulators: turn them to level the deck so it doesn't rock.

6. Ground loops: laptops, chargers and house systems

If the buzz is there on every channel, even with the turntables unplugged, look at the wider rig.

• Unplug the laptop charger for a minute. If the buzz stops, the charger is part of a ground loop. Native Instruments list the laptop power supply as a common cause of hum in DVS setups.
• Plug the mixer, laptop and powered speakers into the same power strip.
• Use balanced XLR or jack leads into powered speakers where you can, rather than RCA adaptors.
• Getting a buzz only when you plug into a club or house system? DJs on Reddit agree a DI box with a ground lift switch is the usual way to break that loop.
• Never remove or tape over the earth pin on a mains plug to stop a hum. It's dangerous.

Model notes

• SL-1200MK2 to MK6, M3D, M5G and GLD: the phono lead and earth wire are fixed, wired inside the arm base. If they're damaged you can't just unplug them and fit new ones.
• SL-1200MK7, SL-1210MK7, G, GR and GR2: detachable phono cable and an earth terminal on the deck. Use the supplied cable and earth lead, fitted at both ends.
• Pioneer PLX-1000: comes with a ground wire in the box. Connect it to SIGNAL GND.
• PLX-500 and AT-LP120: connect the earth lead and set the PHONO/LINE switch to match the input.
• Imported decks: Technics made 100V and 120V versions for Japan and the US. These need a properly rated step-down transformer here and can run badly without one. Check the rating label underneath before you plug in.

If you're shopping for a pair, our Technics SL-1210 and SL-1200 price guide explains the differences between the models.

When it's a repair

If you've been through everything above and one deck still hums, these are the signs it's the deck or its cables:

• The hum stays with the earth wire firmly connected, on any mixer.
• The hum follows the deck when you swap it onto another channel.
• Hum or crackle changes when you wiggle the phono cable near the deck.
• The earth wire has come away from the deck, or its spade is broken.
• The mixer's earth post has snapped off.

On MK2 to MK6 decks the phono and earth leads are fixed inside, so a broken wire means opening the deck and soldering in new leads. Please don't open it yourself. New phono and earth cables are £30 per deck, and while the deck is open we check the earth inside the arm base. A worn lead can also be behind one channel cutting in and out. On MK7 and G series decks the cable unplugs, so a new cable may be all you need.

If it isn't obviously the cables, our diagnostic is £30, deducted if you go ahead with the repair. A full Technics service is £90, or £150 for a pair. Any repair is subject to diagnosis and parts availability. You can book in on our service and repair page, and courier collection and return is £20 per unit if you can't drop it in.

What to send us

Send a short video with sound: the hum, then you turning that deck's channel fader up and down. Add a photo of where the earth wire connects on the deck and on the mixer, and tell us the models of deck and mixer.

FAQ

Do I need the earth wire if I use a phono preamp?

Yes. A preamp doesn't replace the earth. Connect the earth wire to the GND post on the preamp, amp or mixer the deck plugs into. DJs on Reddit who skipped it because they had a preamp were told to start by adding the ground wire.

Can I use a Technics without the earth wire?

It will play, but expect hum. Technics tell you to connect it. Some older decks have been modified to earth internally, but unless you know yours has, treat a missing earth wire as something to fix.

Why is my turntable quiet and humming through my speakers?

Almost always because it's going into a line or AUX input with no phono stage. A Technics needs a PHONO input or a phono preamp. Turning a line input right up to hear it brings the hum up too.

Why does only one of my decks hum?

Swap the two decks between mixer channels. If the hum follows the deck, check that deck's earth wire, headshell and phono lead. If the hum stays on the same mixer channel, the problem is on the mixer side.

Still humming?

Most hum is a setup fix: the earth wire, the right input and a tidy-up behind the decks. If yours isn't, send us the video and we'll tell you honestly whether it's setup or a repair. And if you're after another deck, have a look at our used Technics and Pioneer turntables.