What is the phono line switch on a turntable?
It is a switch that turns the turntable's built-in RIAA preamp on or off. Set it to LINE and the deck can feed powered speakers or any line-level amplifier input. Set it to PHONO and something else in your chain must supply the preamp.
Picture a common Saturday-afternoon scenario. You have just unboxed a turntable, the record is ready, and there are two cables to connect to a pair of speakers. On the back of the deck sits a small slider marked PHONO and LINE, with no explanation anywhere on the box. Choosing the wrong position is not dangerous in most cases, but it is the difference between a system that sounds right and one that is either distorted or almost inaudible. Understanding the switch makes the whole setup decision straightforward.
[1]What the switch actually controls
According to Audio-Technica's support guidance, the PHONO/LINE switch turns the turntable's internal RIAA preamp off and on, so the deck outputs the correct signal level for whatever it is plugged into. A record's signal on its own is very low, and vinyl is cut with an equalisation curve introduced by the Recording Industry Association of America in the 1950s, which reduces low frequencies and boosts high frequencies so more audio fits in the groove. The RIAA preamp reverses that curve during playback and raises the signal to a normal line level. The switch decides whether that correction happens inside the turntable or somewhere else in your system.
[1]When to choose each setting
- Choose LINE when connecting directly to powered speakers, which have their own built-in amplifier and power connection, or when feeding a stereo amplifier through a line-level input such as Aux, CD or Tape.
- Choose LINE when using Bluetooth, because the receiving device is unlikely to have a phono preamp on board.
- Choose PHONO when the turntable feeds a dedicated PHONO input on a stereo amplifier, which applies its own RIAA preamp, or when you are using a separate external preamp box.
- Never set the switch to LINE while also plugging into an amplifier's PHONO input. Audio-Technica warns this stacks two preamps, producing a signal that is too high, which distorts the audio and could potentially damage the speakers or amplifier.
A concrete comparison
Take two hypothetical setups with the same deck. In the first, the turntable connects straight to a pair of powered desktop speakers. The switch goes to LINE, the internal preamp does the work, and music plays. In the second, the same turntable feeds a stereo amplifier driving passive speakers, and that amplifier has a PHONO input on its rear panel. Here the switch goes to PHONO, the deck's internal preamp is bypassed, and the amplifier's own phono stage corrects the signal. If you plugged that PHONO-level output into a plain line input instead, Audio-Technica notes the audio would be very quiet even with the amplifier turned up high. Some decks, such as Audio-Technica's AT-LP140XP, output at phono level only, because they are professional DJ turntables ordinarily used with mixers that already include a phono preamp, so always confirm your specific model's options before buying cables or accessories.
[1]Two extra details worth checking
- Grounding: a hum in the speakers can often be fixed by connecting the ground wire between turntable and preamp or amplifier. Audio-Technica suggests playing a record with and without the ground connected and keeping whichever gives the better result, noting that decks with external power supplies may not need it at all.
- Preamp quality: if you use the PHONO setting with an external preamp box, these vary vastly in price and quality, so it is worth researching before buying, as it affects the sound.
One thing the switch cannot tell you is what your other equipment actually contains. A powered speaker's manual will confirm it needs a line-level input, and a stereo amplifier's rear panel will show whether a PHONO input exists. Those two facts, plus your turntable's switch, complete the picture. The registry here on RecordPlayerHub lists which models include a phono stage alongside other specifications, which is a quick way to check before you buy.
[1][2]Practical next step: before connecting anything, look at the input you plan to use on your speakers or amplifier. If it is a line-level input or the speakers are powered, set the switch to LINE. If it is a dedicated PHONO input, set it to PHONO. Then play a record at modest volume and listen for distortion or excessive quietness, and adjust the switch accordingly.
[1]Sources and dates
- https://www.audio-technica.com/en-eu/support/how-to-connect-your-turntable-to-speakers · accessed 2026-10-18
- https://recordplayerhub.com/ · accessed 2026-10-18