Phono vs line: which input should your turntable use?

Phono and line describe different signal requirements

For ordinary magnetic-cartridge playback, a phono stage supplies the gain and playback equalization needed before the signal reaches a normal line input. RIAA equalization is the standardized recording/playback frequency-response relationship used in this ordinary chain. A phono stage is therefore doing more than simply adding volume.

A line input is intended for an already suitable line-level signal. It does not replace missing phono gain and equalization. Both signals may use the same RCA connector shape, so choose by the documented function, not by whether a plug fits.

The Pro-Ject Phono Box specifications separately identify gain, cartridge modes, RIAA equalization and a line output. The AT-LP120XUSB manual, page 8, shows how a turntable's PHONO/LINE switch changes its output and the appropriate destination. Check your model's instructions before assuming the same switch behavior.

Match the output to one of four destination cases

Cartridge-level PHONO output into a matching PHONO input

This is an ordinary route when the receiving stage suits the cartridge. The complete phono-processing function is at the receiving input. Any earlier built-in phono stage must be absent or bypassed as instructed.

Cartridge-level PHONO output into a line input

Required phono processing is missing from this route. Provide a compatible phono stage, either by enabling a documented built-in stage or by inserting a suitable external one. Simply increasing the amplifier's volume does not supply the missing equalization.

Processed LINE output into a line input

This is the ordinary route for an enabled turntable phono stage or an external stage's output. Use a documented line input such as AUX or another input identified as line level. Input names vary, so inspect the manual if the function is unclear.

Processed LINE output into a PHONO input

This sends an already processed signal through another complete phono stage. Change to a suitable line input, or bypass the earlier stage if the equipment supports the intended route. The Phono Box manual, pages 2–3, specifically separates its cartridge input from its line-output destination.

“One appropriate phono stage” means one complete phono gain/equalization function, not necessarily exactly one physical box or one gain element. A compatible moving-coil step-up device can form part of a phono front end; its presence alone does not imply duplicated RIAA processing. Such arrangements need their own documented compatibility.

Match the cartridge, not just the MM or MC label

Record the actual cartridge and stylus, then check the required gain and electrical loading against the stage's supported settings. Moving-magnet and moving-coil labels are starting points, not universal prescriptions. Some high-output moving-coil cartridges use a different suitable arrangement from low-output designs.

For a bounded specification example, Audio-Technica lists the AT-VM95E at 4.0 mV under a stated 1 kHz, 5 cm/s test, with recommended loading of 47 kΩ and 100–200 pF. These are that cartridge's conditions, not values to copy onto every pickup. A music signal does not remain at one fixed voltage, and a published input sensitivity is not necessarily the maximum allowed input.

If a cartridge has been replaced, the turntable's original package description no longer proves what is installed. An unknown cartridge or vintage input needs identification before its settings can be confirmed.

Recheck the route before diagnosing a fault

Use a short connection card: cartridge identity, phono-stage mode/gain/load, turntable output switch, receiving input and signal-ground instructions. Make plug or mode changes with the equipment powered down as its manuals direct.

Insufficient level or distortion can prompt a mode check, but the symptom does not identify a unique cause. Ortofon's troubleshooting guidance also includes tracking, alignment and input selection. Check the documented route before buying another stage or changing cartridge settings by guesswork.

For the complete equipment chain, see turntable setup. For mechanical adjustment, use tracking force. For noise, follow the external hum and buzz checks, without changing mains protective earth.