Turntables

Adding a Turntable to Your Stereo: Phono Preamps Explained

You plug in a turntable, drop the needle, and hear almost nothing: a faint, thin sound with no bass. Or you hear it far too loud and harsh. Both problems come down to the same small box that many first-time vinyl buyers have never heard of, the phono preamp.

This guide explains what a phono preamp does, how to tell whether your gear already has one, and how to connect a turntable cleanly to an integrated amp, receiver, powered speakers or soundbar.

Why turntables need a phono preamp

A turntable cartridge produces a tiny electrical signal, far weaker than the line-level output of a streamer, CD player or phone. A moving magnet cartridge typically outputs a few millivolts; a moving coil cartridge often outputs much less. That signal needs substantial amplification before an amplifier's line inputs can use it.

There is a second job too. Records are cut with the bass reduced and the treble boosted, following a standard curve called the RIAA equalization curve. This lets grooves fit more playing time and keeps surface noise down. On playback, the phono stage applies the reverse curve, restoring the bass and taming the treble. Without it, a record sounds thin and bright even if you turn the volume way up.

How to tell if you already have one

Many AV receivers have no phono input at all, and neither do most soundbars or computer speakers. Older stereo receivers and integrated amps very often do.

Connection recipes for common setups

Turntable to an amp with a PHONO input

1. If the turntable has a PHONO/LINE switch, set it to PHONO.
2. Connect the RCA cables to the amp's PHONO input.
3. Attach the ground wire to the amp's GND terminal.
4. Select PHONO on the amp and start at low volume.

Turntable with built-in preamp to a line input

1. Set the turntable switch to LINE.
2. Connect to any line input: AUX, CD, LINE.
3. Do not use the amp's PHONO input in this case.

Turntable with no built-in preamp, amp with no PHONO input

1. Connect the turntable to the input of an external phono preamp, and attach the ground wire to the preamp.
2. Connect the preamp's output to a line input on your amp, receiver, powered speakers or soundbar.
3. Plug in the preamp's power supply.

MM vs MC cartridges and what your preamp must support

Moving magnet (MM) and the closely related moving iron types are the most common. They have relatively high output, user-replaceable styli on most models, and work with any standard phono stage. Most turntables sold as complete packages come with one.

Moving coil (MC) cartridges typically have much lower output and need a phono stage with more gain, or a step-up transformer, to bring them to a usable level. Many enthusiasts prefer them, but they are usually more expensive and the stylus generally cannot be swapped by the user.

A small number of MC cartridges are "high-output" and designed to work into a standard MM input. Check the cartridge's specs if you are unsure.

Settings you may see

• Gain: how much the stage amplifies. MC needs more.
• Load (resistance): MM cartridges are almost always designed for a standard 47k ohm load. MC cartridges vary, and adjustable loading lets you match the manufacturer's recommendation.
• Capacitance: some MM cartridges are sensitive to total capacitance, including the tonearm cable. A few preamps offer adjustment.
• Subsonic or rumble filter: reduces very low-frequency energy from warped records, which can make woofers flap visibly.

Grounding and hum: fixing the most common problem

A loud hum when the phono input is selected is the most common turntable complaint, and the cause is usually simple.

• Connect the turntable's ground wire to the GND terminal on the phono stage or amp. Loosen the terminal, slide the wire's spade or bare end under it, and tighten.
• Make sure the RCA plugs are fully seated.
• Keep the phono stage and its cables away from power transformers, power cords and wall-wart adapters.
• If the turntable has a built-in preamp and you are using LINE mode, the ground wire may not be needed; follow the manual.
• If hum continues, try connecting the turntable alone with no other sources attached to narrow down the cause.

Built-in vs external phono stage: is an upgrade worth it?

Built-in phono stages in turntables and amplifiers are designed to be convenient and are perfectly listenable. An external phono preamp can offer lower noise, more accurate RIAA equalization, MC support and adjustable settings, and you can keep it when you change amplifiers.

For most people starting out, use what you have first. Consider an external stage when:

• Your amp has no phono input.
• You want to try an MC cartridge.
• You hear noticeable hiss or hum from the built-in stage after fixing grounding.
• You have upgraded the turntable and cartridge and want the rest of the chain to keep up.

Cartridge and setup, meaning correct tracking force, alignment and a level platter, often make a bigger difference than the phono stage. A stylus force gauge and a basic alignment protractor are cheap tools that help.

Buying a used turntable or phono stage

Used turntables can be good value. Check that the platter spins at the correct speeds, that the tonearm moves smoothly, that the auto-return works if present, and that the stylus is not worn or bent. Budget for a new stylus unless the seller can confirm it is recent. If the deck has a built-in preamp, test both PHONO and LINE outputs.

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