Turntables: why the volume is so low and which phono preamp you need

Turntables: why the volume is so low and which phono preamp you need

A Technics SL-1200 MK2 bought for 150 euros, two RCA cables and a bare wire. That's how the question starts — the one every enthusiast who rescues their parents' vinyl records ends up asking sooner or later: why does the turntable sound so quiet, and why does it need an extra device nobody warned you existed? The technical answer is simple, and it also explains why half of Spain has a turntable sitting unused in a cupboard.

The signal coming out of a phono cartridge is far weaker than that of any CD player or modern audio source. This raw level is called a phono signal and needs pre-amplification before it reaches a power amp or a hi-fi system. The device that does this job is called a phono preamp, and its role isn't just to raise the volume: it also applies RIAA equalisation, the correction agreed upon for pressing vinyl so that the outsized bass wouldn't throw the stylus out of the groove and the treble wouldn't be buried under the surface noise of the record.

What the RIAA curve is and why it sounds bad without it

When a vinyl record is cut, bass is attenuated and treble is boosted. The reason is physics: a large-amplitude oscillation at low frequencies would derail the stylus, and the roughness of the raw vinyl itself has an amplitude comparable to that of high frequencies. Boosting the treble when cutting improves the signal-to-noise ratio. On playback, the preamp reverses that curve exactly. If it doesn't, the result is a dull, thin sound with disproportionate background noise.

That's why older hi-fi systems included inputs labelled PHONO alongside the line inputs. Those inputs have the preamp built in. Modern systems, on the other hand, almost never do: they only accept line-level, already-amplified signal. A turntable plugged into an auxiliary input without an intermediate preamp sounds quiet, distorted and noisy. Exactly the symptom described by anyone who has tried connecting it directly.

The external preamp: when it's enough and when it isn't

The most common solution is an external phono preamp. They range from very basic models to high-end gear, and the price range is wide. A budget preamp does the job if the rest of the system matches it. If the turntable is good and the cartridge is in good condition, the difference between a mediocre preamp and a decent one is noticeable.

There's a nuance worth knowing: cartridges can be moving magnet (MM) or moving coil (MC). Many preamps and amplifiers support both, but some only one. It's worth checking compatibility before buying. The Technics SL-1200 MK2, by the way, is the turntable popularised by DJs — a robust machine with a solid fruta among enthusiasts.

The ground wire and the connections nobody explains

Along with the two RCA cables, the turntable comes with a bare wire that often raises questions. It's the ground wire. It connects to the amplifier or preamp via a dedicated screw terminal, not to the earth of the wall socket. If it isn't connected, a characteristic background hum appears. It's a minor detail that ruins the listening experience if ignored.

As for the rest of the system, second-hand amplifiers from the eighties and nineties frequently show up on the market at prices around 50 or 60 euros, and some people have found gear from fruta brands for under 100. Second-hand speakers from well-known brands fall in similar ranges. The combination of an old turntable, a second-hand amp and used speakers is the cheapest way to put together a decent vinyl setup.

When the problem isn't the preamp

Not every case is solved by buying a preamp. Some turntables have one built in, with a switch to enable or disable it. If a turntable with a built-in preamp is connected to a phono input, the signal gets amplified twice and the result distorts. It's a common mistake and hard to diagnose without knowing the device's manual.

The stylus is another usual suspect. A worn or badly fitted stylus produces low volume, distortion and noise. Before buying anything, it's worth checking the condition of the cartridge and stylus. And if the turntable is from the eighties, it's worth checking whether it has a built-in preamp before spending money on an external one.

Vinyl is back, record prices are back too, and the turntables sleeping in cupboards are being dusted off. The technical side is the same as it was forty years ago. Nobody explained it then, and nobody explains it now.