If you’re new to the world of vinyl records, it may surprise you to learn that you cannot simply plug your turntable into most sound systems, just as you might do with any other piece of audio equipment.
If you’ve ever tried plugging your turntable into the input marked as “aux” or “TAPE” on your sound system, you’ll likely notice that firstly, the signal is very weak, and secondly, it sounds exceptionally thin and tinny.
Before you can fully enjoy those sweet vinyl tones, your turntable signal must first pass through a phono preamplifier (preamp), either built into the turntable itself or as an external unit.
What is a Phono Preamp?
In a nutshell, a phono preamp (or phono stage) is an audio component that performs two critical functions. Firstly, it will amplify the signal level up to a level suitable for the standard AUX input on your stereo. Secondly, it will apply an equalization curve to inverse the standard frequency adjustment made during the record cutting process.
Let me explain further…
The first aspect is fairly simple to understand. The signal produced by a record cartridge is very weak; much lower than the standard signal level produced by most other consumer Hi-Fi electronics. A nominal output level from a phono cartridge is 1 mV (0.001 V). The Aux input on your stereo system requires a signal level of 100 mV (0.1V). To meet the required level, a typical phono preamp will boost your signal by 40 – 50 dB.
The second function requires a little more explaining. Records are cut with the bass frequencies reduced, and the high frequencies boosted. This equalization helps to permit longer recording times by keeping groove dimensions small, while also increasing sound quality and decreasing record wear. A phono preamp acts to equalize the signal in an attempt to bring it back — as close as possible — to the frequency response of the master recording. The entire process is referred to as the RIAA (Recording Industry Association of America) equalization curve, which became the general industry standard during the 1950s.
Which preamp do I need?
It depends greatly on your budget and cartridge type. Your turntable may have a built-in phono stage, in which case you’re good to go. Also, if your sound system has an input labeled “phono” with a ground screw next to it, there’s a good chance this input has a built-in phono preamp stage. However, in many cases, you will find that an external preamp will sound better than your built-in option.
There are two types of phono preamps: those designed to work with moving magnetic cartridges (MM), and units designed to work with moving coil cartridge types (MC). By far the most common cartridge design is moving magnetic. The output of a moving coil cartridge is even lower than that of a moving magnetic design, and there requires a higher level of amplification. Some preamps will cater for both designs, with a simple switch that adjusts the preamp accordingly.
Personally, I currently use a Radial J33 phono preamp, which is actually designed more for professional studio and live stage, and with that comes some great connectivity advantages – such as additional outputs for a laptop or recording device. For most home Hi-Fi setups, though, it’s perhaps not the most living-room friendly device in that it’s heavy duty in its construction and design.
For a more living room or listening space friendly alternative, there are plenty of options on the market, ranging from affordable options at the $50 price point to as much as your wallet can stand.
From here, there are some lovely sounding preamps from Cambridge Audio, some of which cater very easily for both MM and MC cartridges.
If you can stretch beyond the affordable category, brands such as Musical Fidelity offer a feature-rich design that tips into the realm of higher-tier audio at $1000. And yes, it doesn’t stop there; you really can spend as little or as much as you want on this, but that’s a topic for another day. For the average listener with a MM cartridge, a budget of between $200 and $300 dollars (£200 and up) is a great basis from which to start your search for a preamp that will serve you well for many years, and many LPs to come.