This is understandable, because the phono stage is invisible. It does not have a tonearm to admire or a driver to inspect. It is a small box, or sometimes no box at all, that sits quietly between your turntable and everything else. But of all the components in a vinyl system, it is the one where the quality of engineering has the most direct and audible effect on what you hear.
If you have ever wondered why your records sound a bit dull, or slightly flat, or less alive than you expected, the phono stage is the first place to look.
What a phono stage actually does
When a stylus tracks the groove of a record, it produces an electrical signal. That signal is extraordinarily small. We are talking about millivolts: a tiny fraction of the voltage produced by a CD player or a streaming device. Before that signal can go anywhere useful, it needs to be amplified significantly and corrected for something called the RIAA curve. That is the job of the phono stage.
The RIAA curve requires a brief explanation because it is fundamental to how vinyl works and most people have never heard of it.
When a record is cut, the audio signal is not recorded flat. High frequencies are boosted and low frequencies are reduced. This is done deliberately, for practical reasons: boosting the treble and cutting the bass allows more music to fit on each side of a record without the groove becoming physically too wide to press. The trade off is that on playback, the process needs to be reversed. The phono stage applies the inverse RIAA curve, reducing the treble and boosting the bass back to the correct proportions, while simultaneously amplifying the entire signal up to a level that the rest of your system can work with.
Do this well and the result is accurate, dynamic and alive. Do it poorly and the result is exactly what many people describe when their vinyl system disappoints them: a sound that is slightly veiled, bass heavy, or lacking in the top end detail and openness they were expecting.
Do you already have a phono stage?
Quite possibly yes, and quite possibly it is not doing its job as well as it could be.
Many integrated amplifiers include a built in phono stage, accessible via an input labelled "Phono." If your amplifier has one of these, you are already covered at a basic level. But here is the thing about built in phono stages: the amplifier manufacturer had a budget for the entire unit. The phono stage is one component among many, and in a carefully cost engineered product it is often not the component that received the most attention or the highest quality parts. A separate phono stage, by contrast, is a product built entirely around doing this one job well.
If your amplifier does not have a phono input at all, you will need a separate phono stage. There is no way around this. Without one, the signal from your turntable will be inaudible at normal listening volumes, and whatever you can hear will be tonally incorrect.
The simplest way to check: look at the back of your amplifier. If you see an input labelled "Phono" (and sometimes a small ground terminal nearby), you have one. If all your inputs are labelled as line-level inputs (CD, Aux, Tuner and so on), you need a separate phono stage.
MM and MC: the cartridge question
There is a complication worth understanding before you buy anything.
Turntable cartridges come in two main types: Moving Magnet (MM) and Moving Coil (MC). They work on different principles and produce different output voltages, which means they have different requirements from a phono stage.
Moving Magnet cartridges are the most common. They have a higher output voltage and are straightforward to design phono stages for. Most built-in phono stages and the majority of budget to mid-range separate phono stages handle MM cartridges. If you have a standard turntable with an included cartridge, it is almost certainly MM.
Moving Coil cartridges have a significantly lower output. They require either a phono stage with a high gain MC input, or an additional device called a step up transformer (SUT) to raise the signal to a level that a standard MM phono stage can then process. MC cartridges are generally found on higher-end turntables and are the choice of more experienced listeners. They reward the additional complexity with a sound that many describe as more agile, more transparent and more dynamically alive.
If you are just getting started with vinyl, MM is the sensible choice. If you are already there and thinking about a significant system upgrade, MC is the direction the path eventually leads.
Built in vs separate: what the difference actually sounds like
This is the question most people ask once they understand what a phono stage does. Is the one inside my amplifier good enough? And if not, what does a better one actually give me?
The honest answer is that it depends entirely on the built in stage you already have. Some amplifiers, particularly from brands that take their phono stages seriously, include genuinely capable circuitry. Naim, for example, builds phono stages into several of their amplifiers and the quality is not an afterthought. A Rega Fono built into a Rega amplifier is similarly serious.
In many other cases, however, the built in stage is adequate rather than good. The capacitors are budget components. The power supply is shared with everything else in the amplifier. The gain is set at a compromise value rather than optimised for your specific cartridge.
Moving to a separate phono stage of reasonable quality typically produces an improvement that is audible within a few seconds of comparison. The soundstage opens. High frequencies that were slightly soft become more defined. The bass tightens and gains texture rather than just weight. Quiet passages in music become quieter and more present simultaneously.
This last point is about noise floor: the level of background hiss or hum that all electronics produce to some degree. Because the phono stage is amplifying a very small signal, any noise it generates gets amplified along with the music. A well designed separate phono stage with a good power supply is significantly quieter than most built in alternatives, and the result is that music emerges from a blacker background. Detail that was previously masked by low level noise becomes audible.
What to look for when buying a phono stage
If you are in the market for a separate phono stage, whether new or pre-owned, here is what to consider.
MM only or MM and MC? If you have an MM cartridge and no plans to change, an MM-only stage is fine and your money goes further on the quality of that single circuit. If you are running an MC cartridge or considering one, you need MC capability, and ideally adjustable loading to match the stage to your specific cartridge.
Build quality matters more here than almost anywhere else. The power supply is particularly important: a phono stage with a separate or well isolated power supply is almost always quieter than one sharing a smaller internal transformer with the rest of the circuit. Some phono stages have an external power supply as an optional upgrade, which is worth knowing about when you are comparing pre-owned options.
Brands worth looking for on the used market include Graham Slee, who build no-nonsense, well engineered phono stages at accessible prices. The Rega Fono series are excellent, particularly when matched with a Rega cartridge on a Rega turntable. The Musical Fidelity V-LPS is a compact and genuinely capable unit that turns up regularly at sensible prices. At a higher level, the Cyrus Phono Signature and the Naim Stageline are both outstanding and appear on the pre-owned market regularly enough to be worth watching for.
At the serious end of the spectrum, the Chord Electronics Symphonic and the Linn Linto represent significant engineering at a level where the phono stage stops being a supporting component and becomes an argument in its own right.
The bottom line
If you care enough about vinyl to be reading this, you care enough to pay attention to your phono stage. It is not a glamorous component and it is rarely the thing anyone photographs for social media. But it is doing the most difficult and consequential work in your entire system, amplifying the weakest signal by the largest amount, and the quality of that work is audible every time you put a record on.
A decent separate phono stage is often the single upgrade that produces the most obvious improvement for the least outlay. The pre-owned market is particularly strong here: a three year old Graham Slee or Rega Fono bought used will outperform a budget new unit at the same price without question.
If you are not sure what you currently have or what you should be looking at, get in touch. We know this territory well and we are always happy to talk through your setup before you spend anything.
For the serious listener : loading, topology and the transformer question
If you are already past the basics, here is where it gets genuinely interesting.
MC loading. Every moving coil cartridge has an internal impedance, typically between 2 and 40 ohms depending on the design. The loading resistor on your phono stage should sit at roughly ten times that figure: too high and the top end becomes bright and etched; too low and it rolls off and dulls. Most phono stages with adjustable MC loading offer values from 10 to 1000 ohms. Getting this right for your specific cartridge is not an audiophile ritual, it is a measurable frequency response adjustment. The Cyrus Phono Signature and Naim Superline both offer fine-grained loading adjustment for this reason.
MM capacitance loading. Less discussed but equally real. The inductance of an MM cartridge and the input capacitance of your phono stage form a resonant circuit. Mismatch them and you get a frequency peak, typically between 15 and 20kHz, that adds brightness without adding information. Correct capacitance loading, usually between 100 and 300pF total including cable, tames this. Most quality phono stages allow you to switch input capacitance values.
Active gain vs step up transformer. For MC, the debate between an active MC stage and a passive SUT (step up transformer) is genuine. A well specified SUT adds no active noise and some argue it has a more organic, lower distortion character. The counter argument is that a first rate active MC stage from something like a Linn Linto or Chord Symphonic is now so quiet that the SUT's character becomes a coloration you are adding rather than a problem you are solving. Both camps are right about something. The right answer depends entirely on your cartridge and your ears.
Active vs passive RIAA. Most phono stages implement the RIAA correction curve in the feedback loop of an active gain stage. A passive implementation places a passive filter network between two gain stages, which some designers argue has a more natural, lower phase shift character. The measured differences are subtle. The audible differences, for those who can hear them, are real.