Phono stages boost the tiny voltage signal from a phono cartridge about a thousand times to line level voltage (such as from a CD player) and also apply a frequency equalization curve (bass boost-treble cut) to correct the frequency equalization (bass cut - treble boost) applied when cutting a record.
They vary in sophistication and performance from:
- a simple on board chip (so 'phono stage' can be checked off a list of functions)
- a dedicated internal board sharing the power supply within a preamplifier or integrated amplifier
- a stand-alone phono stage component with its own internal power supply
- a stand-alone phono stage component with its own separate external power supply.
As you might expect, the more expensive and sophisticated phono stages will make your records sound better in a number of ways - bass, soundstage width and depth, dynamics, air and clarity. The magnitude of this effect is not subtle because the delicate very low voltage signals involved are closer to the "noise floor" and so power supply, circuit board layout and screening become even more critical than line level components. The physical separation of the R and L circuits, balanced versus non-balanced, how load settings are implemented, and the purity of the power supply and potential interactions are all critical. The RIAA equalization that phono stages contain boosts low frequencies and attentuates high ones; an important factor in managing the overload and distortion characteristics of the circuit design.
Entry level phono stages are usually for moving magnet cartridges only. More expensive ones add moving coil capability while some are moving coil only. In those with moving coil capability some use internal step-up transformers prior to a moving magnet circuit design, while others are designed from the ground up for moving coil cartridges without using a step-up transformer. To cater to the different moving coil cartridge outputs, moving coil phonostages have a range of load and sensitivity options that will affect the sound.
At kemela we can demonstate how changing gain and loading settings affect the sound.