Features
The type of pickups ("heads") for which the phono stage is designed
— MM. Moving Magnet Pickups: As the stylus moves through the tracks, it vibrates a permanent magnet, which induces current in the fixed coils. Among the main advantages of such devices are simplicity and relatively low price. They provide a fairly high output level, which, in turn, simplifies the design and reduces the cost of phono stages. However MM-cartridges in general are somewhat inferior to MC in terms of quality and sound fidelity; however, these moments are largely subjective, moreover, they directly depend on the price category of the “head”. Note that some types of MC pickups (models with a high output signal level) can also be connected to phono stages of this purpose.
— MC. Pickups using a moving coil circuit — it is connected to a needle and during operation it oscillates relative to fixed magnets, due to which a signal current is created. Such pickups are said to be superior to MM cartridges in sound quality; at the same time, they are noticeably more complex and expensive. Moreover, the latter is also relevant for phono stages: they are difficult to design and require a high gain, since the output signal level of
MC pickups is usually low — less than 0.5 mV (there are exceptions, but very rarely).
—
MM/MC. Phono stages that can work with both MM and MC heads; the selection is usually made manual
...ly by means of a switch. For details about the features of both types of pickups, see the corresponding paragraphs. Also note here that such universal correctors are convenient, but they are often inferior to specialized models in terms of performance.Frequency range
The range of sound frequencies reproduced by the phono stage. When evaluating this parameter, it is worth keeping in mind several important points. Firstly, in this case, not the entire bandwidth is taken into account, but the range in which the uneven frequency response of the phono stage (according to the RIAA standard) does not exceed the value specified by the manufacturer. Secondly, the human ear is only able to perceive sound within the range of 16-20,000 Hz (in some people, up to 22,000 Hz). Ideally, the audio system should cover this entire range — otherwise, some of the low and/or high frequencies may be cut off; but to provide a wider range from a practical point of view does not make sense. Nevertheless, there are phono stages with quite solid performance, for example, 5 – 35,000 Hz. These specifications are usually a "side effect" of high quality audio circuits and are advertised by the manufacturer for promotional purposes.
Another point to consider when choosing is the frequency range of other components of the audio system. For example, it is hardly worth looking for a phono stage with a lower threshold of 16 Hz, if the power amplifier only supports frequencies from 40 Hz and higher.
As a note to this clause, the RIAA ripple present in the frequency range may be indicated. In most models, it is from ±1 to ±6 dB; the lower the value, the smoother the frequency response and the better the sound.
Input load capacity (MM)
The input capacitance of the phono stage when working with an MM type pickup (see "Intended use").
This parameter determines compatibility with a specific pickup. The selection rule in this case is as follows: the total capacitance of the phono stage and connecting wires must correspond to the capacitance of the “head”, in extreme cases, at least not exceed it (otherwise the sound will deteriorate noticeably). In order to simplify this matching, it may be possible to adjust the
input capacitance(see "Adjustments").
External power supply
The presence of an
external power supply unit(PSU) in the device.
Most often, the meaning of such an arrangement is to move the PSU, which is a potential source of interference, outside the case, to the maximum distance from the components of the phono stage. This is especially true for high-end models. In some cases, an external PSU may also be provided to reduce the size and weight of the device; this moment, on the contrary, is typical mainly for correctors of the budgetary level.
