Comparison Rega Fono MC vs Rega Fono MM

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.

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.

The highest root mean square (RMS) output level that a phono stage can provide. Actual level may be lower depending on input signal level and gain

Recall that a phono preamplifier usually operates in the form of a preamplifier, boosting a weak signal from a pickup to a line level for transmission to a power amplifier. The minimum signal level sufficient to feed the power amplifier is about 150 mV; however, phono preamps usually provide higher values. This is done on the basis that the higher the intrinsic signal, the less it is affected by external electromagnetic interference. The maximum for modern phono preamps is actually 2 volts on the RCA outputs, higher values can be found on the XLR outputs.

In addition, some nuances of matching the phono stage and an external amplifier are associated with the output level; detailed information about this can be found in special sources.

The gain provided by the phono stage when working with an MM type pickup (see "Intended use").

This parameter describes how much the signal level at the output of the phono stage increases relative to the level at the input. It is traditionally written in decibels; you can convert decibels into "times" using special formulas or tables. Knowing the gain, you can estimate the actual level of the output signal when using a particular pickup. For example, if the characteristics indicate 35 dB (56.2x), and the “head” outputs 5 mV, then as a result, the signal level at the output of the phono stage without additional processing will be 5 * 56.2 = 281 mV. Accordingly, the input sensitivity of the power amplifier with which this model is planned to be used should be less than 281 mV (however, 150 mV is considered the standard minimum for such amplifiers).

Note that the output level of MM cartridges is noticeably higher than that of MC cartridges, so the gains for them are generally lower (although there are exceptions).

Input sensitivity of the phono stage when working with an MM type pickup (see "Intended use").

Input sensitivity is the lowest root mean square (RMS) signal level at the input, at which the phono stage is able to “perceive” this signal normally, process it correctly and amplify it. Accordingly, compatibility with the pickup directly depends on this indicator: the signal level from the “head” must not be lower than the input sensitivity of the phono stage.

Note that MM pickups are noticeably superior to MC pickups in terms of signal power, so the sensitivity threshold for correctors for them is relatively high — usually about 4 – 5 mV. At the same time, there are correctors with a higher "threshold of perception" — more than 100 mW; they must be connected through special step-up transformers or other similar equipment.

The input impedance of the phono stage when working with an MM type cartridge (see "Intended use").

Input impedance is the AC resistance at the Phono input. This is one of the parameters that determine the compatibility of a phono stage with a particular pickup. The general rule is that the input impedance of an equalizer should be greater than the output impedance of the pickup. And the most popular formula for accurate calculations is "10:1": the input resistance should be 10 times higher than the output resistance of the "head". In some situations, another impedance ratio may also be optimal; these points are described in more detail in special sources. However, in the case of MM, the standard option is just 4.7 kOhm at the “head” and 47 kOhm at the input of the phono stage.

The gain provided by the phono stage when working with an MC type pickup (see "Intended use").

This parameter describes how much the signal level at the output of the phono stage increases relative to the level at the input. It is traditionally written in decibels; you can convert decibels into "times" using special formulas or tables. Knowing the gain, you can estimate the actual level of the output signal when using a particular pickup. For example, if the characteristics indicate 74 dB (5010x), and the pickup outputs 0.5 mV, then as a result, the signal level at the output of the phono stage without additional adjustments will be 0.5 * 5010 = 1005 mV, which is more than enough for direct connection to power amplifier (the minimum level for this is 150 mV). At the same time, we note that among MC phono stages there are models with a rather low gain, designed for specific application formats — for example, to work as a preamplifier for an MM phono stage.

The input capacitance of the phono stage when working with an MC 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").

Input sensitivity of the phono stage when working with an MC type pickup (see "Intended use").

Input sensitivity is the lowest root mean square (RMS) signal level at the input, at which the phono stage is able to “perceive” this signal normally, process it correctly and amplify it. Accordingly, compatibility with the pickup directly depends on this indicator: the signal level from the “head” must not be lower than the input sensitivity of the phono stage. Otherwise, step-up transformers or other similar equipment may be required for normal operation.

Note that for most MC pickups, the signal level is several times lower than for MM; accordingly, the phono stages for them have a high sensitivity — in tenths of a millivolt. However, there are also models with a higher "threshold of perception" — more than 100 mW.