Comparison NAD PP4 vs NAD PP 3i

The dynamic range of a phono stage is the difference between the maximum signal level it can produce and the maximum level of self-noise (which inevitably occurs in any electronic audio device). In a sense, this parameter is similar to the signal-to-noise ratio (see below), but in this case we are talking about the difference between the maximum signal and noise levels, and not between the average ones.

The greater the dynamic range, the more advanced the phono stage is considered (ceteris paribus). In top models, this figure can exceed 90 dB and even 100 dB. We only note that in universal devices (see "Intended use") the ranges for MM and MC may differ — the first is usually higher, and it is given in the characteristics.

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 output impedance in this case means the internal resistance of the analogue audio outputs of the phono stage. Without going into too much detail, the meaning of this parameter can be described as follows: the lower the output impedance, the less the voltage drops at the output of the phono stage (actual signal level) when an external load is connected.

There is an opinion that, ideally, the output impedance of the phono stage should be as low as possible (and the input impedance of the load connected to it, on the contrary, should be as high as possible). This is partly true, but in some situations, on the contrary, models with a high output impedance perform better. Therefore, this indicator in modern phono stages can be different — from a few ohms to several thousand ohms. The choice of the optimal value depends on the external load with which the device is planned to be used; there are many specific nuances here, they are described in detail in special sources.

— Level. The ability to adjust the level of the output signal (RMS). This function is used primarily to adjust the phono stage for an external power amplifier. Any such amplifier has a limit on the maximum input signal power, otherwise there is an overload with all the ensuing consequences (from sound distortion to electronics failure). This control allows you to avoid such situations: if the output level of the phono stage is too high, it can be lowered, and when connected to a less sensitive amplifier, it can be increased accordingly. Theoretically, due to this setting, you can also change the overall volume of the sound, but in fact this is highly discouraged, it is better to use controls specially designed for this.

— Input sensitivity. The ability to change the input sensitivity of the phono stage. For details on input sensitivity, see the relevant paragraphs; here we note that ideally its value should be the same or slightly lower than the input signal level. For example, for a 4 mV MM cartridge, a corrector sensitivity of 3 mV or 4 mV is allowed, but 5 mV will no longer be enough. Conversely, too low a sensitivity threshold can lead to system overload. This setting allows you to set the optimal value for a particular pickup.

— Input impedance. This adjustment allows you to select the optimal ratio between the output impedance of the pickup and the inp...ut impedance of the phono stage. For details on input impedance, see the corresponding paragraphs. Also note here that this function is especially important for MC cartridges (see "Intended use"), because. MM-heads usually have a standard resistance of 4.7 kOhm and do not require tuning.

— Input capacity. The ability to change the input capacitance of the phono stage to adjust it to other components of the system — in this case, the pickup and connecting wires. Recall that, ideally, the total capacitance of the corrector and wires should be equal to the capacitance of the "head", otherwise an unpleasant coloration and additional distortions may appear in the sound. Without adjusting the input capacitance, achieving this match can be very difficult. This feature is especially relevant for working with MM cartridges.

— Balance. Ability to manually distribute the volume level between the right and left stereo sound channels. In this way, you can "shift" the audible sound to the right or left as you wish. In phono stages, this function is useful primarily because on worn and/or poor-quality records, the balance is often knocked down, and in order to bring the sound back to normal, you have to resort to manual tuning. This setting can also be useful in other cases, for example, if the acoustics of the room itself lead to a balance shift. At the same time, we note that balance control is not a key function for phono stages: firstly, it can also be provided in other components of the audio system (receiver, power amplifier); secondly, additional adjustments complicate the device and increase the likelihood of sound distortion. As a result, this feature is practically not found in high-end models.

The presence of a noise reduction system in the phono stage. The general purpose of such systems is already clear from the name; in this case, noise reduction can work both with the amplifier's own noise (thus increasing the signal-to-noise ratio), and with extraneous noise from external sources (for example, the rustle of a needle on a record).

This function can be found in phono stages of various levels, from the most budgetary to the top ones. Accordingly, the quality of its work may also vary. Anyway, however, two points should be noted. On the one hand, noise reduction can really improve the sound, making it clearer. On the other hand, additional processing of the audio signal inevitably introduces its own distortions into it, and during the operation of the noise suppressor, the reliability and detail of the sound may suffer, and quiet fragments may “fall under the distribution” along with extraneous noise. Therefore, this function is often turned off.