Comparison Cambridge Duo vs Cambridge Solo

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 signal-to-noise ratio provided by the phono stage when working with an MC-type pickup (see "Intended use")

This parameter describes the relationship between the average output level and the average noise floor of the device. The higher it is, the clearer the sound is, the less extraneous interference it has. On the other hand, it is worth remembering that the overall sound quality provided by a phono stage depends on a number of other parameters. As a result, an advanced model with high sound quality may have a lower signal-to-noise ratio than a low-cost device.

Note that circuits for MC cartridges usually give a lower signal-to-noise ratio than for MM cartridges; this is due to the technical features of both.

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

The lower this indicator, the less distortion the phono stage gives, the more reliable the output signal is. It is impossible to completely avoid such distortions, but it is possible to reduce them to a level that is not perceived by a person. So, it is believed that the level of harmonics of 0.5% and below is no longer audible even to a “trained ear”. However, it should also be borne in mind that the quality of the audible sound is also affected by distortion from other components of the audio system. Therefore, the harmonic distortion of the phono stage should not just be below 0.5%, but as low as possible. Values in hundredths of a percent are considered a good indicator, values in thousandths and below are considered excellent.

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.

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

The 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". However, in some situations, another impedance ratio may also be optimal; these points are described in more detail in special sources.

Variable input impedance models are available, see "Adjustment" for details.

- RCA. Most often, in this case, a linear output is meant in the form of a pair of RCA connectors (“tulip”) - one for each stereo channel. This output is designed to transmit a line-level audio signal to other system components - for example, an audio receiver or active speakers. The RCA connector itself is considered standard for a linear interface; inputs of this type are available in most stationary audio devices.

- XLR. Another type of line output (see “RCA” above), in this case, built on XLR connectors. The main advantage of this interface is that it provides the so-called. balanced connection, allowing you to work with long cables without compromising sound quality. In addition, the connectors themselves provide a tight connection and are equipped with latches for additional reliability. On the other hand, they are noticeably larger than the same RCAs, and therefore are used mainly in professional phono stages, for which the mentioned advantages are key.

- USB (type B). Output for connecting a phono stage to computer equipment. The presence of this connector allows you to digitize audio compositions from records and other media (for example, from tapes and reels) and save them in computer memory for further processing or for transferring to a smartphone/MP3 player, for example.

— Coaxial S/P-DIF. Audio output...for digital sound transmission via RCA connector. This connector should not be confused with a “regular” linear RCA - in this case, one socket and a fundamentally different signal transmission format are used, it is also advisable to have a special shielded cable. In terms of capabilities, the coaxial interface is similar to the optical one and differs from it, on the one hand, in being more sensitive to interference, and on the other hand, in being a more durable and unpretentious cable.

— Optical. Another type of digital audio output that uses, as the name suggests, a fiber optic cable. The main advantage of this connection is its complete insensitivity to electromagnetic interference. On the other hand, the cable itself is quite delicate and requires careful handling.

- On headphones. Specialized output for connecting headphones directly to the phono stage. Typically uses a 3.5 mm mini-Jack or 6.35 mm Jack connector. Note that direct connection of “ears” in this case is provided not so much for ordinary listening to music, but for special tasks. For example, a DJ playing a set or a sound engineer recording music from a record to an external device can use headphones to constantly monitor the sound entering the phono outputs.

- Trigger. A service output that allows the phono stage to be used to automatically turn on other components of the audio system. When “waking up,” the corrector sends a control signal through this output, and devices connected to it with trigger inputs turn on automatically. This eliminates the need to enable each component separately.