This is a story about the step-up transformers that are necessary for listening to records, which are experiencing a resurgence in popularity these days.
Before we talk about MC step-up transformers, let's first talk about the basic method of listening to records. When listening to a record on a turntable (record player), the record needle is used to convert the sound information engraved in the grooves of the record disc into music signals, which are then played back.
Generally, the preamplifier of a pre-main amplifier or separate amplifier has a dedicated phono (phono equalizer) input for listening to records. The output terminal from the record player is connected to this phono input to listen to music.
There are two main types of record cartridges (record needles), MM (moving magnet type) and MC (moving coil type), depending on the power generation method used to convert the sound of the record into an electrical signal.
In the days when vinyl records were common in households, record needles were generally of the MM type. The MM type, with its high output voltage and easy handling, could be connected directly to an amplifier with a phono input to enjoy listening to records. For this reason, MM-type needles are inexpensive and durable.
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Another type of cartridge, the MC (moving coil) cartridge, is more complex and requires higher precision than the MM cartridge. The MC (moving coil) cartridge is more complex in construction and requires higher precision than the MM cartridge, but it has a better sound response and wider frequency range. Generally, MC cartridges are considered to be "expensive and high-performance," and are mainly used in the mid- to high-end class. In fact, audiophiles overwhelmingly use MC cartridges, and there is a wide range of products available.
However, due to its structure, the output voltage of an MC cartridge is lower than that of an MM cartridge, and is only about 0.1~0.3mV, less than 1/10 of the output of an MM cartridge.
Therefore, the volume is too low to be used in the phono input of an amplifier as it is. Therefore, a step-up transformer or head amp is necessary to raise the output voltage to the MM-type level without degrading the sound quality level.
Since it is dedicated for MC cartridges, it is also called "MC transformer" or "MC head amp.
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Step-up transformers are more widely used than head amps. They are available in a wide variety of shapes, sizes, and designs, and the prices are very competitive. The step-up ratio varies depending on the transformer's winding ratio, and there are two types of input impedance: HIGH (high) and LOW (low). Because the mechanism is simple, differences in the performance of the core and winding materials and the structure of the transformer have a large impact on the sound, but each has its own character and is characterized by direct and powerful reproduction.
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A head amplifier, on the other hand, uses amplifying elements (semiconductors, etc.) to electronically increase the input signal, so a power supply is required. In terms of sound quality, most of them are flat and have a wide range.
A step-up transformer has excellent noise immunity and stability because it does not have a power supply unit. However, depending on the installation environment, external influences may cause noise, and if the ground wire is not properly connected, a hum may also occur, so care should be taken. On the other hand, some head amps may require noise countermeasures around the power supply due to current flow.
When selecting a step-up transformer, there are two main types of MC cartridges: low (low) impedance type and high (high) impedance type.
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In addition to the phono equalizers built into preamplifiers and pre-main amplifiers, there are stand-alone phono equalizer amplifiers. Depending on the product, there are a wide range of models, such as those with MM input only, MC-compatible models with a built-in step-up transformer, and equalizers that use a large current output to provide ideal amplification for MC cartridges, so you can choose the combination and model that best suits your preferences.