Designing an amplifier for signals from a record player is probably the most demanding task in analogue audio technology. The total amplification is 63dB, with MC even 83dB. This means that in extreme cases (MC) the input signal is amplified by a factor of around 14000 (!). In the simplest case (MM), this is still around a factor of 1400. The signal voltages coming from the turntable’s pick-up system are simply incredibly low, especially with MC systems.
The first challenge is to amplify only the useful signal and not any interference. However, because the wanted signal is so small, interference of any kind quickly becomes problematic. In addition, the inherent noise of the amplifier must be low. Both of these factors speak in favour of retaining our fundamentally balanced signal routing in the phono module and thus lead directly to the decision to use input transformers. Since a transformer is always a perfect “differential amplifier”, and unlike many electronic circuits this is also the case with high asymmetry, it provides a high degree of interference suppression at the input. Transformers are not uncommon for MC amplifiers and these also provide the first 20dB of gain, which corresponds approximately to the usual difference between MM and MC systems. To our knowledge, however, the idea of working with input transformers even with MM is completely new. However, because the source impedance is much higher with MM than with MC, no up-conversion takes place here and the signal passes through one-to-one.
In both cases, the balanced signal required for further processing is obtained very elegantly, even if the record player is connected unbalanced via cinch. However, almost all MC systems and some MM systems can also be connected balanced via XLR. This is highly recommended!
The input transformers, including the corresponding matching elements for capacitance (MM) and impedance (MC), are mounted on small plug-in assemblies. The following stages are then identical for both variants, MM and MC. As we believe that the widely used active RIAA equalisation has decisive disadvantages in terms of dynamic behaviour and therefore only measures better than it sounds, we rely on a classic passive RIAA equalisation in several stages, which are decoupled by linear amplifier stages. This provides inherent noise far below that of the record medium and, at the same time, a great speed in order to optimally follow the dynamic events in the music.