A phono MM or MC board can optionally be used in the V 70 SE, V 70 Class A, V 80 SE, V 110 SE and HP 300 SE. This additional board is internally connected to the phono input, which is then no longer available as a high level input.
The technology of the phono equalizer amplifier is based on passive RIAA equalization with an active 2nd order subsonic filter. The phono amplifier is completely made of semiconductor technology. The subsonic filter suppresses low-frequency interference in the infrasound range caused by wavy plates and pickup/tonearm resonances. The passive, feedback-free equalization guarantees absolutely natural sound properties of the phono amplifier. Usual equalizer topologies with equalization within the negative feedback and without an effective subsonic filter only achieve moderate sound properties; subsonic interference also worsens reproduction in the fundamental tone range.
There are two phono boards to choose from, an MC or MM board. The boards can be easily inserted. This is done by the specialist dealer or a specialist workshop.
The MC board can be used without restrictions for almost all MC systems; it is optimized for low and medium output systems. The MM board has a standard input impedance and is therefore suitable for all high output MC and MM systems.
The principle of the record is based on mechanical scanning: music signals are cut into the record as an audio track and mechanically sampled by the pickup. In order to be able to integrate the entire frequency range from 20 Hz to 20 kHz into a sound track, low frequencies must be reduced and the upper frequency range must be increased. The ratio of boost or cut is defined and is referred to as RIAA equalization.
A phono amplifier must therefore be able to reproduce the RIAA equalization exactly in order to avoid tonal distortions. An accuracy of 0.5 dB across the entire frequency range and channel equality of 0.1 dB are minimum requirements.
Subsonic filters
In addition, the Phono RIAA is equipped with a subsonic filter (-3 dB at 15 Hz).
Wavy records and unfavorable pickup/tonearm combinations can lead to significant low-frequency interference that affects bass reproduction. These low-frequency levels can be attenuated with the switchable subsonic filter. The corner frequency is outside the audible range at 15 Hz.