MMC4000

The cartridge is all important. Even a superb turntable in a high specification record-based music system is totally dependant on the cartridge. The cartridge is the only component which comes into direct contact with the record and the one which transmits the complete sound picture. The quality - and the price - of a cartridge is partly determined by what is technically known as the 'Effective Tip Mass' (ETM). This is the weight of the diamond plus the weight of the cantilever - and the lower the ETM the better.

So how can something so incredibly light be so finely engineered? The MMC cartridge was a stunning example of Bang & Olufsen's continual insistence on quality. 'MMC' stands for Moving Micro-Cross, a design principle which resulted in the complete integration of all components - stylus, cantilever, coils and magnet became the patented moving-iron principle upon which all B&O cartridges were based. The MMC principle gave the finest groove separation and produced extremely accurate sound reproduction of records. The unique MMC system employed a cross-shaped armature which, among other advantages, guaranteed exceptional stereo separation since each channel moves on a separate axis.

The job of any pickup cartridge is to transform the record's physical profile (groove modulation) into corresponding electrical signals (which are then amplified or enlarged by the amplifier and turned into audible sound waves by the loudspeaker).

The MMC 4000 was in effect a renamed though slightly upgraded SP15 cartridge when it had been developed especially for the Beogram 4000. This pick-up cartridge was specially designed for use in Bang & Olufsen record-players with tangential arms such as the Beogram 4002. It can be use in other arms on decks from other manufacturers, with an adaptor.

It was designed to track SQ 4-channel quadraphonic-encoded matrix records and also tracked both mono and stereo records extremely well. It gave an excellent frequency rate with high channel separation and was fitted to Beogram 4000-4002-4004.

Quadraphonic sound

Bang & Olufsen produced two quadraphonic systems in the 1970s. The top model was Beosystem 6000 which comprised Beomaster 6000 and Beogram 6000. Beogram 6000 was a development of Beogram 4000 in that it was a tangential tracking turntable. It had an inbuilt CD4 decoder which was switchable. When 'on' it would detect the presence of the carrier frequencies and a display would illuminate on the record deck's display as '4ch'. The output of the Beogram was at line-level whether in 2- or 4-channel mode. The deck was attached to Beomaster 6000 via a 5-pin DIN lead with all the pins being wired. In Beomaster 6000 there was a replaceable board with a SQ decoder as standard. This was manually switchable. The operator therefore still needed to know the type of quad recording that was to be played. The purpose of the removable board was to allow upgrading should the record industry ever get its act together and find a common standard!

The stylus is an elliptical naked diamond, radii 5x17u.

Recommended tracking force is 1g.

Each MMC 4000 is designed as an integrated unit.

This meant that all critical components were designed and constructed as an entity in order to give optimum performance.

The stylus unit is not separately replaceable as it was part of the integrated unit.

Frequency range was 20-30,000 Hz ± 3 dB. Effective tip mass was a mere 0.5 mg and compliance was higher than 30x10-6 cm/dyne.


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Large photo

Manufactured: 1974 - 1980
Designer: Subir Pramanik
Colours: Silver

MMC4000 Product Specifications

Elliptical naked diamond
Radius of curvature 5 x 1,7 mm
Frequency range 20 - 25000 Hz+/- 1,5dB
Channel separation 1000Hz > 20dB
40 - 10000Hz > 20dB
Channel difference <1,5dB
Intermodulation <1%
Recommended stylus pressure 1g
Compliance 30 x 10(-6)cm/dyne
Effective tip mass 0,4mg
Output mV/cm/sec. 0,6mV/47kOhms