RD770 Monstermat - Eventide Audio

The RD770 Monstermat was created to solve the problem of broadcasting in stereo to a predominantly mono audience. It did this by making sure that the tape head was aligned for broadcasting so that the audio played was in stereo, also solving the problem of tape phasing and noise on cartridge machines.

Monstermat stands for “MONoSTEReoMatrix,” and it recorded the sum of two signals on one tape track and the difference between them on the other, making the misalignment of the tape heads less relevant since the mono signal (L+R) would always be recorded together. When listening to a mono signal one wouldn’t hear bad frequency response or flanging. Full stereo was restored on playback and dematrixing, while old mono carts could be played on stereo machines with the full mono signal on both channels. However, the stereo listener would still experience some channel separation, but that would not be much of an issue unless the headphones were equipped with a quality receiver.

DBX Noise Reduction improved the signal-to-noise ratio of the cart machine. The automatically switching DBX Noise Reduction System made it so that both encoded and non-encoded carts could be mixed.

The unit was available in two formats:

Record/Play: Providing encoding and decoding for one cart machine

Play/Play: Can handle two cart machines in the play mode

RD770 Monstermat Front View.
The Eventide RD770 Monstermat. Note the 4 DBX Noise Reduction Cards.

Mentions of the Monstermat

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Interested in more RD770 Monstermat history? Check out our Flashback blog.