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TOSHIBA 4 channel QM decoder

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Wurly1

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Dec 15, 2019
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No reverberation unit is required to generate them after the fact, they already exist in the recording, which is why no quad decoder I’ve ever come across uses such a thing.
Of course substracting Left from right bring up the differences and reveal a lot of the recorded echoes and stereo effects.
Then you state the effects settings are nothing else than variations of the matrix equations to bring up more or less of these echoes effects.

The mystery of the little box is solved then.
It only contain some matrix circuits in a shielded enclosure.

i'm still puzzled by this diagram and the hard to read content of the first box
 

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J. PUPSTER

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Of course substracting Left from right bring up the differences and reveal a lot of the recorded echoes and stereo effects.
Then you state the effects settings are nothing else than variations of the matrix equations to bring up more or less of these echoes effects.

The mystery of the little box is solved then.
It only contain some matrix circuits in a shielded enclosure.

i'm still puzzled by this diagram and the hard to read content of the first box
I turned it, adjusted and blew up- looks like O (or Q) MD unit and - OM (or Q) effect switches.

OMG OMD.jpg
 

MidiMagic

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What the heck is QM Dolby? QM is neither Dynaco or Dolby matrix. Also from the Midi-Magic Quad Systems page:

If you refer back to that page & section it can be seen that QM involves both encoding of front & rear chs, & matrix decoding of both sets upon playback. The QM/EV4 is has a relatively wide front sound stage, narrow rear left to right, & good separation of front to back. That is neither Dolby or Dynaco.

The earliest Sansui decoders such as the QS-1, QS-500B, and others also had similar modes of operation. The Sansui had not one but two concert hall modes. These were easy tricks back then, various matrix blending, EQ tailoring & all done with out any delay or reverb added. You're right delay is common on modern receivers but that the Toshiba was not one of them. Dolby Matrix with delay had not even been invented then so there's no reason to expect QM would be in compliance with Dolby.

I base my comments on 50+ years involvement with surround sound & audio electronics.
If you read the entire page, you would find that I referred to the Japan Phonograph Record Association (JPRA) and the Electronic Industry Association of Japan (EIAJ). Each produced very similar standards for matrix recordings. These standards are the source of the labels used by many manufacturers:

- RM - Regular Matrix - Equal-separation basic matrix
- QM - Quadraphonic Matrix - Forward-oriented basic matrix
- PM - Phase Matrix - All SQ-related matrix systems
- CD-4 - Compatible Discrete - CD-4
- UX - Uniform Matrix - All UMX-related matrix systems

The title headings on my page are based on these categories, showing which standard applies to which matrix.

Toshiba simply said their decoder conformed to the QM standard. So do EV, Dynaquad, and Dolby Surround.

QX and XM are not standards of either JPRA or EIAJ. They were trademarks of Denon.

I have a Sansui reverb that has a spring box only 4 inches long. And it can be switched to send the output to L-R in the output.
 
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