Such a coincidence that you ask, I was literally wondering the same thing yesterday. I suppose it would have to first check for cd-4 carrier, then check for presence of 90 degree OOP modulations for SQ, otherwise just assumes RM, probably can be fooled with certain recordings.Exactly how did this “Automatic Switching” work? I know that some high end tape decks have this for Dolby NR but I think that uses some kind of test tone that you have to insert via the deck at the start of the recording. How did a ‘computer’ figure out whether a recording was in SQ, CD4, or QS way back in 1974? Seems kinda fishy but I could be wrong I guess.
...How did a ‘computer’ figure out whether a recording was in SQ, CD4, or QS way back in 1974?
The ad actually mentions "analog" computer circuitry, which was definitely alive and well during that period, and would have been well-suited for the type of detection circuits furui describes above.
Interesting approach. Seems like Onkyo had genuine concerns about the level of consumer confusion in the quad market. Would be nice to know how well it worked in practice, teasing out all the details between the various matrix formats.
If the system automatically indicate if a non-quad stereo recording has SQ-like elements, that itself is interesting/useful because it provide a suggestion of which recordings decode more actively in SQ than RM, which is less common than the other way around.Would be nice to know how well it worked in practice
I had a very quick look at the circuit diagram and surprise, surprise there's no "Analog Computer"! All I could see was a relay that swapped between the outputs of the CD-4 Demodulator and the Matrix Decoder dependent on whether the CD-4 Carrier Pilot lamp was triggered. The Matrix Decoder was based on the Sony CX-050 basic SQ decoder ic with a bunch of transistor based front-back logic stuck on the output. Nothing clever at all.
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