Quote Originally Posted by emaidel
The answer to that specific question is an emphatic, "No." Today's 5.1 surround systems, and quadraphonic sound from the 70's have almost nothing in common, except that both provide sound from more than two point sources. Your friend's "quad" turntable is nothing of the sort, but most likely a standard turntable, fitted with a cartridge designed to play old "CD-4" records. It had a two-channel output that had to go into a "demodulator" for the four signals to be separated, and then fed into four different channels of amplification. Most quad receivers had a demodulator already built into them. There never was anything called a "quad turntable."

The other forms of quadraphonic sound (at least on records) were SQ and QS or "Regular Matrix, " or "RM" for short. they didn't require a special cartridge, but had to have their signal fed into a "decoder," and then also into four channels of amplification. Again, receivers had both SQ and RM decoders built into them too, but of widely varying quality and separation. And lastly, there were discrete four channel tapes.

None of the decoding equipment in today's surround receivers properly decodes SQ, QS or anything of the sort, and none have CD-4 demodulators in them either. I suspect also that few have even got phono inputs at all.

They do, however, provide far better isolated sound sources than most quadraphonic formats ever did, and also have center channel outputs (which no quad setup ever had), and provide a subwoofer output too (the term "subwoofer" didn't even exist in quad days.)

I have a 5.1 setup in my living room which came as a "package deal" when I bought my house. Insofar as accuracy and sonic fildelity go, it leaves much to be desired, but when it comes to listening to 5.1 movies, the effect is amazing. It consists of a cheapo JVC receiver with five so-called "discrete" outputs, each capable of 100 watts (I'm not holding my breath on the veracity of that one!), and a sub out. I think it provides a wonderful enhancement to the enjoyment of DVD rentals, nor is there any doubt where the sounds are actually coming from unlike days of quad when isolation of the four channels wasn't always particularly good. Howeverf, it pales in comparison to my far superior 2-channel system which I have elsewhere in my house when it comes to any serious listening.

So, yes, today's surround-sound receivers do a pretty decent job of separating a multitude of different sound sources (front left, front right, rear left, rear right and center), but most of us audio enthusiasts or audiophiles still prefer the "old-fashioned" 2-channel variety for serious listening. And anything labeled "quadraphonic" from the 70's just won't work through today's surround equipment. I may be wrong on this one, but the four discrete outputs from tape sources probably can't be used either, because I don't think today's surround-sound receivers have four separate inputs to accomodate them.

Hope all of that was helpful.
I agree with emaidel regarding turntables. There was never a quad turntable but Audio Technica created the Shibata stylus to track ultra high frequencies that were later demodulated along with the standard frequencies into the four channels.