Sansui Louie said:
Half-correct. The QRX X500's had HALF of what became the X001 Vario-Matrix equation. I believe they had the same ENCODER, but the decoder that the X001 series had was not fully developed yet.
You're actually about "half" correct SL.......QS encoding which creates the QS quad signal to be decoded WAS the same throughout the quad years from inception to the end. However........encoding has nothing to do with the receivers....none of which have the ability to "encode" anything! All the Sansui QR/QRX receivers dealt strictly with "decoding". And there are actually three variations of decoders built into the Sansui QR/QRX series over their production span:
QR/QRX-4500/5500/6500/7500 contain what we commonly refer to as the basic QS decoder as originally designed (also can be called the "RM" or regular matrix decoder). Capable of 3-12db of interchannel separation.
QRX-5500A/7500A and QRX-5001 have the partially developed vario-matrix decoder circuit containing two of the three custom ICs for full Vario-Matrix decoding. Their actual performance is more akin to the first generation decoders as the missing "control" IC is the biggest factor in increasing interchannel separation. Capable of 3-12db of interchannel separation.
QRX-6001/7001/8001/9001/777/999 and QSD-1/2/1000 decoders contain the full three "QS" IC based Vario-Matrix Type A decoder. This decoder was design limited by Sansui to 20db of interchannel separation. And, Sansui notes that "in theory" it is capable of infinite interchannel separation. After modification and recalibration I get 35db plus from these decoders depending on the source material.
In the "quad" community we refer to only the latter units as the "Vario-matrix" decoders.....simply because without all 3 of the "Vario-matrix" ICs actual decoder performance is tremendously limited in comparison.
Note that NOTHING changes on the "encoding" side of the equation...so "Vario-matrix" really only applies to the decoding of source material!
Sansui Louie said:
The difference on playback is about 12-15db of separation between the two rear channels.
Only partially true...."quad" interchannel separation is measured between any two speakers of a four speaker arrangement....so you have ratings for "between front left/right", rear left/right, front left to rear left, front right to rear right, and diagonally........front left to rear right and front right to rear left.
Interchannel separation IS NOT always the same in every direction! The basic QS decoder could only reach 12-15db of separation "diagonally" or between left front - right rear and right front - left rear. It's front left - right separation was only 3-7db.........and was considered the major "flaw" of quad decoding as it wasn't capable of maintaining normal stereo separation between the front channels. This is the key that CBS's SQ quad latched onto as SQ maintains normal stereo separation between the front channels while sacrificing separation between the other channels.
With the introduction of Vario-matrix Type A in 1974 Sansui achieved 20db of separation IN ANY DIRECTION.......and their notation of possible "infinite" separation applies only to the diagonally opposed channels. This development was key because during the quad years the best that the full logic SQ decoders could obtain was 12-15db of separation. I also think this is why Sansui chose to limit the separation to 20db.......as that bested anything else on the market at the time while maintaining a "stable" surround sound field.
Sansui Louie said:
Is it Vario-Matrix? Sort of. Put it this way...ALL QRX series receivers are Vario-Matrix and a big improvement over the QR series. The QRX-X001 series are the cream of that crop, with an improved DEcoder over the X500 series.
Not really.....Vario-matrix was an evolution of the basic QS algorithm designed specifically to increase the separation ability of the original design which they referred to as "QS Regular Matrix" and wasn't fully implemented until the introduction of the QRX-7001 in 1974.
Sansui Louie said:
Also, the errant reports of 35 watts per channel are not correct. This is a myth propagated by confusion with the QRX-7001, which WAS 35 watts per channel. It's not a linear comparison, just because they both start with a 7. In fact, the QRX-7500 was top dog of that lineage, above the QRX-6500 (which resembled the earlier QR-6500), the QRX-5500 (which resembled the QRX-7500) and the QRX-4500 (which resembled the QR-4500).
Sansui rated the QRX-7500 at variously either 28 or 30 watts per channel X4 (which is what we quad guys care about!
) into four 8ohm speakers. The same method for the QRX-7001 puts it at 35 watts per channel.
And at 30watts X4 the QRX-7500 WAS the top dog of the "first generation" QRX receivers.......but not the QRX-*001 series with their beefier amp/power supply sections.
Sansui Louie said:
The 4500's were 27 watts per channel. The 6500's were rated at 37 watts per channel. The 5500 was rated at 30 watts per channel. It would logically follow that their top of the line receiver at the time would be > 37 watts per channel.
I'd have to pull the literature to verify.....but the key is to make sure you're looking at their rating "X four channels" into 8ohms to make an apples to apples comparision.
Sansui Louie said:
Orion says 50, and I'd be inclined to believe them, as at the time, Sansui's TOTL 2 channel receivers were of the 50-60 watt class.
I have my own Orion book.......and its full of errors like that! It's a good reference but it certainly isn't definitive for technical specifications (or years of manufacture)! :thumbsdn:
QB
