CD-4.....close to perfection!

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gvl_guy

1K Club - QQ Shooting Star
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For the first time since I had my original compact Panasonic quad system back in about 1976 with the CD-4 demodulator built into the turntable, have I heard discrete quadraphonic sound from vinyl like I heard today. :SB The right cartridge, demodulator and nice clean album and....perfection! A special thank you goes out to one of the members of the Old School Quadraphonic Facebook page, (not sure if he's here on QQ) for helping me to acquire the semiconductor cartridge at an extremely reasonable price that makes all the difference in the world.

The Doobie Brothers The Captain and Me sounds pretty fantastic this afternoon, including the quiet passages in Clear As the Driven Snow, the last track on side 1 of the album (and yes, closer to the center, which is always harder to track.)
:51QQ
semiconductor.jpg
TechnicsCD4.jpg
Doobies.jpg
 
We should all keep remembering that this is an early 70's system, way ahead of its time, and sizable engineering challenge for what they were trying to do on the LP medium with the technology available at that time. It is a miracle it works as well as it does (when it works), you are basically tracking ultrasonic frequencies (very tiny modulations) as high as 45 kHz with a diamond pointed mechanical transducer racing through the soft vinyl.
 
We should all keep remembering that this is an early 70's system, way ahead of its time, and sizable engineering challenge for what they were trying to do on the LP medium with the technology available at that time. It is a miracle it works as well as it does (when it works), you are basically tracking ultrasonic frequencies (very tiny modulations) as high as 45 kHz with a diamond pointed mechanical transducer racing through the soft vinyl.
Not to mention that, particularly in the inner grooves, the wavelength of those frequencies isn’t much bigger than the vinyl molecules themselves. Extremely high precision plastic formation!
 
Not to mention that, particularly in the inner grooves, the wavelength of those frequencies isn’t much bigger than the vinyl molecules themselves. Extremely high precision plastic formation!
Speaking of inner grooves....
I pulled out my Quadrafile record & played the CD-4 side. When I purchased this I had phased out my Kenwood 9940 with CD-4, so this was almost like a virgin being played for the very first time. PF's Money sounded just as it should with perfect bounceaphonic mix and clean. What really impressed me was Tubular Bells as the last track. I will mention that the Quadrafile CD-4 disc does not have a huge lead out section/groove like most CD-4's do. It The length & cutting is just like a stereo record. Tubular Bells played clean all the way through, no sandpaper noise. Oldfield's voice moves around from speaker to speaker as he "introduces" the instruments. It does this with no ambiguity. In the right rear there is an instrument that sounds like a triangle but according to liner notes is a glockenspiel. This is exactly the kind of sound at the end of a record that I would expect to affected by CD-4 nasties but it is clear & mellow all the way through.

This leads me to re-think the CD-4 challenge. It seems most everyone (who cares about it) is trying to figure out the perfect hardware combo for the best CD-4 play back. Certainly that's part of it but most are also using vintage test and music records to evaluate this. I have Zappa's Apostrophe, Captain & Tenille, Melissa Manchester that is essentially good as new. Maybe others but I'm not doing a systematic search. They play back perfect through a Marantz 400B. So while hardware set up is important, focusing on that as always the problem might not be the solution.
 
I think Vivian Stanshall was the Master of Ceremonies on Tubular Bells? So his voice introduces the instruments.

Mike did the Piltdown Man vocals though! Apparently Richard Branson insisted Mike sing on the LP, so that's what he got. Funny :D

One of these days I'll find a CD4 decoder & find out what the fuss is all about. I want to hear the sandpaper!
 
I think Vivian Stanshall was the Master of Ceremonies on Tubular Bells? So his voice introduces the instruments.

Mike did the Piltdown Man vocals though! Apparently Richard Branson insisted Mike sing on the LP, so that's what he got. Funny :D

One of these days I'll find a CD4 decoder & find out what the fuss is all about. I want to hear the sandpaper!
Wow, Mr Gumma! Good catch. Considering I bought this album new in quad, after all this time I just ass-umed it was Oldfield's voice. I haven't heard of or thought in decades about Vivian Stanshall's name, not since listening to The Bonzo's. I think I still have Granny's Greenhouse buried in a box somewhere...

It's been fun listening to the Tubular Bells excerpts on the Quadrafile album. But I don't have much interest in playing the whole album again. Because Oldfield is nothing if not repetitious and a little goes a long way. Also, probably just like you I am concerned about catching the COVID Ommadawn variant.
 
Interesting test last night. I played some of the UD-4 tracks from the Quadrafile record. Over simplifying, UD-4 had an Ambisonic like 2 ch matrix as the base band and enhancement chs frequency modulated at a high frequency like CD-4. For more better details you can check this out:

http://pspatialaudio.com/matrix_h.htm
When I did this I had three surprises. The first is that the CD-4 RADAR lamp lit up. I had no idea what carrier frequency UD-4 used but it's either the same or close enough. Also playing the track Electronic Footsy, the positions were not great but definitely identifiable. In this test track there are wurbly-blurbly noise that moves to a speaker position, then it is identified by a voice (left front...) followed by a few seconds of white noise. And then the wurbly noise moves on. With each of these I could predict where the voice was going to call out the position identity. It wasn't sharp more like a basic QS/RM decoder but it did work. Lastly the bass was boosted significantly I have no understanding why this is but there it was. Boomy. I listened to a bit of PF's Money and it too was bouncy and seemed to carry the location info but like someone took a discrete method & turned the separation control down.

I was surprised at how very good the Ambisonic tracks from AP's Stereotomy played on the Surround Master in Involve/QS. I might have to try UD-4 through that method sometime.
 
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Understanding the differences between QS/RM, H, UD-4/BMX, and UHJ:

This is the Poincare Sphere (also called the Scheiber sphere) depicting stylus motions on a phonograph record, as seen from the right side.

- I (olive green) is in phase, and lateral stylus motion.
- O (violet) is 180 degrees phase, and vertical stylus motion.
- L (cyan) is left channel stylus motion at 45 degrees.
- R (red) is right channel stylus motion at 45 degrees.
- K (black) is clockwise circular motion (SQ LB).
- A (brown) is anticlockwise motion (SQ RB).

qsp-psax.jpg


QS uses I for front, R for right, O for back, and L for left.
UD-4 uses K for front, R for right, A for back, and L for left
H uses F for front, R for right, T for back, and L for left.
UHJ uses J for front, R for right, H for back, and L for left.

- All of these play each other's left and right signals the same way - full separation.
- QS and UD4 each play back none of the front-back separation of the other.
- H and UHJ are actually very close to each other.
- QS and H each play back half of the front-back separation of the other.
- UD-4 and H each play back half of the front-back separation of the other.
 
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