CD-4 - The thin line between success and failure, but still in the fight!

[Quad D]

I bought a pair of QSI-5022 chips just for the heck of it. I was thinking maybe I could build a demodulator based on this circuit:
https://www.sm5cbw.se/sm5cbw/rt/ca754.htm
Would this work for strain gauge?
If anything they will probably sit next to my spare Tate chips as quad memorabilia.

It will work but you will need to build a biasing circuit for the strain gauge bias, is is external to the IC,

 

[Sonik Wiz]

I bought a pair of QSI-5022 chips just for the heck of it. I was thinking maybe I could build a demodulator based on this circuit:
https://www.sm5cbw.se/sm5cbw/rt/ca754.htm
Would this work for strain gauge?
If anything they will probably sit next to my spare Tate chips as quad memorabilia.

Speaking of CD-4 chips, I found some interesting info here in a previous QQ post:
https://www.quadraphonicquad.com/forums/threads/sansuis-for-cd4-good-bad-or-ugly.23570/#post-339282
Maybe someone has some updated info?

I did notice that only the Marantz 400B & Sansui used the Hitachi chips. And the HA-1328 chip listed for Sansui is actually a Vario-Matrix chip.

 

[Quad D]

Speaking of CD-4 chips, I found some interesting info here in a previous QQ post:
https://www.quadraphonicquad.com/forums/threads/sansuis-for-cd4-good-bad-or-ugly.23570/#post-339282
Maybe someone has some updated info?

I did notice that only the Marantz 400B & Sansui used the Hitachi chips. And the HA-1328 chip listed for Sansui is actually a Vario-Matrix chip.

Well, sensitivity of detection is not the issue with Sansui's, since to my surprise even the Shure V15 III with OEM elliptical stylus plays the CD-4 pretty well. So the V15 VxMR and many others.

 

[furui_suterioo]

I read on here that the QRX-90001 built in demodulator is the "holy grail" when tweaked, it was a post by QB.

 

[Quad D]

I read on here that the QRX-90001 built in demodulator is the "holy grail" when tweaked, it was a post by QB.

Possibly he meant the QS and Vario-Matrix processing, which can be tweaked for maximum separation (he called that adjustment "holy grail").

 

[furui_suterioo]

4) The "Holy Grail" CD-4 demodulator that I recently discovered in the 8001/9001 which is totally redesigned from the 7001.

This post is nearly 20 years ago now!
There was a more specific post but o can't find it.

Possibly he meant the QS and Vario-Matrix processing, which can be tweaked for maximum separation (he called that adjustment "holy grail").

 

[fredblue]

Possibly he meant the QS and Vario-Matrix processing, which can be tweaked for maximum separation (he called that adjustment "holy grail").

he meant it has the CD4-392 chip, also inside the JVC 4DD-50, Grundig Quadro, a couple of Akai receivers and at least one other model with auto carrier lock that escapes me now

 

[Quad D]

he meant it has the CD4-392 chip, also inside the JVC 4DD-50, Grundig Quadro, a couple of Akai receivers and at least one other model with auto carrier lock that escapes me now

I got confused by this "Holy grail" thing, it seems QB was using it for many different things in Quad.

 

[Sonik Wiz]

he meant it has the CD4-392 chip, also inside the JVC 4DD-50, Grundig Quadro, a couple of Akai receivers and at least one other model with auto carrier lock that escapes me now

My first CD-4 box was a Sansui QC-04. It was almost all discrete no special chips. It utilized the CD894A chip to demodulate. But it really looked like a more generic IC utilized for this than anything purpose built. Plugged in to my Sansui QS-01. Seemed to work pretty good but I smoked a lotta pot back then.

As you mentioned above the demodulator used in the Sansui QRX-9001 is the CD4-392. It seems like a very good chip & I found some specs on it. Preview:

https://www.elektormagazine.com/magazine/elektor-197512/5
Full story, scroll to pg 31 on the pdf:

https://worldradiohistory.com/UK/Elektor/70s/Elektor-1975-12.pdf

 

[Doug G.]

That sounds like quite a project! It's amazing enough that you found a pair of the QSI chips.

Demodulation with those chips should be independent of using magnetic or strain gauge cartridges, although I haven't looked closely at the schematic for an SH-400 democulator, lately.

The only real difference in the demodulator, as a whole, is that one supporting strain gauge cartridges must supply the voltage necessary for the strain gauge cartridges to work. It's in the form of a DC voltage bias on the outputs of the cartridge. There is not a separate line to supply the voltage. Nor is there a separate input in the QSI chip, itself, for magnetic or strain gauge input. Any differences are taken care of in circuitry before the chip.

If I have totally messed this up,due to faltering of my once brilliant mind, please let me know.

Doug

 

[steelydave]

I got confused by this "Holy grail" thing, it seems QB was using it for many different things in Quad.

Given the number of people "Quad" Bob Herndon ripped off and the number of shoddy "upgrades" he did to people's equipment over the years, I'd take any decade-old reccomendation from him with a meteor-sized grain of salt.

 

[fredblue]

Given the number of people "Quad" Bob Herndon ripped off and the number of shoddy "upgrades" he did to people's equipment over the years, I'd take any decade-old reccomendation from him with a meteor-sized grain of salt.

its an interesting idea and i'm not entirely sure it was his theory in the first place?

wasn't there that German Barry Manilow "This One's For You" shootout where they used the CD4-50 and Grundig Quadro, both having the chip?

the CD4-50 trounced the Grundig and sailed through the torture test (the CD-4 disc, not Barry's music! ) but either way, i have to say that little Grundig unit sounds quite different from my 4DD-5 and CD-400B, fuller somehow than the JVC and brighter than the Marantz and when its working, its great!

for me its major drawback (well there are two since the stock demodulator came with Din Connections for the Phono Input rather than RCAs) the other is a bigger issue for eternal fiddlers like wot i am! and that is the separation screws, which are quite recessed in the casing, small plastic affairs, difficult to access and adjust.. although the idea i think was that it was set and forget, not one for the eternal fiddlers among us!

 

[furui_suterioo]

That sounds like quite a project! It's amazing enough that you found a pair of the QSI chips.

It was more a quad-prepper impulse than actual intent to build a demodulator, at least not yet. I had never searched for them before today and they came right up, maybe they aren't too rare. The seller still has 2 left:
https://www.ebay.com/itm/3342516577...=2047675&ssuid=&widget_ver=artemis&media=COPY

 

[kfbkfb]

http://www.amazon.com/dp/B07L3G9TBS?pldnSite=1
I confess, I'm not a big fan of vinyl records (most of mine have been upgraded to CDs, but I kept all of my vinyl records and 45s), however, in many cases it's a very good way to get the quad/surround sound mix of an album (not a fan at all of Q8 tape cartridges).

I've generally used the Discwasher brand of record cleaner, but my newest (40 year old) turntable is belt drive and won't work with the Discwasher system.

I'm considering getting more involved with CD-4 (new cart, maybe the software CD-4 demod) and I want a way to thoroughly clean CD-4 discs.

Anyone tried the cleaner in the link (or have another recommendation)?


Kirk Bayne

 

[Quad D]

I have no patience for the ultrasonic cleaners (and am skeptical of cheap ones) and rack drying, so I use Record Doctor. It cleans pretty well (unless dirt is inprinted in grooves by very bad styluses), if you can tolerate the vacuum noise. The more elegant solution is VPI HW 16.5 cleaner, fast, quiet and efficient, but 4x more expensive, or Okki Nokki somewhere in between.

 

[edisonbaggins]

http://www.amazon.com/dp/B07L3G9TBS?pldnSite=1
I confess, I'm not a big fan of vinyl records (most of mine have been upgraded to CDs, but I kept all of my vinyl records and 45s), however, in many cases it's a very good way to get the quad/surround sound mix of an album (not a fan at all of Q8 tape cartridges).

I've generally used the Discwasher brand of record cleaner, but my newest (40 year old) turntable is belt drive and won't work with the Discwasher system.

I'm considering getting more involved with CD-4 (new cart, maybe the software CD-4 demod) and I want a way to thoroughly clean CD-4 discs.

Anyone tried the cleaner in the link (or have another recommendation)?


Kirk Bayne

That's as cheaper as I've seen an ultrasonic.
Tempting, at a price like that, if it's not a POS.
I mostly hand clean. Different brushes, G2 solution, lint free cloths and such. Depends on how dirty they are to start.
I loooooove shops that clean their inventory! A little perk.

 

[kfbkfb]

Quad D:
Have you bought any used CD-4 discs (I bought 2 for the first time ever this year, but they both seem to need a through cleaning, although I believe the used records stores did clean them [I asked one if they used an ultrasonic cleaner, they said no])?


Kirk Bayne

 

[Quad D]

Quad D:
Have you bought any used CD-4 discs (I bought 2 for the first time ever this year, but they both seem to need a through cleaning, although I believe the used records stores did clean them [I asked one if they used an ultrasonic cleaner, they said no])?


Kirk Bayne

I bought all of my CD-4 records used, most of them needed cleaning. Due to their limited availability I had to resort to ebay, with all of the goodness of sellers' very stretchable definition of "VG condition". Eventually they clean fine (I had to clean some of them twice), but one or two were maimed by the worn styluses and there is not much you can do here even with cleaning.

 

[kfbkfb]

Interesting about the worn stylus damage to CD-4 discs - from what I've read, a true Shibata stylus will contact a little of the upper 1/2 of the groove and pick up the audio & carrier clearly:

http://pspatialaudio.com/CD-4 wear.htm
https://www.sound-smith.com/articles/stylus-shape-information

I can think of one case where a CD-4 disc could become undecodable - a CD-4 disc played repeatedly with a badly worn Shibata stylus, which would damage the carriers too much.


Kirk Bayne

 

[Quad D]

Interesting about the worn stylus damage to CD-4 discs - from what I've read, a true Shibata stylus will contact a little of the upper 1/2 of the groove and pick up the audio & carrier clearly:

http://pspatialaudio.com/CD-4 wear.htm
https://www.sound-smith.com/articles/stylus-shape-information

I can think of one case where a CD-4 disc could become undecodable - a CD-4 disc played repeatedly with a badly worn Shibata stylus, which would damage the carriers too much.


Kirk Bayne

The tortured discs still had the carrier CD-4 signals, but it became very cartridge dependent will they play with or without sandpaper distortion. The record was like an abused flea market find, it would sound noisy and crackly on non CD-4 playback as well. Than it became my torture CD-4 test disc...... AT VM540ML, for example, plays it almost normally, like any worn record, with full CD-4 decoding and no sandpaper distortion.