CED VideoDisc and Player Discussion

[Vatch]

Dear All,

If someone has some knowledge or has owned different players, I was wondering whether the stereo audio is different or about the same in different models; for example the SGT200/250 vs. SJT300/400. The earlier Laserdisc players used better analog audio components and sound and I'm interested in whether this is likewise true with CED.

Good day,
Johnny

P.S. So many good movies!

[ketonic_dude]

That sounds like a question for John Stevens over at CEDatum. I do know the SKT models used different circuitry then the SJT models and since the K's came out after the J's I would assume they would be better or more updated. Not sure if it has anything to do with the audio. I would also a think that stereo sound is going to be the same for all the players. I don't think CED was too advanced in the sound department compared to a laserdisc. But I could be wrong.

[SelectaVision420]

in my opinion, all the stereo players are the same, its the disc you put in that has the differences, all the discs i have that are CX encoded are better than the ones that aren't... maybe its just me?
_________________
Sears 274 & 934(80150,10&11350),sft100,sgt250,sjt090,100,101,200,300,400,vp550, VP4000!
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[Vatch]

Thanks alot for the replies! It makes alotta sense that the disc matters most! I play records alot and wonder why this skipped my mind...Still, I would think that there would be differences (however minor) between the different player series as they used different type styluses and audio components I would think. From what I understand, all stereo CED's are CX encoded, the system was designed that way.

[cbertra2]

On my SJT 400 the CX logo cannot be found anywhere on the player. If the player had CX capability the logo would be on the player. I think RCA came up with its own CX decoding scheme to avoid paying royalties or maybe they only had to place the logo on the disc. My laserdisc players all have the CX logo on the player. Then this is just my guess.

[Vatch]

Huh, I never thought about that. Yep, all newer Laserdisc players I've seen have that logo (I have the old VP-1000 which did not have CX, though I have the R-1000 external decoder). From what I've read, all stereo CED players use CX for the stereo discs, though some discs aren't marked either. Perplexing, but fun stuff!

A good Memorial Day to you and all,
Johnny

[Vatch]

Dear all,

It seems this has now been pretty much all figured out (at least to my satisfaction)! I post the following in the hope that maybe some will find the following info. helpful, and also fun to read!

I wrote to CEDatum, as was the good recommendation, and Don (name Daxi Don here) has given permission to post his response about stereo players in general, and also the CX system.

The full correspondence follows (the CX paper .pdf files are not seeming to be included, but are also very helpful in understanding CX, if you must find them, I recommend CEDatum over me). I must add, that now that I understand pretty well the use of CX, I surely know why it was chosen here (and also with Laserdisc) over DBX, which I have seen posted by some who state that DBX should have been used instead.

My extrapolation: The CX system was created to do noise reduction and dynamic range expansion, and especially to do so without destroying the sound if used on a player without CX capability. A stereo CED (always CX encoded) would therefor still sound good on a mono CED machine, which were (and still are, to my knowledge) the most common players. Laserdisc did this as well, to thankfully keep the early adopters satisfied with good sound. The DBX system would have not have allowed for this compatibility.

The mostly full correspondence follows (now we also know why RCA didn't need the CX symbol on the player, for CBS created CX):


Johnny,

The info I sent you were handout notes from the CED Workshop ( June 2013) hosted by CEDatum.

Yes, you can post all or part of this info on the forum.

Don (Daxi Don is my CEDMagic Forum User name.)

Dear Don,

Thanks so much for this wealth of information! I really appreciate it and believe it or not, it all makes sense now!

A good day to you,
Johnny

P.S. if you don’t mind, can I please post your message on the forum (with reference to you, of course)?

On May 26, 2014, at 11:12, Cedatum <cedatum> wrote:

Hello Johnny,

RCA had a business relationship with CBS labs. CBS pressed CED videodiscs at their plant in Georgia. RCA received a license to use the CBS CX noise reduction system for CED videodisc. I am attaching technical information on the CX system. The design is entirely analogue.

All RCA CED players use the same circuitry for Stereo and Dual channel audio. The only difference is the PC board component layout in the different models. Japanese CED player manufacturers also included CX in their players per the CED license agreement with RCA.

The audio processing circuitry does include several adjustments that were made on the production line. CED players are now 30+ years old and it is possible that the some adjustments may now not be at the optimum settings. This may account for the perception that some players seem to be better or worse that others in sound quality.

The audio board adjustments are simple to do and info is included in the CED player service manuals.

Notes:

A/ There are several custom ICs used in the audio processing . CEDatum stocks these parts.

B/ The RCA "G' line players ( SGT200 and SGT250) have the audio on a separate plug-in board. This is convenient . If you suspect and audio problem with your G line player, you can just sent us the audio board for repair - We do not require the player.

C/ Good test disc. If the stereo on your CED player does not sound right, here is an easy system check. Play a dual track disc ( Jane Fondas Workout is an example) If the audio system is working correctly you should here the same level and quality of sound from Track A and Track B.


I hope this info is helpful. Don at CEDatum.

[Mayor West]

This is great, thanks for sharing!