CD-4 Disc Demodulator JVC 4DD-5 . Please help.

[surroundme33]

Looks like your front to back separation may need further adjustment, when you get your Fisher disc adjust the signal with the front channels turned all the way down and adjust the separation control until you can just barely hear the tone. Don't forget that you are not going to achieve the kind of separation you are used to with digital media, with analogue sources you should expect anywhere from 20-30 db, depending on the cartridge. This means that you may still hear some sound bleed, but you normally wouldn't listen to only one channel at a time. Now, I can't tell from the wave forms what you're hearing, but if you could post a a sample, I'd be interested in hearing how loud the sound bleed is. Also, don't forget that you are dealing with a piece of electronic equipment that is at least 35 years old and no doubt it may not be performing to spec. Let me ask you this: do the chimes seem like they are moving around you or does the bleed blur the image so much that you can't tell where it is coming from? Also, is the sound distorted? You may have a disc that has a damaged carrier signal, though in my experience that usually causes a "gritty" sound.

Thanks Quadjoe for responding. I have posted a DTS version in a previous post (although this was recorded with the Grado Cartridge - the AT12Sa is similar. Here is the link again http://sendshack.com/download/4htqi64

And regarding bleed - it bleeds very loudly front to back - even if i place the adjustment in the hardly audible range. I am going to say (although i can't really confirm) that it sounds like an SQ with a very early decoder with poor separation. Please, listen to my DTS sample and let me know..

Thanks again..

 

[Doug G.]

Does the AT12Sa at least track better so you don't get any distortion or "sandpaper" sounds? I have an AT912Sa which is just a little newer version and it works well for CD-4 and I would expect your 12Sa to also.

It's very important that the top of the cartridge is parallel to the record surface so the VTA is correct. It is more critical to get this right on with a Shibata because of the long vertical (bearing) radius. The long contact area needs to be parallel to the groove modulations.

I track my 912Sa at 1.5 grams and the stylus is the same as on yours so that should work.

You may need to mess with the anti-skate setting to eliminate mistracking in either channel.

But yes, I would wait until you get a test record with tones on it. It's much easier to adjust the separation controls while there is a continuous tone. I'm glad Joe mentioned that you have only the rear channel active while you are adjusting for the minimum output - left first and then right. I forgot to expound on that \:^)

Forgive me if you are already doing most of this stuff. I'm just covering everything I can think of off the top of my semi-gray-haired head.

Doug

 

[quadjoe]

Surroundme33, I did listen to your recording, and I see what you mean. I can hear some front to back separation, but it isn't as good as it should be. There is a possibility that your carrier adjustment is off, which you will need to do with the Fisher disc when it arrives, there is a track for making this adjustment. Do the front to back separation controls seem to make any difference as related to their adjustments, or is it the same no matter where it is set?

 

[proufo]

If you get desperate, try opening the demod's enclosure and move the cables around.

 

[surroundme33]

Does the AT12Sa at least track better so you don't get any distortion or "sandpaper" sounds? I have an AT912Sa which is just a little newer version and it works well for CD-4 and I would expect your 12Sa to also.

It's very important that the top of the cartridge is parallel to the record surface so the VTA is correct. It is more critical to get this right on with a Shibata because of the long vertical (bearing) radius. The long contact area needs to be parallel to the groove modulations.

I track my 912Sa at 1.5 grams and the stylus is the same as on yours so that should work.

You may need to mess with the anti-skate setting to eliminate mistracking in either channel.

But yes, I would wait until you get a test record with tones on it. It's much easier to adjust the separation controls while there is a continuous tone. I'm glad Joe mentioned that you have only the rear channel active while you are adjusting for the minimum output - left first and then right. I forgot to expound on that \:^)

Forgive me if you are already doing most of this stuff. I'm just covering everything I can think of off the top of my semi-gray-haired head.

Doug

I will tell you something about the AT12sa - it really has a well-rounded beautiful sound. It's a little bright, but that's ok - i tend to favor that anyway. It tracks well, and i have tried every setting from .75 to 1.25 for vertical tracking, and nada..

I have made those types of setting adjustments you have mentioned. First with listening to the front Left channel and turning the screw adjustment so that very little sound of the Left rear channel is heard. However, no matter how much low i adjust it - sound is close to being equally as loud. Please, take a listen to the DTS sample post i made... you will hear what I am encountering.

Oh, and when you fasten the cartridge correctly to the headshell of the turntable, its hard to not align it parallel to the surface.

Thanks for replying douge G.. After tinkering with all the adjustments, my head is now fully gray!!:yikes

 

[surroundme33]

Surroundme33, I did listen to your recording, and I see what you mean. I can hear some front to back separation, but it isn't as good as it should be. There is a possibility that your carrier adjustment is off, which you will need to do with the Fisher disc when it arrives, there is a track for making this adjustment. Do the front to back separation controls seem to make any difference as related to their adjustments, or is it the samThe no matter where it is set?

Thanks Quadjoe for listening to the sample. You may be right about the carrier adjustment.. However, no matter how i adjust the carrier adjustment setting (it has 10 stops), it makes no real difference. The front to back separation controls act like gain controls. The ratio of sound from front to back is the same, no matter where i place it

I will continue to wait for the test record to arrive.. When it does, it's another round of testing.. If that fails, i think i'm giving up on cd-4 - as i can't afford to keep buying equipment in hopes that it works right. Also, i am not great at fixing electronics if they don't.

 

[surroundme33]

If you get desperate, try opening the demod's enclosure and move the cables around.

Thanks Pablo for replying. You know.. I did open the top of the enclosure, and i looked at the wires and circuit board inside. I don't know what they do, nor what is what or where. I did spray some compressed air, to clean some dust - but it was for the most part dustless. I put the cover back on, and much to my dismay... no difference.

 

[quadjoe]

You should definitely hear a difference in the sound when you adjust the front to back separation (there should be at least more/less distortion). I suspect you may have a defunct demodulator unit, but first, do this: look at the back of the unit, and you'll see a 2 Ch/4Ch switch, for CD-4 it should be in the 4Ch position. If this is the case, remove the cover, and spray either TV tuner spray or Deoxit on the inside of the switch and move it back and forth several times, next spray the front/back separation pots and then move the adjustment screws (on the outside back of the unit) back and forth several times making sure you turn them their full range of adjustments. Do the same for the 30khz pot if you can reach it (don't spray the circuit boards). Put the cover back on, hook it up and make all of your adjustments over again. When I first got my 4DD-5 unit, when I turned it on all I got was a god-awful hum, cleaning the 2Ch/4Ch switch cured the problem (it still works to this day). You may simply need to clean the adjustment parts to restore performance. I don't know why I didn't think of this at first, it may not work, but it is worth a try. Let me know how it works out for you.

 

[surroundme33]

I want to thank everyone here for trying to help me with CD-4. I have FINALLY received the Fisher Calibration record for CD-4.. Looks like the people from Enoch Light and Project 3 are behind the LP concept. Very cool! :sun

I have managed to adjust the demodulator (at least the one I have here) as best as possible. I have tried everything from altering the VTA going from .5 pressure all the way to 1.5 grams pressure, I have used every combination of Anti-skate with the VTA. I tried 2 different shells for the arm.. I can't think of anything else I can do..

So, here is a DTS WAV (about 32 seconds) of the channel information. It is smeared all over the place. When i listen to a specific channel, i can faintly hear bleed from all the other channels - especially the one adjacent to that channel. For instance, If i am solely listening to Left Back - I can faintly hear Right Back, Right Front and the louder Left Front.

This whole experience has been disastrous for me. Especially monetarily. I guess the only way i am going to know for sure there is something wrong with my demodulator, would be to purchase another one.. Unfortunately, for right now i have over-exceeded my spending limit on e-bay :yikes

So, i will end my post here with a WAV DTS of the best i can accomplish with my demodulator and over 425 dollars worth in expenses.. Download the 30 second sample here http://sendshack.com/download/117cfsde

 

[surroundme33]

You should definitely hear a difference in the sound when you adjust the front to back separation (there should be at least more/less distortion). I suspect you may have a defunct demodulator unit, but first, do this: look at the back of the unit, and you'll see a 2 Ch/4Ch switch, for CD-4 it should be in the 4Ch position. If this is the case, remove the cover, and spray either TV tuner spray or Deoxit on the inside of the switch and move it back and forth several times, next spray the front/back separation pots and then move the adjustment screws (on the outside back of the unit) back and forth several times making sure you turn them their full range of adjustments. Do the same for the 30khz pot if you can reach it (don't spray the circuit boards). Put the cover back on, hook it up and make all of your adjustments over again. When I first got my 4DD-5 unit, when I turned it on all I got was a god-awful hum, cleaning the 2Ch/4Ch switch cured the problem (it still works to this day). You may simply need to clean the adjustment parts to restore performance. I don't know why I didn't think of this at first, it may not work, but it is worth a try. Let me know how it works out for you.

The pots are not dusty - they are actually very clear. There is no break-up of audio signal when i turn the knobs to indicate debris. It is generally a good idea to use de-oxit on vintage gear though.. So, if i run across some, i may give it a try.. Thanks for trying to help, i do appreciate it.

 

[quadjoe]

I just listened to your .wav file, and I think that it is much better than the chimes, though I haven't fed it to my receiver yet, I'm just listening on my headphones. Keep in mind though, that I'm listening through the DTS processor in my sound card (Creative Soundblaster X-fi), and my headphones are capable of producing a very realistic surround stage. I'm going to burn the file to a dvd in a few minutes and play it on my home theater system to see if I can hear the cross-talk that you are hearing. I'm definitely hearing the voice move around me in the headphones, though so that is a good sign, but also I have no way to isolate only one channel. It is a shame that you have spent so much for such disappointing results, CD-4 is worth the trouble when you finally get it set up.

 

[quadjoe]

Surroundme33, sorry for the delay in posting my results from listening to your DTS file on my home theater system, but I've been having back problems which kind of ruined my weekend. I'm much better now. I see what you're problem is: the cross-talk between channels is very pronounced on the front, as the rear channels are decoding rather clearly, if at a little lower volume, but they are where they are supposed to be. Don't forget that you may hear a little cross-talk between channels as analogue sources are rarely better than 40 db in any format, far, far less than you'd be used to in the digital domain. That said, your front to back separation is off for the front channels and is allowing the sound to bleed to the rear. I trust that you followed the set-up procedures correctly, so, try this: back off on the front to rear separation a bit to see if it clears up. Like you, I'm beginning to get the feeling that your demodulator unit may be defective, which is a problem given the rarity of qualified repair people and limited funds for having them done. I'm going to keep researching to see if there is any other solution for you that won't require further outlay of cash. Best of luck to you.

 

[surroundme33]

Surroundme33, sorry for the delay in posting my results from listening to your DTS file on my home theater system, but I've been having back problems which kind of ruined my weekend. I'm much better now. I see what you're problem is: the cross-talk between channels is very pronounced on the front, as the rear channels are decoding rather clearly, if at a little lower volume, but they are where they are supposed to be. Don't forget that you may hear a little cross-talk between channels as analogue sources are rarely better than 40 db in any format, far, far less than you'd be used to in the digital domain. That said, your front to back separation is off for the front channels and is allowing the sound to bleed to the rear. I trust that you followed the set-up procedures correctly, so, try this: back off on the front to rear separation a bit to see if it clears up. Like you, I'm beginning to get the feeling that your demodulator unit may be defective, which is a problem given the rarity of qualified repair people and limited funds for having them done. I'm going to keep researching to see if there is any other solution for you that won't require further outlay of cash. Best of luck to you.

Quadjoe, i have done everything you have just suggested. What you hear in that DTS file is the best it's going to get with my demodulator. However, I have VERY GOOD NEWS :banana::banana::sun

Someone here has been reading my thread, and has volunteered to send me his personal unit for trouble shooting. When the unit arrives (it's another JVC 4-DD5), I will update with results.

BTW, hope your back gets better. Hope it's nothing very serious.

 

[quadjoe]

That is great news! I hope that you get good results with the other demodulator. If all of the record companies had gotten behind CD-4 back in the 70s, Quadraphonic Sound might have gotten off the ground. I always felt that the biggest impediment to the adoption of Quad was the lack of a disc standard. People just didn't want to have to figure out what format they were listening to and then selecting a switch on their receiver to get the proper decoding.

Thanks for asking about my back. I pulled a muscle, so it's nothing serious, and it is slowly improving.

 

[quadjoe]

Quadjoe, i have done everything you have just suggested. What you hear in that DTS file is the best it's going to get with my demodulator. However, I have VERY GOOD NEWS :banana::banana::sun

Someone here has been reading my thread, and has volunteered to send me his personal unit for trouble shooting. When the unit arrives (it's another JVC 4-DD5), I will update with results.

BTW, hope your back gets better. Hope it's nothing very serious.

Surroundme, I've been watching this thread hoping to hear how things went with the unit you got for troubleshooting. Any news yet? Please let us know, we're anxious to hear about your results.

 

[surroundme33]

Surroundme, I've been watching this thread hoping to hear how things went with the unit you got for troubleshooting. Any news yet? Please let us know, we're anxious to hear about your results.

Quadjoe, The unit has been shipped just this past Friday (9-19-2010).. I haven't received it yet. As soon as it arrives, I will continue with the tests. Thanks for the response. I have my fingers crossed. :sun

 

[The Quadfather]

Hey Surroundme33:
I have written many times in this forum about adjusting CD-4 demodulators. I use a 4DD5, and it's a fine demodulator. If you do a search for a post entitled "The Proper adjustment of a CD-4 demodulator" you will find one of these writings. Hope it helps.
The Quadfather

 

[surroundme33]

THe Quadfather: Thanks for replying to this thread. I did a search, however, I could not find the post you are referring too.. Can you provide a link? Thanks.

Quadjoe: I received the other demodulator later part of last week. I am still conducting some tests throughout this weekend. I am also learning a little more about how this CD-4 technology works. I will post my findings in best detail as I can when I'm done with the tests.. Thanks.

 

[sukothai]

I've found the latest rev of vBulletin's built in search function to be very poor and have begun using Google to search the site. The following search turned up Quadfather's post about 10 results down:

site:www.quadraphonicquad.com/forums The Proper adjustment of a CD-4 demodulator

 

[scifi]

https://www.quadraphonicquad.com/forums/showthread.php?10330-Proper-Adjustment-of-a-CD-4-demodulator