Am I correct in my thinking?

So after many years of promising myself I dug out my old quad equipment this weekend and set it all up. Spent most of the time playing with the JVC 4dd5 demodulator. I do get the " Radar " light to come on but when it comes to nulling out the rear channels, no null, the control acts like a volume control. NO rear channel information, just duplicates the front information. Tried the demodulator in the Sansui receiver, exactly the same problem. I bought one of those " Saunders" CD-4 carts a few years ago, just got around to installing it this weekend.
My thinking is that it is not reproducing enough of the above 30KhZ information to supply the unit with the L-R information. My turntable does have the correct low capacitance cables ( it worked back in the 70's) and I am using the cables that came with the 4DD-5. Any thoughts on getting the thing to work, or any suggestions on a reasonable priced cartridge...I guess I am out what I payed for the Saunders cartridge.Thanks in advance.

Calling all Quad techies :bump:

First, we need more facts, such as: what amp/receiver are you using. And most of all, make sure cables, cart and speakers are correctly wired up so that everything else lines up correctly (don't forget to make sure your speakers are connected properly lest you have phase issues).

As for the demodulator, the JVC 4DD-5 was not, IMO, nearly the best CD-4 demod you could have bought at the time. I found this out back in the day, because my first demod was the Sylvania DQ3700, which was the 4DD-5 under another name. It would decode decently but only under optimum conditions, and that included having the Shibata stylus and cart and a good, powerful amp to match.

I need you to verify this much about the 4DD-5: it should have a back plate with (from left to right): 2CH Direct Out with an on/off switch (which for 4-CH playback should obviously be set to OFF); PHONO IN; 4CH OUT; CD-4 Adjust screws. These should be manipulated so as to balance your front and rear speakers to your needs and preferences. Finally, under the unit is a 30KhZ LEVEL screw with 0-10 adjustments on the circumference. THIS adjustment may be important, because the cart and stylus you're using at this time may not line up with the original factory spec, so you try to compensate for any lack of separation or distortion by taking a screwdriver and moving the screw (which is factory set at 10) to 0, and adjusting by increments to see if there is any sonic improvement. A lot of hassle, I know, but often the cart and stylus are the villain here, since despite claims don't always track CD-4 discs properly (and some CD-4 discs will NEVER track properly).

This all assumes that the demodulator is the problem, but how your system and cart are wired--or the condition of the amp/receiver--may be the culprit. The only way to determine the issue is to experiment.

ED

My Ed Saunders CD-4 cartridge has worked fine through my Sansui QRX-9001 demod. I wouldn't count it out as bad quite yet.

I would expect SOME kind of CD-4 performance from the Saunders cartridge even if it is not the best and from what I've read from several users like Gregg, it should be fine.

The radar lighting up is just the beginning. That just indicates the demodulator is getting some level of the 30kHz carriers. There may not be enough to enable the demodulator to strip the audio signals from the carriers. Adjusting the carrier level control may correct this using a signal off an adjustment record. I adjust mine for a strong, relatively distortion-free signal. It doesn't need to be completely distortion-free however. Just so it sounds like a pretty good sine wave. Then set the separation controls for minimum output from the back channels, one-at-a-time, using the appropriate signals from the record.

This procedure has always worked for me and if it doesn't, it probably indicates a problem with the demodulator. But, if you are getting duplicate stereo out of it, it seems unlikely there wouldn't be at least some CD-4 performance.

I should add that double stereo from a demodulator indicates that it isn't switching into 4 channel mode which would normally be because the demodulators aren't seeing the 30kHz carriers in spite of the radar being lit (although, normally, the radar being lit should indicate there is enough carrier level for the demodulators - it would depend on the circuit design). That could be due to either the carrier level not being high enough or there actually is a malfunction of the unit.

Doug

It should also be pointed out that you can get the red light indicator with some mono or stereo vinyl depending on many factors (groove wear can cause the demod to light up, for example) although generally, you don't get it consistently. But with virtually any CD-4 source, if you're not getting the red, it means there is something not working in the chain--which points to either the demodulator, or the cart/stylus. A problem with the amp is not relevant to the actual decoding process.

ED

Thanks for all the replies. My set-up..Realistic Linear Tracking Lab2100 or Sony Ps3000 turntables. Demodulators ..JVC 4DD5 or the internal demodulator in my Kenwood ( not Sansui ) KR9940. I have switched between combinations of turntables and demodulators. Saunder cartridge switched between the two turntables.
Here is the problem. with either demodulator or turntable I can get the " Radar " light to come on. Using the " Warner - Electra - Atlantic Demo Quadraphonic" demo LP, using the adjustment band that sets the cd-4/ channel adjustment the control acts as a volume control controlling both front & rear at same time. When the channel id band is played, the front and rear signal is reproduced in both the front and rear. Using the band for adjusting the minimum distortion of the carrier, the control does work.. On the 4dd5, the 2 channel direct out is off. The last thing that I tried was to play a never used CD-4 disk, the results - the same as before. I also get the same results if I replace the Saunders cart with the generic Audio Technika cart that came with the Lab 2100.
Any suggestions ..on how to proceed. I would hate to have to buy a new cartridge but I will if I have to. Anyone have experience with the Grado carts. I can't remember the model but it seems there was a "gold" or "silver" with a response up to 50KhZ. Thanks again.

Based on your explanation, it sure is pointing to the cartridge because that's the common component in all of your trials. It's still strange, though. I can usually get some kind of CD-4 performance from even stereo cartridges as distorted as it is. In your case, as I said before, it's like the demodulators aren't even switching to CD-4 mode but staying in double stereo.

Doug

Doug... I have reached the same conclusion. I rigged up a set of ear buds to left front and left rear channel. there is a slight amount of separation between front and rear. Pretty much the same results with the cartridge that came with the Radio Shack turntable and the Saunders cartridge. No distortion just very poor separation. I guess I could be working with two bad demodulators, at this point it may be time to give it up. Don't want to invest $200.00 or so for a cartridge that may or may not solve the problem. Thanks to all for the tips.

Well, I wasn't quite ready to give up so I dug out the Pioneer CD-4 decoder board I rescued from an Ebay "parts only" purchase. Built a power supply board, hooked it to the "Saunders" cartridge...Problem was TWO bad decoders. The Pioneer board has a bad right front/rear output (the chip that also is the noise reduction) but at least I have cleared the cartridge as the problem. Now if I can find a HA1336 chip I will be in business. Thanks to all.

Yes, unfortunately, these components are about 40 years old and CD-4, with it's tuned circuits, is even more likely to fail than regular solid state equipment from that era.

I have been real lucky in that both my SH-400 and SE-405 work fine except the SH-400 does have a weaker output with MM cartridges in the left. There must be a slight problem in the left MM input circuit because it works great with Semi-conductor cartridges. I just use the SE-405 instead of the Technics for MM cartridges and it works perfectly.

Doug

Got real lucky..searched EBay and found a US supplier that had a few NOS. Should have within a week. Hope that will solve the problem. We shall see. Again, thanks to all.
Dom