Demodulator differences?

[captainwrong]

While I'm waiting to for my AT331 to get here, thought I'd ask a question I've been wondering for a while. Other than having a pot for carrier adjustement v.s auto adjusting is there much of a difference between different makes of demodulators? Just wondering of the CD-4 world has it's Tate or Variomatrix I should keep my eyes peeled for.

 

[The Quadfather]

It is my understanding that some demods are better than others. The JVC 4DD5 is what I use, and it's pretty good. Some prefer the Marantz demodulators to the 4DD5. I once had a Claricon demod that was rather poor, because the power supply was hummy, and there was no carrier level adjustment. It needed one, for it wasn't automatic, it just didn't have one. I probably would have installed one by now, but fortunately, I found a JVC instead. The principles of a CD-4 demodulator are simple and well understood by engineers. Not like matrix decoding ala Tate, which is proprietary. With CD-4, it is similar to the way a stereo signal is placed on a monaural FM radio signal. The system is discrete, so there is no "snake oil" decoding or enhancing. It is just simple science.
The differences between demodulators will manifest itself in the quality of the circuitry itself, (would it be a good sounding piece of gear if it was just a phono preamp?) and it's ability to accurately demodulate the difference subcarriers in each channel without distortion. A demodulator unit is actually two demodulators in one box that operate independently of each other. One for left channel, and one for right. Any demod will produce good separation, even a poor one. The question is, with how much distortion? A demodulator that is built as a quality piece of gear by a quality manufacturer will provide acceptable performance. The cartridge and stylus are actually more important, because if you don't deliver the signal intact, the demod can't decode it properly. Even the Claricon performed half decently, once I had provided it with a good signal. (and a better power supply). I believe with a carrier level pot, it could have acheived CD-4 nirvana. So, buy a demod with a good name and you shouldn't be disappointed. See "CD-4 equipment that works well" in this forum. Happy Hunting!

The Quadfather

 

[captainwrong]

Ok, that's pretty much what I thought. I have a JVC also and even with a Grado, I'm getting good results on some discs. Finally got my AT 331LP yesterday, but I was wondering if it would be worth it to upgrade the demod as well.

Thanks.

 

[The Quadfather]

Some say that the Marantz gives richer bass than the JVC. The one with the manual carrier adjustment pot is better. I use a JVC and I am happy with it. I might try the Marantz if I get a chance to pick one up cheap. I have a second 4DD5 that doesn't perform as well, and I attribute that to the idea that it hasn't been aligned properly. The first one required repair when I first got it, and at that time, I set the free run oscillator frequencies. Those of you who cannot reach CD-4 nirvana in spite of having tried all of the recommended things should consider having this done by an electronic technician. I wouldn't do it if you do achieve nirvana, because it is obviously set properly. Good Luck

The Quadfather

 

[sspsandy]

I have one of the JVC 4DD5 demodulators hooked up, and it gives me clear, clean, sharp sparation with plenty of bass. I heard that JVC put some kind of circuit in the 4DD5 that gave you better than 35db separation in all directions. I use the CD-4 copy of Hot Tuna America's Choice to see that it is balanced right, that album has sounds panning around the 4 channels all over the place. As good as DVD-A sounds being digital and all, the CD-4 setup holds it's own in the crisp sharp surround and audiophile quality dynamic range department. Add to that the fact that the discs are basically half-speed masters with excellent analogue fidelity, it is still my favorite surround format. As an experiment, compare the songs Love Her Madly and Riders of the Storm from the Best of the Doors Quadradisc with the versions on the LA Woman DVD-A, to my ear the Quadradisc just sounds better, and the quad mix is really superb.

 

[The Quadfather]

Glad to hear someone loves their 4DD5 as much as I do. I was beginning to have doubts. (am I missing something good?) I know what you mean by the quad mix being better. Put the quadradisc of Deep Purple's "Machine Head" against the DVD-Audio version. The mix on the quadradisc whups the DVD A hands down. The only thing the DVD-A has going for it besides fidelity is an extra song. (When a Blind Man Cries) They are both good, however, but I tend to listen to either the quadradisc or a DTS conversion from quad 4 track tape someone gave me.

The Quadfather

 

[captainwrong]

Yeah, now that I've got the right stylus, I'm thrilled with my 4dd-5. I may never go back to matrix again! :rollin:

 

[Obbop]

When I dabbled with CD-4 I used a Sansui QC-4 that seemed to work well. Never lost carrier lock-on even though I was using a so-so Pickering 5000 catridge.

During my quad research I found old magazine articles that told of new IC chips being used in demodulators made after 1974. Further info was unavailable so, if that reporting was accurate, one could assume that later demodulators would work better then earlier ones. Perhaps someone has peeked at the innards of an early and a lter demodulator to determine what differences exist in the chips used.

As to when the new chips entered the mainstream, I do not know. Perhaps with the introduction of new models?

 

[The Quadfather]

There were some fancy chips made especially for CD-4. The Technics SH400 uses these. They are no longer availlable, and I have heard the SH400. It's OK, but I like the JVC 4DD5 better. The chip it uses is a common type used in many demods. This chip is still available. So, if the improvements were made in the chip without changing the number, then theoretically you could improve an older demod by changing the chips and aligning the unit (setting the free run oscillator frequency). This chip was made by several manufacturers as far as I know.

The Quadfather