Grundig CD-4 decoder - new to this - help please

Dear Quad people.
I am new to CD-4 and I bought a Grundig CD-4 demodulator. I have a SME arm, Nakamichi turntable and Ortophon MC20 super II cartridge. I have a surround system.
After spending the day making up din plugs for the Grundig, I have switched it all on and I get the green pilot light coming on when I put on a CD-4 record, which I bought recently.
There is four channels of sound - coming and going. It sounds pretty awful and I would like to know what I need to do to get this all working properly please.
The cartridge output is going straight into the Grundig CD-4 demodulator. I don't know what I should be doing from now on. The unit is opened up and I can see adjustment pots.
There is a pot for the PLL oscillator - I tried twiddling all the pots but nothing seems to improve. There is a 'left' and 'right' pots at the back.
I would be grateful for some advice please.
Thanks a lot.

There are questions I need to ask. First of all, you should have never tampered with the pots inside, unless you are an electronics expert with an understanding of CD-4. It's more likely that it was already closer to right than you are likely to get it by twiddling with the pots, unless someone twiddled before you. Having said that, your best bet is to try to determine where the pots were originally and set them that way. Now, close the cover. Next thing to do is to determine if the cartridge/stylus is right for CD-4. CD-4 has much finer modulations on the record, and if your stylus can't track them, you have no chance of getting good CD-4 sound. You will wind up with a sound that is often described as splattery or sandpapery. You cannot underestimate the importance of this. I use an Audio Technica AT440MLa cartridge with an ATN440MLa stylus. (what it comes with). It's relatively inexpensive, and there are others that work well also, but not just any phono cart will work. The main criteria are:

It must have a Shibata or a linear contact type stylus. Audio Technica's Microline stylus works well. Conical or elliptical stylii do not perform well.
It should have a frequency response out to 45KHZ on the high end. This is less critical since some cartridges have wider response than what the manufacturer claims. This is the case with the AT440MLa.
Note that some carts have a published response out to 50KHZ. It still needs a linear contact stylus to work. Linear contact is generally better than Shibata, being an improved version of it.

If you get the right cartridge/stylus, then you should have distortion free music. The left and right pots on the back are for the purpose of nullifying crosstalk between the main audio which contains the front + rear mix and the subcarrier audio which contains the front - rear mix that is used to extract the original channels in the matrix circuit. (do not confuse this with a matrix decoder, which is not the same thing) If the Grundig is like most other demodulators, then if you turn down the left and right pots on the back, then you will hear only the Front - Rear signal, known as the difference signal from the PLL circuits. It should sound hollow, like it's down in a barrel, but not splattered or distorted. At this point, see if you can achieve this before we go further. Because if you can't, then there is no reason to go further, you will not succeed. I will watch for your reply, but if I get busy and forget, I have written several posts about setting up CD-4 demodulators and you can check the archives. So work on that and tell me what you find.

The Quadfather

The Ortofon MC20 Super is an excellent CD-4 cartridge. It has a line contact stylus and excellent high frequency separation. The problem though, is that it is a low output moving coil cartridge that cannot connect directly to the demodulator. You will need a step-up transformer or prepreamplifier to raise the voltage to a level that the demodulator can use.

Quadzilla:
It would probably be helpful if you listed the make and model of a good preamp to use with his Ortofon cartridge. Not being familiar with the Ortofon, I did not know these particulars, or if it is suitable for CD-4. But if it's a good CD-4 cart, then he's got that part out of the way. On the other hand, the AT440MLa does not need a preamp to work with a demodulator, and might be cheaper than a high end preamp. His call.

We were the largest Audio Technica dealer in the US. They are great cartridges and a great value. It was all I used for several years, UNTIL we became an Ortofon dealer. Ortofon makes moving magnet cartridges, many of which would be suitable for CD-4. No transformer needed for these. I use an Ortofon moving magnet cartridge on my third system.

As Quadzilla suggested, most Ortofon Moving Coil cartridges would require a step-up transformer or a pre-pre amp. For thirty five years, Ortofon MC20 is what I've used for 2ch and CD-4 on my two main systems. I use the T-20 transformer (similar to Verto) and the MCA-76, which is a pre-preamp. It's older and requires AC power. There are a few Ortofon Moving Coil cartridges which are high output, and don't require a step up device.

The improvement, even over an Ortofon moving magnet cartridge is absolutely stunning! The transformer (or pre-preamp) is an extra piece of gear and a couple minutes of extra wiring. The subtle nuances that will become evident and how open the sound becomes will be much worth the price. IMHO, you will not get a moving magnet cartridge to sound this good.

Ortofon page for step-up transformers: http://www.ortofon.com/products/transformers

These transformers are passive, and need no power.

Ortofon ST-80se transformer:


Ortofon Verto transformer:


Many models in the Ortofon MC Quintet and Cadenza lines would be suitable. Remember, you'll need a Shibata or fine line stylus (NOT elliptical) and frequency response to 45khz.

Ortofon MC Cadenza Black (w/Nude Shibata):


Ortofon MC Quintet Bronze (w/Nude Fineline):


Ortofon MC 3 Turbo (High Output w/Nude Fineline):


Finally, who would know more about cartridge design? Perhaps a company that makes cutting heads, which etch out the grooves in record manufacturing. Ortofon cutting head, which was used on many CD-4 LP's:

Dear Sirs
I am pleased to announce I have got the CD-4 to work very well. I figured that output might be the issue and I remembered i have an old Bang and Olufsen MMC1 cartridge in my store. Its a moving micro cross design with a Line contact stylus and sapphire cantilever. The output of this goes straight into the Grundig. And it worked!! I figure for me to use the Ortophon, as mentioned above, requires step up transfomers. For now, it will be easier for me to get a new headshell for my SME 309 arm, so I can swap cartridges over if I want to play CD-4 discs. Are you saying the sound quality will improve if I use the MC20 super? The general sound of quad I have is fully discrete. Its all there. Incredibly it seems to work even at 45 rpm!!! (How?) I thought the decoder had a fixed phase loop lock at 30khz. Obviously it can lock at 40khz too. I bought 7 discs and apart from two, the rest are pretty cheesy. Was there any really decent music made in CD-4 and till what year?
Thanks a lot for your help so far. Regards The Prof.

Quad Linda said:

...
Many models in the Ortofon MC Quintet and Cadenza lines would be suitable. Remember, you'll need a Shibata or fine line stylus (NOT elliptical) and frequency response to 45khz.

Ortofon MC Cadenza Black (w/Nude Shibata):


Ortofon MC Quintet Bronze (w/Nude Fineline):


Ortofon MC 3 Turbo (High Output w/Nude Fineline):

Click to expand...

Are they all nude? What would be the difference between nude and non nude?

Nude is when the diamond is one piece and attached to the cantilever. Non nude is a diamond tip on a base, attached to the cantilever. (An extra interface). Or so I believe..

Hey Quad Linda:
That's some good info you posted there. How about some prices on those carts. After this recession is done, I might want to upgrade if the Ortofon is that good.
Hey Prof:
I am glad to hear that you got the Grundig to work. So you have good discrete quad without distortion? How did you do with getting the pots back where they were supposed to be? Some demods have paint or magic marker marks on the pots making it easy to set them back The PLL should free float at 30KHZ (that is , without input signal or locked condition), in case you want a more accurate adjustment on those, if you can find a low frequency range frequency counter. A lot of of them are made for RF, and won't go that low. Adjustment of other pots is more complex and requires a service manual, especially the ANRS adjustments. Just curious, why would you want the PLL to lock at 40hz? There are no 40hz CD-4 records of which i'm aware. And as far as the type of music, A lot of rock was recorded in CD-4, as well as classical, and even a little country. The general time period for CD-4 was from about 1972 to 1978. The cheesy stuff you refer to was probably Enoch Light or Tony Motolla. There was a lot of that, and due to the cheese factor, they are the easiest to find nowadays. Look to Ebay for recorded material, search using key word "Quadradisc" you can use CD-4 also, but the search engines generally confuse it with CD. You can also use "Quadraphonic" or any of it's other spellings, replacing the second "a" with "i" or "o". You will get matrix recordings and tape recordings this way, but there will be some CD-4 recordings among them. By the way, UD-4 is a different system, and won't work with a CD-4 demodulator, but those are pretty rare, like chicken's teeth. But if you see one, leave it for the very few people who actually have a UD-4 demodulator. Incidently, the line contact stylus performs well for stereo and matrix quad records as well, so there is no need for shell swapping. Happy Listening!
The Quadfather

Pricing can be found at music direct or needle doctor. They aren't cheap.

Yes, we were saying that adding an Ortofon MC cartridge will be a quantum leap in fidelity. Kind of like when you got your first good car after trading in that beater. If you remove most of the weight at the end of the cantilever inside the cartridge, you will have a far more responsive device. What weighs less: a magnet, or a coil of wire which weighs less than human hair?

In moving magnet, the magnet rides at the opposite end of the cantilever from the stylus. Hence, it moves and the coils of wire are stationary. In moving coil, the coils ride at the opposite end from the stylus. The magnets are stationary and the coils move.

Yes, Prof, you are correct about nude stylii. Bonded stylii use a metal shaft attached to the cantilever. Nude stylii are affixed directly to the cantilever. Less to go wrong. If a bonded diamond comes unglued from the metal, you would be attempting to play your vinyl with a hunk of metal which isn't shaped like a fine line, conical or elliptial.

Yes, I see your point about the difference between a moving magnet and a moving coil. Weight is everything. But it seems to me that a moving coil design would be very fragile, with that thin wire attached to a vibrating object. How well do these carts endure, and can the stylii be changed, or do you just change the whole cart? My first stylus for my AT440MLa lasted 10 years. I am just breaking in the second one. Thanks,

The Quadfather

Most MC cartridges require being sent to factory for a new stylus. The coil has never presented a problem for me. I've owned over a dozen cartridges.

While there has been some that have had success with using MC carts for cd-4, it is not something that I would recommend be attempted by an amateur, or someone on a budget. I've attempted this twice now, with 2 cartridges that have appropriate stylus type and shouldn't have a problem with the frequency range, but was unable to get adequate results with either. The challenge seems to be with the step up part of the setup....from playing around with a marantz cd-400 which has a manual adjustment for the carrier, I think the issue I've run into is that the step up was stepping it up beyond the level that the demodulator can handle for cd-4, despite it being within the range that is normal for the cartridges I'm using.

One thing I learned the hard way was not to pair vintage ortofon step ups with new ortofon cartridges. Some guy on the phone for needledoctor.com assured me that the MCA-76 would pair perfectly fine with a rondo bronze. I later found out from exchanging emails directly with ortofon's support that no, this is not the case, their older cartridges were at a lower level, and so those step ups will be too much for a modern ortofon cartridge. So, while there is a cd-4 button on the MCA-76 which suggests that paired with an appropriate cartridge it should be a good setup for cd-4, that will mean tracking down a vintage ortofon cartridge to pair with it....and they ain't cheap. My biggest problem with trying to do cd-4 with MC at this point is that it takes trial and error with very expensive equipment, and after being burned twice, I'm done. Besides....we're dealing with a noisy format that has a limited frequency response at best....I have to question if the money and effort to put together a cd-4 setup with a MC cartridge, which it seems nothing was ever designed for this pairing to really work properly, is even worth it...will it really be that much better than what some really nice MM cartridges are capable of?

Although, I have been curious about how a high output MC cartridge would do. I was looking at the ortofon X5-MC, which looks like would be a good match, and without needing a step up may eliminate the issues I ran into. But, with a price tag in the $500 neighborhood....I didn't feel like taking the gamble, and decided to instead invest half of that amount in retipping the stylus on my trusty MM signet cartridge, of which I can no longer find a suitable stylus for. It has served me well, all of my conversions (except for 1 or 2 recent ones) have been done on this, and I think they speak for themselves.

I did play around with an AT440MLa, and have to say....I wouldn't recommend it. I suppose someone that needs an easy starting point might start here, but....it just doesn't perform perfectly. I did get some adequate results off of some of my Japanese imports....but some things gave me sandpaper on it that should be able to playback properly. I can't help but wonder if the 150MLX would be a better suggestion from Audio-Technica. I can't say I recommend it, being that it's only rated to go up to 30kHz. But, the 440MLa is only rated up to 20, and from what I've read online the 150MLX is inspired by the signet line, which I know I've yet to get anything to outperform my signet, so I would think that there's a good chance the 150MLX would do better than the 440MLa....but once again, that's an expensive risk. I also wonder how the Ortofon 2M Black would do....another one that isn't rated to go up as high as cd-4 requires, another expensive risk. Interesting considerations....but ultimately I decided to invest in sticking with what has served me well.

To the Quadfather - I am an engineer in electronics, with Pots I always return them to where they were originally. On vintage gear they benefit from a move to remake the contacts properly. I usually note the resistance before I do it of course, and the position.
The B&O MMC1 has proved to be far in excess better than my Ortophon, which may work better with some amplification. I made a small pre-pre amp based on a NE5532 chip to boost the output of the Ortophon, like a microphone amp. I haven't tried it yet because the MMC1 cartridge worked straight away. For the cartridge to work it has to be able to work up to 50khz. The MMC1 specs are +- 1db to 20 khz. Due to its tiny size, and sapphire cantilever and Line contact stylus it has a very high frequency response. The Ortophon MC20 series 2 goes to 40 khz which isn't enough it seems.
As for the 40khz synch, no, this is just that for an experiment I tried the CD-4 record at 45 rpm instead of 33.3 rpm. Amazingly the discrete 4 channel still works. I thought the frequency stability was designed for only 33.3 rpm, but it seems there is quite a range of speed tolerance. On switching off the motor the synch pilot light goes at about 20 rpm, then of course you start to hear the FM track as it decends into the audio band.
I have a german service manual for the Grundig. I read somewhere that it was a JVC design. Is this the case? Are there any ways of optimising it without a test record? If not is there a test record for hire?

Hey Prof:
The JVC 4DD5 circuit board was sold to Marantz and Sylvania to use in their designs, Sylvania used the JVC case as well. I have seen other rebranded JVC 4DD5's as well in photos. It is possible that the Grundig could be one of these. Post a photo of the circuit board (topside) and I can tell you if that is what it is. I don't know if JVC sold any of their other designs for rebranding, The 4DD5 was the most prevalent and was the design that JVC seems to have settled on, their most successful. It's a good demodulator. Since you are an engineer as am I, you are several steps ahead of the game as you can maintain your own equipment. That is a valuable skill, and getting more so as our equipment gets older. By the way, watch out for that glue that the japanese used to glue down large electrolytics. Especially in power amplifiers where there is some heat. It will over time corrode the leads of circuit components. Also avoid ROHS certified electrolytic capacitors. They just don't last. A severe liability in quadraphonics where longevity is an asset. I stand by the AT440MLa, It's a good entry level cart, Cost now is about $175.00 . It will yield good performance, though you have to track it a little heavy, about 1.75 grams instead of the recommended 1.5 grams. I get no sandpaper with mine. It tracks clean. It is a little bright though, something I have always acknowledged. Of course, if you want a high end cart, there are many available, as testified to by many on this forum, that do a superb job with CD-4, I have stayed with the 440MLa simply because I can afford it and I have seen no reason to change. It has performed well for me.

Great Quadfather - good info. At the moment I am learning the system. Would I be right in thinking the bandwidth dynamics are not as great as a regular record? The sound is quite clean, I don't know if the channels could be improved on, but its working. I am more familiar with SACD and DVD-A sound quality of course. I tried SQ and thought it very ineffective. I think its a joke to call it quadraphonic. Its not really is it? Anyway let me know what I can expect in terms of sound dynamics and frequency response. All the Quadradiscs I have seem very economical in the bass. I noticed the groove modulations are very low too compared to a normal record.

Hey Prof:
You are correct in thinking that the performance of a Quadradisc could be questioned, especially by young ears. Older ears, not so much. In order to make room for the 30khz wide carriers they had to cut the front + rear mix on the main audio off at 15KHZ. The carrier audio also has the same limitation. So the system cannot transmit anything to the speaker above 15KHZ. Some folks can hear that high, I could when I was young. I remember hearing TV sets that had a problem with the 15KHZ horizontal sweep oscillator. It isn't a pleasant sound. Nowadays, I get to laugh as others complain about it, at least as long as analog sets are still around. So, to me the 15KHZ frequency response limit is not a problem. I doubt there is anything up there anyway, except harmonic overtones. The CD-4 demodulator box is actually two demodulators, one for the left side and one for the right. Left Right separation is maintained with vector modulation just as it is with a stereo record, and the demodulators just separate front to back per respective channel. The demodulators are very similar to the way FM stereo demodulators work in FM radios. The main difference is that the carriers are crowded in closer to the main audio, producing that 15KHZ limit. The other difference is the difference signal before modulation is fed through an ANRS encoder to reduce high frequency noise. The demodulator has an ANRS decoder to restore the original signal. ANRS is somewhat similar to the old Dolby B system used on tape recorders of the era to reduce tape hiss.

As far as SQ goes, You will not find many SQ systems that can do a good job of retrieving the original 4 channels. SQ records start with a four channel recording and the encoder mixes it down to two. Phase shifting techniques are used in order for the decoder to extract the original information back to their respective channels. The trick is, how do you unscramble an egg? Only a few decoders can do it well, and it's still not as good as CD-4. But there is no frequency response limit other than what a stereo record has, and if you use your CD-4 turntable there certainly won't be any restrictions from the playback system. QS is a different system, but it uses the same techniques, just the phase angles are different. SQ was Columbia Record's system. There's a lot of recorded music on these systems that are not availlable on CD-4, so they are worthwhile.

The decoders that are known for performing well are:
The Audionics Space and Image Composer
The Fosgate 101
The Lafayette SQ-W (or L, I'm not sure which)

The others range from fair to "I can't hear any separation at all"

The worst are the Pioneer units. Most of the ones built in to the receivers and amplifiers aren't that good. Marantz receivers had a plug in module so that if advances came, you could easily upgrade. I think they produced only one upgrade. Audionics had intended to produce an upgrade for the Marantz receivers but they didn't survive long enough to do it. It would have been a good thing, because Marantz produced some mighty fine quad gear.

QS is Sansui's system, and the best decoders for that is the Sansui Variomatrix decoder. Note that not all Sansui decoders are Variomatrix. I have never had one, so I can't vouch for it, but I hear they're pretty good. Sansui allowed anyone to produce quad records using QS, but they had to pay to use their QS logo. So there were records produced under other markings such as Command Quadraphonic or it was referred by equipment manufacturers as Regular Matrix or RM.

Occasionally you can find an Audionics Space and Image Composer or Fosgate 101 on Ebay. Be prepared to lay your money down, for they don't go cheap. I have seen up to $2000.00 for the Audionics and somewhat less for the Fosgate. Both are Tate licensed systems and are very good.

To me the best example of a CD-4 recording is Joan Baez "Diamonds & Rust". Especially the song of the same name. She's an extreme leftist, but this particular album, unlike her other ones, does not have much political content, so it's enjoyable by those who don't share her views. And her voice is pure gold, a pleasure to listen to. Probably the worst CD-4 is Cat Stevens Greatest Hits, which is a challenge for any CD-4 setup. If you can track this record without splatter, don't mess with it, because you have it set up right. Happy Listening!

The Quadfather

I agree that the AT440MLa works well for CD-4. When it is new, there may be a bit of mistracking but as it breaks in, it becomes near perfect.

And, as far as the CD-4 bandwidth, heck there aren't that many people who can hear above 15kHz reliably anyway (especially among us original quad nuts) and, as Quadfather said, and it is definitely true, there are only harmonics up there. I think a lot of people who claim to hear a difference between a system able to reproduce to 20kHz and one to 15kHz are deluding themselves a bit.

Mainly, any differences heard between regular two channel records and quadradiscs is more due to limitations placed on the actual mastering and pressing operations. Like reducing the level to squeeze the information into the more outer grooves and reduction of lower frequencies in an effort to avoid mistracking of the ultra-sonic frequencies.

With a good system, however, these differences can be minimized and also, there are some CD-4 records, mainly later ones, which weren't as subject to those limitations as much and have full bass and higher levels. I believe they may have discovered it wasn't necessary to resort to such drastic measures to assure good tracking.

I haven't heard the Joan Baez record but I'll take Quadfather's word for it that it's a good one. I'll also mention "Sundown" by Gordon Lightfoot which is also one of the best quadradiscs of all time.

I do the same thing with pots before I turn them if I don't have a procedure. Measure the resistance and you can get them back exactly where they were.

Doug

You can always get a pair of graphic equalizers to up the bass a little bit.

The Quadfather said:

I have seen other rebranded JVC 4DD5's as well in photos. It is possible that the Grundig could be one of these.

Click to expand...

No, it's not. The Grundig is smaller in board design. And besides of the metal housing the printed circuit board has its own shielding box inside the housing.

-Kristian