Confused about CD-4 Gear - will a modern cartridge with shibata work

[jji666]

Fellow Quad enthusiasts: apologies if the answer is buried somewhere in existing threads and my search terms didn't find it. But I have been reading extensively and not found a direct answer.

My question is, I have an Ortofon 2M Black cartridge with a Shibata stylus (on a Rotel RP-855). I've read that one needs a Shibata stylus for proper CD-4 decoding. However, I have also seen references to needing a "CD-4 cartridge" although it seems others are just using cartridges not designated specifically for CD-4 as long as it has a shibata stylus. Will my Ortofon 2M Black work?

Second question is I would really prefer not to bypass my current phono preamp, but I notice that CD-4 demodulators have phono inputs, not line level (like an SQ demod would). But I've also seen that some appear to have "direct stereo out" - so do these CD-4 units basically have a bypass to output the unequalized cartridge signal to a standard stereo phono preamp when not decoding CD-4? If so, would there be any degradation if the signal path is TT->CD-4 Demodulator->standard stereo phono premap when listening to stereo recordings?

Thanks in advance for the help!

 

[Doug G.]

Welcome.

Your Ortofon would probably work fine for CD-4 but the most important specifications are frequency response and separation. Not so much the stylus shape. The main reason for the development of the Shibata stylus was to enable tracking up into the necessary frequencies while maintaining satisfactory record wear.

It's just that, usually, an elliptical will not be able to track at 20kHz and higher while maintaining satisfactory separation at those frequencies.

A cartridge/stylus must have a response up to 45kHz and good separation up at those frequencies too because the two channels before demodulation must remain their own channels.

CD-4 cartridges are called that because they have a stylus that can track those ultrasonic frequencies and they also usually have coils in them at lower inductances to aid in the ultrasonic frequencies not being attentuated between the turntable and demodulator. Lower capacitance (100pF or less) cables help here too. Of course, this only applies to magnetic cartridges since these things don't affect strain gauge cartridges.

But, it is not magic or anything. CD-4 cartridges are only different in that they can operate in the ultrasonic area to get the signals that need to go to the demodulator to the demodulator. Several cartridges designated as standard two channel actually will work with CD-4. The AT440MLa being one of them. It has what is known as a line-contact stylus which is similar to the Shibata.

Yes, most CD-4 demodulators enable bypassing the demodulator and feeding directly into a phono input on an amp. or whatever. There are a pair of jacks on the demodulator you connect to the amp. and throw the switch on the demodulator to "Direct" or whatever the particular manufacturer chooses to call it. The signals from the turntable then go directly to the amp. There are just switch contacts through which the signals must pass so little signal degradation occurs.

Also, the term "demodulator" refers to CD-4 devices which turn 2 physical channel information into 4 channels of information. A matrix device (for SQ, QS, EV, etc.) is not referred to as a demodulator but, rather, a "decoder". Technically, a CD-4 device could also be called a decoder because it does "decode" the 2 physical channel information but, in the quad heydays, the two terms were differentiated so one knew to what was being referred.

Doug

 

[Disclord]

Also, the term "demodulator" refers to CD-4 devices which turn 2 physical channel information into 4 channels of information. A matrix device (for SQ, QS, EV, etc.) is not referred to as a demodulator but, rather, a "decoder". Technically, a CD-4 device could also be called a decoder because it does "decode" the 2 physical channel information but, in the quad heydays, the two terms were differentiated so one knew to what was being referred.

Doug

Back in the quad day, the mainstream magazine articles always seemed to avoid mentioning it, but the CD-4 system was, besides being discrete, also a matrix system i.e. a discrete matrix; it used a 4:4:4 matrix, which was absolutely required for stereo/mono compatibility, but it was not a lossy 4:2:4 matrix system like SQ (SQ -and QS - could more properly be called N:2:M systems because 4 inputs were not a film requirement, especially with the SQ Position Encoder - and 4 outputs were not a firm requirement; for decoding any number of speaker feeds/channels could be derived, if the decoder designer chose to do so - sadly, none did) But CD-4 IS a Matrix system too, just like FM Stereo and the now-obsolete BTSC Zenith/dbx Stereo system for television. They both used 2:2:2 matrixes for compatibility too. (Motorola's AM Stereo system uses a 2:2:2 matrix also as did RCA's Stereo CED VideoDisc)

 

[jji666]

Thanks for the quick responses! That's very helpful. The next logical question is, is anyone actually successfully using an Ortofon 2M Black with a CD-4 rig?

(As an aside, my reference to an SQ device as a "demod" was a typo - yes, decoder is the accurate term).

Thanks again!

 

[mferrocosta]

I have the same questions. I would like to know what kind of stylus contact could extract the information in cd-4 discs. I have interest in moving coil cartrigdes especially Dynavector Karat 17D3 wich has a channel separation of 30db at 1khz and frequency response going at 100 Khz

 

[Disclord]

I have the same questions. I would like to know what kind of stylus contact could extract the information in cd-4 discs. I have interest in moving coil cartrigdes especially Dynavector Karat 17D3 wich has a channel separation of 30db at 1khz and frequency response going at 100 Khz

You shouldn't have any problems tracking and demodulating the CD-4 difference signal carriers.

 

[Doug G.]

Any cartridge/stylus having specifications which meet the CD-4 standards will work for tracking CD-4 discs.

Like I said above, it is not magic or anything. A CD-4 cartridge just has the ability to track at frequencies up to 45 - 50 kHz at separation good enough to enable the demodulator to differentiate between the two carrier derived signals.

Of course, you ideally want to use a stylus which spreads the tracking force over a larger area to be easier on the grooves.

And even though the original specs. called for lower inductance of the coils in the cartridge and working into a 100K load instead of the typical 47K load to avoid attenuation of the ultrasonic signals, it was found that that particular feature was not as critical as the response and separation.

As with many things, there is the ideal and not so ideal but still finctional.

Doug

 

[mferrocosta]

What kind of Stylus do you heard that works besides Linear Contact and Shibata ? I plan to buy a affordable but good Moving Coil cartridge after Lou Dorren demodulator is finished to listen both CD-4 SQ and Stereo. Dynavector 17D3 uses a exotic, very very short ,cantilever and stylus called micro-ridge http://www.dynavector.com/products/cart/e_17d3.html I would'nt risk $900 without faith.
Would be easier to choose if we could mod the cantilever and stylus like in moving magnet and we could heard sound samples of different MC.

 

[Doug G.]

None but that isn't what I was saying. I'm trying to stress that the overall cartridge/stylus specifications are what is important, not the stylus type.

Lately, there has been the idea that any cartridge with a Shibata will automatically work for CD-4 when that isn't necessarily true.

Now, it happens that cartridges that DO work for CD-4 have Shibata or line-contact styli but the emphasis should be on the overall specifications.

I have had some cartridges with elliptical styli that came close to working but fell a little short. I believe there were other parameters of the cartridge that contributed to the failure other than just the stylus type.

The cartridge you are talking about has a stated response out to 100kHz which is fine, if true and there would be absolutely no problem with CD-4. However, you quoted a separation of 30dB @ 1kHz which means nothing for CD-4. Any good stereo cartridge will have a similar specification. What is importanat for CD-4 is the separation at ultrasonic frequencies (above 20kHz). You need to find out what's going on up there with that cartridge.

Doug

 

[jji666]

I think I just have to cop to being dense about some of these things. Here are the published specs for the Ortofon 2M Black - it doesn't appear to contain the information necessary to determine whether it will work:

Specifications:
Output voltage at 1000 Hz, 5cm/sec. 5 mV
Channel balance at 1 kHz 1 dB
Channel separation at 1 kHz 26 dB
Channel separation at 15 kHz 15 dB
Frequency range at - 3dB 20-31.000 Hz
Frequency response 20-20.000 + 2 / - 0 dB
Tracking ability at 315Hz at recommended tracking force 80 µm
Compliance, dynamic, lateral 22 µm/mN
Stylus type Nude Shibata
Stylus tip radius r/R 6/50 µm
Tracking force range 1.4-1.7g (14-17 mN)
Tracking force, recommended 1.5 g (15 mN)
Tracking angle 20°
Internal impedance, DC resistance 1.2 kOhm
Internal inductance 630 mH
Recommended load resistance 47 kOhm
Recommended load capacitance 150-300 pF
Cartridge colour, body/stylus Black/Black
Cartridge weight 702 g
Replacement stylus unit 2M Black

Can you tell from this whether it has the necessary specs? I'm not a newbie to analog but unused to getting so much into the specs, so sorry if this is a dumb question.

 

[Doug G.]

Not dumb at all. It is difficult to tell from the specs whether or not that cartridge would work for CD-4.

There is an indication it is down 3 dB at 31kHz and if it stayed there up to 45kHz it would be expected to be fine but we can't tell if that is the case.

Same with separation. 15 dB at 15kHz but what about at higher frequencies? We can't tell by the published specs.

Of course, if you look at the specs for the AT440MLa, you would not think it would work either (only claimed to have response up to 20kHz) but it does. Evidently, AT decided to change their policy re specs because the earlier AT440ML had a stated response up to at least 33kHz and there's no reason to believe the later version would be much different since they both have basically the same line contact stylus.

It was by chance that CD-4 nuts found the 440MLa worked anyway. Somebody just decided to try it and found it does. Others also tried it and confirmed.

The Dynavector is a little different because if it really does have response to 100kHz, there's no doubt about that being good for CD-4. The main consideration would then be separation.

So you'll just have to decide whether to try the Ortofon or not. If it works, it works. If not, you have a decent 2 channel cartridge.

Doug

 

[jji666]

Thanks Doug G.! Actually I already have the cartridge - the decision is whether to buy a demodulator and pick up some Quadradiscs. I'd probably never buy a cartridge specifically for CD-4 since I have TT space limitations. But there are a few I'd love to play.

OK final question: how do I know it's working correctly? Do demodulators have any sort of "signal lock" indicator or anything like that?

 

[Doug G.]

Oh yes, I see in your original post you said you have the cartridge.

Demodulators all have a radar light that illuminates when the 30kHz carrier signals are present coming off the disc and out of the cartridge.

However, most regular stereo cartridges will have enough response at 30kHz to light the radar. What's important, of course, is what's going on at all of the frequencies mentioned before.

You will immediately know if the cartridge is working for CD-4 or not. If it does, you will hear undistorted sound from all four speakers and discrete (only the sounds that are supposed to come from any given speaker will come from there).

If it's not working, you will hear anything from mild breakup at louder passages (similar to record damage but worse) to unbearable, raucious "sandpaper" distortion.

Don't worry. It's not one of those things in HiFi for which you have to listen carefully. It will be obvious.

Part of the joy of CD-4, however, is conquering the variables and experiencing the wonderfullness of it when it works. Jim Morrison's whispers out of the back speakers in "Riders On the Storm", the guitar out of the right back speaker in "You're So Vain", the guitar solo out of the left back speaker in "Moonlight Drive", and many more.

So, of course, I would encourage you to get a demodulator and give it a go. I'm glad I persued CD-4.

Doug

 

[jji666]

Thanks again. Being is we are all on this forum I imagine that most of the folks here consider acquiring audio gear a good in and of itself - something new to play with and explore. So I probably will pick up a CD-4 demodulator and see how it works. I have one quadradisk - Aqualung - and we'll see how it goes... Thanks for your help and encouragement!

 

[surteess]

Will this work with CD-4 ?

Technics SL-10 together with the original EPS-310MC cartridge (frequency response 10Hz - 60kHz) - I would not use the internal MC pre-preamp within the TT as the frequency response is 20Hz - 20kHz only.

I actually have 2 more of these cartridges that have never been used.

Any thoughts about this setup I have had since new?

thanks

Steve in New Zealnad

 

[Doug G.]

If the specification for frequency response is accurate for that cartridge and the separation specs. meet CD-4 standards, there is really no reason it wouldn't work.

There is really no definitive way to tell other than trying it, however, as it is not designated as a CD-4 cartridge.

You just have to take a chance. This is true with any stereo cartridge which may perform outside of its intended limits. Like the AT440MLa.

The only reservation I would have with that cartridge is the elliptical stylus which may be a little harder on the ultrasonic engravings than a line contact type stylus. I wouldn't worry TOO much about it though.

Of course, you would also have to provide a prepreamp with the required frequency response to elevate the signal level of the MC cartridge to that needed by the input of a typical demodulator.

Doug

 

[surteess]

Doug,
thanks for the response - I already have a MC Pre-amp that is flat to 50kHz, one I designed about 25 years ago for a friend of mine that only had conventional MM I/P to his Hafler Pre-amp.

 

[quadnewbie]

Sorry Doug but you are just plain wrong, a stylus has to have a frequency response of at least 30,000 db to begin to read the frequencies encoded in CD-4. All these expensive cartridges are made for stereo and linear contact is not always shibata. Best result would be to shop at the bay and get an old audio-technica at12, 14 or 15sa cartridge with a nos stylus. They were made for quad and the only one made today specifically for old cd-4 records is the Ortofon 2m black. At $700 you could buy a few old cd-4 cartridges on the bay!

 

[quadjoe]

Over the years I've tried a variety of cartridges for CD-4 playback with varying degrees of success. The Ortofon should work as long as you can boost the output of the cartridge to the range required by the demodulator without attenuating the high frequencies. For me, the most surprising cartridge to work with my CD-4 demodulator was the Grado Prestige Blue. Grado claims that it tracks to 50kHz, even with an elliptical stylus, and lo and behold it did work with my JVC 4DD5 demodulator. I suspect that the Shure M97Xe might work if equipped with a JICO SAS stylus. I actually was able to track a CD-4 record with the Shure and its stock elliptical stylus through about half a side before the carrier began to break up. I also have two vintage AT cartridges: the AT-14Sa, which I bought new (a whopping $75!!) in 1975, and I just got a NOS 12Sa. Styli for both cartridges are readily available, though they can be pricey (I paid over $100 each for 2 replacements for my AT-14Sa). I also have an AT-331LP that is supposed to be good for CD-4, though I haven't tried it yet, but I intend to.

 

[Doug G.]

Sorry. Post in error.