Turntable / cartridge selection for CD-4

[Colin Dunn]

I've been reading some things and am wondering what I should upgrade in order to get a good CD-4 setup. I already have access to a JVC CD-4 demodulator, so now my attention turns to the table and cartridge. The purpose of this setup is to be able to play back and archive quad vinyl (CD-4, QS, or SQ). I can do software decoding of the SQ/QS by recording front channels only off the JVC demodulator, and then processing the resulting stereo file in Audition.

At home, I have three turntables available to me:

1) Audio-Technica LP120 (this is an entry-level but fully adjustable table that looks like a Technics SL-1200 clone, but doesn't spec as well as an actual 1200), outfitted with the entry-level Audio-Technica cart it came with. If I use this table, I'd need a different cartridge. I would bypass the built-in phono preamp and use the CD-4 demodulator as a phono stage.
2) Technics SL-1210MK2 (currently in my main system), outfitted with a Denon DL-160 cartridge. I tried a little CD-4 on this; I did get carrier lock and back channel sound. I believe it has a line-contact stylus, but before I play a bunch of CD-4 vinyl on it repeatedly, I want to be sure this isn't a CD4-vinyl-destroying machine.
3) A Sansui SR-636 (currently without a cartridge installed). I've tested that it powers up but owing to the lack of cartridge, haven't played any vinyl on it yet.

Between the Technics SL-1210 and the Sansui SR636, which is the better table for CD-4 vinyl playback? I've read that low-capacitance wiring is recommended. I'm pretty sure the stock Technics SL-1210 does NOT have low-capacitance wiring. Would the Sansui represent an improvement in that respect?

And then, if I use the Sansui, it has an incompatible headshell with the Technics / Audio-Technica, so I would want to acquire a CD-4 specific cartridge to use with it. Having just ordered a multichannel audio interface for my computer (MOTU 828MK3 Hybrid), I don't have an unlimited budget for a high-end NOS CD-4 cart ... so I was thinking of the Ed Saunders cart. Are there other alternatives in the sub-$200 price range I should be considering? Preferably the cartridge should have a replaceable stylus (not sure if the Ed Saunders cart falls in that category).

And then a couple esoteric technical questions -
1) Should I be looking for a cartridge optimized for 100K-ohm resistance or 47K ohm resistance?
2) How about tonearm / cartridge interaction (mass and compliance)? The Technics SL-1200 is considered a medium-high mass / medium-low compliance arm. How about the Sansui SR-636 stock arm (I don't know about its mass/compliance characteristics). How does this influence my cartridge choices?

 

[Colin Dunn]

Answered some of my own questions...

I found an eBay listing for a NOS JVC 4MD-20X cartridge, along with 4DT-20X stylus. Snapped them up, and just in time ... 10 minutes later, someone else bought the second of the two cartridges available for sale. From past postings on this forum, this was one of the better-regarded CD4 cartridges from the '70s.

So then the question remains - which table to use it on? The Technics SL-1210 or the Sansui SR-636, based on arm mass/compliance and wiring capacitance? Both these tables have hard-wired phono out cables.

 

[Doug G.]

The JVC cartridge should be fine.

As far as which table to use, I think I would install the new cartridge into the Sansui since it doesn't have one yet. If you get good CD-4 reproduction, leave it in there. if you have problems, try it in the Technics.

Although the Sansui doesn't appear to have been designed specifically with CD-4 in mind, I think it will work OK.

Doug

 

[Colin Dunn]

The JVC cartridge should be fine.
Although the Sansui doesn't appear to have been designed specifically with CD-4 in mind, I think it will work OK.

Are there certain vintage tables that are preferred for CD-4 playback? Perhaps a high-end JVC from the CD-4 era? Other alternatives?

Another thought that had crossed my mind was to get a high-quality vintage linear-tracking turntable and put the CD-4 cart on that. Since my intention is to transfer vinyl to digital, I want the highest quality I can reasonably afford. I know linear trackers are of some controversy; I would be thinking of a "high-end" one that sold for several hundred dollars in the '70s, rather than the cheapie "close-and-play" types that sold for under $250 in the '80s.

 

[The Quadfather]

A linear tracking turntable is not necessary for good CD-4 reproduction. The Technics table was made during the quad era, and, as a market product, is a survivor. I don't know if the modern incarnation has low capacitance wiring, but if your turntable is from the quad era, it does. In fact, most quality turntables of Japanese design made during the quad era, will have the low capacitance wiring. The most important thing is actually the stylus. I have used an Audio Technica AT440MLa sucessfully for several years now. The cartridge is not rated for CD-4 but it works just fine. And by fine, I mean really well. Note that if you buy this cart, a new stylus has to be broken in. Do this by playing several stereo records before playing a CD-4. It won't harm the record if you play a CD-4 right away, but it might not track well, and therefore the result might be disappointing. Track it a little heavier than what the manufacturer recommends, about 2 grams. It won't hurt the record, and it will track better. You might want to try it on several turntables, since you have them, but I suspect the Technics would be good. I have written many words in this forum about CD-4, an archive search should reveal them. My early experience with CD-4 was miserable, and I have learned much. Good luck and happy listening.
The Quadfather

 

[Colin Dunn]

After successfully getting CD-4 carrier detection and 4-channel sound out of the Technics SL-1210 and Denon DL-160, I'm no longer as worried about wiring capacitance, unless that will significantly degrade the quality of my upcoming vinyl rips. Mainly, I was interested in the questions to be sure I'm getting the best quality possible (within a reasonable budget that is ... there are some turntable setups that cost as much as a house!) when preserving these recordings.

 

[quadjoe]

Answered some of my own questions...

I found an eBay listing for a NOS JVC 4MD-20X cartridge, along with 4DT-20X stylus. Snapped them up, and just in time ... 10 minutes later, someone else bought the second of the two cartridges available for sale. From past postings on this forum, this was one of the better-regarded CD4 cartridges from the '70s.

So then the question remains - which table to use it on? The Technics SL-1210 or the Sansui SR-636, based on arm mass/compliance and wiring capacitance? Both these tables have hard-wired phono out cables.

I'm the guilty party. I saw the 4MD-20X and I couldn't help but buy it. I also ordered 2 new styli for it from LP Gear, and a good thing too, the unit was supposed to be NOS, but I examined the stylus with a microscope, and it was used, I'm sad to say. Oh well, such is the chance you take on eBay. I have really enjoyed listening to this cartridge and it tracks CD-4 really, really well. I get no break-up or "sandpaper" quad with it. It is mounted on my Technics SL-1200MK2 that is only 3 years old, but I bought it through KAB and I had them do the Cardas rewire for the tonearm to make sure it was low-capacitance. You should try the JVC cartridge on your Sansui turntable, it will probably work fine.

 

[The Quadfather]

If you turn down the separation controls, you will then hear only the audio from the carrier signals. It normally sounds hollow, but if you can listen to this and it is clean with no distortion, then it's working good. Reset the pots and enjoy the quad. That's as good as it gets.
The Quadfather

 

[Colin Dunn]

I got the JVC quad cartridge. I don't have a microscope, so I wasn't able to determine if the stylus that came on the cartridge was new or used. The cartridge box was not sealed but the cartridge was bolted down within the package. The extra stylus appeared to be new (it's in a sealed package).

I mounted it on the Sansui SR-636 and tried it out. Treble is a bit bright (probably owing to the extended high-frequency response). CD-4 appeared to play fine, with no break-up or sandpaper distortion.

Tonight, I'll calibrate the demodulator and attempt a CD-4 vinyl rip.

 

[quadjoe]

Sounds like a good plan. Don't forget that the cartridge may have some break-in time before the response smooths out. It will probably become less bright after about 10 hours of play is my guess.

 

[Colin Dunn]

Trying to calibrate the CD-4 demodulator left me with more questions than answers.

The test record has me turn the separation controls to minimize the volume of the back channels. But that results in hardly any sound at all ... and the separation controls at their far counterclockwise position. If I turn the volume way up, I can hear the "hollow" sound (not distorted, but seems to be mostly ambient sounds on a couple of CD-4 LPs I tried). But I assume raising the separation controls is mixing in front-channel audio into the back channels? Is there another way I should be trying to set the controls since the test record's approach didn't seem to work?

Does this mean I'm not getting an intact signal to the demodulator? I do get a carrier light and it's solid (doesn't flicker or go out).

 

[quadjoe]

I'll start with your last comment first: The carrier light should go out when it isn't receiving a signal. For example, if the stylus is not in the groove of a CD-4 disc (the carrier signal should go on just before the music starts, and should go off shortly after the last track finishes playing), if you're playing a stereo record it should be off, if the tonearm is in its rest position, it should be off. I suspect that the 30kHz adjustment control (located on the bottom of the 4DD-5) may be turned all the way to its most sensitive position. Try adjusting it to one of the middle settings and see how it goes from there. There is a band on the set-up disc to help you adjust the carrier signal (it shouldn't sound distorted.) Also, when making the adjustments the 2 Ch direct switch on the back should be set to "Off." For the front to back separation adjustment controls, be sure you receiver's front channels are turned all the way down, and adjust each side so that the tone is at its lowest level. You may indeed have to back off this just a bit to avoid distortion. Finally, let me ask you: Does the channel identification track play properly? Each channel should play the sound in turn (the usual order goes, Front Left, Front Center, Front Right, Right Center, Rear Right, Rear Center, Rear Left, Left Center.)

 

[Colin Dunn]

quadjoe -

The light goes out unless I am playing CD-4 vinyl. However, when I am playing a Quadradisc, it's on solid.

I tried playing with the 30KHz carrier setting and tried all settings from low to high. I did not get significant distortion in any setting, but I didn't get any more difference signal (it was at a very low level, a good 30-40dB below that of the main signal).

When I play the channel ID track, front-left and back-left play out of both speakers. Same for the front-right/back-right pair. It's as if there is no discernment at all between front and back channels. I suspect I'm not getting enough difference signal to have the demodulator derive separate channels, and am getting "dual-stereo" output of the LP instead.

The 2-channel direct switch is off. I tried moving on/off just to be sure it wasn't stuck in between.

Right now, I'm not sure if the issue is phono wiring capacitance, or if this particular demodulator just isn't working.

 

[quadjoe]

It is possible that the wiring capacitance could be attenuating the signal, but if the CD-4 Radar detector is functioning only when playing a Quadradisc, then it should work. Do something for me, if you haven't done it already: play a regular stereo record and see if the Radar light comes on. If it does, the demodulator has a problem. One other thing, if the unit you're using is well-used, open the cover and spray the 2-Channel Direct Out switch with either some Deoxit or TV tuner spray, then work the switch back and forth several times. Believe it or not, I had a similar problem with my old unit when I first received it, and cleaning that switch cleared it up!

 

[Colin Dunn]

It is possible that the wiring capacitance could be attenuating the signal, but if the CD-4 Radar detector is functioning only when playing a Quadradisc, then it should work. Do something for me, if you haven't done it already: play a regular stereo record and see if the Radar light comes on. If it does, the demodulator has a problem. One other thing, if the unit you're using is well-used, open the cover and spray the 2-Channel Direct Out switch with either some Deoxit or TV tuner spray, then work the switch back and forth several times. Believe it or not, I had a similar problem with my old unit when I first received it, and cleaning that switch cleared it up!

The CD-4 radar light does NOT come on when playing a stereo LP.

The demodulator I'm using appears to have been new old stock. The unit was still in a bag and the instruction book / test record were still sealed. It must have sat on a shelf for 40 years. I'll try the De-ox-it on that 2-channel direct out switch (also need to clean up contacts on some other stuff). I did try turning that switch off and on a few times during my previous troubleshooting efforts.

When setting up, how loud is the difference signal supposed to be? The level was far, far below (like 30-40 dB) below the level of the main front signal. I would think to get cancellation and any front-back separation that this signal would need to be much louder than it is.

 

[flavio81]

When setting up, how loud is the difference signal supposed to be? The level was far, far below (like 30-40 dB) below the level of the main front signal. I would think to get cancellation and any front-back separation that this signal would need to be much louder than it is.

I have the EXACT same problem! Someone can shed a light on what component is at fault? I use the ubiquitous JVC 4DD5 rebadged as Fisher.

 

[quadsearcher]

I get separation on my 4DD-5, but I did replace every electrolytic capacitor in it. I spot checked a few first and found an outright bad one in the ANRS circuit. As I was changing them I saw electrolyte leaking, even from the ones that checked good. That's why I went ahead and changed them all (plus I already had them in stock).
However I since borrowed the Marantz version and nothings ever been changed in it, it works fine.

I wish there was a test record put onto disc so (with the level padded down to TT level) I could use the disc to set separation. Those test records are expensive by themselves.

I'm going to play around with setting separation this weekend. I'm hoping to get some good transfers before I have to return the TT/cart I borrowed.

 

[Doug G.]

I don't really want to cause any disappointment here but NOS with electronic equipment doesn't necessarily mean anything good. Although transistors, I.C.s, resistors, switches, contacts, and jacks and plugs will pretty much be fine other than if dirt has penetrated, capacitors sitting all those years might just have well been used.

The chemical reactions between the inside elements of capacitors can render them unuseable even if the piece has never been used. Of course, I have also seen old capacitors that remain fine too but it's a crap shoot.

But, the first thing to do is to get a setup record, turn up the 30kHz controls until you get a useable signal (a little distortion won't matter for checking things out) using the appropriate signals, and then, listening to only the back channels one-at-a-time, adjust the separation controls for minimum output from the back channels with the appropriate signals.

I disagree with some other CD-4 enthusiasts in that I believe a setup record is mandatory for proper adjustment unless you know exactly where different instruments/voices are supposed to be on any given music record. It just leads to confusion otherwise.

I like the Harman-Kardon record the best because there is a guy announcing what to do before each tone (signal) instead of having to refer to the record sleeve.

EDIT: Bah, if I could remember earlier posts! I see you have tried a record but were unsuccessful. It's difficult to troubleshoot over the 'net but it sounds like you aren't getting enough carrier level which could be attenuation in the wiring or the amp. in the demodulator.

Doug

 

[quadjoe]

The CD-4 radar light does NOT come on when playing a stereo LP.

The demodulator I'm using appears to have been new old stock. The unit was still in a bag and the instruction book / test record were still sealed. It must have sat on a shelf for 40 years. I'll try the De-ox-it on that 2-channel direct out switch (also need to clean up contacts on some other stuff). I did try turning that switch off and on a few times during my previous troubleshooting efforts.

When setting up, how loud is the difference signal supposed to be? The level was far, far below (like 30-40 dB) below the level of the main front signal. I would think to get cancellation and any front-back separation that this signal would need to be much louder than it is.

It's good that the carrier light only comes on when it's supposed to.

The difference signal is supposed to be audible, but faint (I've never measured just how low), and it should be adjusted with the front channels turned all the way down, as Doug G. said. I have the Fisher CD-4 set-up record (that came with my Fisher version, that bit the dust over 20 years ago), and the announcer clearly calls the difference signals the Front right and left warble tones. So they are supposed to be faint.

 

[flavio81]

I get separation on my 4DD-5, but I did replace every electrolytic capacitor in it. I spot checked a few first and found an outright bad one in the ANRS circuit. As I was changing them I saw electrolyte leaking, even from the ones that checked good. That's why I went ahead and changed them all (plus I already had them in stock).
However I since borrowed the Marantz version and nothings ever been changed in it, it works fine.

I wish there was a test record put onto disc so (with the level padded down to TT level) I could use the disc to set separation. Those test records are expensive by themselves.

I'm going to play around with setting separation this weekend. I'm hoping to get some good transfers before I have to return the TT/cart I borrowed.

My problem is that the difference signal is there, but it's so faint that, after correctly adjusting separation, i have to turn the volume on my amplifier to the max to be able to listen to the (very soft) music.

I'll try to do what you say, many thanks. What do you use to check capacitors?