Discrete Quad Record Player?

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wiztom
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Discrete Quad Record Player?

Post by wiztom » 15 Mar 2019 18:27

Hello

I need some information in regards to a TT for discrete quad LP's. Do I need a special quad record player or just any TT with a special cartridge and stylus? I have two QRX-9001 which plays Discrete Reel to Reel, but only have an Audio Technica-LP120 for records.

Thanks for any input.

zlartibartfast
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Re: Discrete Quad Record Player?

Post by zlartibartfast » 15 Mar 2019 20:14

You will need a Shibata or Line Contact stylus that can reproduce at least 40kHz, a very low mass tonearm, and very low capacitance wiring. You will also need an external CD-4 demodulator to decode the rear channel info.

Most of the gear that was made for CD-4 (discrete quad) is over 40 years old now. The Precept PC440, that I just retired, is an example of a cartridge made for CD-4.

https://www.vinylengine.com/library/precept.shtml

For a turntable, I'm not certain. Mine is a Technics SL1300, which was marketed as a CD-4 compatible component. I've never tried it with CD-4. I don't think your LP120 is suitable for that purpose.

Do you already own CD-4 LP's in good condition?

nat
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Re: Discrete Quad Record Player?

Post by nat » 15 Mar 2019 21:05

The arm doesn't need to be low mass, but the other information is correct. The carrier signal for CD4 was above the normal 20 kHz top end of most human's hearing and the limits of the standard recording system, so very fine line styli needed to be made to read the ultrasonic signal, and low capacitance cables were needed to keep from rolling off the ultrasonic signal.
I am with zlartibartfast in wondering if you have a bunch of CD4 records in good condition. They aren't being made, and the high frequency groove modulations can be damaged by playing them with inferior equipment (though vinyl is surprisingly durable).
I think it's cool that you want to try to play them, but recognize that it is a complicated and somewhat whimsical quest you are engaging in. I wish you success.

wiztom
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Re: Discrete Quad Record Player?

Post by wiztom » 15 Mar 2019 23:49

zlartibartfast wrote:
15 Mar 2019 20:14
You will need a Shibata or Line Contact stylus that can reproduce at least 40kHz, a very low mass tonearm, and very low capacitance wiring. You will also need an external CD-4 demodulator to decode the rear channel info.

Most of the gear that was made for CD-4 (discrete quad) is over 40 years old now. The Precept PC440, that I just retired, is an example of a cartridge made for CD-4.

https://www.vinylengine.com/library/precept.shtml

For a turntable, I'm not certain. Mine is a Technics SL1300, which was marketed as a CD-4 compatible component. I've never tried it with CD-4. I don't think your LP120 is suitable for that purpose.

Do you already own CD-4 LP's in good condition?
I am looking at a couple of JVC 4MD-20X with the matching Stylus. The Sansui QRX-9001 is probably one of the best CD-4 Quad receivers made. I have flagged several Discrete quad vinyls on e-bay at various prices and conditions. Thanks for your response.

wiztom
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Re: Discrete Quad Record Player?

Post by wiztom » 16 Mar 2019 01:15

nat wrote:
15 Mar 2019 21:05
The arm doesn't need to be low mass, but the other information is correct. The carrier signal for CD4 was above the normal 20 kHz top end of most human's hearing and the limits of the standard recording system, so very fine line styli needed to be made to read the ultrasonic signal, and low capacitance cables were needed to keep from rolling off the ultrasonic signal.
I am with zlartibartfast in wondering if you have a bunch of CD4 records in good condition. They aren't being made, and the high frequency groove modulations can be damaged by playing them with inferior equipment (though vinyl is surprisingly durable).
I think it's cool that you want to try to play them, but recognize that it is a complicated and somewhat whimsical quest you are engaging in. I wish you success.
Does the TT need to have an arm with an 8 connector shell, (4 separate output cables), or only the standard 4 connector shell with two output cables for quad?
There are quite a few quad records on e-bay. Actually there are more LP's than reel to reel. I have a Tascam 34B that plays the couple of quad reels I have. With a TT I can record them to tape and play them.

Thanks

Doug G.
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Re: Discrete Quad Record Player?

Post by Doug G. » 16 Mar 2019 03:18

The only real difference between a regular two channel stereo turntable and one capable of CD-4 reproduction is the low cable capacitance stipulation. The ultra sonic frequencies from the LP MUST be preserved for the demodulator to use to separate all four channels (not just the back channels). If those frequencies do not get from the groove to the demodulator, you don't have a chance. Low capacitance cables assure the ultra sonic frequencies will not be attenuated.

The assumption here, of course, is everything else is equal - a turntable capable of keeping the stylus in contact with both groove walls which usually means an anti-skate system to equalize contact. Certainly, better tables have this and CD-4 is more dependent than two channel reproduction but it's not really a difference.

There are only two channels coming off the record/cartridge in any system, two OR four channel. The separation of channels is all done within the decoder, for matrix quad and the demodulator for CD-4. Only four output pins on any cartridge.

Doug

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Re: Discrete Quad Record Player?

Post by macshifi » 16 Mar 2019 03:21

To start with, the only special equipment you need for successful cd-4 playback are as follows: cd-4 cartridge with Shibata stylus, cd-4 demodulator to retrieve the 30 kHz to 50 kHz signal from the record, the receiver you already have, and, of course, the turntable with low capacitance cables. Playing a cd-4 record with a standard conical or elliptical stylus will do no harm to the record, because the stylus rides just above the ultrasonic rear channel, which is the exact reason why a Shibata stylus has to be used for proper playback of a cd-4 record. I will also mention, while we're on the subject of cd-4 records, according to the person who developed cd-4 records, these records were mastered at 1/3 speed to ensure proper mastering of the discs and stampers, however, some people on E-bay will state that the records were cut at 1/2 speed, which is not correct, but I can no longer point anyone in any direction as to proof of what I have stated here, because the information is no longer accessible online, but I did print the articles that I had found online about 10 years ago.

Mark

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Re: Discrete Quad Record Player?

Post by zlartibartfast » 16 Mar 2019 18:13

wiztom wrote:
16 Mar 2019 01:15

Does the TT need to have an arm with an 8 connector shell, (4 separate output cables), or only the standard 4 connector shell with two output cables for quad?
The wiring in the table is 2 channel, so 4 wires altogether. The rear channel information is derived from the decoding process, which in the case of the QRX 9001, is internal to the receiver.

regarding the low-mass tonearm - As I understand it, the cartridge needs to have high compliance, and be able to track @ 1.5g or less. Thus, a low-mass arm is needed. I could be wrong - it has happened before.

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Re: Discrete Quad Record Player?

Post by wiztom » 17 Mar 2019 05:00

Thanks to all who replied. You have increased my knowledge of TT for quad records.

Doug G.
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Re: Discrete Quad Record Player?

Post by Doug G. » 17 Mar 2019 06:32

The 30kHz engravings are the full length of the groove. A non CD-4 cartridge just skips over the ultra sonic engravings without damaging them. Special vinyl was developed for CD-4, harder than regular vinyl for two channel records.

JVC and RCA, in collaboration with Lou Dorren, tested CD-4 records played with typical two channel cartridges, over three hundred times, and the ultra sonic engravings remained intact.

The original cartridges for CD-4 did not track at necessarily low tracking forces, the majority tracking at 2 grams or more, but the net tracking force was no different from stereo cartridges tracking at 1 - 1.5 grams because of the dispersed pressure from the stylus shape (Shibata). It wasn't until a little later that cartridges were developed to track at 1 - 1.5 grams by Empire and Pickering/Stanton, thus reducing pressure on the groove even further.

Many lies were told, back in the day, about CD-4 due to the rabid competition between matrix (SQ, QS, etc) quad and CD-4 discrete quad. CD-4 records being destroyed by playing on a regular stereo turntable was a major one. When CD-4 is set up properly and rules followed, there is really no comparison regarding separation prowess.

Doug

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Re: Discrete Quad Record Player?

Post by scrapjack+ » 17 Mar 2019 11:47

I would like to second what Macshifi stated.
Any turntable can be made to be capable of CD-4 provided it is given two things
Low capacitance cables in the tone arm wiring. Some have this already, I believe most made around the 1980's.
Shibata stylus

As for as dynaquad, EV-4/stereo-4, SQ, and QS, any turntable will work. Unlike CD-4, there are multiple software decoders for these.


By the way, It sounds like you're just getting started with quad. Congratulations, I hope you enjoy hearing new versions of your favorite classic songs by the original artists.

You mentioned quad reels which are quite obscure, and presumably expensive, as is everything quad. I just want to make sure you are aware of the discrete quad 8-tracks (Q8) which are much more common and one of the cheapest quad formats to setup(my player was $15). Granted most Q8's I was interested in had record equivalents, however your taste in music may differ. You can recognize quad 8-tracks easily because they have two programs instead of 4. The two missing programs are used for the rear channels. Quad 8 track players I have seen usually say "4 channel" instead of "quadraphonic". They also had allot of compilation demos made by car dealerships, if you collect car stuff as well as music. If there is a big hole in the back top of the cartridge, that is an elusive 4-track, not an 8 track, they were the predecessor format, and none are quad. In theory you could record Q8 from a stereo player and just have to overlap the programs in a software of your choosing, to be archived in a file format of your choice. I have never tried that method, but expect it'd work.
diffrent tracks.jpg
(144.35 KiB) Downloaded 98 times
Also there is a forum specifically dedicated to all things quadraphonic and above, many of my early searches kept leading me back to that site, it may be of help to you.www.quadraphonicquad.com

Doug G.
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Re: Discrete Quad Record Player?

Post by Doug G. » 17 Mar 2019 18:06

I probably should have written, above, that the 30kHz engravings are the full height of the groove instead of length. In other words, all the way from the bottom of the groove to the top.

There has long been a misconception that the ultra sonic engravings are only near the bottom of the groove. No so.

Doug

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Re: Discrete Quad Record Player?

Post by Doug G. » 17 Mar 2019 18:10

A turntable without anti-skating is unlikely to be successful with CD-4. You need to have equal pressure on both groove walls.

Doug

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Re: Discrete Quad Record Player?

Post by wiztom » 17 Mar 2019 19:37

scrapjack+ wrote:
17 Mar 2019 11:47
I would like to second what Macshifi stated.
Any turntable can be made to be capable of CD-4 provided it is given two things
Low capacitance cables in the tone arm wiring. Some have this already, I believe most made around the 1980's.
Shibata stylus

As for as dynaquad, EV-4/stereo-4, SQ, and QS, any turntable will work. Unlike CD-4, there are multiple software decoders for these.


By the way, It sounds like you're just getting started with quad. Congratulations, I hope you enjoy hearing new versions of your favorite classic songs by the original artists.

You mentioned quad reels which are quite obscure, and presumably expensive, as is everything quad. I just want to make sure you are aware of the discrete quad 8-tracks (Q8) which are much more common and one of the cheapest quad formats to setup(my player was $15). Granted most Q8's I was interested in had record equivalents, however your taste in music may differ. You can recognize quad 8-tracks easily because they have two programs instead of 4. The two missing programs are used for the rear channels. Quad 8 track players I have seen usually say "4 channel" instead of "quadraphonic". They also had allot of compilation demos made by car dealerships, if you collect car stuff as well as music. If there is a big hole in the back top of the cartridge, that is an elusive 4-track, not an 8 track, they were the predecessor format, and none are quad. In theory you could record Q8 from a stereo player and just have to overlap the programs in a software of your choosing, to be archived in a file format of your choice. I have never tried that method, but expect it'd work.
diffrent tracks.jpg
Also there is a forum specifically dedicated to all things quadraphonic and above, many of my early searches kept leading me back to that site, it may be of help to you.www.quadraphonicquad.com
I suddenly have another question.
Is the low capacitance wiring actually in the tone arm or just from the solderboard out; ( RCA cables). I cant imagine what low capacitance cabling would be with those small wires in the arm.

Appreciate the info on the Q8's. I have seen them on E-Bay, but not so much the eight track players. I would have no clue what to look for there. I think the last 8 track I had was a Panasonic car player with a cassette adapter back in the 60's.

Thanks

wiztom
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Re: Discrete Quad Record Player?

Post by wiztom » 17 Mar 2019 19:40

Doug G. wrote:
17 Mar 2019 18:10
A turntable without anti-skating is unlikely to be successful with CD-4. You need to have equal pressure on both groove walls.

Doug
Doug this is good info. I have a couple of questions:
Is the low capacitance wiring actually in the tone arm or just from the solderboard out; ( RCA cables). I cant imagine what low capacitance cabling would be with those small wires in the arm.

Do you have any suggestions on turntables to buy for CD-4 quad usage?

Thanks

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