Will any of my stuff work with CD-4?

Discussion in 'Turntables' started by N8Nagel, Dec 5, 2018.

  1. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    I have a Technics SL-1650 and also two Micro Acoustics MA2002e cartridges, will either of them decode CD-4, or do I need to have my Dual 1229Q repaired and will I need a different cartridge? Just curious.

    I can't test as I don't have any CD-4 LPs and the only decoder that I have is a Marantz CD-400, working condition unknown (although I have verified that it works as a 2 channel phono preamp.) Just trying to plan my next moves.

    The MA2002e is only rated to 20 kHz, but then again I'm pretty sure so is the AT440MLb which is a known good CD-4 cart. I don't know if the 1650 is good either, but rumor has it that the cables that Technics used back then were low capacitance and decent quality. So maybe someone's tried it?
     

     

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  2. Nashou66

    Nashou66 AK Subscriber Subscriber

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    You'll need a cartridge with either a Shibata needle which Quadraphonic sound is what it was developed for, or a line contact or micro ridge stylus.

    The tables don't matter as much i'd think.

    Nashou
     
  3. tcdriver

    tcdriver AK Subscriber Subscriber

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    To successfully play a CD-4 (aka Quadradisc) disc, you will need the following:

    1. CD-4 encoded record. It should say CD-4 or Quadradisc on the cover.

    2. CD-4 demodulator, either stand alone or built into a receiver, preamp or integrated amplifier.

    3. CD-4 capable phono cartridge. i.e. capable of frequency response to 45kHz. The carrier frequency, 30kHz., is frequency modulated from 20kHz. to 45kHz.

    4. Turntable with low capacitance arm wiring and low capacitance interconnects. The total capacitance from headshell to the end of the cable that plugs into the CD-4 capable phono inputs should be < 100pF.​

    Some examples of CD-4 (Quadradisc) records:
    [​IMG]
     
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  4. Doug G.

    Doug G. Addicted Member

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    Excellent, tc!

    Doug
     
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  5. smokenguns22

    smokenguns22 AK Subscriber Subscriber

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    So tcdriver,
    Would the tone arm need 4 cables coming out to feed the receiver??
    Or do you just use the 2 ch cables out TT the receiver decides from there?

    Will most tonearms be compat with cd-4 cart?

    Sorry-new to quad but very interested

    Thx
    Smokey
     
  6. tcdriver

    tcdriver AK Subscriber Subscriber

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    Two audio cables are required. For CD-4 operation they feed the CD-4 demodulator, either a stand alone box or built-in to a quadraphonic receiver. If one uses a stand alone demodulator, there will be four outputs (FL, FR, SL, SR) that feed line level inputs to a quadraphonic receiver.

    Most CD-4 capable phono cartridges, from the quadraphonic era, tended to be high compliance, lighter tracking, which would make them better suited to lower mass tonearms.
     
    Last edited: Jan 25, 2019

     

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  7. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    In addition to what tcdriver said above, all wiring from the cartridge to the CD-4 demodulator needs to be low capacitance because that needs to be able to carry a signal up to about 50 kHz I think? Way higher than the normal 20-22 kHz anyway. So both the cartridge needs to be able to read that signal, and the wiring needs to be lower capacitance than is required for 2 channel audio so it doesn't attenuate the higher frequencies too much. Capacitance is already a big deal in phono interconnects due to the fact that crap cables can actually attenuate high audible frequencies, never mind the ultrasonics that CD-4 encoding uses. Now if I did try to play a CD-4 disc on my rig and it didn't work, it'd still play, it'd just only play in stereo, the "Radar" light would never light up on the decoder and I wouldn't get sound out of the rear channels.

    https://en.wikipedia.org/wiki/Compatible_Discrete_4#Operation

    Which is really why I was asking in the first place, as I don't know whether anyone's ever successfully used a SL-1650 or a MA2002e to decode CD-4. But since I don't have any CD-4 discs, nor do I know if my CD-400 is in top shape, and finally, my Marantz 4270 is apparently in the process of driving the second tech to work on it nuts, it's hard for me to run a truly valid test, hence my question.
     
  8. tcdriver

    tcdriver AK Subscriber Subscriber

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    To more directly answer your questions:

    1. If you can successfully use the MA2002e, the capacitance does not matter because of the unique nature of the transducer. If the MA2002e does not work out, then you need to measure the capacitance on your SL-1650 from the headshell to the ends of the interconnects. If it is less than 100pF you are good to go using that turntable as it is. If not, you still may be able to replace the interconnects with low capacitance cables to get to the less than 100pF maximum. If you do not have a capacitance meter, your tech should.

    2. The MA2002e uses an elliptical stylus which would suggest a very high probability is that it is not suitable for CD-4 playback, however; it would not hurt to try it. ​

    Micro-Acoustics Model 2002-e Specifications
    - Stylus Configuration: .0002 x .0007 elliptical diamond
    - Frequency Response: 5 ~ 20kHz +/- 1.5dB
    - Tracking Force Range: 0.7 - 1.4 grams
    - Cartridge Weight: 4 grams
    - Channel Separation: Nominally 30dB at 1kHz, 15dB at 10kHz
    - Output voltage: 3.5 mV each channel at 5 cm/sec. peak recorded velocity
    - Load Requirements: 10k to 100k (not critical)
    - Cable Capacity: 100pF tp 1,500pF (not critical)
     

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