Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]
- Thread starter loudorren
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Quadro-Klaus
Member
Lou, that's great. Would it be in silver or black? What about a 4-Ch line in instead of a 2-Ch line in?
loudorren
Well-known Member
Hello Quadrafiers,
Bob, Romano, JonUrban, bmoura, Quadtrade, Quadro-Klaus,
Thanks for comments, The box will be black as will the front and back panels. The lettering will be white.
The wide band line input and line output are for people who want to experiment with digitizing the CD-4 signal, archiving it, and then playing it back through the demodulator to get discrete Quad output. It is not a typical audio line in and out.
Lou Dorren
Bob, Romano, JonUrban, bmoura, Quadtrade, Quadro-Klaus,
Thanks for comments, The box will be black as will the front and back panels. The lettering will be white.
The wide band line input and line output are for people who want to experiment with digitizing the CD-4 signal, archiving it, and then playing it back through the demodulator to get discrete Quad output. It is not a typical audio line in and out.
Lou Dorren
Even we have now a look to a black demodulator (the first in this manner?), so we will nevertheless see "black". The set looks really pretty and the main points are the inside values. Although by a color black this demodulator is a real ray of hope, that CD-4 enters now a further or new dimension of quality. Only my piggy bank is now always looking anxious, thinking for that day,when I must rob it to buy this demodulator. Some may ask now too, how long we must feed this piggies, when this demodulator is available.
The Quadfather
1K Club - QQ Shooting Star
Hey Lou:
That looks real good. What will be the dimensions and will there be rack ears available?
The Quadfather
That looks real good. What will be the dimensions and will there be rack ears available?
The Quadfather
My piggy bank is going to meet an "unfortunate end"... :banana:
Mark Z
Mark Z
Lou, how would I play SQ records using the phono preamp of the demodulator?
loudorren
Well-known Member
Hello proufo
Just play the record. It is after all a 2 channel stereo record. IF you want to connect your "SQ Decoder" you would connect the RIAA, or RIAA + LPF or the Left Front and Right Front outputs to the Left and Right inputs of the "Sq Decoder".
Lou Dorren
Just play the record. It is after all a 2 channel stereo record. IF you want to connect your "SQ Decoder" you would connect the RIAA, or RIAA + LPF or the Left Front and Right Front outputs to the Left and Right inputs of the "Sq Decoder".
Lou Dorren
Lou, I too am impressed. As I get older and further away from the 70s when I was deployed in Southeast Asia during the first years of Sansui Quad, the memories and the music I started to collect there get more precious. Looking forward to having the opportunity to own your CD-4 package and experience a rebirth, as well as being able to experiment a little. I wish I was more technical, but I can follow much of the discussion Thanks for your effort; I am sure it is a labor of love for you.
Ken
Ken
loudorren
Well-known Member
Hello CD-4ophiles,
zabble, RenoKen,
Thanks for the posts!!
Lou Dorren
zabble, RenoKen,
Thanks for the posts!!
Lou Dorren
Justforthesoundofit
Member
- Joined
- Jul 10, 2007
- Messages
- 16
Lou,
Pardon my ignorance in the matter, but as I understand from one of your earlier comments, the ceramic CD-4 cartridge was superior to the magnetic. Why then did everyone else go with the magnetic? I would have to believe the ceramic cartridge to be less expensive to manufacture and have less circuitry (no preamp or RIAA filter).
Rick
Pardon my ignorance in the matter, but as I understand from one of your earlier comments, the ceramic CD-4 cartridge was superior to the magnetic. Why then did everyone else go with the magnetic? I would have to believe the ceramic cartridge to be less expensive to manufacture and have less circuitry (no preamp or RIAA filter).
Rick
loudorren
Well-known Member
Hello Quadies,
Justforthesoundofit,
Rick, The Technics 450c, 451C, and 460C were not ceramic. They were silicon semiconductor strain gage cartridges. During the Quad days, every pro audio engineer that I demonstrated these pickups to, converted to them. They did not suffer from velocity hysteresis, common with moving magnet and moving coil pickups, nor did magnetic field build up occur since there was no magnets involved in the construction.
The semiconductor pickup is not a generator type cartridge. It must be DC biased somewhat like an electret microphone. As it tracks the groove, it's resistance varies with the groove undulations. The generator type pickups must create an AC voltage on the output from groove undulations. Because there is some time (nano to micro seconds) for the magnetic lines of flux to build and collapse (hysteresis), some harmonic (THD) and inter modulation (IM) distortion can be created in the output.
Magnetic field build up happens over time. The result is a gradual reduction in output. Clever pickup design can minimize both of these effects, however it is a good idea to have a phono cartridge de-magnetizer (NOT TAPE HEAD)
and use it about every 6 months. One other point, the semiconductor cartridge left and right outputs are out of phase, so one output must be inverted by the preamplifier.
Lou Dorren
Justforthesoundofit,
Rick, The Technics 450c, 451C, and 460C were not ceramic. They were silicon semiconductor strain gage cartridges. During the Quad days, every pro audio engineer that I demonstrated these pickups to, converted to them. They did not suffer from velocity hysteresis, common with moving magnet and moving coil pickups, nor did magnetic field build up occur since there was no magnets involved in the construction.
The semiconductor pickup is not a generator type cartridge. It must be DC biased somewhat like an electret microphone. As it tracks the groove, it's resistance varies with the groove undulations. The generator type pickups must create an AC voltage on the output from groove undulations. Because there is some time (nano to micro seconds) for the magnetic lines of flux to build and collapse (hysteresis), some harmonic (THD) and inter modulation (IM) distortion can be created in the output.
Magnetic field build up happens over time. The result is a gradual reduction in output. Clever pickup design can minimize both of these effects, however it is a good idea to have a phono cartridge de-magnetizer (NOT TAPE HEAD)
and use it about every 6 months. One other point, the semiconductor cartridge left and right outputs are out of phase, so one output must be inverted by the preamplifier.
Lou Dorren
on the other hand,if you use it for stereo only ,(and don't care about recording stuff) you can get away with just reversing the phase on one channel of speaker terminals. (i.e. just wire your stereo speakers out of phase)
Hey Lou,
What type of cartridge will be included with your new demodulator??? Will replacement stylus be available??
Hows your testing coming along???.....any updates would sure be appreciated....I just cant wait!!!!
Thanks,
Mike
What type of cartridge will be included with your new demodulator??? Will replacement stylus be available??
Hows your testing coming along???.....any updates would sure be appreciated....I just cant wait!!!!
Thanks,
Mike
Regarding CD-4 Quadraphonic playback
using a "stereo" phono cartridge:
Quoting from the 1973 consumer's guide to
FOUR-CHANNEL SOUND:
JVC answers leading questions on the CD-4 disc
For example, JVC has found that a $12.95 Shure
cartridge purchased at Radio Shack plays
satisfactorily as popular-class equipment.
I know that CD-4 approved cartridges were rated
A, B or C but I know of no rating system for
"stereo" cartridges that could be used for CD-4.
It might be informative to try some of the well
known brands of "stereo" cartridges with the
2008 CD-4 demodulator to see how poor channel
separation and (possibly severe) roll off in
the 20kHz to 45kHz range affect the CD-4
demodulation process.
Kirk Bayne
using a "stereo" phono cartridge:
Quoting from the 1973 consumer's guide to
FOUR-CHANNEL SOUND:
JVC answers leading questions on the CD-4 disc
For example, JVC has found that a $12.95 Shure
cartridge purchased at Radio Shack plays
satisfactorily as popular-class equipment.
I know that CD-4 approved cartridges were rated
A, B or C but I know of no rating system for
"stereo" cartridges that could be used for CD-4.
It might be informative to try some of the well
known brands of "stereo" cartridges with the
2008 CD-4 demodulator to see how poor channel
separation and (possibly severe) roll off in
the 20kHz to 45kHz range affect the CD-4
demodulation process.
Kirk Bayne
Justforthesoundofit
Member
- Joined
- Jul 10, 2007
- Messages
- 16
Lou,
Like I said, pardon my ignorance. I love to learn as much as I like to listen to the music. Are phono cartridge de-magnetizers still available?
Thanks,
Rick
Like I said, pardon my ignorance. I love to learn as much as I like to listen to the music. Are phono cartridge de-magnetizers still available?
Thanks,
Rick
loudorren
Well-known Member
hello CD-4 Supporters,
ChristopherLees, That is one way, however don't forget that you need DC bias on both channels to make the semiconductor pickup operate. Also if you want to listen to FM radio or a CD player it might be easier to add a DPDT (Double Pole Double Throw) switch on one speaker to easily change phase. I have included a circuit diagram in this post.
aludra,
Mike, Pickup to be announced, replacement pickups and styli will be available. Circuit board artwork now in progress.
kfbkfb,
Kirk, More 1973 advertising hype. "Plays satisfactorily" generally means light the CD-4 indicator, less than 10% breakup distortion and not very good separation. In my opinion, why settle for less when you can get more!
Justforthesoundofit,
Rick, the Aesthetix MC Cartridge Demagnetizer! is available from:
http://www.musicdirect.com/product/49736
for $199.00. It is a good one that I recommend.
Lou Dorren
ChristopherLees, That is one way, however don't forget that you need DC bias on both channels to make the semiconductor pickup operate. Also if you want to listen to FM radio or a CD player it might be easier to add a DPDT (Double Pole Double Throw) switch on one speaker to easily change phase. I have included a circuit diagram in this post.
aludra,
Mike, Pickup to be announced, replacement pickups and styli will be available. Circuit board artwork now in progress.
kfbkfb,
Kirk, More 1973 advertising hype. "Plays satisfactorily" generally means light the CD-4 indicator, less than 10% breakup distortion and not very good separation. In my opinion, why settle for less when you can get more!
Justforthesoundofit,
Rick, the Aesthetix MC Cartridge Demagnetizer! is available from:
http://www.musicdirect.com/product/49736
for $199.00. It is a good one that I recommend.
Lou Dorren
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wa6ubw
Active Member
I don't think anybody but Lou Dorren could make a single switch into a system.:spot
(note the carefully chosen "song & dance" smiley)
(note the carefully chosen "song & dance" smiley)
Regarding CD-4 Neutrex Predistortion:
(1963) RCA Dynagroove information:
http://www.stereophile.com/asweseeit/95/index3.html
The predistortion phase of Dynagroove--the adding
of complementary distortion to offset the effects
of stylus tracing distortion--appears now to be
based on sound engineering principles, even though
the amount of predistortion that is added is
predicted on the normal amount of tracing distortion
produced by a 0.7-mil stylus, a size that has been
generally abandoned by the high-fidelity industry.
Is CD-4 Neutrex predistortion set to provide the
minimum (sum signal) playback distortion with a real
Shibata stylus, Line Contact (type) stylus, Elliptical
stylus or a range of stylus shapes?
Kirk Bayne
(1963) RCA Dynagroove information:
http://www.stereophile.com/asweseeit/95/index3.html
The predistortion phase of Dynagroove--the adding
of complementary distortion to offset the effects
of stylus tracing distortion--appears now to be
based on sound engineering principles, even though
the amount of predistortion that is added is
predicted on the normal amount of tracing distortion
produced by a 0.7-mil stylus, a size that has been
generally abandoned by the high-fidelity industry.
Is CD-4 Neutrex predistortion set to provide the
minimum (sum signal) playback distortion with a real
Shibata stylus, Line Contact (type) stylus, Elliptical
stylus or a range of stylus shapes?
Kirk Bayne
