If you could purchase any CD-4 demodulator.....

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MidiMagic

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There were obviously shortcomings in the setups.

Doug
All of them were playing in audio store showrooms. They were probably playing the same record day after day.

Most of these were in malls. And most of the faults I heard were due to contamination in the grooves (e.g. loud bangs).

I was present when one CD-4 record was ruined. A woman used a powder puff while looking in a mirror next to the turntable.

Is a clean room needed to have CD-4? Where I lived at the time, a clean room was an impossibility.

I have never actually known anyone who actually had a CD-4 setup (except my abortive one). All of my friends who had quadraphonic systems had matrix systems.

I live in a college town and most of the people here are students. Students didn't have the money for CD-4 equipment, especially during the oil embargo and recession in the early and mid '70s.

I saw basically the following equipment in homes and apartments:
- Many compacts with built-in Dynaquad or similar clone
- Several 4-channel reel systems. Most were being used for studios.
- Q8 players (a few in cars)
- Compacts with matrix decoders (many with both RM and SQ)
- Compacts with Q8 and matrix.
 

Doug G.

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Of course, there's no way I can tell what people were doing wrong in the past but it was obviously something because, as I said, playing CD-4 records, for me, is no different from playing regular two channel LP's. I don't have my system in an environment anywhere close to a clean room. Care for my CD-4 records is NO different from care for any of my other LP's. It just works.

I have nothing against matrix systems and they can be very effective. They just don't quite measure up to CD-4.

Doug
 

fredblue

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above all, for me content is king.
there's some fantastic stuff on CD-4 and a number of my all-time favourites are on CD-4, by contrast i've only a relative handful on QS while the majority of my absolute favourite Quads are on SQ, so i just live with SQ's shortcomings if there's no discrete option, its all good clean (vinyl) fun! 🙂
 

Wurly1

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Is there an "All-transistor" (no ic) external demodulator just like the one inside my SS-1100D system?
I ask because they work differently from the ic kind which use PLL circuitry to lock to the 30khz carrier. I suspect the sandy noise experienced by many happened when the 30khz carrier gets too low in amplitude causing the PLL to unlock.
On my all transistor system, there is no PLL, the demodulator circuitry is tuned to the 30khz carrier and simply detect the signal from there. Pretty much like an FM radio tuned to only one station, channel 30khz.
Another issue is the time used to demodulate the rear signals. It is critical for good front-rear separation and imaging. I wonder if that delay is affected when the PLL has difficulties to lock-on?
Don't get me wrong, I know PLL circuits does a great job in many applications such as in FM receivers, motor speed controls and more.
I just wonder why they didn't made any ic models based on the same simpler "one frequency¨ tuner design.
 

Owen Smith

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The JVC 4DD-5 is the most common demodulator as I understand it, and is entirely discrete transistor based. A number of other demodulators from other manufacturers were basically a 4DD-5 in different box.
 

kfbkfb

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I suspect the sandy noise experienced by many happened when the 30khz carrier gets too low in amplitude causing the PLL to unlock.
Recent research into CD-4 yielded this info about "sandpaper Quad":


Kirk Bayne
 

Wurly1

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The JVC 4DD-5 is the most common demodulator as I understand it, and is entirely discrete transistor based. A number of other demodulators from other manufacturers were basically a 4DD-5 in different box.
I found the service manual on vinylengine. It's very similar to the one in my system. It use filters and detectors to demodulate the 30khz carrier.
How does it perform compared to those using PLL circuits?
 

Soundfield

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I found the service manual on vinylengine. It's very similar to the one in my system. It use filters and detectors to demodulate the 30khz carrier.
Yes, interesting. Whilst it isn't an "entirely discrete transistor" design (there are 6 ics) it doesn't use a PLL - it's still a bit more complicated than yours though - I wonder why these demodulators got so complicated (and apparently in the process, increasingly difficult to set up and use?
 

Wurly1

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Recent research into CD-4 yielded this info about "sandpaper Quad":


Kirk Bayne
Very interesting.
Many of the PLL type have carrier level adjustments. According to your post, I believe the carrier level on CD-4 records may vary from on record to the other. Such variations may affect the ability to lock-on to the carrier signal. Of course there are some automatic carrier level circuits to compensate.
 

Wurly1

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Yes, interesting. Whilst it isn't an "entirely discrete transistor" design (there are 6 ics) it doesn't use a PLL - it's still a bit more complicated than yours though - I wonder why these demodulators got so complicated (and apparently in the process, increasingly difficult to set up and use?
There is only 2 adjustments: Front-Rear separation for Left and Right on mine which have about 40 transistors.
The JVC have many inner trim pots
 

kfbkfb

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Yes, the CD-4 carrier level decreases from the outer to the inner grooves (not by much though), varies due the frequency response of the phono cartridge (the upper sideband 45kHz may be weaker than the lower sideband 20kHz) and may be different on different CD-4 discs (discs mastered with the RCA Quadulator have the carrier level ~4dB higher than discs mastered with the JVC mastering systems).

The limiter in the QSI 5022 (for example) removes carrier level variations and thus makes it much easier to (FM) demodulate the difference signal.

A CD-4 demod is a fairly simple device:
Low pass filter (could be DSP) to get the baseband/sum signal and apply RIAA deemphasis,
bandpass filter (could be DSP) to get the carrier,
limit carrier,
demod FM,
deemphasis for FM,
and then the usual bugaboo - decoding ANRS,
(possible adjustment [could be automatic]) add/subtract sum/difference to get 4 original channels.


Kirk Bayne
 
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Wathen1955

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I used a JVC 4DD-5 back in the 70's, and I was able to buy a brand new one off of ebay last year. The person that I bought it from, his father passed away and he had it still in the original box with all the cables, instructions, and CD disc. His father grabbed it when a store that he worked in went belly up. It was in storage all this time never used, so I bought it for $300.

It is a pain to setup as the adjustments are underneath the unit. I guess the mfg decided that once adjusted, you probably won't be needing another adjustment. I'm more concerned with the unit and the capacitors since it's been sitting unused all this time. The electrolytic caps will still degrade over time even when you don't use it, so I make it a habit of turning it on every time I turn on my main system so it gets some use. I noticed it does sound better once it warms up.
 

Wurly1

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I used a JVC 4DD-5 back in the 70's, and I was able to buy a brand new one off of ebay last year. The person that I bought it from, his father passed away and he had it still in the original box with all the cables, instructions, and CD disc. His father grabbed it when a store that he worked in went belly up. It was in storage all this time never used, so I bought it for $300.

It is a pain to setup as the adjustments are underneath the unit. I guess the mfg decided that once adjusted, you probably won't be needing another adjustment. I'm more concerned with the unit and the capacitors since it's been sitting unused all this time. The electrolytic caps will still degrade over time even when you don't use it, so I make it a habit of turning it on every time I turn on my main system so it gets some use. I noticed it does sound better once it warms up.
My all transistor CD-4 demodulator wasn't working either when i bought it 2 years ago. After replacing all electrolytic capacitors, it came to life and worked flawlessly ever since.
 

Doug G.

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I have never understood putting any controls on the bottom of a unit, regardless of how often/seldom any given control may have to be adjusted. The SE-405, although the separation/carrier controls are right up front, they are still on the bottom so the only way they are semi easy-to-use is if the unit sits at the top of any stack.

My Heathkit -29 series units are the same. Although they are great for having input level adjustments so you can have all inputs at the same level when you change from one to another and it makes the loudness control more meaningful, the controls are on the bottom so you have to flip the receiver or amp on it side to adjust them, a real pain. The earlier Heathkit receivers/amps had these controls right up front and although I realize putting them on the bottom, mounted right on the preamp boards was a production/cost measure, it certainly is irritating to the user.

Doug
 

Wurly1

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I have never understood putting any controls on the bottom of a unit, regardless of how often/seldom any given control may have to be adjusted.

Doug
I think it's to avoid kids messing around with your settings.:)
It reminds me of the cleaning lady we had at my parent's home back in the 70's.
Our Fleetwood color TV had a set of picture controls hidden on the upper right rear of the cabinet. They acted as a "picture preset" selectable thru a switch on the front of the cabinet. So if anyone mess around with the front control, this button switch to the back preset and dad was happy. :geek:
The problem was, everytime the cleaning lady moved the furnitures around, she would inadvertently mess with the presets. That was driving my dad crazy!:poop:
 

jupp369

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hat could be played back through the demodulator! I thought th
Hi par4ken, don't know what you found, but maybe it's me. I posted a short message before some month..

Recording? Very easy:

Solder a cable behind the RiAA equalizer output capacitor and record it on Computer.
Feed in again at (almost) the same point via Capacity, but disconnect RiAA, i.e. before the resistor bridges, filters and before the CD4 demodulator circuit.
Works great!
Small switch (2xUm) with 2 sockets Out, 2 sockets In via e.g. 4.7uF (Panasonic SEH 405 still needs 2 resistors each about 22k for the DC voltage symmetry).
If possible use low-capacitance cables, e.g. the thicker RGB or composite.

In the JVC 5436 the RiAA is on top, the circuit board can be turned easily. Unhook the scale rope - otherwise there may be mourning!
2 long conductor tracks calls for cutting (so that the output resistance chains are retained).
From the left (C411 / C412 4.7uF-) out to the switch and recording, Input via pins 407/408.
With the JVC 5446 I would lift the pin from the C407 / C408 (on the demodulator board) and solder it there. Feed in again via connections 407/408.

For recording I use the Panasonic SEH 405 and an (older) MSI with Realtec HD audio.
Record + edit with Audacity (freeware), save as WAV 192kHz / 24bit (96kHz gives triangels) and see the 30kHz sinus!

For playback I have some Fantec XMP600 and Icy media players (others do it also) connected via RGB cable !
NEVER use HDMI - use RGB !!!! With the HDMI handshake, the TV mostly reports back: send less than 20kHz.
Also works well with Data DVD.
If you do playback from PC, check the maximal output frequency in your driver app, should say 192kHz. My MSI's do it, but my HP laptop can only 48kHz.

Calibration: think, there is no new calibration at the receiver/decoder needed. The volume can be controlled by the player and separation refers to the decoders circuit.

Now I have recorded around 150 songs, playing without problems, and without always getting up for record change. Editing takes a bit time to get out the knocks (Audacity repair function), and you can also rise the 30kHz with the equalizer to a good level.
And my vinyls are on e-bay..
 

jupp369

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Hi Wurly1, do you have a system with PLL circuits?
I would be interrested to know which type the chips are, so my next Quadro amplifier gets much smaller.
(Normal Stereo PLL need a 19kHz carrier to activate them instead looking for the 36kHz carrier.)
 

Doug G.

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Speaking of demodulators :D, there are quite a few on eBay right now. Many more than there used to be a few years ago. Sellers want more money than, say, 10 - 15 years ago (I paid less than 50 bucks apiece for both my SH-400 and SE-405) but hey, wadda ya gonna do?

Also, the only difference between an SE-405 and SE405H HAS to be the cartridge supplied with the base unit. The SE-405 came with an EPC-460CM4 cartridge and the SE-405H came with an EPC 450C II. If you look at the actual demodulator itself, it just has SE-405 as the model number.

Doug
 
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