"Frankenstein" CD4 Demodulator

[jwb474]

This is my 1st effort to combine the best of both worlds in CD4 technology. My 2nd effort, "Bride" posted earlier was an easy slam dunk to get a CD4-392 based demodulator, but it suffers from the CD4-392's major flaw: It's ARNS and Matrix circuits did not perform as they should and these circuits are the heart of separation performance. When JVC Labs realized this, instead of putting out a new CD4-392, they developed the PTL (Phase Tracking Loop) demodulator. This IC corrected the CD4-392's flaws and improved the tracking. The CD4-392 has a lock range of around 50db. As a guess the PTL would have a range of 70db. But it was the end of the 70s and it was all over. As we hear know the JVC 4DD-5 and Marantz CD400 are actually really good performers and with the Matrix mods that have been published they will perform better than a CD4-392 in that area. The CD4-392 based assembly out of a Sansui QRX I found would be a good candidate to merge with a JVC 4DD-5. As a side note the design of the Fisher assembly that I used the other project is not nearly as suitable to do this job. Attached are the very preliminary drawings on how I intend to proceed with this project.

 

[proufo]

Many thanks!

How I wish I could understand what you do!

What is the source file for your Frankenstein rig?

 

[4-earredwonder]

This is my 1st effort to combine the best of both worlds in CD4 technology. My 2nd effort, "Bride" posted earlier was an easy slam dunk to get a CD4-392 based demodulator, but it suffers from the CD4-392's major flaw: It's ARNS and Matrix circuits did not perform as they should and these circuits are the heart of separation performance. When JVC Labs realized this, instead of putting out a new CD4-392, they developed the PTL (Phase Tracking Loop) demodulator. This IC corrected the CD4-392's flaws and improved the tracking. The CD4-392 has a lock range of around 50db. As a guess the PTL would have a range of 70db. But it was the end of the 70s and it was all over. As we hear know the JVC 4DD-5 and Marantz CD400 are actually really good performers and with the Matrix mods that have been published they will perform better than a CD4-392 in that area. The CD4-392 based assembly out of a Sansui QRX I found would be a good candidate to merge with a JVC 4DD-5. As a side note the design of the Fisher assembly that I used the other project is not nearly as suitable to do this job. Attached are the very preliminary drawings on how I intend to proceed with this project.

Amazing amount of technology involved but having lived through the SQ/QS/EV~4/CD~4 era with all the paraphernalia involved, IMO, the hardware and software of the time really did SUCK and when I switched to Quad Open Reel, including a dolby b 4 channel outboard decoder.....I finally got a taste of what they were really trying to accomplish but unfortunately, the Vinyl surround software clearly outnumbered that of QR by a WIDE margin.

As an aside, when Dutton Vocalion released those 12 RCA CD~4 SACD 4.0 remasters last year [actually, 6 two~fers] from the original QUAD master tapes, I was listening to the Floyd Cramer SACD and on my system the sound was superb and I shook my head and remarked "how did they EVER expect to extract this extraordinary and ultra quiet level of sonics from a CD~4 disc with the poor pressings, crappy cartridges and not ready for primetime CD~4 demodulators of the day?"

I SINCERELY do wish you the best of luck in your endeavor and perhaps with today's superior turntables (don't know about the CD~4 cartridges which I suspect IS the weak link) and increased level of performance from pre/pros, you WILL have better luck than I EVER did from those early 'attempts' at reproducing Quadraphonic sound from vinyl records.

 

[proufo]

(don't know about the CD~4 cartridges which I suspect IS the weak link).

I have little doubt that excellent results could be achieved if someone knowledgeable puts effort into 1) making digital rips at half-speed of CD-4 records (with a regular cartridge) and 2) developing a pre-processing method to optimize them for demodulating.

Then what is needed is to mod a demodulator (sorry!) so the analog signal of a digital player could be fed into it, bypassing all the previous stages.

You seem to be attenuating the output of the Tascam to phono level.