Quadios - "CD-4 -> Stereo" downmix listening

[kfbkfb]

I know my idea is kinda off-the-wall, however, I estimate that, due to having a marginal CD-4 setup, I've listened to my CD-4 LPs in stereo probably 95% of the time.

Given the excellent sound quality of the Rhino Quadios, I was wondering if anyone has listened to their Quadios in stereo with L=LF+LB and R=RF+RB (to get that CD-4 in stereo listening experience)?


Kirk Bayne

 

[DeanRay]

Excellent question - hope we see some responses. I've recorded all of my quad LPs (200+) to stereo. What I've found is most of the CD-4 LPs have different "stereo" mixes as compared to the "regular" LP. I do not hear as much difference for all other quad formats.

 

[kfbkfb]

Back in the 1970s, I thought quad sound would catch on and CD-4 would be the "winner" for LPs.

I bought the CD-4 releases of albums when possible, but I only had a stereo system, didn't get a good CD-4 demod until 1992-12.

AFAIK, the RCA single inventory CD-4 releases used the CD-4 -> stereo downmix as the stereo mix for stereo 8 track and stereo cassette releases of the album (and stereo LP releases outside the USA) - the Elvis Aloha from Hawaii is an example of this.


Kirk Bayne

 

[DeanRay]

I agree with you - I thought CD-4 was WAYYYY better than all the other formats when it came to separation. Some of the SQ LPs I have sound about the same when compared to playing the stereo LP and simply adding various digital processing, via my Yamaha receiver. I still have my JVC 5456-X that my brother bought for me when he was in the army - we're talking 1975 or so. Wouldn't trade it for the best SQ/QS/RM/whatever quad format receiver.

 

[quicksrt]

I’ve been meaning to do some quad to stereo fold-downs using Quadio releases as working parts.

Thanks for the reminder.

I think I’ll start with AWB and four hits from Bread using Quadio masters. Then try a couple AF SACDs. I think SACDs require a high-frequency noise filter switch on the recorder.

 

[jaybird100]

Back in the 1970s, I thought quad sound would catch on and CD-4 would be the "winner" for LPs.

I bought the CD-4 releases of albums when possible, but I only had a stereo system, didn't get a good CD-4 demod until 1992-12.

AFAIK, the RCA single inventory CD-4 releases used the CD-4 -> stereo downmix as the stereo mix for stereo 8 track and stereo cassette releases of the album (and stereo LP releases outside the USA) - the Elvis Aloha from Hawaii is an example of this.


Kirk Bayne

I had heard they combined the rear channels into the corresponding front channels when played in stereo. CD-4 didn't use phase shifting, as the matrix formats did/do. A CD-4 record, if played through a matrix decoder, will act the same as any stereo record. A surround effect can be created, but it's nothing like what the CD-4 mix will sound like.

 

[barfle]

I have a handful of CD4 LPs, but so far have never heard them in quad. My renovation of a Marantz demodulator isn’t going all that well - terrible distortion and noise, so I have a fairly large troubleshooting and alighnemt project ahead of me.

 

[MidiMagic]

If you played the CD-4 records with a regular stereo pickup, it might be the cause of the distortion and noise.

 

[jupp369]

I have a handful of CD4 LPs, but so far have never heard them in quad. My renovation of a Marantz demodulator isn’t going all that well - terrible distortion and noise, so I have a fairly large troubleshooting and alighnemt project ahead of me.

I recorded also my CD-4's together with the stereo's with a normal amp and got angry that all where distorted.
Than I got the idea that I recorded also the carrier, 'cause a normal amp has no filter (starting at 15kHz) and when I played my recordings over a CD-4 demodulator I got the 4 channels again.
Maybe it would help for testing to put a small capacity after the MM-pre amp (so around 1 nanoFarad) ..

 

[barfle]

I recorded also my CD-4's together with the stereo's with a normal amp and got angry that all where distorted.
Than I got the idea that I recorded also the carrier, 'cause a normal amp has no filter (starting at 15kHz) and when I played my recordings over a CD-4 demodulator I got the 4 channels again.
Maybe it would help for testing to put a small capacity after the MM-pre amp (so around 1 nanoFarad) ..

I can imagine the CD4 carrier and the tape bias signal could interfere with each other and be pretty audible. TBH, I don’t believe I ever had a CD4 record and a tape recorder at the same time.

I’ve set the CD4 project aside for the moment. The preamp seems to be working reasonably well - stereo comes through well, and when the demod is switched off, the CD4 recordings play stereo OK. The problems are in the demodulator. It’s not a simple circuit, and the service manual isn’t clear about all the adjustments.

When I first tried it, I found it had a blown fuse. I opened it up and saw that it had about 100 aluminum electrolytic capacitors in it, so I ordered replacements and also replaced the tin-plated RCA connectors with gold-plated ones. I have a signal source that can provide the required frequency-modulated carrier to set the PLLs, but I have several other demands on my time for a couple of weeks.

Believe me, the noise and distortion weren’t caused by the carrier leaking into the amps. I’d recognize the intermod, and that wasn’t it.

 

[barfle]

If you played the CD-4 records with a regular stereo pickup, it might be the cause of the distortion and noise.

It’s a CD4 capable cartridge with a new Shibata stylus. This is not carrier interference. It’s a demodulator in need of tuning and alignment.

I’ve played a few of my CD4 LPs with a Shure V15 type 5 MR back in the day, and they were reasonable. No interference from the carrier back then. But I’ve had some turntable issues for the last decade that I’m addressing (finally!) now. Hopefully, I’ll have the geat to play all my records by summer.