Non-LP sources of CD-4 music

[No Quarter]

Hi, just got my Marantz 4400, CD-400B and 4-channel pickup up and running, and have bought a few LPs on ebay. And it sounds amazing I think, especially live performances like Elvis in Madison Square Garden. This of course gives me appetite for more music. Without being too technical myself, the CD-4 is "just" music with the rear signal in a higher frequency area, right? If so, are music files like that available on CDs? On Youtube? Is there a Spotify for CD-4 music?

I've tried to play some youtube videos that claim CD-4, but the CD-400B box does not convert to quad, and the "radar" light doesn't light up.

Thanks

 

[furui_suterioo]

Hi, just got my Marantz 4400, CD-400B and 4-channel pickup up and running, and have bought a few LPs on ebay. And it sounds amazing I think, especially live performances like Elvis in Madison Square Garden. This of course gives me appetite for more music. Without being too technical myself, the CD-4 is "just" music with the rear signal in a higher frequency area, right? If so, are music files like that available on CDs? On Youtube? Is there a Spotify for CD-4 music?

I've tried to play some youtube videos that claim CD-4, but the CD-400B box does not convert to quad, and the "radar" light doesn't light up.

Thanks

CD-4 demodulator will only work with CD-4 records, unlike SQ and QS which will work with any stereo source. The rear channels on a CD-4 record are actually summed with the front channels and only the difference signal is in the higher frequency carrier so that there is no loss of sound when played in 2ch.

 

[No Quarter]

CD-4 demodulator will only work with CD-4 records, unlike SQ and QS which will work with any stereo source. The rear channels on a CD-4 record are actually summed with the front channels and only the difference signal is in the higher frequency carrier so that there is no loss of sound when played in 2ch.

But a CD-4 LP can be recorded on a 4 channel tape recorder, and played with full effect? Can't the sound, including the high frequency carrier be digitized and then shared?

 

[par4ken]

But a CD-4 LP can be recorded on a 4 channel tape recorder, and played with full effect? Can't the sound, including the high frequency carrier be digitized and then shared?

A four channel tape recorder does not have the necessary frequency response to record the high frequency carrier. It can obviously be recorded after demodulation by the CD-4 Demodulator onto a four channel tape.

It is possible to record the LP digitally if the sample rate is high enough, ie. 96 or 192 KHz. Some here have done it, the files can be played back (and recorded from) a modified CD-4 Demodulator. Others have recorded the LP flat and then used software to decode it, there is a thread about that here as well. The software runs on Mac.

 

[Doug G.]

You should search out and read material about how CD-4 works. It will lead to a much better understanding and less mystery.

Doug

 

[kfbkfb]

https://worldradiohistory.com/Archive-Poptronics/70s/1972/Pop-1972-09.pdf#page=12

A fairly good explanation of CD-4.


Kirk Bayne

 

[MidiMagic]

You Tube does not have the bandwidth to carry the carrier.

 

[jupp369]

s me appetite for more music. Without being too technical myself, the CD-4 is "just" music with the rear signal in a higher frequency area, right? If so, a

CD-4 is like Stereo Radio, but instead 27kHz they used 300kHz (no higher frequency in the rear). You can easily record it to Computer after the first amplifier (RIAA), but that need a peace of wire. You have to play it back at the same place, before the frequency filters and the Demodulator circuit. I recorded all my CD-4 on computer with Audacity and cleaned them (.wav 24/192kHz (not lower!!))
YouTube plays mpeg and mp4 or variations from them. so they are limited to 2x 24kHz. Take a closer look with Audacity zoom if you see the 30kHz in thoose "CD-4" files.

 

[jupp369]

I recorded all my Quadradisc without problems and I play them from Data-DVD oder media-player without any loss.
Of course there are many traps:
24/192kHz WAV is needed or you get triangles instead a fine sine. Audacity is a useful tool with it's repair function.
Don't connect any HDMI, the handshake will limit your output to 20kHz! Use RGB.
And you need a new wire (need 2 out and 2 In = 4) soldered just behind the first amplifier after phono input, the RIAA equalizer. I did with 5 / 3 amplifiers from JVC and Panasonic without problem.
With my old XP compi that was no problem, but win7 and higher has limiters for In and Out. So I use now an external analog - USB made for musicians (Focusrite Scarlett 2i2 = 150$) and I'm very satisfied, no hum, direct USB - wav.
Sorry can't send you a sample, because yahoo limits all attachments to 25MB.
If you want to do it, ask more info.

 

[mblindsey]

I recorded all my Quadradisc without problems and I play them from Data-DVD oder media-player without any loss.
Of course there are many traps:
24/192kHz WAV is needed or you get triangles instead a fine sine. Audacity is a useful tool with it's repair function.
Don't connect any HDMI, the handshake will limit your output to 20kHz! Use RGB.
And you need a new wire (need 2 out and 2 In = 4) soldered just behind the first amplifier after phono input, the RIAA equalizer. I did with 5 / 3 amplifiers from JVC and Panasonic without problem.
With my old XP compi that was no problem, but win7 and higher has limiters for In and Out. So I use now an external analog - USB made for musicians (Focusrite Scarlett 2i2 = 150$) and I'm very satisfied, no hum, direct USB - wav.
Sorry can't send you a sample, because yahoo limits all attachments to 25MB.
If you want to do it, ask more info.

I don’t mean to hijack this thread, but I’ve searching for the “definitive guide to digitizing CD-4 records”, I hope my reply stays within the spirit of the thread.

I’ve read enough to know it can be done, and I think I have all the gear to do it, but I’ve not seen mention of soldering this wire anywhere yet ((probably just missing it the awesome pile of expert knowledge on this site), and I’m probably missing other things too . Ultimately, I would like to create a bit for bit digital representation of the actual analog vinyl media. I don’t know if that would be supported in a single FLAC file, or If I would need (some number of) individual WAV files to represent both the audio and the carrier signal. I envision a world where my discs are backed up, can be played via computer, but still must be demodulated within software or an outboard CD-4 decoder. For the later, the computer would be sending sending that vintage decoder exactly what it is expecting to receive (probably need to attenuate that signal?). Any pointers? I have to think this has been done already by some smart person around these parts . Much to learn and many questions…. Thanks!

— Michael (noob ramping up as fast as I can)

p.s. pointers to best practices for cleaning up clicks and pops, as they do happen, is appreciated too.. I’ve never done a “needle drop” … think that’s term for digitizing vinyl? I’m a Mac guy, but have Windows and Linux too. I use an older RME UFX interface, but also have a Sound Devices MixPre 6 II that can record high bit/sample rates too (33bit float).

 

[kfbkfb]

An all software CD-4 decoder (2 decode options, has pop/click reduction option):

Stereo Lab - JVC CD-4 Decoding in software

JVC CD-4 decoding in software

pspatialaudio.com

Needledrop amplifiers:

Groove Sleuth MICRO

non equalising phono preamplifier non equalizing phono preamplifier non equalising phono preamp low-cost non equalising phono preamplifier groove sleuth non equalising phono preamplifier

www.phaedrus-audio.com

(Pspatial Audio is taking suggestions for additional CD-4 decode modes)


Kirk Bayne

 

[jupp369]

There are many threads here around
Needle drop is the simplest way: get your compi at the needle, and play back same way.
"Working CD-4 (software) Demodulator!" is the tread. But I'm not satisfied with that: very low voltage, delicate to distorsions (and I got my neighbours cellphone ringing in it)

My recommendation is recording after the RIAA: handsome voltage, easy to edit, simple playback into a demodulator. Look into your amp's circuit to find the point where the signals are splitted and take a look at wav: music , maybe it helps.
Audacity is excellent

 

[gene_stl]

Working CD-4 (software) Demodulator!

http://www.pspatialaudio.com/JVC_CD-4.htm ^^^ Please email them. Kirk Bayne

www.quadraphonicquad.com

 

[barfle]

While I haven’t done any digitizing of CD-4 records, my understanding of the RIAA curve is that it would virtually eliminate any vestige of the carrier, at least down 20dB (1%), so I’d see if I could find a preamp without the EQ. Then digitize at 192kHz at least to WAV, in order to record the frequencies of the carrier with any hope of retrieving them.

And I’ll admit, I’m not sure what you’re trying to achieve. If it was me, and I know it’s not, I’d record a 4-channel 96k/24 bit FLAC of the output of a decent analog decoder. Of course, I’m interested in how this pans out. Keep us posted.

 

[par4ken]

Jupp is tapping the signal out of the demodulator (after the preamp, before the demodulation is done) and then reinserting the recorded version back into the same place. His method requires a modified demodulator. The RIAA equalisation done inside the demodulator does not affect the subcarrier (obviously, or it wouldn't work)!

I suppose that you could also record using a flat preamplifier and then feed that into the phono inputs of the demodulator after attenuating the signal to match the cartridge's low level output.

 

[kfbkfb]

(and I got my neighbours cellphone ringing in it)

I don't understand this - AFAIK, this problem hasn't been reported elsewhere - there are these options:

Groove Sleuth MICRO

non equalising phono preamplifier non equalizing phono preamplifier non equalising phono preamp low-cost non equalising phono preamplifier groove sleuth non equalising phono preamplifier

www.phaedrus-audio.com

Working CD-4 (software) Demodulator!

It may be of help to read the following links regarding making CD-4 needle-drops: General advice: http://pspatialaudio.com/needledrop.htm CD-4 specific: http://pspatialaudio.com/JVC_CD-4.htm#levels Best, Richard

www.quadraphonicquad.com

Kirk Bayne

 

[mblindsey]

And I’ll admit, I’m not sure what you’re trying to achieve.

The original thought that came to mind was “How can I take the (arguably complex) 45-50 y/o analog physical media, and preserve an exact copy of it, unprocessed by EQ/demodulation, in a digital format?” Is that a smart thing? Maybe not - still learning. It was just the first crazy idea that popped into my head. Like, copy a CD-4 record as easily as I can transfer a DAT tape to a computer, with source matching destination exactly (<- used loosely … of course there is an extra ADC step added minimum)

I appreciate all the responses here, the pointers, and don’t be shy about telling me “that’s a really bad idea” - cheers!

 

[furui_suterioo]

I'd like to go the modded demod route just so that the equipment still gets used. We should start a "How to mod your demod" thread.

 

[jupp369]

Jupp is tapping the signal out of the demodulator (after the preamp, before the demodulation is done) and then reinserting the recorded version back into the same place. His method requires a modified demodulator. The RIAA equalisation done inside the demodulator does not affect the subcarrier (obviously, or it wouldn't work)!

I suppose that you could also record using a flat preamplifier and then feed that into the phono inputs of the demodulator after attenuating the signal to match the cartridge's low level output.

As you know, the RIAA is needed for MM-coils to compensate the frequency response.
Of course you can use a flat amp. and do the equalization later with your audio editor (audacity has a scheme for that).
But, don't care, the 30kHz is strong enough to survive the RIAA without a bypass. Later you can also lift the carrier with the editor.
As I said before, I think, you can also use any phono pre amp because the industrie would not spend extra money for a LowPassFilter in the case that someone might come with a quadradisc.

 

[MidiMagic]

Jupp is tapping the signal out of the demodulator (after the preamp, before the demodulation is done) and then reinserting the recorded version back into the same place. His method requires a modified demodulator. The RIAA equalisation done inside the demodulator does not affect the subcarrier (obviously, or it wouldn't work)!

I suppose that you could also record using a flat preamplifier and then feed that into the phono inputs of the demodulator after attenuating the signal to match the cartridge's low level output.

The block diagrams of CD-4 supplied in the 1970s show that the carrier is split off just after the first preamp. Then the demodulation is done, and then the RIAA de-emphasis is applied.

The original thought that came to mind was “How can I take the (arguably complex) 45-50 y/o analog physical media, and preserve an exact copy of it, unprocessed by EQ/demodulation, in a digital format?” Is that a smart thing? Maybe not - still learning. It was just the first crazy idea that popped into my head. Like, copy a CD-4 record as easily as I can transfer a DAT tape to a computer, with source matching destination exactly (<- used loosely … of course there is an extra ADC step added minimum)

I appreciate all the responses here, the pointers, and don’t be shy about telling me “that’s a really bad idea” - cheers!

The problem is that the recording medium would have to have a frequency response out to 50KHz

As you know, the RIAA is needed for MM-coils to compensate the frequency response.
Of course you can use a flat amp. and do the equalization later with your audio editor (audacity has a scheme for that).
But, don't care, the 30kHz is strong enough to survive the RIAA without a bypass. Later you can also lift the carrier with the editor.
As I said before, I think, you can also use any phono pre amp because the industrie would not spend extra money for a LowPassFilter in the case that someone might come with a quadradisc.

RIAA is not needed for just certain kinds of magnetic cartridge. It is needed for all magnetic cartridges. Ceramic cartridge bars are specially "cut" so the ceramic itself has the RIAA curve.

The RIAA recording curve has several purposes:
1. Increase recording time by reducing the deep bass to reduce cutter swing at low frequencies.
2. Increase high frequency response by increasing the high frequencies sent to the cutter.
3. Make all records play the same way - a standard.

The RIAA playback curve is the opposite of the recording curve. It boost the bass and cuts the treble in exactly the same amounts the recording curve changed them. The result is an exact reproduction of the original sound.

Note that both curves steeply cut frequencies lower than 15Hz and higher than 22KHz.