Is there a way to decode Quad records with Diamond Cut?

[HearToTemptYou]

I've picked up a few quadraphonic records, and I was wondering if there was a way to decode the rear channel info using some combination of filters in Diamond cut.

I'm currently running DC-ART version 3.12 (I know, I know, I should really upgrade... and I will soon.)

I'm mostly interested in the SQ and CD-4 systems. (I know the CD-4 system isn't likely going to be decoded, since it uses frequencies that most sound cards can't hear.)

The SQ format is a matrixed audio system though, and it's something that I'm pretty sure could be decoded in software.

What I'm trying to do is decode these quad records, and then burn them to DVD disks as DVD-Audio.

Any ideas?

Thanks as always.

[DJBohn]

Hi HearToTemptYou,
I've done several SQ Quadraphonic LP's. Personally, I restored them no differently than any other ordinary stereo LP. I don't have an SQ or QS decoder, but have found SQ and QS is fairly compatible (but not perfectly) with the more modern Dolby Pro Logic Surround Sound which is more or less a "grandchild" of the old quad systems (other than CD-4 which is a discrete 4 channel system). With CD-4 however, you may have a problem finding a compatible phono cartridge as they require a very wide response - up to (I believe) 40,000Hz or more!
I think you would find it a lot easier to obtain a proper decoder unit on eBay or somewhere and use prior to restoration, then process each channel independently. This would probably be the easiest approach. You should have no problem with your early DC product creating the center channel & subwoofer channel for a real DVD 5.1 surround effect!

[HearToTemptYou]

In regards to the CD-4 system, I figured out a way around the stylus frequency response limitation, although it causes other problems.

If you have a turntable that can play back at half speed, that's the way to do it. It slows down the record enough that the computer (or whatever) can capture the full set of frequencies on the record. You can then speed the recording back up digitally, and if your sample rate was high enough, still have all the high frequencies!

The only problem is that once you have those high frequencies, what do you do with them? You still need a CD-4 decoder. Also, slowing the record down screws with the equalization of the original record, although I'm sure that can be corrected in DC-ART.

Looks like I'll have to keep an eye on Ebay for some Quad decoders.

[DJBohn]

New CD-4 cartridges

Hi HearToTemptYou,
If you are in the market for a NEW FRESH STOCK CD-4 cartridge, I found someone that has been working with Audio Technica to create a custom built model that should work for your needs. It uses a conventional cartridge combined with a special Shibata stylus designed for CD-4. It only runs for about $60 and his customer feedback has been very positive on it. Some are even saying it works better than models that were available during the quad era. You can find it on eBay or contact edsaunders@bellsouth.net directly for information. Once you find a CD-4 demodulator, this should work much better for you than your half speed technique.