Working CD-4 (software) Demodulator!

[proufo]

This is not related strictly to playback of CD-4 records, but to using a CD-4 record for setting up VTA, for all records.

 

[fredblue]

oh yes, i've found that to be true!
the better i've got the turntable side of things setup for CD-4 the better everything has become, SQ & QS LP decodes through the Surround Master improved, the lot!
i was saying in a PM to a QQ friend recently i've been astonished how changes to things like VTA (which you can't adjust on all turntables) made such a difference.

 

[J. PUPSTER]

oh yes, i've found that to be true!
the better i've got the turntable side of things setup for CD-4 the better everything has become, SQ & QS LP decodes through the Surround Master improved, the lot!
i was saying in a PM to a QQ friend recently i've been astonished how changes to things like VTA (which you can't adjust on all turntables) made such a difference.

I’ve also read that variance in vinyl thickness effects VTA; maybe it should be renamed to “Very Tiresome & Anal”
Seriously what the ‘ell you’ve gotten me into Freddie?

 

[fredblue]

I’ve also read that variance in vinyl thickness effects VTA; maybe it should be renamed to “Very Tiresome & Anal”
Seriously what the ‘ell you’ve gotten me into Freddie?

haha.. i'm sure disc thickness does have an effect but most 70's Quad vinyl is (for better or worse) thin and floppy and not like many modern heavier weight pressings so you can set up the turntable for optimal playback of the Quad LPs and it'll probably be alright for all those 180g digitally sourced rekkids an' all

 

[kfbkfb]

So...

Anyone have any requests for another version of the
Stereo Lab CD-4 Decoder?

(I haven't thought of anything beyond my post #143,
which I just edited to try to better explain what could
be included in the HQ/Classic CD-4 Decoder)

Kirk Bayne

 

[Banjo800]

I bought the Audiophile Edition this past weekend. While it's not quite as good as the QRX-8001 CD-4 Demodulator, still it is very good indeed. I made some comparisons and was quite pleased with the results.
The CD-4 decoder and the upcoming WOW! addon is why I bought it. I collect some old C&W records and quite a few of those are off center, some a little and some a lot. WOW! will be a welcome addition to my software arsenal!
As far as requests for adds/changes to the CD-4 addon, I would like to see a true full decode. From reading this post and the answers Mr. Brice has given, I can see why it is the way it is, but still, the point of quad has always been discreet 4 channel sound. I do feel like the trade-off of using a software decode is worth it, especially if you do not have a hardware decoder.
Excellent software and not just for CD-4!

 

[kfbkfb]

The Stereo Lab HQ/Classic CD-4 decoder option was created to provide a
high channel separation CD-4 decode. I haven't purchased the Stereo Lab
software yet, so I can't comment further.


Kirk Bayne

 

[Mendemender]

I would like to see a true full decode.

There is an option to select which does just that. It works fine for me although you'll soon notice the "sandpaper" if your disc isn't in good condition.

 

[proufo]

There is an option to select which does just that. It works fine for me although you'll soon notice the "sandpaper" if your disc isn't in good condition.

I tend to believe that any demodulating that does not include FM-level adjustment with a test record cannor be full.

 

[Mendemender]

I tend to believe that any demodulating that does not include FM-level adjustment with a test record cannor be full.

With a hardware decoder you need to set it up with a test record. However in software the decoding doesn't need to be done in real time. You can "adjust" the levels in software to find the ones that give the maximum difference between front and back. The results are just as good if not better than using a test record.

 

[proufo]

With a hardware decoder you need to set it up with a test record. However in software the decoding doesn't need to be done in real time. You can "adjust" the levels in software to find the ones that give the maximum difference between front and back. The results are just as good if not better than using a test record.

Of course, but test records are meant exactly for that. And the levels should not be content-dependent.

 

[Mendemender]

Of course, but test records are meant exactly for that. And the levels should not be content-dependent.

A test record just enables you to adjust the levels to get maximum separation front to back. Theoretically, any record will do. It’s just that when listening to music it’s difficult to determine when separation is maximum so test records provide simple sounds such as front only or back only which make the adjustment easier. Software is more flexible in that respect and can do it by analyzing the music. The correct levels shouldn’t be dependent on the content.

Having said that, I don’t know how well that works in practice. Maybe Richard has some numbers.

 

[Banjo800]

Some of the things I have noticed when comparing the Sansui QRX-8001 with the Stereo Lab CD-4 option:
1. The Sansui will provide greater separation than either of the 2 CD-4 options in Stereo Lab.
2. Stereo Lab has more "Sandpaper" effect than the Sansui, i.e. the same record played thru Stereo Lab would produce a "sandpaper" effect in areas where the Sansui did not. However, there was never a significant amount of this noise and the cleaner and newer the record the better Stereo Lab performed.
3. While the visual picture of the WAV file looks quite a bit different between the two methods, the actual sound of the files are quite similar. I believe there is a bit more blending of channels with the software.
4. No matter what, the Stereo Lab CD-4 demodulation software is a MAJOR accomplishment. It still needs some tweaking, but with the proper setup does an astounding job.

My setup for this endeavor consists of a Rek-O-Kut Ultra pre-amp, a Dual 1249 turntable equipped with an AT 440MLa cartridge (I also tried an AT15S with similar results), into a Maya44 Xte 4 channel sound card (I used 2 in - 4 out, of course).
On the subject of clean records, it is stated on the Stereo Lab site that the records must be extremely clean to produce the best results. I use the Spin-Clean method with fairly good results, but I have a couple or three records that look good, but have a tremendous amount of popping and crackling. The Sansui handles these fairly well and I remove the noise with other software afterwards. The Stereo Lab is hit or miss with these as you would guess. Now, I'm thinking of trying one of those ultrasonic methods, but wonder if it REALLY does that much better.

The bottom line, I guess, is that for 90 bucks, the Stereo Lab Audiophile version is a worthwhile investment if you're into this kind of thing.

 

[kfbkfb]

http://www.pspatialaudio.com/CD4_classic.htm^^^
The web page has been updated to include a decode
of a JVC CD-4 test disc (I haven't downloaded Audacity
software yet, so I can't check the F/B channel separation
provided by the HQ/Classic w/automatic separation)


Technics/Panasonic developed a moment to moment
automatic F/B channel separation circuit in ~1974 which
appeared in several of their later model Quad Receivers,
I don't recall anyone here on QQ testing this automatic
separation system.

Maybe the Stereo Lab HQ/Classic decoder could offer
a choice of the old Technics method or the new method.


Kirk Bayne

 

[kfbkfb]

http://www.aes.org/e-lib/browse.cfm?elib=20544^^^
JAES paper detailing the "soft fail" CD-4 Decoder.


Kirk Bayne

 

[kfbkfb]

Some Food for Thought on the (CD-4 F/B) channel separation issue:

http://www.quadraphonicquad.com/for...rround-master-sm-465.17227/page-3#post-171125^^^
"Please note both obtained great results but frankly anything more that 12 dB is just a numbers chase."

(this is where I got the 12dB number in my earlier post)


Kirk Bayne

 

[quattro64]

Hi All,

Just to let you know that there is a new version of Stereo Lab available from today (3.1.14) which includes a quadraphonic decoder for BBC Matrix H (HJ) material. This will also work reasonably well for UMX, BMX, UD-4 discs.

Best,

Richard

Hi Richard,

Any progress on the un EQ'd setting for this software that would be usefull to us Strain Gauge cart owners??

Thanks!

 

[Brice]

Hi Richard,

Any progress on the un EQ'd setting for this software that would be usefull to us Strain Gauge cart owners??

Thanks!

I have drafted the software specification for this (mostly defined in post #113). I did ask at the end of that post whether it would be possible to supply me with a demo file of a needle-drop made with a Panasonic strain-gauge cartridge. Is there any chance of this? I don't want to go ahead and develop this without any test material to check it's working properly.

Best,

Richard

 

[quattro64]

Oh yes, got ya. I remember now, It may take me a bit to get my SG arm back in the rotation :-(

 

[Brice]

Oh yes, got ya. I remember now, It may take me a bit to get my SG arm back in the rotation :-(

That's no problem. Let me know if and when you have something. It might be better to contact us via Pspatial Audio support when you do as I don't monitor this forum religiously.

All the best,

Richard