Lou Dorren: A new CD-4 Demodulator!!! [ARCHIVE]

[rolvkarsten]

Great, Lou!
Thanks a lot.
I hope all this does not hinder your new CD-4 demod too much http://www.johana.com/~johana/dorren/.

Rolv-Karsten

 

[herby]

The diagrams are nice. Thanks, Lou. The important thing to note is that the composite output (the right side of the diagram) on BOTH methods when correctly tuned is IDENTICAL. You can make the signal either way, but the end result is the same. This is not obvious to a casual reader, but with some (very) higher math one realizes that it is the case.

 

[kfbkfb]

Regarding Neutrex and the CLC:

I don't have a copy of the RCA Quadulator AES paper,
but I remember that the people who developed it
did listening tests with and without Neutrex and
decided to not include Neutrex in the RCA Quadulator.

The CLC conditionally increases the carrier level by
about 4dB, considering that after 100 plays, the
carrier level may drop about 3dB, does the CLC really
do very much to help carrier recovery?

Referring to my previous post about storing the entire
CD-4 signal in a 2 channel digital audio recording,
if Neutrex and the CLC are not used, would (standard
stereo LP) Diameter Equalization seriously disrupt
carrier recovery?

Kirk Bayne

 

[loudorren]

Hello kfbkfb,

Kirk, RCA decided not to use Neutrex because they used Dynagroove (Reduced license fee paid to JVC). CLC does improve long term playback of the sub-carriers and maintains the 20dB sub-carrier to main channel ratio at peak main channel levels. The diameter EQ is only applied to the main channels and has no affect on the sub-channels. The control of all of these subsystems include the lathe and cutting head in the signal loop. Variable pitch and variable depth cutting stylus control are very important. Without these the playing time of an LP would be considerable less than 30 minutes per side. Your idea will work if the lathe and cutting head are included in the loop when cutting.

Lou Dorren

 

[kfbkfb]

Regarding the CD-4 Sum Signal/Baseband
recorded level:

I set my cassette deck meter to show
-3dB using the "standard level" on the
Shure era-III test LP.

Love theme from the Godfather
APD1-0001 Peaks at -3dB

Carly Simon No Secrets
EQ5049 Peaks at +6dB

Carly Simon Best of (has some
of the songs also on EQ5049)
EQ1048 Peaks at +3dB

Blackbyrds Flying Start
FPM-4004 Peaks at +3dB

Edgar Winter {SQ encoded}
PEQ31584 Peaks at +3dB

I would think, in order to maximize
the Sum Signal/Baseband S/N ratio,
the CD-4 recorded level would always
be as high as possible, however, it
seems there was a wide variation
(nearly 10dB) in the recorded level,
why?

Kirk Bayne

 

[loudorren]

Hello kfbkfb,
Kirk, The level you see is based on the time used on that side. Generally, the longer the content the lower the level. This is controlled by the variable pitch and variable depth system on a relative basis. The mastering engineer will calculate the absolute maximum level to be used based on the particular program material length. The engineer will then review the content for the side being cut and make test cuts of the loudest sections at the minimum pitch for that level and verify with a microscope that there are no groove kisses at that level. If there are, the engineer will either lower the record level slightly (only a few kisses) or widen the minimum pitch (lot of kisses). Another test cut is then made and microscopically viewed. If every thing is good (no kisses) the the master is cut at that level, pitch and depth. Two or three iterations are not uncommon when setting up to cut a master. I am not surprised by a 15dB difference between the loudest and softest peak levels on stereo and CD-4 LP levels. This is why, as a mastering engineer, I can tell you that we all loved to master 45 RPM singles over LPs because they were all short, loud and mostly monaural!

Lou Dorren

 

[rolvkarsten]

I thought I had posted all my JVC technical papers on CD-4, but it seems I have not. Here is the "All you ever wanted to know about the CD-4 disk system". Please excuse the not so good scan. Maybe I 'll do a better one one of the days. In the meantime...

http://www.yousendit.com/transfer.php?action=download&ufid=5D690E0702F5531C

Rolv-Karsten

PS. It's only good for a limited amount of downloads over one week. Are there some place we could host such documents oneline?

 

[rolvkarsten]

Lou et al.
With your new demodulator coming up, do we need a new quad amplifier to accompagny it as well? The old quad amplifiers and receivers were designed pre-Otala, pre-Transient Intermodulation Distorion. Today's 5.1/6.1 receivers in my opinion also usually lacks in different ways.
An amplfier built to modern standards, but with the vintage look! Would that be something?

RK

 

[proufo]

Lou et al.
With your new demodulator coming up, do we need a new quad amplifier to accompagny it as well? The old quad amplifiers and receivers were designed pre-Otala, pre-Transient Intermodulation Distorion. Today's 5.1/6.1 receivers in my opinion also usually lacks in different ways.
An amplfier built to modern standards, but with the vintage look! Would that be something?

RK

I'd be satisfied with an integrated 5.1 switchbox.

 

[The Quadfather]

Any modern 5.1 amp equipped with analog inputs would work. OK, here's an idea for the demodulator. branch off the undemodulated outputs from the preamp, mix them together and run it through a low pass filter to get a .1 output for the subwoofer. Viola! 4.1 audio!

The Quadfather

 

[rolvkarsten]

I'd be satisfied with an integrated 5.1 switchbox.

It was to a large degree a joke!
But the switchbox is neccessary as most surround equipment of today is equipped with only one analogue multichannel input. In my setup this is occupied by the Denon DVD-3910 universal player.
RK

 

[rolvkarsten]

Any modern 5.1 amp equipped with analog inputs would work. OK, here's an idea for the demodulator. branch off the undemodulated outputs from the preamp, mix them together and run it through a low pass filter to get a .1 output for the subwoofer. Viola! 4.1 audio!

The Quadfather

But Quadfather, this is normally done in the AV Receiver?

RK

 

[Quadro-Action]

This discussion will go something away from the new demodulator. But nevertheless my comment for the connection between quadraphonic sets and new amplifier. I think, for really quadraphonic fans, who own beneth a demodulator also a decoder, 4-channel tape and 4-channel Q8 machine (and SA-CD and DVD-Audio player an 4-channel mini-disc), the one or at most two 5.1 inputs of modern AV receiver are many or too less. So I have connected new stereo pre and power amplifier (2 and 2) which allowes a connection of seven 4 (5.1) inputs for the quadraphonic and surround sources. And also blu ray player have the digital-decoder inside and analog outputs. So we can go back to the roots, which is for many of us the coming Dorren-Demodulator.

Dietrich

 

[kfbkfb]

(May be a little off topic)

Is it time to propose compatible
discrete 5 channel FM to the FCC?

FMmono=C(enter front)
+L(front)+R(front)
+LS(urround)+RS(urround)

FMstereoL=0.5C+L+LS
FMstereoR=0.5C+R+RS

FMquadraphonic
LF=0.5C+L
RF=0.5C+R
LB=LS
RB=RS

EDIT on 2008-02-12:
A carrier containing C only could be added
(in quadrature) to the "76kHz" carrier.
By using the above channel reassignments,
Discrete 5 channel FM would then be
compatible with Quadraphonic FM,
Stereo FM and Mono FM.

Kirk Bayne

 

[herby]

No, there is no need for ANY 5.1 system. It can all be done AFTER the fact. The current 5.1 systems are all stupid anyway. In the movie mixes (where the 5.1 is used mostly) they are quite lazy and put all the dialog in the middle instead of panning properly to the left or right (or the rear channels). The silly ".1" channel which is supposed to be "non directional" is a joke. Low frequencies ARE directional (listen to where thunder comes from). As Quadfather said in message #226, a simple mix/lowpass is all you need.
Attempting 5.1 is a waste of time. Quad is the best, don't corrupt it!

 

[Quadro-Action]

For music listeners with hifi loudspeakers is the usual LFE Channel unnecessary - only, if one is working with little satellite boxes and need additional bass. And the best of the quadraphonic technic is, that it is the most economic technic. A quadraphonic mixdown is also done with 5 channles. Because the fifth is "only" the phantom center, so are needed only 4 channels for the transmitting. And the listener at home will hear nevertheless 5 channel surround, but in all hinsight easier as the today surround with a 5.1 (7.1?) setup and some complicated adjustments - look only to a quick change of the balance front-back, which is sometimes needed by not ideal surround-mixdowns. And of course, one can have in most situations also a well around sound by video-surround with a 4-channel installation. And for an best exhaust of our 4-channel music gems in CD-4, we need further on the new Dorren Demodulator.

Dietrich

 

[herby]

Solution: Buy 4 good quality speakers. Yes, the nice massive ones that have a full range reproduction capability. Anything less is inferior.

p.s. Full range: 50-15,000 Hz (at the power necessary to do the job).

 

[rolvkarsten]

Not if you are using the 5.1 channel direct inputs. They just pass the discrete input signal to the amplifier with no bass management.

Hmmm. The problem with this concept is that the frequency response of the 5.0 channels of a DVDA or SACD goes from DC and up, just as low as the LFE. OK, the problem is halvway solved by the player's bass management. Halfway because probably SACD is then necessarily converted to PCM.

In my opinion all music shall reside in the 5.0 channels. No bass related to the music belongs in the 0.1 (LFE) channel. The bass manager's job is to route the bass to the subwoofer.

But I also see your point...

 

[loudorren]

Hello Al QQ people,

Installment IV is now up a http://www.johana.com/~johana/dorren.

I Will answer other questions at next post.

Lou Dorren

 

[bmoura]

Hello Al QQ people,

Installment IV is now up a http://www.johana.com/~johana/dorren.

I Will answer other questions at next post.

Lou Dorren

Is there a problem with the link to Part IV? I can't seem to get it to download.