Conference cookie::notes$archive:cd_v1

I read about this in Hi Fidelity about a year ago.  I believe that
the "L-R" signal is not absent, but merely lower level than it should
be.  The Carver device takes the L and R signals, recombines them to
form "L+R" and "L-R", amplifies the "L-R" signal a little, then
regenerates the L and R signals again.  It also adjusts the phases
of everything to be correct after this amplification.

Carver's comment was that this scheme would work ok until people
learn that CD's are not vinyl and they CAN record full level "L-R"
signals without worrying about the limitations of the medium.
In the meantime, he makes a little money with the gadget.

Carl

I'm glad to see someone helped with how the Time Lens works.  I have
noticed that even with fully digital recordings that this device still
adds depth to the music and when it is turned off the music just seems to
calapse.  I guess it's one of those things where if you don't have it, 
you dont't miss it.  

--Dlae

XXXXXX^(this line)
Can't even type my own name!

--Dale

	The problem that Carver is trying to correct is caused mostly by 
the accuracy of digital recording, to the point of highlighting flaws, 
and the CD technology being temporarily ahead of the recording 
technology. Over many years of analog recording, mikes were fine tuned 
to compliment the analog recording process. Rather than having flat 
responses, they raised those frequencies that were attenuated in the 
recording / mastering / vinyl / replay process. Those same mikes, used 
with digital recording and reproduction technology no longer give the 
desired flat response. Once the recording and microphone technology 
catch up with digital, this problem should go away. It all depends on 
what you are conditioned to hearing as being "right".

Can't see why mikes had to be tweaked to give a "flat response,"
when the recording process uses a well specified RIAA equalization curve
to address the limitations of the medium.  Nice thing about that 
equalization is that preamp phono sections know how to undo it.

	Funny thing about preamp phono inputs and their equalization; 
you can't connect your CD palyer to one. The phono inputs are low level 
(or VERY low level depending on cartridge type) inputs, requiring much 
amplification by the preamp. The CDs all output "standard" level 
signals, just like a tape deck or the preamp itself. If any correction 
is needed, the preamp ain't going to do it for you, or at least todays 
preamps won't.

Some clarification maybe.  Due to certain limitations in the 
record mastering process and media, records are recorded with a very
non-flat equalization (I think the high frequencies are emphasized).  The
phono section of pre-amps are designed to restore a flat response.  This
equalization/de-equalization curve is specified by the RIAA (Record Industry
Association of America?).

[Phono sections have relatively high gain because
cartridges put out a few millivolts (even less in some moving coil designs,
as mentioned). CD players have a builtin pre-amp, supplying the requisite 
voltage for an AUX input, say.]

Anyhow, the CD recording/playback process does not require any special
equalization, therefore none is needed in the preamp.

{An interesting side note - tapes are recorded with a non-flat equalization,
and if you only listen to Dolby encoded FM broadcasts,say, then your CD might
be the ONLY medium you listen to that does not require equalization in the
home}

Well I'm no expert, maybe the CD format does include equalization, does anyone
know?

on the other hand..

I suppose it is more difficult for phono cartridges to trace out-of-phase
information than in-phase ("mono" or "center channel") information.  Out-
of-phase info would cause the cartridge to 'zig' in one plane and 'zag' in the
other.)

Therefore it might be reasonable to assume that the recording process (for
LP's) is designed to reduce out-of-phase information - something not required
for CD's.

	Actually, the out of phase (L-R) signal is what Carver found to
be lacking in the CD recordings, and puts back in whth his "black box" I
seem to recall that something of the mechanics of a phono pickup
emphasizes this signal, so we are used to hearing music with the
stronger L-R signal. Since the CD pickup is not mechanical, it does not
emphasize the L-R signal, and we hear the difference. Which is correct,
what we are used to, what the CD gives us, or what Carver changes it to?

re .-1

"What we are used to" is, I think, correct.  "What the Carver changes it to"
is supposed to be "what we are used to".  "What the CD gives us" is whatever
the recording engineer gave the CD.  I think the L-R signal is de-emphasized
when put onto vinyl because of mechanical limitations of groove size and 
stylus movement.  Apparently, the mechanics of the stylus pickup makes of
(compensates) for this de-emphasis.

The problem comes when the de-emphsized L-R signal is copied directly to
CD.  There is no playback mechanism to compensate for the reduced signal.
Carver tries to compensate, and is probably not necessary for CDs which
are properly recorded.

I believe that response #9 is correct is its analysis.  But until the
engineers realize that the de-emphasis is not necessary there will be
a problem with CDs.  As far as old recordings are concerned, I don't
think the record industry will be re-mastering any recordings to 
eliminate the de-emphasis.

--Dale