Conference cookie::notes$archive:cd_v1

    I am in no way technical but at over 150k bucks a crack it can't
    be all that bad.
    

    Gee, Dave, do you think we could use one of LDP's products here?
    What is the successor to the MINC anyway?
    

    The PDP12 :-)
    
    Jeff
    

    RE: .1  The big bucks are for the 24/36/48 track beasts while a
    Sony F1, or PCM 1610, or even the home use 2-tracks are in the 1-10K
    range.
    
    As far as I know, no recorders oversample or use digital filtering.
    They rely on 11+ pole "brick-wall" analog filtering to prevent sampling
    frequencies beyond 20Khz.  If CD players were still so crude, the
    public wouldn't accept them they way they did 1st and 2nd generation
    machines.  I'm sure the CD industry is in no rush to make public
    the (lack of) technology used in digital recording.  Mastering isn't
    done with megabytes and big winchesters, its done with tape machines.
    
    Why should Audio, Stereo Review, or High Fedelity ruin business
    by saying how much work digital recording needs?  They tried their
    best to tell you that even the first generation players were perfect,
    but the truth eventually came out anyway.  About the only reviews
    I've seen of professional recording equipment has been in Studio
    Sound, the professional sister publicaton to HiFi News & Record
    Review.  
    
    This month, HFN&RR did publish reviews of 3 home PCM recorders.
    Like CD players, 400Hz square waves rang from edge to edge.  Analog
    does not do this.  There is a good illustration of 1khz square waves
    in Philip Greenspun's article that appeared in both the Absolute
    Sound and Computer Music Journal.  His article exposes many of the
    problems with digital recording and suggests solutions too. 
    
    
    This morning I took another look at my set of Sony PCM 1610 schematics.
    The 1610 is the most popular digital machine in the recording industry.
    It is a 2 track player/recorder to be used with a U-matic type
    professional video tape machine.  This machine is commonly used
    to make AAD CDs, converting a 2 track master into a CD master tape
    to send off to the CD plant.
    
    Besides not using oversampling or digital filtering, and using
    "brick-wall" analog filters, the parts quality wasn't too good.
    The microphone input goes through a transformer, 6 operational
    amplifiers, a black-box "brick-wall" filter, and an electrolytic
    coupling capacitor before reaching the analog-to-digital converter,
    with each one degrading the signal by some amount.  Various ceramic,
    tantalum, and mylar capacitors also populate the signal path.  The
    A/D converter is of unknown quality.  Power supply regulation is
    fair.  Sony uses 3-terminal fixed regulators with chokes and capacitor
    filtering.  Much better is possible, but costs more to do.
    
    Good converters from Burr-Brown vary in quality and price ($100-$300),
    though poorer monolithic converters exist on the market for ~$40.  I
    can't see Sony using the good ones.  I suggest people visit the
    Dec library and read up on A/D conversion.  Its tough to do well.
    
    After reading about how difficult A/D conversion is, I have absolutely
    no faith in DAT recorders.  At consumer price levels, they will
    have too many compromises to sound good.  Expect to read that they
    are wonderful ... until someone wants to sell you a better one.
    
    I'm trying to learn more about digital recorders, but its very hard
    to get access to any information -- especially when the information
    is harmful to sales.

   .4 puts his finger on what I find wrong with modifications of CD
   players, as a meaningful way of getting better sound.  How can simply
   substituting a few capacitors, or an opamp, possibly nullify any damage
   that has been done to the signal prior to you're getting it?

   It is much more difficult to build an antialias filter/track-hold/A-D
   converter than the DAC used in a player, so much that the DAC's in players
   are surely better than even Burr Brown A-D devices (at least oversampling
   dynamic element matched units like the Phillips).

   Rather than worrying about A-D converter specs, or what scope waveforms
   look like, talk to someome who has used something like the PCM-F1 for
   some live recording in 16 bit mode; even better listen to some live
   tapes of theirs.  In spite of its theoretical weaknesses, digital audio
   does seem to work well - without the fuss of tuning up an analog tape
   machine to get a really accurate recording.  CD's that sound inferior
   do so because of inept recording engineers, not opamps.

   - Jim

    This is the sort of chicken-egg circle that analog disk suffered
    thru for years.     A LOT of the recording equipment was trash.
    The same arguement that Jim states was used for disk playback for
    years by many in the trade and press (whats the point in striving
    for playback perfection if the material is rubbish). Up to a point
    that makes sense (I feel that point is what you call the average
    consumer).  What stubborn folks (like TAS) found was that when someone
    actually did make decent playback equipment (ARC and Grado were
    among the earlier ones in prem'o stereo playback equipment) there
    were actually records that were well recorded.  That seems to have
    started a snowball, small at first and only among audio nuts, which
    resulted in a cottage industry producing records as well as they
    as they could (in contrast to the biggies which aimed at quanity).
    
    The point is, the suppliers will only do as good as the people with
    the bucks (us) demand.   
    
    As long as the industry thinks there is no market for better they
    wont bother.  I am willing to bet that since the CD player mods
    have started cropping up and rumblings of elitist players become
    louder, the sources of our best analog disks have begun hacking
    the PCM et. al. recorders they used to 'prove' CD inferior to their
    direct transcription analog systems. If the process is anything
    like it was in analog development, it will take a few iterations 
    to identify the sore spots and implement a solution (the analog
    portion of the CD process should be a piece of cake by now, so
    my guess is the learning will take place in the analog conditioning
    and conversion to digital).
    
    Now, as playback systems go....the stuff I have 'seen', mostly thru
    this file and the contributors, indicates that the majority of the
    equipment from the original manufacturers contains the same blend of
    design/quality/hype as the previous 20 years of analog only equipment
    by these same folks. One may or may not agree that there is room
    for improvement. The folks who found improved sound in analog only
    equipment thru parts changes are finding exactly the same opportunity
    in CD playback because the same analog parts are being used as before.
    The only major difference is that the CD signal needs about 300
    times less amplification than that from an analog disk or tape and
    different non-linear processing (filtering/eq).  Once the analog
    playback section has been exercised to death by the audio amateur
    I think the next step is to begin to understand the D/A processes
    and how to improve on them.  During all this it would be wise to
    make as much press noise as possible (TAA, TAS, etc., etc.) to keep
    the equally paranoid recordists (Sheffield Labs, etc.) stimulated
    and soldering irons hot - thats how we nuts will improve the front
    end.

    Walt

    RE: .4
    
    Sorry, I did forget about the recording engineer.  S/he could ruin
    everything.
    
    Making whatever equipment as good as possible will minimize further
    losses.  And, unless the CD player and rest of the playback system
    is very good, recorder limitations won't appear.
    
    Digital recorders require tuning too.  There is a good-lengthed
    section in the PCM-1610 manual on this.  Isn't there any for the
    F1?  The F1 is one of the poorer digital recorders.  Nakamichi sells
    a modified version of it using better parts.
    
    Data conversion has been around for a while and the technology exists
    for good 16-bit aquisition.  Making a top quality recorder or player
    is only a matter of money.  The importance of good capacitors has
    been known for over 10 years, yet its still a rare to find them
    in audio equipment.  Most consumers won't pay the extra money. 
    Neither will many recording studios - though the good ones have
    techs that modify everything.
    
    Unless the CD buyers demand better recordings, they won't happen
    (exept for the rare case of a tempermental artist-type who doesn't
    like his sound and reverts to analog).  Face it.  Records are meant
    to sound good on AM and FM on cars and portables using compressed
    signals to maximize coverage and advertising revenue.  After that,
    they are supposed to sound good on $400 rack systems.  The old RCA
    and Murcury recordings were designed to be as good and accurate as possible
    and that's why audiophile's value them so much today.
    
    When writing record labels asking for what you've always wanted
    to see on CD, ask them about the recording equipment's quality.
    Act semi-naive, otherwise they'll think you're in the biz and ignore
    you.  Appear CD-crazed.  Tell them you love digital and that CDs
    look so neat.  Be sure and ask when you can re-purchase all your
    favorite recordings on DAT for car and portable use.  Act a nerd.
    Labels catering to classical and yuppie fans instead of teeny-
    boppers will be more receptive because their customers buy quality.
    
    Windham Hill would be a good label to push.  They (like Sheffield,
    Reference Recordings, Wilson et al) sell based on quality, yet are
    also large enough to say to Sony: "Hey, how about making a good
    digital recorder?"

    I know the F1 is not a perfectionist design (I just happen to have heard
    recordings on it, and can't speak for some of the other recorders) -
    still, you should hear some tapes made on it by a good amateur recordist.

    Some of the Boston chapter AES members (Brad Meyer, Dick Burwen, etc)
    have had excellent results with this machine.  I think some of the
    staff at Goodwins may have tapes they've done, and their playback
    equipment is certainly top notch.

    It is much more important to convince the big record labels that we
    want natural sounding recordings without a lot of multimiking and
    other gimmickry than to concentrate on equipment.  Look at the small
    labels like Sheffield - their records are so good mainly because of
    their technique, the equipment they use only plays a very small part.

    Consider something like bicycle racing: putting a titanium freewheel
    on your bike won't help you win any races - you have to be fit to do
    that.  Even though you could measure the few ounces difference in
    weight, I'm sure noone could tell riding on the road.

    A good place to read up on digital audio is the AES conference
    proceedings from Rye, NY from a few years back (1984?).  The papers
    spanned just about the whole subject.  I could provide some other
    pointers to important papers I've read, but don't have the information
    handy right now.

    - Jim

    Re: .2
    
    The successor to the Minc?  VAXlab.  See PYRITE::VAXLAB for any
    more information on this subject.

    Re: responses to original question
    
    Thanks, keep them coming...
        
    						-Dave

    re .-1
    I see by my Sales Update that VAXlab offers an A/D converter
    called the ADV11-DA which will go 50kHz, but only offers 12 bits
    of resolution!  When can we expect the 16-bit oversampling version
    Dave? :-)