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New technologies


utcsrgv!pyeung Jul 19, 1982 10:33 AM
Posted in group: net.audio
In the audio industry, whenever a new technology is developed/being developed,
there is always propaganda telling us how good this new technology is/will be
and the old stuff is going to be obsoleted. However, most of the time, these
promises were never fulfilled or at best fulfilled partly.

Some examples are
(1) direct drive vs belt drive turntable - the few "best" sounding on the market    are still belt driven ones (i.e. Linn Sondek, Oracle ...). These turntables
    match the best direct drive turntables on paper and they do sound better.
    For sure, direct drive turntables are, in general, very low in noise
    figures and wow & flutter etc. However, men do not listen on specs.
    As a matter of fact, it is widely known that direct drive turntables
    generate a lot of "noise" in the sub-sonic region which is filtered
    out during measurements. These sub-sonic noises do affect signals at
    higher regions.
(2) we were told that the so called NEW CLASS A amplifiers would be THE
    design for all future amplifiers since they are more efficient than
    pure class A amps while they do not switch as class AB amps do.
    However, the first NEW CLASS A amp (from Threshold) which was aimed
    at the high end market is a flop and none of the NEW CLASS A amps
    from Japan (from where 90% of the amps are using the NEW CLASS A design)
    can make it in the high end market. I listened to some medium priced
    New Class A amps about two years ago and I was not impressed.

Now, we have the digital technology on the horizon. Digital technology does
provide  high dynamic range, low noise, low distortion ... etc. However,
will it replace analogue records, say, within 5 years? I don't think
so. Sure, in long term, digital technology will become the main stream
and analogue records will be completely wiped out, but that will take at
least 10 or more years.
 
There are still many obstacles and problems, to name a few:
(1) price, you can buy a phono record player for less than $200 but
    I can't perceive the price of a digital record player can drop to such price    (at least not in 5 years)
(2) standardization, take a look at 4 channel technology, it killed itself
    by having more than 3 systems on the market. The same applies to digital
    records, there are at least two systems from Japan and Philips Compact Disc.    Although it seems that Philips will win out just as they did when cassettes
    were introduced, the standardization on tape is not yet agreed upon.
    (The standardization in Japan is not yet made international)
(3) D/A conversion is still the weakest link in the system, much has to be
    improved in this respect. The same applies to the anti-aliasing circuit:
    in theory, a wall filter is needed to filter out signals above the
    frequency = 1/2 of the sampling rate. Obviously, this means a very high
    order low pass filter is needed => high cost + accurate alignment.
    Another disadvantage of higher order filters is that they ring like hell.
    Philips tackled this problem by using a mixture of digital filtering +
    a third order low pass filter. This seems quite effective, but digital
    filter is quite expensive.
(4) the theoretical 96 db S/N (16 bits) is quite optimistic - noises are
    generated from the A/D, D/A circuits and, as a matter of fact, white noise
    is added to the signal before it is converted to digital. This is needed in
    order to eliminate the problem in digitizing very low level signals. Thus
    a S/N figure of 70 db is more realistic.
(5) home digital taping (from analogue) source can become quite frustrating:
    you have to watch the recording level very carefully since  
    when a digital recording clips, it does clip like crazy. The increase in
    distortion is almost exponential.
(6) the "fixed number" system being used has a characteristic which is
    substantially different from analogue system - higher distortion at low
    level and low distortion at high level. This may not be desirable since
    most of the time, music signals are at a relatively low level (for
    example, in a domestic environment, the amplifier is working at the region
    of 5 to 10 watts at "normal" listening level while the output may
    jump to 70 to 100 watts (provided the amp is powerful enough) during
    the peak of the music)

 
To make my point clear, I am NOT against digital technology, I am only being
cautious. I think there is an urgent need in standardization and room must
be left for future development. For example, the Japanese standard called for
a single sampling rate of 44.something KHZ, this may not be acceptable by most
audiophile. The "fixed number" digitization is deficient,
I think a "floating number" system is much better (although more expensive).

I won't be the first to buy a digital player/recorder, but definitely,
I will move into it only when the technology is proven to be superior to
the analogue technology.