LBC: Sound Quality was Re: The Complete Bitches Brew Sessions, II

Mike Curtis ironman@MOONLINK.NET
Thu Dec 3 12:45:13 EST 1998


Vincent has it pretty well nailed here.  Assuming a good A/D-D/A
converter in recording and playback, digital is extremely accurate.
Regarding low level detail, digital is actually better than analog, due
to its 90 dB dynamic range.  The best you can get from
phonograph records is around 60 dB, and that's on audiophile
quality recordings.  More typical is around 40 dB.  The human ear
can hear a range of some 120-plus dB.  This is why most vinyl
recordings utilize a lot of compression (Compressor: an electronic
device that quickly turns the volume up when the music is soft and
quickly turns it down when it's loud).  That's why the recording of
"Shout" sounds virtually the same volume throughout despite the
repeated "A little bit softer now" and "A little bit louder now".  The
original, I'm sure, went from concert volume to barely audible, and
back up to concert volume.

Tubes (which can be - and often are - used in analog or digital
recording and playback) actually alter the pure sound, but they do
so in a very pleasant to the ear manner, "warming" it up by taking
the edge off it.  This is a result of space charge, a characteristic
unique to vacuum tubes ("valves" to you Brits - and actually a
much more descriptive term in regard to what tubes actually do)
which I'll describe briefly below.

Also, there is no perfectly linear amplifying device.  All of them
introduce some degree of distortion, even audiophile grade gear.
The goal of great audiophile gear is to minimize distortion and that
the remaining distortion is as much of the "pleasant" variety as
possible.


THE SIMPLE EXPLANATION OF SPACE CHARGE:

Basically, a tube consists of three elements - cathode, grid, and
plate or anode.  The cathode is heated to cause it to emit
electrons.  These are collected by the plate.  The grid is a
screenlike element between cathode and anode that attracts or
repels the electrons emitted from the cathode, causing a much
larger fluctuation in the electron flow.  This is reversed in phase - if
the input goes more positive, the output goes more negative, and
vice versa.

When the electrons hit the plate, some "boil" off, causing a cloud
of electrons around the plate.  The effect of these electrons is to
oppose change in the signal.  This is more pronounced at higher
signal levels and higher frequencies, so as the volume goes up, the
sound is softened more.  It is most noticeable when the amplifier is
driven "too hard", into clipping, as is commonplace in guitar
amplifiers these days.  This is why vacuum tubes are the device of
choice for overdriven guitar and bass.

Solid state amplifiers do not exhibit this effect.  While these are
great as clean amplifiers, they're quite poor when overdriven.  They
clip immediately - and harshly - as soon as their maximum is
reached, producing a range of harmonics not at all dissimilar to
fingernails on the blackboard.

Even at lower volumes, tube amplifiers soften the sound.
Technically, this is not accuracy, but is distortion of the original
signal.  However, it is a desirable distortion, bringing a warmer,
fuller sound to the music.

> On 2 Dec 1998 13:04:39 -0800, in bit.listserv.blues-l,
> seether@ROCKETMAIL.COM (Ocky Milkman) wrote:
>
> >More than that, tubes preserve harmonics and low level
> >ambient detail, both of which are completely stripped by
> >digitizing, yielding a flat 2 dimensional soundstage and
> >instruments that sound too like one another. They also
> >provide tons more midrange information, resulting in what is
> >recognized as a "warmer" sound but is in fact a closer
> >approximation of what the human ear hears. om
>
> Don't mean to beat a dead horse here...... but :)
>
> So if a good recording was made with tube based equipment and
> carefully transferred to CD ie: digital - we would end up with a flat two
> dimensional sound stage with instruments that sound like each other -
> devoid of warmth???
>
> Since low level ambient detail are completely stripped by
> digitizing.......
>
> I don't think that is quite right.....
>
> Tubes do have sound characteristics of their own, and I agree, yes
> they do sound good on some material.
>
> Digitization will lose some sound information, but it is pretty minor,
> because there are some spectacular recording on CD out there - both
> recorded digitally and with analog.
>
> I am not disagreeing some processing and transfers to digital have
> been poor and even abominations - but the wholesale condemnation of
> digital?
>
> I am not ashamed to admit CDs are my first choice in my record
> purchases - because the majority do sound good to me.  I am usually
> very disappointed when they sound poor - whereas when I was buying
> vinyl - I accepted flaws as norm and was very pleasently surprised
> when I got a great sounding record.....
>
> Perhaps our standards and expectations have changed?
>
> Or perhaps we are using exaggerated statements to illustrate some
> quite subtle points?
>
>
>
>
>
> --
>
> Vincent
> vt@pipeline.com
>


--
IronMan Mike Curtis the one man blues/jazz band Reviews, cuts from IronMans CD
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