Hi-Fi VCR's Hidden
Audio Capabilities
Recently, an acquaintance dropped me a note to describe a
pleasant discovery he'd made. "In order to tape a long radio show I recently attached
an output from my receiver to my VCR," he wrote. "It worked, but more than that,
I was surprised at the high quality of the sound. I have since had a couple of audiophiles
tell me that VHS is actually a very good medium for audio. Can you tell me if this is
true, and if so, why?"
Yes, it's true, but many of the owner's manuals that come
with videocassette recorders neglect to mention the fact, even though for many of us it
constitutes one of the main benefits of that machine. My guess is that the manufacturers
think it will confuse ordinary consumers, while dedicated audiophiles will figure it out
on their own.
When the various electronics companies were trying to come
up with a workable and economical consumer video system in the 1960s and '70s, they
lavished very little concern on the audio performance of their machines. The challenge of
packing a reasonable video image onto a tape of manageable size forced them to use a
moving-head system that would allow a very low linear tape speed; the slower the tape
unwound from one reel and was taken up on the other, the smaller the cassette could be.
But video needs to process a lot of information in a very
short time, and that traditionally meant high tape speeds. That could be accomplished by
cranking the tape through the machine very quickly, which was how audio extended the upper
part of the sonic range. Given the very wide bandwidth necessary for video, however, that
was hardly practical, so a process of "helical scanning" was used instead. In
it, the tape winds obliquely around a spinning head drum that records a series of long
diagonal tracks on the tape packed closely together side by side. It's a technique that
lets the machine use a high "writing" or "tape-to-head" speed, but
moves the tape itself slowly past the mechanism.
The system produces pretty reasonable pictures, although
some compromises had to be made in the interests of keeping the costs down and in the
knowledge that most TV sets back then couldn't come close to reproducing the full
bandwidth of a broadcast video signal anyway. But in terms of audio, both the common video
systems -- Beta and VHS -- were disasters.
While the video was recorded using the helical scan
technique, the audio was simply recorded in a narrow linear track along the edge of the
tape. Because the tape moved so slowly, the audio performance was awful. Many people
didn't really notice because the speakers in their TV sets had pretty terrible sound as
well, but as viewers became more sophisticated and started hooking their VCRs into their
stereo systems, the woeful state of VCR audio became apparent. Splitting the minimal track
in two to make stereo only made matters worse.
As one of its ploys to rescue the faltering Beta system,
Sony came up with a way to add high-quality sound to videotapes, and called it Beta Hi-Fi
(generically, it's called "AFM", for "audio frequency modulation"). It
was a technique already in use on the laserdisc, in which the stereo audio signal is
modulated onto the video carrier and recorded with it; in tape terms, that meant that the
audio could take advantage of the high bandwidth of the spinning head, and could produce a
very high level of audio performance.
Perhaps rashly, Sony claimed that while the technique could
be adapted to Beta, there was no way it could be applied to VHS. Predictably, VHS Hi-Fi
appeared shortly thereafter with all the same benefits, even if achieved in a slightly
different manner. Nowadays, virtually all commercially recorded tapes have hi-fi sound
tracks (they also retain the lousy linear sound, for compatibility with older machines),
and all but the lowest-rung VCRs are capable of recording and playing in the system.
The hi-fi audio is basically transparent. If your VCR has
it, it will automatically record the high-quality system (and the linear one as well); in
playback, it will default to the hi-fi sound; if it doesn't find it, it will switch to
linear.
None of that means you have to do anything special to take
advantage of the benefits of hi-fi sound when it comes to recording or playing video. But
there is nothing to say that video has to accompany the high-quality sound; the VCR
functions very well as an audio-only recorder.
There are several advantages in using VHS for audio. First
is that the system is much less dependent on machine/tape matching than is ordinary
cassette recording; you are much more likely to get good results by plopping any old tape
into a VCR than into a normal tape deck. Second, the quality is not significantly degraded
if you use slower speeds, which means that a T120 cassette can hold up to six hours of
high-quality recording. Third is that you can use the VCR's timer to record things when
you are absent, just as you can with TV programs. The difference in this case is that the
VCR doesn't have a built-in FM tuner, so you'll have to use an external one and leave it
turned on (but you don't need to keep the speakers on, so it won't disturb those who don't
want to listen).
The main drawbacks are the sheer awkwardness of keeping
track of and accessing such huge programs; unless you have a very accurate tape position
indicator, it'll take you a while to find a three-minute song five hours into a tape. The
other is that very few VCRs let you set your input levels or monitor them with meters.
Instead, they rely on automatic level controls which sometimes work fine and sometimes
"pump" or fluctuate annoyingly.
But for most material, VHS hi-fi works very well. To use
it, simply hook any high-quality audio source into the audio line inputs of the VCR and
record as if you were taping a TV program. You may have to select the input on the remote
with some machines; often you don't. Some early machines required you to provide some sort
of video signal when recording audio, as the video controls the movement of the spinning
head, and that meant the tapes made on such machines contained a peculiar combination of
music and totally unrelated pictures. Today's machines provide a dummy video signal (the
ubiquitous blue screen) when they don't detect incoming images, and that makes audio
recording somewhat easier and somewhat less surreal if you forget to turn off the TV when
playing back.
All in all, it's an excellent recording system, and one of
the best-kept secrets in audio. You may well have had the capability all along.
...Ian G. Masters
ian@mastersonaudio.com
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