| Editorial November 2004
The Home-Theater Bypass
Home Theater & Sound has reviewed a wide array
of home-theater gear over the past several years. Components discussed in these pages
range from speakers to processors to projectors to cables. We’ve also discussed
system models: just how all of this stuff fits together to make a home-theater setup work.
I’ve been a proponent of the multichannel preamplifier
for several years now. Our writers have reviewed, and I’ve written about in my
"Surrounded!" column on SoundStage!,
some mighty fine examples of the breed. In fact, I recently spent some time with the Audio
Research MP1, which you’ll be reading about here in a few weeks, as soon as reviewer
Anthony Di Marco has finished taking its measure. I thought that its functionality, sound
quality, and general ergonomic thoughtfulness made it a wonderful centerpiece for my
surround-sound system. It’s unfortunate that components such as the MP1 have been
more or less abandoned by the industry.
The system model based on a multichannel preamp is fairly
simple: a component such as the MP1 controls source switching, channel calibration, and
volume level. The source player, a DVD-based machine, decodes discs and applies processing
-- most often DTS or Dolby Digital -- and feeds the multichannel preamp through analog
cables. The multichannel preamp then drives the system’s amplifier(s).
I’ve favored this arrangement because it seemed to me
to be logical for two important reasons: keeping all the digital processing and decoding
within the source player confines the digital manipulation to a single component. After
all, the disc player must output the signal from the high-resolution music formats of
DVD-Audio and SACD in the analog domain anyway (although this is changing, slowly). It
also made sense from an upgrade standpoint: We all know digital components have the
shortest shelf life, and that multichannel preamps such as the MP1, with their mature
analog technology, should remain "current" for years. This scenario would
hypothetically mean that consumers would want to upgrade only one digital device, the
source, as processing technology continued to improve. I foresaw, back when the universal
A/V player was introduced to the market, a couple of digital and analog inputs eventually
showing up on source players so that the processing power the player already contained
could be used with other components. How hard would it have been to have a Pro Logic II
decoder in the DVD player so that a "Red Book" CD signal could be output in
surround as well?
Alas, my predictions missed the mark. Source
components’ processing powers have still not advanced beyond a rudimentary level
(excepted by only a few products, such as the Linn Unidisk SC). Beyond basic Dolby
Digital, DTS, and some barely functional bass management, the processing in source players
is all but nonexistent. As a result, the consumer has been left with a second system
model: that of a surround-sound processor handling decoding when fed a digital signal from
the source player. But that leaves us with a dilemma: As DVD and surround
processing improve, there are now two components in any given system that will need
upgrading. Perhaps that was the industry’s plan all along.
The rosy spot in all of this is that some companies have
introduced genuinely upgradeable surround-sound processors and have supported these units
with regular updates. These are decent hedges against having to scrap an expensive
component when Dolby releases a shiny new processing mode everyone just has to have. But
while I’ve been known to drop a few dimes on gear, I just can’t get excited
about a $10,000 surround-sound processor when I know its cutting-edge features will be
supplanted at half the price within two years.
There is another solution: the home-theater bypass, aka the
unity-gain input. This feature, fairly standard fare among today’s multichannel and
two-channel preamps, allows an external processor to control the volume of two or more
channels when these are routed through a specified input on the preamp. The advantage of
this setup is that, when listening to sources such as two-channel SACD, DVD-Audio, and CD,
you can maintain the highest level of sound quality by not using a processor and
instead routing the signal straight from source to preamp. But then, when the need arises,
you also have access to the latest surround formats via a separate processing component.
This does complicate your system somewhat, because you have to add a dedicated processor;
one of the latest receivers is a good choice for most systems.
The upside is that you can invest in a top-quality preamp
that won’t become obsolete as you remove it from the box. When it’s time to
update your processing, you won’t have to ditch your preamp functions -- source
switching and volume control -- as part of the deal. Is this arrangement perfect? Not
hardly, but it’s a viable alternative, and that one many people, including me, have
already adopted.
...Jeff Fritz
editor@hometheatersound.com |
