Understanding Receivers
When most of us think of a typical
music system for a home, the system we envision consists of a receiver, a couple of
loudspeakers, and a CD player. Receivers are popular because they are convenient and
economical. Receivers come in many models and types, so when you're thinking of buying a
new system or upgrading the one you've already got, your first order of business will be
to ask yourself what sort of receiver do I want?, what sort do I need?, and what
sort can I afford? However, in order to understand what you want and need in a
receiver, it's a good idea to first understand what a receiver is and what it does.
A receiver is the control center of most music systems. It
enables you to switch easily between sources of music (CD player, cassette tape deck,
MiniDisc player, DAT deck, etc.) and allows you to control volume, and bass and treble as
well. It does all of this by combining, into one piece of gear, three separate components:
a preamplifier, amplifier and tuner. Most people choose to buy a receiver rather than the
three separate components because receivers are more affordable and are simpler to set up
and operate. This doesn't mean that receivers are for everyone. Lots of folks choose to go
the separates route because they like the flexibility that comes with being able to mix
and match the strengths of various amps and preamps with their particular speakers and
source components.
It can get a bit complicated when trying to choose
separates, however. Consider that you'll have to decide whether you'll need a
pre-preamplifier, a tubed or solid-state preamp, a passive preamp, or maybe even no preamp
at all, in addition to figuring out whether you want a stereo power amplifier or monoblock
power amps and whether you want to bi-amp or not. If figuring out these sorts of things
seems complicated, it's likely that you'll head straight for the receivers at your
electronics store. Let's take a look at the fundamental parts of those blessedly
straightforward receivers.
The preamp
The preamplifier is the nerve center of the receiver. It
performs a couple of major functions: it routes the signals from your source components
(these signals are called line-level signals) to your amp and it serves as a volume
controller.
So when you choose to listen to a compact disc, for
example, the CD player sends a line-level signal to your preamp, which then controls the
system's playback volume according to your specifications before passing the signal on to
your amplifier.
When shopping for a receiver, you'll notice that some
models have preamplifier outputs. These are connectors that feed a line-level signal to a
subwoofer, if you like, or a separate power amp. Preamp outputs are a great feature for
those looking to add bass to their sounds with a sub or for those who'd like to add a
separate, more powerful amp to their system.
The amp
The amplifier is the heart of the receiver; it pumps out
the powerful signals that drive the loudspeakers. The amplifier receives from the preamp,
signals which originated from your source components, which it then boosts before sending
them on their way to your speakers.
The power ratings for the amplifier section of the receiver
are what most consumers pay attention to when making a purchase and they're the ratings
that are most easily, and often, manipulated by manufacturers eager to sell
less-than-great equipment.
A typical power rating for a typical receiver at a typical
electronics store looks like this: 100W RMS x 2 into 8 ohms (40Hz-20kHz) at 0.5% THD.
Let's break this down bit by bit. First, "100W RMS x 2
into 8 ohms" means this receiver delivers 100W of continuous power into both
channels, with an 8-ohm speaker load. (Ohms are a measure of resistance to the flow of
electricity.) The next phrase in our typical power rating -- "(40Hz-20kHz)" --
indicates the range of sound available when the receiver is putting out its maximum power.
(Humans can typically hear from 20Hz-20kHz, so the receiver described by this power rating
isn't giving us some of the very low-end signals.) And, finally, "at 0.5% THD"
describes the total harmonic distortion (THD) this receiver adds to the signal generated
by your source component. The lower this number, the less the receiver will distort your
music.
Ways in which power ratings are manipulated: A
simple way to manipulate power ratings is to list them without the "RMS" (Root
Mean Square -- a mathematical calculation which describes the average power output)
designation. The "RMS" designation lets you know that the ratings are for
continuous power, not peak-power capability (you want continuous power, not just when the
lead singer screams over a big guitar riff in a thunderous peak of sound).
Also, sometimes manufacturers will leave off the part of
the specification that tells you that the rating refers to the power of the receiver with
both of its channels driven. If a rating doesn't say "x 2" (or "x 5,"
for the five channels of an A/V receiver), then you can assume that it's for one channel
driven. Naturally, a receiver appears most powerful when driving only one channel.
The tuner
This is simply the part of the receiver that does the
receiving -- in this case, it's AM or FM radio signals which are then fed into the preamp.
Other features
DSP modes: These digital signal processing (DSP)
modes are touted as enabling your receiver to make your music sound as if it was recorded
in a concert hall, cathedral, nightclub, etc. Some people enjoy the big, boomy distortions
that DSP modes offer, but remember, your music collection was recorded in recording
studios (except for your live albums, of course), and you'll probably enjoy the music most
if it sounds as much like it did to the musicians in the studios as possible.
Input/output jacks: These are the jacks on the back
of the receiver where you plug in your source components (inputs) and speakers (outputs).
It's always a good idea to count up all of your source components and check to see that
the receiver you're considering for purchase has at least that many inputs. Also, it can
be convenient to have one or more input jacks on the front of the receiver in case you
ever want to quickly hook-up your portable MiniDisc player, DAT recorder, etc.
Tape monitor: This lets you listen to one
source as you record a second source on a tape deck, or you can listen to a recording as
it's being made.
Bass boost switch: This amplifies the bass.
Tuner presets: This function allows you to choose
which radio stations you'd like to have available with the push of a button.
Treble and bass controls: These allow you to
increase or decrease the levels of bass and treble in your music. Again, remember that
when you change the tones of the sounds you're hearing, just as you do when you engage a
DSP mode, you're distorting what the musicians created in the recording studio, and what
you presumably paid to hear when you bought their CD.
Balance controls: These allow you to shift emphasis
from one channel to the other or to maintain equal levels between the left and right
channels. As with the DSP modes and treble and bass controls, you should be aware that
when you change the balance controls, you're changing the music -- your music collection
was recorded with a perfectly (hopefully) symmetrical balance between the left and right
channels.
A/B speaker selection: Allows selection of a main
set of speakers, a second set of speakers (usually in another room), or both.
Outlaw Audio's Model 1050 offers six channels of power
and various DSP modes for use in multichannel music and home-theater systems.
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One of the first things you'll notice when
you begin to shop for a new stereo receiver is that there aren't many new stereo receivers
to choose from any more. As home-entertainment technology has evolved, natural selection
has nearly killed off the two-channel receiver. In the place of the venerable stereo
receiver stands the new A/V (audio/video) receiver, ready to be plugged into your DVD
player and home-theater surround-sound system.
The good news here is that there are tons of affordable A/V
receivers that do superb jobs of playing back music in stereo. Plus, A/V receivers are
multichannel, allowing you to play the five, six, seven (and more) channels available in
the Dolby Digital and DTS formats. This means, of course, that you'll need five, six,
seven (or more) speakers in order to hear the soundtracks of those DVDs as they were
intended to be heard. It also means that you're going to have to make choices about which
type of sound-processing format you want (Dolby Digital 5.1 and DTS are two examples) and
if you want to be able to listen to the new DVD-Audio or SACD formats for recorded music.
But those are choices generally outside the parameters of GoodSound!.
We assume that you're more interested in music than in movies and that you're trying to
understand what a receiver can do for you when listening to Chopin, R.E.M. or Britney
Spears rather than while watching Gone With the Wind or The Matrix. Luckily,
it's now possible to listen and watch with equal pleasure. Today's affordable receivers
offer lots of features that were not long ago priced in the stratosphere or simply
unavailable.
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