Posted by Sean Naismith on June 13, 2000 at 22:25:14:
In Reply to: I need advicee on buying a new amp posted by Joel on June 06, 2000 at 02:13:29:
Whether you're looking for your first amp or getting ready to upgrade to a massive rack
system, it's important to take the time to carefully assess your needs, consider your budget,
and shop around. Don't be swayed by clever salespeople or your friends, no matter how
convincing they may be. Your amp is a vital element of your sound, and if you rush into an
unwise purchase, you'll be shopping again soon (and trying to unload a used amp). With that
in mind, here are a few things you should know before you spend any of your hard-earned
An amplification system has four main components: preamplifier, signal processor, power
amplifier, and speaker cabinets. The preamplifier has an input jack, where you plug in your
instrument cable. The preamp's main job is to prepare the signal coming from your bass to
be amplified, primarily by boosting its amplitude (voltage). Most preamps have a signal
processor section, which may be as simple as bass and treble tone-control knobs. In most
modern amps, this section includes an equalizer, and it may also have built-in effects units,
such as a compressor and/or chorus.
After the signal has been adjusted by the preamp and modified by the signal processor, it's
passed along to the power amplifier. This is where it's increased to the voltage level required
to be loud. Because a low-frequency sound is harder to produce than a higher-pitched
sound, bass amps must have lots of output power. Today, even small amps often produce
100 watts RMS or more, and large power amps rated at 600-800 watts RMS are
becoming more common. The last step in the signal chain is the speaker cabinet, where
electrical energy is converted into mechanical energy by the speakers. To do this, the
electrical signal is passed through a voice coil attached to a flexible cone; as this cone moves
in and out, it produces sound waves in the air.
There are three types of bass amps. The simplest is a combo amp, which has all of the
components in a single unit. Your first amp is likely to be a combo amp, and you'll probably
have one throughout your career, for practicing and rehearsing. Combo amps typically have
one or two speakers mounted in an enclosure that also includes the preamp, signal
processor, and power amp. The most common configurations are 2x10 (two 10" speakers),
1x12 (one 12" speaker), and 1x15 (one 15" speaker), although many other combinations
exist. Generally speaking, combo amps are the least expensive type, with list prices
beginning around $200.
For most club gigs, you'll use a stack or piggyback system consisting of a "head" (sometimes
called a "brain") and one or more speaker cabinets. In this type of system, the preamp, signal
processor, and power amp are all contained in the head enclosure. A stack is quite flexible;
speaker cabinets can be added or changed easily, and the head can be replaced by a
different unit. Typical two-piece systems for club gigs start at around $700 and prices range
well into the thousands.
Today, more and more professional bassists rely on a rack system. This is a more
sophisticated version of a stack, with separate preamp, signal processing, and power amp
components mounted in a roadcase. Because a rack system is modular, it's easy to upgrade
one component while keeping everything else the same, and various signal-processing units
can be added over time. Many rack systems are either stereo (with separate power amps
for left and right channels) or bi-amp (with separate power amps for high and low
frequencies). While a rack is by far the most flexible type of rig, it's also the most expensive.
If you want to put together even a fairly simple rack, the cost will probably begin around
$1,000--and that's before you buy the speaker cabinets.
Now that you know the basics, here are five essential questions to ask yourself before you
go amp shopping:
Where will I use this amp?
If most of your gigs are in tiny clubs, don't buy a system that won't even fit onstage. And
don't forget to consider how you'll be transporting it: Can you get it into your car?
How loud do I play?
As a general rule, if you have to turn your amp up more than halfway to get sufficient volume,
you need more power. Clean bass requires lots of headroom, so make sure you've got
enough power to handle the gigs you play.
Is it reliable?
Most modern gear is built to stand up to years of on-the-road abuse, but it can't hurt to ask
around. If there's a good electronics-repair shop in your town, check with the technician to
see which bass amps are on his bench too often.
Can I try it out?
A music store is not a real-world sonic environment. If the dealer won't let you test the amp
on a gig, try another dealer. You may have to make a deposit or provide some other form
of security, but that's a small price to pay when you're pondering a major purchase.
Can I afford it?
There are two sides to this question. Obviously, you can't buy an amp if you don't have the
money (and beware of time-payment deals--they're usually a ripoff). On the other hand, you
shouldn't buy a "bargain" amp that's underpowered or unreliable. In the long run, it will turn
out to be more expensive. Balance the cost of the amp against your real needs and consider
all the alternatives. Look at used amps, too; although they must be checked carefully, they
often represent outstanding value.
A final point to consider is whether you prefer the sound of tube or solid-state circuits. For
bass players, this isn't quite as volatile an issue as it is with guitarists, many of whom would
rather eat ground glass than plug into a solid-state amp. With regard to circuit design,
modern bass amps are available in three "flavors": all-tube, all-solid-state, and hybrid.
All-tube amps, which are available from Ampeg, MESA/Boogie, Trace Elliot, and other
companies, have tubes in both the preamp and power amp. (Even these amps, it should be
noted, usually have some solid-state circuitry in the signal-processing section.) Many bassists
swear by this design, insisting that nothing sounds as warm as an all-tube amp; others are
turned off by the heavy weight and maintenance requirements of tube amps, especially since
good replacement tubes are becoming more difficult to find. Not surprisingly, all-solid-state
amps are now far more common, and they are offered by many manufacturers, including
Carvin, Fender, Gallien-Krueger, Peavey, and Randall. Loud, reliable, and lightweight, these
amps feature much more sophisticated circuitry than the early "transistor amps," which were
noted for their sterile sound and frequent meltdowns. Hybrid amps combine both types of
circuits, using tube preamps and solid-state power amps. Made by ADA, Hartke, Hughes &
Kettner, SWR, and others, these systems are growing rapidly in popularity. Which type
sounds best? That's up to you.
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