Choosing an Amp
As a devotee of more than one Internet guitar forum
I have observed the same thing time and time again, people that seem to
have the wrong amplifier for their needs.
One thread I recall seeing was devoted to a beautiful hand-wired
amp of about 45 watts. While
everyone rightfully sang the praises of the sound the amp produced there
were also almost unanimous comments that the amp was too loud.
It occurred to me at that very moment that many people end up in
the same boat, they have an amp that sounds great but it’s too loud for
them to turn it up into its sweet spot in their normal use.
Technical Stuff
Logic would tell us that a 100 watt amp
is twice as loud as a 50 watt amp but this is one time where simple
logic fails us. When
telephones were invented it quickly became necessary to learn how to
measure sound. Without this
it would have been impossible to design a telephone system that operated
at a consistent volume. The
unit of measurement became the “bel”, named for Alexander Graham Bell.
One bel represented what we would perceive as a doubling of
volume. What is interesting
is that it takes ten times as much power to add 1 bel to the volume of a
sound. Think about that for
a moment, if you are listening to an amplifier that is putting out 1
watt it would take 10 watts to make it seem twice as loud to your ear.
When it comes to dealing with sound
pressure levels the bel was found to be a bit cumbersome to deal with so
the decibel was adopted as the standard of measurement.
Three decibels (3db) is a barely perceptible change in volume and
requires a doubling of power to accomplish.
Once again, if you are listening to an amp putting out 1 watt it
would require 2 watts to turn the volume up enough to be noticeable.
So, based upon this information a 100 watt amp is barely any
louder than a 50 watt amp.
We can actually see the relationship
between watts and volume in practice if we look at one of the most
famous lines of amplifiers ever made, the blackface Fenders of the ‘60s.
There was the Champ at 6 watts, the
Princeton
at 12 watts, the Deluxe at 22 watts, the Super Reverb at 45 watts and
the Twin at 85 watts. Each
of these amps is roughly twice as powerful as the model below it.
Had there been a 65 watt amp in between the Super Reverb and the
Twin the difference in volume between it and either of its neighboring
models would have been indiscernible.
One more thing and then well get a bit
less technical, I promise.
The louder a sound is the smoother it sounds to our ears.
With or without distortion an amplifier sounds smoother when it’s
operating loudly. Beyond
that, when an amp is driving harder it tends to compress adding to the
impression of smoothness. In
short, when it comes to Rock and Blues the louder you play through your
amp the better it’s going to sound to your ears.
Trouble Rears Its Head
So someone hears their favorite
guitarist on a recording or in concert and wants to sound the same.
The most natural thing in the world is to buy the same guitar and
amp as your hero and turn it on . . . and be disappointed in what you
hear. Even with identical
gear it’s not always so easy to capture the sound you hear in a
recording or a concert. The
first, and possibly most important reason is the fact that you are
probably not playing at high volume when you are at home.
Even when playing a gig at the local watering hole you are
probably 20 or 30 decibels below concert volumes and the sound, by the
very nature of sound itself, will be different.
Recordings made in commercial studios are sometimes also made
with the amps screaming at top volume.
Recording studios usually don’t have to worry about offending
their neighbors.
Knowing Your Needs
The first step to choosing an amp that
sounds good is to accurately assess your needs.
If you are playing mixed-bag material at small clubs you probably
would never need even as much as 50 watts unless you were competing with
a very loud drummer. If you
are playing strictly at home 15 watts is more than you are likely to
ever use, for that matter even 5 watts is probably overkill.
The picture gets a bit cloudy if you
are looking for natural overdrive.
Most tube amps will get louder as you turn them up but at some
point or another they quit getting louder but instead get more distorted
as they are turned up. OK,
that’s simple enough but the strength of the signal going into the amp
can, and likely will, have an effect on the breakup point of the amp.
When an amp is turned-up near the top of its clean range a note
played softly will sound clean while a note played hard will be broken
up.
So, What Does it Take to Get Good Sound?
There are probably as many answers as there are
opinions of what constitutes a good sound.
A lot of people that play Rock and Blues want some degree of
overdrive and spend a lot of effort trying to find the perfect
compromise. Many people prefer the sound of an amp breaking up on its
own over the sound of an effects pedal so smaller amps can be desirable
if you don’t want to offend the neighbors with excess volume.
But even if
all of this comes into focus there is one more element that is forgotten
at times, the fact that the same sounds are perceived differently at
different volumes. Even if
you find a home-sized amp that emits the exact same sonic spectrum as
the amp that some guitar hero uses at a concert it will still not sound
the same because equal loudness contours make sound seem different at
different volumes. The
response of our ears is much more flat at high volumes than at low
volumes.
I’ve seen stereos that had a “loudness”
button that changed the equalization of the sound so that it sounded
loud even at modest volumes.
Another way of achieving a similar effect is by using a compressor.
It doesn’t actually change the equalization but it does soften
the initial attack of each note and delay the decay of each note,
accomplishing these things by manipulating the volume automatically.
This fools the ear into thinking that the volume is louder than
it actually is. It is my
contention that much of what we like about the sound of a cranked up
amplifier comes down to compression.
Tube amps will compress naturally at higher volumes as the tubes
lose their ability to follow the volume changes accurately and the
result is natural compression.
One big problem is that we tend to try
out amps at high volume and then we take them home and find that they
don’t sound as good as they did back at the music store.
Acoustics are tricky at times and it’s easy to be fooled by sonic
behavior that is contrary to intuition.
So What Amp is Right?
That subheading is only there for comic
relief. There is no single
answer for a “right” amp. I
do think that there is a tendency on the part of most people to buy a
larger amp than is really needed.
It’s also my opinion that trying to chase some ideal sound is
usually futile. Commercially
produced recordings are usually heavily processed and it’s entirely
possible that the sound we hear on a recording is not all that close to
the live sound of the artist.
Even concert sound is the product of the soundman to a great
extent.
As a very general suggestion I would
say that choosing a smaller amp is usually a safe choice.
Also, a compressor is a great way to simulate the sound of a
concert at loud volume.
Beyond that it only makes sense that you can only do so much within the
volume constraints that reality places upon all of us.
