Buying an Amplifier


Speaker configuration

Some amplifiers, such as many 50 watts combo amps, or even MG15MSII "Microstack" offered by Marshall, have 2 speakers, despite having basically the same amplification circuit of its single-speaker siblings. Sometimes, such 2 speakers configuration may even use a smaller diameter speakers (eg: 2 x 10 inch instead of 1 x 12 inch).


One thing to keep in mind is that a multiple speaker configuration will create phase cancellation., as well as producing frequencies from different speakers that arrive at the ear at very slightly different point in time. The end result of phase cancellation is that it creates a smoothing and rounding off effect, with a slight blurring of the notes. This can give a feeling of a fat texture. Obviously, the flipside is that it lose the tightness and definition of the sound.

Obviously, by having more speaker cones, it will have greater air moved: For example, given the depth is approximately equal, a 2x10 have the surface area of 157sqin, while a 1x12 only have 113sqin. Also, it will have increase power-handling capability, or more precisely, they split the amp output. Thus, given same amplification head, a 2 speaker configuration will have louder volume, but not as much power.

Types of Unit

DI Unit (including amp modelers)

Many so called Amp modelers and micro-amps, especially in regard to Rockman, are actually DI Units. basically, these units transform the unbalanced, high impedence signal from the guitar into a signal that can be used by the headphone, or even connect directly to line-in or balanced mic-input, allowing direct input of guitar to the mixing desk in a recording studio without losing the tone and quality of an amp. Furthermore, the guitar oreinted amp modelers can also be used as modelers or effect units that can be plugged into a guitar amplifier to provide volume.

Another benefit of using a DI unit is that they are compact, while they can go loud and getting that particular tone. This is particularly true for amp modelers and "headphone amplifiers", as their embedded electronics frequently a verysystem most of the time, these may provide a much better alternative, as they are usually cheaper: The Behringer V-Amp 2, for example, is less than $100 dollars.

There are two kinds: one is an analog modeler, which is commonly used in modeling amp (Amplifier that actually tries its best to emulate a certain tone instead of just amping it), and digital computer modeling, such as Line6's POD 2.0. The benefit of using amp modeler is that it allows you to use such effects even in recording, as well as a more easy to maintain equipment — true tube, after all, is a nightmare to maintain.

What amp modelers and effect units does not do, however, is provide the volume; for those, you will need to hook it up to a powerful amplifier, or a loud P.A. system.

Combo Amps

Busking amps

In essence, they are practice amps that have a battery attached. Naturally, that means they are gonna be more expensive. 15 watts on average, but Pignose Hog 30 can go to 30 watts, while Crate's Taxi Series have some that have 50 watts with 10 inch speakers. They will usually provide 6 to 10 hours in one charge. Also, make sure they can take AC power in too when needed. Do note that they are actually quite weak in terms of overdrive. On the other hand, rock and metal music is not exactly busking music, either — soft and light music that add to the atmosphere (usually a park or something) is usually preferred, and thus, the watt amounts is usually enough. A good one is Vox's DA5 (veyr tiny and small) and DA15, as they have modelling processors for an approximation of a tube amp.
Small gig amplifiers

From 30 watts upward, these combo amplifiers the smallest package which is considered suitable as a stand-alone amplifier for small gigs. The standard is usually 50 or more watts of power and one 12 inch speakers, though some manufactures may use less wattages of 30 and 40, while employing more than one speakers. In better models, sound quality begins to approach levels acceptable to professional musicians. Quality is always important, but perhaps even more so in the case of the 1x12 combo - with a good one, you'll prove the doubters wrong, but with one of the many duds, you won't be taken seriously. The 1x12 is not a big amp, and if you want to bring it to a serious audition or gig without enduring a storm of eye-rolling and chuckling, it had better stand out from the crowd. These cost about 180 to 450 dollars.

Heads, Cabinets, and Stacks

When purchasing the two, make sure of the ohmage of the cabinet, and the power rating for the head at that ohmage. Make sure the cabs RMS rating is about the same as the head's power output at the ohmage of the cab. A head can be solid-state or tube, the latter being less durable, but sounds better and is more expensive. A good solid-state head costs 200 to 600 dollars and a good tube head costs 500 to 1400 dollars. A cab in a half stack should be a 1x15, a 2x12, a 4x10 or a 6x10. These typically range from 250 to 650 dollars.

Tube vs Solid State

On the note of volume, a tube amp is in general louder, given the same watt; a 5 watt tube amp can rival the power of the 30 watt solid state amp.
Tubes amps have a very organic tone and are sensitive to their input signal. The harder you dig in with your pick, the more they tend to break up and distort. The softer you strum, the warmer and breathier they appear to sound. Multiple preamp gain stages can sometimes push an amp to the point where you do not hear the pick attack on the string. Finding a balance where pick attack and sustain are clearly articulated is the sign of a superior matched preamp and power section. With a great tube amp, the subtle changes you make with your pick and finger pressure can be heard so that you can create your own identifiable style.

Modeling

Another solution is to use modeling amp with onboard effects, which is basically a combination of a very clean power amplifier with the tone modeling unit producing all the tone. Some may consider this as the swiss-army knife of amplifier. The best of these amps can reproduce the sound of many other units with passable accuracy, and you have instant access to those cool effects that make even crappy guitarists sound good - delay, chorus, flanger, reverb, etc. With enough effects, your little old grandmother can sound like a rock star. Okay, that's an exaggeration, but if guys like me can sound good, you can too.
Another note to keep in mind is that solid-state amps have a fast attack time, where the note is immediately present when strumming. Modeling amplifiers seem to have a bit of a lag between your pick attack and the sound produced. Tube amps have a compression that is dependent upon pick attack. Ultimately, what sounds right depends on the player.

Physical size

Just because you can afford to have a very powerful amplifier (in both money and wattage) does not imply you should get said amplifier. A problem for a traveling musician (especially those poor students that take public transportation) is that, for a high wattage, you will have to pick up a big amplifier that can be too cumbersome to carry, while a small enough amplifier may be bad for gigging.

For example, if you live in a small partment (especially Japanese apartment), you may have to get a smaller and weaker amplifier. Aside from obvious quieter sound, the smaller physical space available may also make storing even a full size 1x12 amplifier difficult.

In another example, Traynor's TRM30 (1 x 10" x 30w)and TRM40 (2 x 8" x 20w ) are both good audition amplifiers. However, the TRM30 is taller, while TRM40 is wider. Furthermore, TRM30 is at 21 pounds, while the TRM40 is at 34 pounds, about one and a half times as heavy. Considering that a some people may have to carry their entire recording setup — a laptop, effect units, guitar— the slight difference in mass and dimension may makes the difference in the ease of carry.

Typical features

Essential

  • Input - where you guitar cable goes in
  • Power button - turn it off and on
  • Master Volume - on a tube amp, this could be the only knob that you can touch, which in this case double as gain

An amplifier that only have these three is Epiphone's Valve Junior, seen as the cheapest reliable tube amplifier.

Almost standard

  • Gain — determines the amount of distortions. The higher it goes, the more over drives it has. (And shattering your dreams: 11 doesn't mean it's better than 10 of another amp, if both are turned to the max!)
  • EQ / Tone - Used to control the tone of the sound. May have only 1 knob (simply general tone), two (treble and bass), or even a 7 band EQ that not control treble, midrange, and bass, but also other including prescene.
  • Phone output — used to plug in headphone so you can practice in the middle of the night.
  • Channel selection — most modern solid-state practice amp have two channels; one for clean signal, and one for a overdriven output

Other stuff

  • Modeling - One way to solve the clipping problem in solid state amp is the use of DSP modeling, which allows one to play tube-like overdriven sound.
  • Extra effects — some units have build in effects, such as reverb and chrous, which can be easily controlled right on the panel by one or more knobs
  • Effect loop — can be a single plug (and need to be split), or seperate plug as "effect send" and "effect return". Used for time-based effects (delay, chrous, looping, phase shift, and flanging), as using the effect loop will preserve the sound and effect of the amp.
  • Line in, 1 or 2 — used to plug in external audio sources. they come out without passing through the preamp, and thus just louder.
  • Line out - used to connect to another power amplifier or PA system.
  • Speaker out - connect to another guitar speaker. Typically only found in head units, but some combo units have them too to make the output even louder.
  • Footswitch plug—allow the use of footswitch to control internal effects, or may even select channel.

Tips

  • For most beginners, a 15 watt amp will be more than enough for your bedroom and small gigs.