Where will I be playing?
In the overview article, I mentioned a number of typical environments where you might want to use your amp. This article will mention a number of factors that might be affected, depending on the environments where you want to play.
To remind ourselves, these were the different environments that I listed in the overview: Bedroom, Home Studio, Professional Studio, Busking, Rehearsing, Small Gigs, Medium Gigs, and Large Gigs. I will mention these where relevant during the discussions of the different factors below.
More specifically, how much power do you need? Firstly, this depends on whether your amp will be a tube amp or a solid state / digital (modelling) amp. Tube amps will generally be louder for the same power rating; one watt can be plenty for home use in a tube amp, but even a small solid state amp is likely to be rated at five watts or more. These days, you might need the most power for playing small gigs, because at larger gigs and in studios you will probably mike up the amp or take a direct line out to the PA system. Many engineers regard 5W as the ideal power rating for a tube amp in a studio.
A lot of amps have options to run in different power modes, which can be useful for playing the same amp in different environments. My Victory V40, for example, has four separate power modes ranging from 0.5W to 40W, meaning that it is usable in almost all situations.
A few amps can run off batteries, which can be especially useful for busking. I’m not aware of any solar powered amps yet!
There are a number of practical features, as opposed to the tonal features discussed on the Sounds page, that are included on some amps. These include tuners, additional line (MP3) or microphone inputs, a built-in metronome or drum section, or an attenuator.
The most essential outputs are the speaker connections, and even many combo amps will have detachable speaker leads which permit you to connect an external cab instead of the internal speaker. These are normally rated for different levels of resistance (4, 8 or 16 Ohms), and you must make sure that you connect to the appropriate output(s) for your speaker(s).
Some amps will also have other outputs including a DI (Direct Input, for a PA system) jack socket, balanced (TRS) output, a headphone socket or a USB port. If you want USB output, check the specifications because some amps have USB ports only for control connections, and cannot output sound through them. Also, even if you are using a different output, tube amps generally require speakers (or a load generator) to be connected, otherwise the power amp can be damaged. For that reason, most tube amps do not include a headphone socket.
If you are regularly moving your amp around, for example between gigs, then the size and weight of an amp can be important. This can be a sore subject for old rockers with gammy legs and bad backs, who don’t want to add sprained wrists and crushed toes to the list!
This is one reason why a separate amplifier head and speaker cabinet can be helpful, to split the weight between different boxes, although conversely some people prefer a combo amp in order to have one box rather than two. As well as the size and weight, look out for other features such as strong carrying handles or protective covers and travel cases.
An extreme version of portability is the BluGuitar Amp1, which uses a Nanotube and can comfortably fit on a pedalboard, weighing only 1.2kg.
Reliability / robustness
This is less of an issue for the home player, but in any professional environment, an amp needs to work when you need it, and so it must be reliable and robust to withstand the inevitable knocks. Major acts always have duplicate equipment on hand, ready for the guitar tech to switch on the fly, but if you are gigging or recording professionally and don’t have that luxury, then reliability and robustness are extremely important. A non-functioning amp will cost you time, money and credibility.
We have already touched upon this subject. Amplifiers come in many shapes and sizes. The classic options are either a combo amp or a head and a cab. However, you also have rack-mounted amps, which are often used by touring musicians, and even some very small amps that will happily sit on a pedalboard. In recent times, some advanced multi-fx units also include amp functionality. Lastly, there’s the “toaster” form factor for Kemper Profilers!
A less obvious issue relating to the form factor is the orientation of the controls. If you regularly stack gear on top of your amplifier, you might find top-mounted controls to be a problem. On the other hand, in some situations they may be very practical.
Also, when you’re playing a gig, the lighting conditions can be extremely variable. It might be very dark at the back of the stage where your rig sits, or you might be under a bright spotlight. In these situations, it can help of the controls are clearly marked and easy to distinguish.
Finally, a lot of amps will have some kind of remote control option. In most cases, this is a fairly basic footswitch that might change channels or activate the reverb, but some amps may have more sophisticated remote controls, for example via a MIDI interface, which may be useful in a studio or a gig.
Lastly, let’s not forget about the look of the amp. Let’s be honest; most amps aren’t particularly beautiful, and some are downright ugly. If your amp is part of your on-stage image, for example, then you may as well get one that will look good.