All amplifiers are not created equal, and what works for one user may be useless to another. With so many options, configurations and features available it can be difficult deciding what amp to buy and what speakers to match them up with.

Different sized speakers have different tonal characteristics, and you should consider speaker sizes the same way you’d consider an amp’s wattage rating. Wattage is a measure of electrical power described most simply as voltage x current (amps). It is an indicator of how much power a speaker can physically take without distorting or physically breaking, whether that is from burnt voice coils or blown speakers.

Exactly how do you come up with the correct amplifier and speaker combination?

Impendence is measured in ohms (Ω), usually 4, 6 or 8. The lower the impedance, the higher the demand the speakers place on the amplifier, which is why matching the impedance of your speakers to your amplifier is important. Most speakers will be 6 or 8 ohms, as are most amplifiers. 2 channel amplifiers are often capable of handling impedances of anywhere from 8 ohms, all the way down to 2 ohms.

If you were to connect 6 ohm speakers to an 8 ohm amplifier, they would put more pressure on the amp than it’s designed to handle, and produce poor sound. There is also the risk of the amplifier overheating, shutting down, or even burning out altogether.

Low impedance amplifiers are used in high quality sound systems and some will run down to 2ohms but also operate above 16ohms. All perform greatly in the 4ohm - 16ohm range which means two 8ohm speakers daisy chained off one channel of the amplifier will give a 4ohm load, therefore giving you the highest performance in terms of wattage output that the amplifier is capable of delivering.

2ohm amplifiers will give an even higher power output than one that will go down to 4ohms. The higher the impedance load, the lower in terms of watts output the amplifier will deliver. You can change the impedance load by altering the way you wire the speakers to the amplifier, allowing you to increase the number of speakers above two 8ohm speakers per channel, without lowering the impedance load the amplifier sees.

If you work out your speakers RMS (root means square) power rating and impedance loading on each amplifier channel, then make sure the amplifier is capable of delivering 50 - 100% RMS power more than the speakers RMS power rating. An example would be, 1 x 200watt RMS 8ohm speaker per channel should have an amplifier capable of delivering 300 - 400watts RMS per channel at 8ohms, and if you use 2 x 200watt RMS 8ohm speakers per channel, you then have 400watts RMS of speaker power handling to play with, this time with a 4ohm amplifier load, and you require an amplifier capable of delivering 600 - 800watts RMS at 4ohms, and so on.

Power handling is measured in watts; it is best represented by RMS. This tells us how much power the speaker can comfortably handle for a sustained period of time before the audio becomes distorted.


 Instrument amplifiers

The standard features for most amps are two channels, one clean and one overdrive. If you are into country, blues or soft rock you can look to amps that produce a good clean sound and softer overdrive. If you play metal or more extreme music you want an amplifier capable of high-gain overdrive. Many amps land somewhere in between that category and incorporate onboard digital effects, but knowing the type of sound you’re after can help narrow down your choices. It’s important to know what you need to meet your requirements.

The power output of an amplifier is labelled in watts. Tube amps are usually louder than solid-state amps of the same power for example a 50-watt tube amp will be much louder than a 50-watt solid-state amp. How much power you need in an amp depends on what you intend to do with it and the genre of music you play.

Drums are loud, even acoustically, and your amp needs to be heard above the sound they make. For a tube amp, anything less than 40 watts will strain to be heard above a live drummer. For solid-state 80 – 100 watts is a safe bet, but when it comes to solid state more is always better.

If you’re only playing in your bedroom, you can use a low wattage amp. However low wattage speakers break up at lower volumes but they tend to disintegrate at excessive volume levels; high wattage speakers may not break up at all. Choose a speaker that has the components you need and one that sounds defined and lively.

If it important you have enough inputs for everything you want to plug in, whether that is your iPod, turntable or USB. Most amps have many features on their back panels, such as a place to plug in a footswitch, external speaker jacks, power cut switches, ground switches and more.