What do they do?

An amplifier does exactly what it sounds like it does; it amplifies. In the audio world, we send the amp a signal and it multiplies the signal to the point that it can run a set of speakers. Ideally, the perfect amp would reproduce the exact same signal it receives except stronger. Unfortunately, this is tough to do and each amplifier adds something to the sound either in the way of sound coloration or distortion.

Amp ratings

Signal to Noise: This is a ratio of the desirable signal to the amount of noise produced by the amp. The higher the signal to noise ratio, the better the rating.

THD: This is the amount of harmonic distortion in the output of the amp. It’s desirable to have the THD rating be as low as possible. 0.1% THD is inaudible.

RMS Power: This is the power number that matters. This is the power that an amp can produce continuously.

· RMS power also comes with an Ohm rating attached. As we discussed before in the electricity section, an ohm is a measure of electrical impedance. When you cut the resistance in half, you double the power. Most amps are 8 and usually 4ohm stable. Some car audio amps are even 2 and 1ohm stable as well. It’s important to know the impedance of your speaker so you know if it is compatible with your amp.

Most people think they need insane amounts of power to get the sound that they need. This is hardly the case in most instances. All speakers have an efficiency rating that states how loud that speaker will play with one watt of power. Pictured at the right of this paragraph, my Focal 6W4311 mids have an efficiency rating of 91db. This means the set will hit a volume of 91db, one meter away, with one watt of power. 91db is a fairly loud listening volume for most people. Every time we double the power we gain roughly 3db of sound. As we discussed before, the decibel system is logarithmic, and for every 10db we perceive the sound to be twice as loud. So if we have 8 watts of power we can achieve 100db of sound. Yet with 128watts we can only get 112db of sound from the same speakers. So, even though we added 128 times the power, we only gained 21db. It’s clear that the first watt is the most important one since it gets us the most output per watt. I’m quite a fan of high efficiency speakers for this particular reason. Pictured below, is a small Sonic Impact amp that I run in my house. It only has 10watts of power and I have yet to turn it up to its maximum output. It’s simply louder than I would realistically ever need. Sales people who tell you that you need a lot of power either don’t know what they’re talking about, want to sell you the more powerful and more expensive model, or think (for whatever reason) that you are running horribly inefficient speakers.

As I stated before, a good amp should reproduce the signal it is given as faithfully as it can. Its sole job is to boost the power of the signal and nothing more. There are a select group of people who feel that certain amps “sound” better than others. This is something that is debated by many people. Tube amplifiers are said to have a warmer sound than solid state amps. I am going to opt not to take a side on the matter of whether or not different amps change the sound or not. In my opinion, if it sounds good; use it. There isn’t any need to complicate matters. I personally want my sound to be as true to the original recording as possible.

Hopefully this information has helped you understand more about audio. If you have any questions you’d like answers to please email me and I’ll answer them to the best of my ability. Thank you for reading!

Content Written by Steven Solazzo