How to choose and set up a stereo amplifier: part one
Whether you’ve already chosen and bought amplification for your system or are yet to exercise your purchasing power, this guide will help you unlock your stereo amp’s full potential.
Integrated vs pre/power
Do you go for an integrated amplifier or separate pre/power boxes? The former is the most simple and convenient – it packs both pre- and power amplification into one chassis. This means everything has been tuned together, saving you the work that goes into matching separate amplifiers.
Two-box amplifiers involve splitting pre-amplification (input selection and volume control) from power amplification. The idea is to keep the sensitive preamp circuitry and the delicate audio signals flowing through it away from the electrically noisy high-current power amplifier section. Having separate power supply sections helps to improve the sound too.
The most obvious way of selecting preand power amplification is by sticking within one brand’s range. Invariably they will have been tuned to work well together. If you plan to mix-and-match, be aware some pairings will work better than others. The best way to find out is by trial and error. And that’s true when it comes to matching source components to your amplification. Sonic affinity can be determined by common sense to some extent. If your source – a CD player, for example – sits on the bright side of neutral, it shouldn’t be partnered with a stereo amplifier with a similar character.
The speaker/amp partnership not only comes down to an amplifier’s power output but also its impedance (measured in ohms) and sensitivity (db). Impedance is a measure of how difficult the speaker is for the amplifier to drive. The sensitivity of a speaker is a measure of how loud a speaker will go for a given input. A good insight into an amp’s muscularity is to compare its power output into eight ohms with that into four ohms. An ideal amp would double its output as impedance halves. Though most won’t achieve that, the closer it gets to it, the better. Though you may be tempted to go for the most powerful amp you can afford, you’ll do better by buying a more sensitive speaker.
That’s because an amplifier’s output has to double to match a 3db increase in speaker sensitivity. But numbers can only tell you so much, and the best way of finding out if components work well together is to use your ears.
The surface your stereo amp sits on can make the world of difference. IKEA furniture is not at the bottom of our list (that’s the floor), but we’d strongly suggest placing it on a dedicated hi-fi rack. Your choice shouldn’t be based on looks alone.
Different materials have different acoustic properties. Generally speaking, glass shelves tend to encourage kit to sound forward, while wooden supports tend to result in a warmer and more rounded balance. All that power can generate quite a temperature, so it’s important to give an amp a few inches of breathing space from a wall or rack to stop it running too hot.