How Much Power Do I Need?

by James Leahy

Amplifier power ratings are similar to money, in that it is impossible to have too much. However, let me first quantify that statement. Never sacrifice quality for quantity, or you will be taking two steps backwards and one step forward.

When it comes to specific power ratings more is not necessarily better. This point is critical to comprehend. What I am about to tell you took me years to understand, and just as many more years to believe.

When listening to, and choosing an amplifier it is only the first 1 watt of an amplifiers output quality that really matters. If that first 1 watt sounds bad, then all the rest that follow will sound equally as bad no matter how powerful.

It is better to have 10 sweet, clear and warm sounding watts than 100 or more awful sounding watts in your system. Too often I have seen customers buy their equipment based on specifications alone wanting a specific power rating or similar. This is like buying a suit off the rack without even trying it on. How many of you out there would do this...? So why do it when buying an amplifier...... A much better approach is to buy what sounds best not what you think should sound best, based on hearsay or brand name. This way you WILL get a system that fits like a tailored suit, not a sloppy mass produced one size fits all approach for your system.

Also with valve amplifiers, 50 watts output power will easily sound like 100 or more transistor watts judging from seat of the pants testing. With most modern loudspeakers offering 89db @ 1w/1m sensitivity or greater 50 valve watts will be more than enough power to blow you out of the room. Typically large floor standing loudspeakers with at least 6.5" woofers or greater give the best return on investment here when looking for a suitable loudspeaker with the power of the amplifier required to drive them needing to be only modest. This formula also goes a long way to provide decent bass response compared with a small bookshelf loudspeaker.

The most important factor when choosing the size of your valve amplifier is to carefully match it's output to your loudspeakers, and lastly your bank account. I say bank account LAST because it should be the absolute lowest factor in your purchasing decision.

If you cannot afford to do the job right and buy what you NEED, then don't do it at all. Half hearted attempts will result in full blown disappointments in no time flat.

You maybe surprised at just how little real world power you actually need to achieve huge dynamics in an average sized listening room with reasonably efficient loudspeakers. There is no such thing as an amplifier that is too powerful for a pair of loudspeakers. The only reason you would go smaller in size for amplification comes down to how much money you wish to save and still get reasonable sound quality.

I recommend that your system begins with loudspeakers that will work properly and sound good in the desired acoustic space. Matching the power amplifier to the loudspeaker is usually a function of driver size, efficiency and budget. Efficiency is not the only determinant - even though they may be very efficient, many speakers with large drivers need tremendous amounts of damping factor and current capability to control the drivers properly.