Amp Basics

As applied to an amp, watts is the unit of measurement for output power. "Bigger" is not necessarily "better," and a 100-watt amp isn't "twice as loud" as a 50-watt amp.
Ohms is the unit of measurement for DC resistance and AC impedance. Usually applies to the impedance of the amp's speaker(s). Important to have "matched" if you replace or add speakers. Commonly 8 ohm, 4 ohm, 16 ohm.

There's a fascinating and invaluable site maintained by an Aussie guy at GMArts , which explains lots of stuff you might never need to know, but which you'll have hours of fun finding out about! Unusually, his discussion of tube (valve) vs solid-state amps is really balanced and informative, rather than simply partisan :wink:

Interesting discussion of guitar tone, and how amps influence it, here.

Very plain and somewhat quirky, but vast, compendium of both useful and useless (well some is to me, YMMV) information at AmpTone - again, hours of harmless and educational fun in your own home!

Interesting discussion of guitar tone, and how amps influence it, {snipped link} here.Cool; that one was new to me. 8)
And this page has some good points on "Amplifier Myths, Fantasies, and Facts." http://www.guitarnuts.com/amps/myths.php

You mentioned looking at the label on the back. The watts listed there are the total power the amp consumes, not the output power.

You mentioned looking at the label on the back. The watts listed there are the total power the amp consumes, not the output power.Good point; I forgot about that. I was thinking only of the usual descriptive stuff like "30-watt amp" and so on.
A few months ago,somebody in my area had an ad in one of those buy/sell/swap weeklies, for a Fender Champion 110, if I remember correctly. They were advertising as being "75 watts." ("I don't think so, Tim." :roll: )

And this page has some good points on "Amplifier Myths, Fantasies, and Facts." http://www.guitarnuts.com/amps/myths.php

Nice one, Doug - that's a valuable page - many thanks!

Mike

Thanks for all the replies guys. I appreciate the information!

As Doug mentioned, a 100 watt amp is not twice as loud as a 50 watt amp.

For volume you have to understand a little about decibels. Decibels is how volume is measured. I believe normal speech is around 70 decibels, a jet engine around 130 decibels. Most loud Rock bands perform anywhere from about 115-130 decibels. This is measured at one meters distance from the speakers.

But volume decreases with distance from the source. Volume decreases by 6 dB whenever you double your distance. So if you were standing 10 feet from your amp, and then moved to 20 feet away, it will seem about 6 decibels quieter. That would be easily noticeable. Standing at the front of the stage you cannot hear your friend screaming to you. But go to the back of the club 150 feet away and you can understand normal speech.

Every 12 decibels is considered a doubling in volume (twice as loud).

Everytime you double the wattage to a speaker you get a 3 decibel increase in volume. This is not twice as loud, but perceptively louder.

You have to understand a little about speaker specs too. You will see speakers rated 100dB @ 1W/1M. This means this speaker will produce 100 decibels of volume at one meters distance with only one watt of power applied. Yep, just one watt.

If you double the power to 2 watts, now this speaker will produce 103 decibels of volume.

If you double that to 4 watts, now it will be 106 decibels volume.

8 watts- 109 decibels

16 watts- 112 decibels

32 watts- 115 decibels (gettin pretty loud now)

64 watts- 118 decibels

128 watts- 121 decibels (this is LOUD)

256 watts- 124 decibels

You can see the pattern. But what is important to see is that a 100 watt amp is only about 3 decibels louder than a 50 watt amp.

And you can see above that it takes a 256 watt amp to be 12 decibels or twice as loud as a 16 watt amp.

So, never be caught up in the numbers thinking you need a 100, 200, 300 watt or higher powered amp. This is just a sales gimmick.

No, go for good tone. It is better to have a 15 watt amp that sounds awesome than a 200 watt amp that sounds like $hit.

No, go for good tone. It is better to have a 15 watt amp that sounds awesome than a 200 watt amp that sounds like $hit.Amen, brother! Preach it!
:D