I am a musician who knows my instruments well, but I don’t know much about the electronics that make them work so well. Specifically, I would like to know the following:
What does the Wattage of an amplifier tell me?
What do Ohms have to do with anything?
Difference between passive and active instruments?
How does compression work?
Are there any common things I might be doing that could mess up the electronics in my guitar, or amp?
Thanks for your help in advance.
Wattage is the output power of the amplifier. This is usually expressed in terms of RMS power (a meaningless term that really means maximum average power). The more power an an amplifier has, the better it’s dynamic range, the less distorted it will be at higher volume levels, and the louder it will sound.
An ohm is the unit of resistance or impedance. As it applies to speakers, it indicates the impedance at some standard frequency, usually 1000 Hz. You want to match the impedance of the speakers to the output impedance of the amplifier for maximum power transfer and proper loading of the amp.
Compression works the same way for audio and video as it does for static files: information that is duplicated is replaced by a shorter marker called a token, and a table containing a list of the tokens and what they represent is created. There’s much more to it than this, but that’s the gist of it.
Make sure not to overdrive your amp by mismatching the impedance of the speakers, as mentioned earlier, or make it drive more sets of speakers than it was intended to. Generally, running an amp at maximum volume all the time is a good way to shorten it’s life. If you need to crank your amp at full volume to get the sound you want, then you need one with more power.
I’m an electric guitar player (and rewirer) and so I can talk a little about impedance. Pickups on a guitar generally go from about 4,000 ohms (or 4k as they say) up to about 20,000 ohms (20k). Each has their advantages/disadvantages.
The lower impedance pickups have a brighter, twangier, sharper sound. The Fender™ sound is exemplified by this twangy sound.
Generally the very high impedance pickups are usually 2 pickups wired to each other in a special way so that they cancel hum and are therefore called “humbuckers”. These pickups have a much higher output than lower impedance single coil pickups. These give a warmer, fuller sound and I think are better for use with distortion. (Then again, Jimi Hendrix played about everything with distortion and he used a Fender Stratocaster™ which has single coil pickups.) However, humbuckers do have a disadvantage in that they sound kind of muddy and dull when you are not playing through distortion.
So, as with a lot of things in life, there are tradeoffs in guitar playing too. Hope this has helped a little.
Q.E.D., Everything you said is gold except this paragraph, which puzzles me. I’m not sure what you are getting at; are you referring to time-compression or error correction, such as is used in playback devices when a tiny slice of recorded sound is faulty and is replaced with a previously memorized one?
To me, compression acts on the volume level; the ratio of loud to soft sound is reduced. Example: if the loudest sound is 20 times the softest naturally (20:1), then compressing it might give you a 16:1 ratio. Not quite as loud, not quite as soft. Everything is squeezed in the middle.
Too much compression not only robs the sound of its “liveliness” but can introduce distortion. But small amounts of compression can be used to keep low volume passages from being lost in a noisy environment.
I was referring to the type of compression used to reduce the amount of data in a digital audio or video stream. But reading your post I think maybe the OP meant the type of compression you are referring to, instead.
Here is some further information on the type of audio compression I was talking about.
Also, compression can add sustain to an electric guitar.
Yeah – you were talking about digital data storage compression, but I think the OP was thinking about real-time audio gain compression as you might find on an effects box or a studio limiter/compressor.
Don’t confuse him! 
And a good link.
I can tell you what passive and active mean.
A passive circuit or component is one that doesn’t require electricity (battery or wall current). Such components are your guitars pickups (although some use active circuitry), the guitars volume and tone controls are passive components and circuits.
An active component or circuit requires electricity. Amplifiers, wah wah pedals, effects boxes, etc fall into this category.
I can tell you what passive and active mean.
A passive circuit or component is one that doesn’t require electricity (battery or wall current). Such components are your guitars pickups (although some use active circuitry), the guitars volume and tone controls are passive components and circuits.
An active component or circuit requires electricity. Amplifiers, wah wah pedals, effects boxes, etc fall into this category.
ARRRRRGGGGGHHHHHH !!!
My first double posting – sorry !!!
:smack:
If running your amp at max (10 or 20…or 11) gets you the sound you want, getting one with more power won’t help, it’ll just make you louder. You’ll have to crank that one, too. Also don’t be fooled by amp “boosters” that claim they’ll double the output of your amp. Horse hockey. They’ll double the distortion.
Typically the power (Wattage) of an amp is stated in terms of the load (Ohms) it can drive. Example: 120 watts at 8 ohms, 200 watts at 4 ohms. A pair of 8 ohm speakers together* = 4 ohms. If you are buying an amplifier for your main sound system ¶ you want the minimum distortion you can afford. If you’re buying a guitar amp, you probably want distortion–but you’ll want to hear it first.
Messing up the electronics in your guitar is pretty difficult, unless you do the Pete Townshend thing on a regular basis. Guitar amp electronics are pretty stable these days except for the tubes (if any). Be sure you replace the tubes with the exact same type. Don’t run any amp thru more speakers than it can handle. The amp and the speaker cabinet should each have a rating (as in the example above).
A compressor squishes the attack (loudest part) of each note, but makes the quietest part louder–compressing the dynamic range. This makes the note hang on longer and decreases distortion. Typically you’ll turn the volume up to get distortion back where you want it. Caveat: when you aren’t playing, it makes the background noise of your kit louder, too. There’s usually a “threshold” setting to get rid of this, but a poor threshold setting might also get rid of sounds you’d like to keep.
With respect to active & passive, I’m pretty sure there are some guitars with built-in active circuitry (usually battery powered) for tone controls.
Active tone controls typically use higher order filters than passive controls, which means they have sharper cutoff frequencies, and can easily implement separate controls for different frequencies (i.e. bass, treble while passive is usually just ‘tone’ which cuts off more highs as you turn it up) They can also provide a bit of pre-amp gain, though there’s little need for that if the amp is set up right.
Another benefit is that there’s better isolation between the volume & tone controls. With passive tone controls, the volume will have some effect on both tone and what the tone control does, and tone control may affect overall volume as well. Active circuitry reduces the effect, though if you don’t mess with the volume control on the instrument, it probably doesn’t matter too much.
Potentially active controls can have a greater effect on the sound, even negatively, since it’s running the signal through more circuitry. Of course, any circuit inside the instrument will affect the sound, I’m just saying it’s easier to poorly implement the active control than to poorly implement the rather simple passive control.
Probably the most important thing to be aware of with electronic instruments is proper grounding (this is more dependent on the set-up at a particular gig than the instrument itself, but the instrument could have its own problems). I think there’s a staff report around on just that subject. Here it is, in fact it’s by Q.E.D.