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| RMS is "Root Means Square" This is the mathematical formula for finding
the basic amount of power an audio amplifier can continuously produce. There is no standard for calculating the RMS rating of an Amplifier. Most amplifiers have the RMS rating posted on the back. 100 watts etc..etc.. Some amps put the RMS rating in accordance to the impedance, 200 watts @ 4 ohms, 100 watts @ 8 ohms (DO NOT GO BELOW THE MINIMUM) Always refer to your owner operators manual for the correct operating procedures and for any information necessary for safe operation. |
| HEY! How many watts is that amp? Is it loud? Is it Tube? The higher the
RMS rating the louder the amp, and the stronger the continuous signal. Then again, it all depends on the impedance and the output design of the amp. A 50 watt British amp puts out about 15-18 watts rms to a 16 ohm load, and 50 watts to a 4 ohm load. The rating of output power and impedance are rounded out to the next highest number or close enough to satisfy the equation. Standards in amp ratings (and popularity) are 100 watts for guitar and 300 - 350 watts for bass. Tube (Valve) amps are the most popular amps for Guitar and Bass. The new digital (amp modeling) amps are very popular too. I won't give my opinion on these products, since I have the original amps they can only try to emulate. When people ask "how many watts per side" or per channel, they are refering to a two channel or stereo amp. A 200 watt per side amp can also be bridged to operate as a 400 watt mono amp. Most P.A. and power amps are stereo and can be used as two mono amps, one channel for the mains and one channel for a monitor mix. Some of the newer instrument amplifiers and speaker cabs are now stereo as well, it is not true stereo, it is only one signal going to two different places. With an effect like a delay running through one side and a dry signal running through the other side you can produce a simulated stereo effect. You can experiment and use your own judgment but, allways refer to your owner operators manual for safe and correct operating procedures. |
| Impedance is the total opposition to alternating current by an electrical
circuit and is measured in ohms. It is the ability to resist electrical power, the lower the impedance, the higher the power that will be accepted. Speaker cabs are rated in accordance to the speaker impedance and to the wiring combination. If you connect two speaker cabs parallel (Daisy Chain) the impedance is split in half. Most audio amplifiers will distribute the power (measured in watts) matching the impedance of the speaker cab (s). Some audio amplifiers have an ohm selector on the back. Never go below the minimun impedance of an amplifier or you will cause some serious damage to your amp. Most amps are rated at 4-8-16 ohms, the same for most speakers and cabs. Some amps are rated at 2 ohm min. Avoid using speakers or cabs of different impedance, since one will draw more power from the amp than the other. Impedance and watts are related, so if the impedance is doubled then the watts are split in half. An amp rated 200 watts @ 4 ohms with two 8 ohm cabs connected = 4 ohms = approx 100 watts per cab = 200 watts. Connected with one 8 ohm cab = 8 ohms = approx 100 watts to that single cab. Amplifiers are all different, and it is a good idea to refer to your owner operators manual for the correct operating procedures and connections. Always remember to use a non-shielded cable for speaker cab connections, and if you are using 2 cabs be sure the cables are of the same length and gauge. Use a heavier gauge for longer lengths, but do not go over the factory recommended length or gauge. click here for speaker wiring guide |