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post #1 of 5 (permalink) Old 09-11-2007, 12:33 PM Thread Starter
Join Date: Aug 2007
Posts: 156
Lightbulb WATTS

This is part of a debate I had on other forum.Maybe it could help people about buying an amp .

When shopping for an amp "for loudness" you have to look at the very minimum,
for the wattage and efficiency of those watts.

For example, take the Mesa 20/20, 20 watts per side, and lets say it has a
Signal to Noise Ratio of 110 db

then take another amp rated at 100 watts with a S/N of 80db

The 20 watt amp is going to sound louder because each of its watts is more
efficient in producing clean sound.

To get a 6 db increase in sound you have to double the wattage....

So in the above example, there is a disparity of 30 db between the 20 and
100 watt amp.... so do the rest of the math

Also, when reading an amp's rated watts (this is more the case with solid
state amps), not all manufacturers adhere to a universal standard in stating
the wattage.

For example, an amp manufacturer may say Amp A is rated at 400 Watts. But when
you go to an oscilloscope the measure its true wattage, you may find that it is
only a 100 watt amp. But at several points of the sound wave it may have spiked
(transients) up to 400 watts. So, the manufacturer goes with the max reading.

Other more forthright manufacturers take the average or mean of the sound wave
and report that as the consistent wattage.

So you'd want an amp that produces a consistent wattage vs a peak wattage.

The same concept applies to speakers when looking at wattage & S/N ratios.
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post #2 of 5 (permalink) Old 09-11-2007, 12:59 PM
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treva you are freaking amazing.
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post #3 of 5 (permalink) Old 09-11-2007, 01:03 PM Thread Starter
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No I'm just ................TREVA

Last edited by TREVA; 09-11-2007 at 01:16 PM.
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post #4 of 5 (permalink) Old 09-11-2007, 01:25 PM
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Actually it's 3 DB each time you double the power.
Also, you shouldn't confuse overall consumption with output ratings.
Just because an amp will munch 1100 watts of power, has no indication on what the actual output to your speakers will be.

Another side note, to go along with speakers, specifically PA speakers.

Often lower end companies will tout their power 'capacity', but it isn't a real indication of what is delivered to the speakers. Many times, a device called a ballast is installed into the crossover. In most cases, this is nothing more than a light bulb! Whatever energy the speakers cannot accept, the bulb dissipates. Lets say You have a pair of PA speakers with a 1200 watt 'capacity' but the driver compliment can only handle 600 W, a resistor and light bulb eat the remaining power in a burst of light and heat. Not the most honest way to rate a speak IMO. I know for a fact that companies like Yorkville, BOSE and others use this practice.

Shop wisely

Last edited by bammbamm; 09-11-2007 at 01:31 PM.
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post #5 of 5 (permalink) Old 09-14-2007, 10:25 AM
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Location: Blackwood, NJ
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Yet again, different frequencies are heard by your ears at varying degrees of volume as well, when created with the same amount of power. 5 Watts of guitar will be louder to your ear than 5 Watts of bass because it is easier for you ear to pick up the higher frequencies of the guitar than it is for your ear to pick up the lower frequencies of the bass. That is part of the reason most guitar heads are about 100 Watts and most bass heads are 300 Watts or more.
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