Another AMP Question

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Antman27

Another AMP Question
« on: 4 Jan 2006, 02:50 am »
OK so can you guys please explain AMPS and Wattts PC
My Denon 3805 is rated at 110 WPC
If I get an external amp (say 100 WPC ) will I be giving my speakers less power ?
OR do I need to CRANK the denon to get to 110 W ?

TomW16

Another AMP Question
« Reply #1 on: 4 Jan 2006, 03:52 am »
Hey Antman,

Most (if not all) amps wattage rating is based on the point of clipping (or distortion measured above 1% or something like that) but I think that if you ask around you will find that not all watts are created equal.  There are the actual watts that the amp will put out on a continual basis playing music driving real speakers and then there are the watts produced by the amp just before clipping under very suspicious circumstances like driving a resistor rather than a speaker.  The marketing folks who create the advertising will use the second scenario to prepare inflated watts for the specifications sheet that consumers will use to compare units.

In reality, you likely don't need too many watts to drive relatively efficient speakers to reasonable sound pressure levels assuming you have a fairly standard sized room.  100 watts should be more than adequate for most people.  The quality of the first watt is the most important to good sound.

Generally speaking, the higher the quality of amp, the more conservative the wattage rating.  That is, a high quality amp will go above the wattage rating before clipping.  A receiver may not reach the maximum wattage rating before clipping.

I hope that this helps somewhat.

Tom

Tweaker

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Another AMP Question
« Reply #2 on: 4 Jan 2006, 07:10 am »
The difference between 110 and 100 watts, all else being equel, is negligable.
Normal volume levels will only require a few watts at best. It is the peaks such as orchestral crescendos that will cause the amp to put very briefly out close to rated power and then only if playing rather loudly. I would be more concerned about the amplifiers current output. One reason why (mass market) receivers tend not too sound good and have trouble driving low impedence speakers is that they usually don't put out much current. A well designed amplifier that puts out 50/wpc and is also putting out a lot of current will usually sound and perform better than a high watt design that is putting out little current, especially into low impedence speakers. I think that was one of the downfalls of Bob Carver's magnetic field power amps and one of the reasons B&K tended to sound so much better. The B&K's had about twice as much current as a Carver with the exact same wattage rating which allowed them to drive speakers with far greater ease. There are many other factors involved in how good an amp will sound but I believe that an amplifiers current rating should be of equel or more concern than its wattage. It's a lesson you learn when you own speakers like Acoustats, Magnepan, and VMPS (4 ohm models).
So if you get an external amp with less wattage but more current you will most likely find it will perform better.
Just my long-winded 2 cents worth.

JLM

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Another AMP Question
« Reply #3 on: 4 Jan 2006, 09:10 pm »
Manufacturers often "creatively" report the power ratings of their equipment, especially in multi-channel rigs.  In fact they design to these "creative" ways of measuring to make products more marketable to the unknowing, not to sound good.   Most use a 1,000 Hz sine wave, not music via reactive speakers when measuring.  And most run only one channel at a time, not all of them.  Of course the vendors here would never do such a thing (honestly).

Bottom line, many 100 wpc HT receivers only provide about 15 "real" wpc with all the channels driven.

Keep in mind that the relationship between watts (rated power) and dB (what we hear) is logarithmic.  A 1 dB increase is barely perceivable, a 3 dB increase sounds half again as loud, and a 10 dB increase sounds twice as loud.  So:

1 watt = 0 dB of gain (compared to the rated speaker efficiency)
2 watts = 3 dB of gain
4 watts = 6 dB of gain
5 watts = 7 dB of gain
8 watts = 9 dB of gain
10 watts = 10 dB of gain
20 watts = 13 dB of gain
40 watts = 16 dB of gain
50 watts = 17 dB of gain
80 watts = 19 dB of gain
100 watts = 20 dB of gain, etc.