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Geoff 12th April 2002 01:48 PM

Amplifier Power Requirements
 
There have been several references recently in other threads to amplifier power requirements, so I thought the following information might be of interest.

Unfortunately I cannot remember the website from which I obtained the data a couple of years ago otherwise I would give the appropriate credit.

Geoff

http://www.gmweb.btinternet.co.uk/SPL.gif

Geoff 12th April 2002 05:01 PM

I have now found the source of these figures. More information on them can be obtained at:

http://www.smr-home-theatre.org/Powe...-How-Much.html

Geoff

tschrama 12th April 2002 05:10 PM

nice revealing tabel ... Thanks for the link..

greetings,
Thijs

GRollins 14th April 2002 10:04 PM

I tried to post Friday, but my ISP suddenly decided that this site didn't exist for some reason.
Nice reference, Geoff. Seems that I recall that the 'average' living room has about 30-40 dB background noise, so you've got to get up above the noise floor before you can begin to hear anything.
On the other hand, I had to buy a house way out in the country before I could get anything like the quietness that I remember as a kid. I suspect that the 30-40 dB figure is out of date...

Grey

tschrama 14th April 2002 10:41 PM

Hi all ...

Your right about some 30 to 40dB SPL background noise, but that doesn't mean that a moderate classical music is played back realisticly at 84dB + 30 to 40dB = 114dB or more. You can easlely hear throuhg some background noise.. I think people don't ussualy listen to music at 110dB.. why? It give you that peeeeeeeeeep after the music has gone.....
greetings..
Thijs

dice45 16th April 2002 12:44 PM

Geoff,

thanxalot! seems like i have done my power need estimations just right :)
Good read!

mefinnis 16th April 2002 03:13 PM

All very true and correct .... but note he differentiates between average and peak power requirements, whereas we are using W-RMS as our amp measure. Remember a 100W-RMS amp can produce far greater peak power - even before it clips.

If you build a power amp in W-RMS to handle the peaks at high volume you are gonna spend some big bucks (both in amplifiers and speakers).

cheers, mark

tschrama 16th April 2002 03:18 PM

Happely a CD player doesn't produce any unpredictable peaks... If you know your systems gain (0dB tot 12dB maybe?) you precisely know your MAXIMUM power needed.. this will be in the order of a couple of Watt ..

Greetings,
Thijs

Dirk 16th April 2002 07:32 PM

Quote:

Originally posted by mefinnis
All very true and correct .... but note he differentiates between average and peak power requirements, whereas we are using W-RMS as our amp measure. Remember a 100W-RMS amp can produce far greater peak power - even before it clips.

Hi, correct me if I'm wrong, but IMHO the difference between RMS and peak power is usually not so big: if the signal reaches the power supply rails during a transient, it has no other choice than clipping ... At the same time, the RMS power can be measured ... just below clipping (OK, including some power supply rail sag during continuous operation at full power).

Regards, Dirk

Geoff 16th April 2002 07:55 PM

Mark

Quote:

Remember a 100W-RMS amp can produce far greater peak power - even before it clips.

I think your comment needs clarification. The peak output power into the rated load impedance is twice the rms power. Higher peak power levels can only be achieved if the load impedance drops due to the speakers characteristics (which may or may not occur at the required frequency) and if the power supply is capable of delivering the additional current.

Also, this higher peak output is only applicable to push-pull output stages. A single-ended Class-A is current limited as well as voltage limited and the peak output power will be no greater than twice the rms power for which the quiescent current was set.

Geoff


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