Audio Systems: amp and speaker comsumptions, qsc amp, qsc plx2

Question
QUESTION: Hi I was looking at the QSC PLX2 3102 and notice that at 4ohms typical is 9.5 amps. So if I hooked up 2 peavey PV215 (one per channel) how many amps would it pull on normal conditions?

ANSWER: Those Peavey PA speakers are 98 db sensitivity and have a nominal impedance of 4 ohms.

The QSC amp specifications are:

CURRENT CONSUMPTION      PLX3102
1/8 Power (pink noise)    8 ohms
4 ohms
2 ohms    6A/120V
9.5A / 120V
14A / 120V
1/3 Power (pink noise)    8 ohms
4 ohms
2 ohms    10.7A/120V
16.5A / 120V
27A / 120V
Full Power    8 ohms
4 ohms
2 ohms    21A/120V
33A / 120V
55A / 120V

See these specifications in their proper form at:

http://www.qscaudio.com/products/amps/plx2/plx3102_specifications.htm



Therefore, if you were to run the amp at full power (which is totally unreasonable for audio/music - which I will explain later) the current draw would be as much as 33 amps.

However,  music power is much less than full power even when you are running the level at full music clipping power.  This is because the average power in music is around 3db to 6db less than rms signal input. If you have ever seen a music waveform on a scope you can tell that peaks are much greater than average.  Under typical music conditions, then, you might expect the amp to be drawing an average of 10 to 15 amps.   And, it would fluctuate according to the music and the level you have it set at.

Does this help?  Let me know further if there is more.

C



---------- FOLLOW-UP ----------

QUESTION: Hi so the volume level would also have a great effect on the amount of current draw to right?Some times I run small test at my house with my equipment thats why I wondered.Don't won't to trip a BREAKER at home while testing!:)

Answer
Of course.  If you put more music power into the speakers it will take more power out of the lines to supply it.

The current draw of the amp when the volume level is set at zero is very small.  As the loudness of the music goes up the current requirement goes up proportionately.  If you were to put an ammeter on the power line you would see the current fluctuate up and down with the music.

C