Question on amp current draw

[jontyrees]

What's the real life current draw of an amp playing music? I know the peak is capped by the fuses on the side of an amp, but how often, and for how long would the draw approach that number, and under what conditions? would it have to be test tones played at max volume?

also - does an amp draw less current when being provided a higher voltage signal - eg 5v preouts instead of 2v preouts - as it would have to work less hard to step up the signal? Or is the draw purely a function of the output in watts? similarly, how does the gain setting affect current draw?

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[jontyrees]

Probably just talking to myself, but here's what Crutchfield says in case anyone is interested:

"To calculate the current draw of an amplifier, multiply the number of channels by the RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be 600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts), then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by 13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the amplifier's approximate average current draw"

So music averages about 1/3 of max current draw. I'm assuming the "double it to account for amp inefficiency" refers to Class A/B, and Class D amps are more efficient.

 

[LosIsATool 5,000+ posts]

To many varibles. Voltage, rise, frequancy, song, efficency

 

[jontyrees]

Yeah - I'm just curious and trying to get a ballpark estimate

 

[i2ain2thunder 10+ year member]

there are many too many variables to try to look at a given amp and guess the draw it will take for music in general.

What we all do is simply plug, play, and check the voltage to our music. Thats the best advice I'm going to give on the subject.

 

[CrossoverOre 10+ year member]

music is too dynamic to nail down a single number and amp efficiency vary too much. You could get an idea if you clamp your power and run test tones.

 

[jontyrees]

Nah - was just curious as to how current draw for music differed from maxed out current draw on a test tone. Crutchfield answered that for me - it's about 1/3 of max on average. I'm sure it's the area under a spiky graph, like a mountain range, vs a tall plateau under a test tone

 

[i2ain2thunder 10+ year member]

If you ask me you should provide amperage for the total amperage draw capable to have the optimal situation, however really what you want to have is proper voltage for your amp. That should be your main concern, and that is something you never know until you try.

 

[LosIsATool 5,000+ posts]

Thing is efficiency gets better as voltage increases and worse as it drops. So music is very hard to gauge.

 

[i2ain2thunder 10+ year member]

I know what you are saying op...its just nothing in the audio industry is that clearly defined or really can be. You are better off playing around with different equipment. Any hands on or first person testing you can do is the best.

 

[maylar 10+ year member]

Nah - was just curious as to how current draw for music differed from maxed out current draw on a test tone. Crutchfield answered that for me - it's about 1/3 of max on average. I'm sure it's the area under a spiky graph, like a mountain range, vs a tall plateau under a test tone

It depends on your music. Human voice has a 10:1 peak to average ratio. I estimate 5:1 for what I listen to. Crutchfield's 3:1 estimate is a safe guess for most cases.

also - does an amp draw less current when being provided a higher voltage signal - eg 5v preouts instead of 2v preouts - as it would have to work less hard to step up the signal? Or is the draw purely a function of the output in watts? similarly, how does the gain setting affect current draw?

Current draw is a function of power.