when do amps give full power

Hi guyz,

Question: When does a amp give full power?  For instance...if you had a 500 watt amp on a 500 watt sub, bridged & wired all correctly. When will that sub see 500 watts.  I have always thought as soon as the amp comes on the power out is what the amp is rated at.   Is the gain setting the "regulator" of how much power goes out?  Then what about the volume on the source unit?

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And also consider how the amps are measured as well. Some companies measure their outputs at different voltages. One company measures their amps output at 48 volts which no consumer car that we are aware of runs on. To get a better rough idea of how much your amp puts out peak is to take the fuse rating and multiply it by the vehicle's voltage at idle. For example, say you have a 1400 watt amp that has a 30 amp fuse in it. 30amps x 14.4 volts = 432 watts from the amp. So that 1400 watt amp is really 432 watts.

If you are looking for an amp that truly hits 500 watts cleanly, look for amps that are CEA compliant. That means they have been tested at the specific settings for the test. It's currently optional for manufacturers to do it, but if you get a hold of one, they will consistantly put out the rated power with no problems.

Wow thanks guys!

Just in case a few of  you wondering...I have a "rockford fosgate mono block 600" rated @ 600watts rms x1 @ 2ohm.  Pushing two rockford fosgate- punch p2 10"s @4 ohm 200watts rms each.   My main concern is am  I putting  too much power to my subs ??

jerryfreeman wrote:

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Hi guyz,

Question: When does a amp give full power?  For instance...if you had a 500 watt amp on a 500 watt sub, bridged & wired all correctly. When will that sub see 500 watts.  I have always thought as soon as the amp comes on the power out is what the amp is rated at.   Is the gain setting the "regulator" of how much power goes out?  Then what about the volume on the source unit?

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Good answer, haemphyst, and to the point of the question. 

An easy way to see how the power output curve steepens when you get toward the high end of the scale is to use a DMM and measure output voltage at increasingly higher levels of output.  You will find it notably surprising that your normal listening levels are far, far below rated output.  It is only at the very end of the volume excursion of the dial that the measured voltage increases dramatically, and that area is often louder than what is comfortable for in-car listening.

When you have the volume at a level where normal conversation can occur, you are probably around 1 or 2 watts.  If it's more than that, it's not by much.

stevdart wrote:

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Good answer, haemphyst, and to the point of the question. 

An easy way to see how the power output curve steepens when you get toward the high end of the scale is to use a DMM and measure output voltage at increasingly higher levels of output.  You will find it notably surprising that your normal listening levels are far, far below rated output.  It is only at the very end of the volume excursion of the dial that the measured voltage increases dramatically, and that area is often louder than what is comfortable for in-car listening.

When you have the volume at a level where normal conversation can occur, you are probably around 1 or 2 watts.  If it's more than that, it's not by much.

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this seems way too easy and probably is not the way to measure amplifier output(takes special equiptment right?) but with your system on can you just measure the voltage output of your amp and get a ballpark figure of what wattage it is putting out,? Doesn't seem like this owuld work as I assume it would be dependant on what driver.impedance it is hooked to but...

greenbroncoguy, I wasn't talking about measuring amplifier output; instead, the method was meant as a way to compare voltage output at various volume levels.  Use Ohm's Law to ballpark the power.

The AC voltage, which is relative to power, stays on a shallow curve until the very end, or highest volume levels.  That's where the curve steepens upward as the voltage rises dramatically.

Steven Kephart wrote:

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(at Adire we used a coil of wire submerged in water)

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These are professional drivers on a closed course.  Do not try this at home. 

aznboi3644 wrote:

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Well...someone needs to make a sticky on how to measure an amplifiers rms output...I got a nice DMM for my birthday and wanna set my gain correctly...most of the threads here just tell people to use a DMM and a sine wave...nothing about the details and what to use and look for and how to really do it

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Some resources for you: https://www.bcae1.com/measpwr.htm, https://sound.westhost.com/power.htm

https://www.bcae1.com/gaincon2.htm

aznboi3644 wrote:

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Ah icic...but does the impedance change with frequency still?

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aznboi3644 wrote:

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Well...someone needs to make a sticky on how to measure an amplifiers rms output...I got a nice DMM for my birthday and wanna set my gain correctly...most of the threads here just tell people to use a DMM and a sine wave...nothing about the details and what to use and look for and how to really do it

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You've made a couple of points here that are not one and the same thing.  One, measuring an amplifier's output requires more than just a DMM, which Steven Kephart talked about earlier in this thread.  But setting gains is another story.  A DMM can be useful, but your hearing is the key...that is to say, by using a DMM to set gain you would be relying on published ratings, whereas when you listen for the start of the clipped tone you can't go wrong.  Sine wave test tones are a must in all cases, and they should be of professional quality and recorded at 0 db. 

We have several outstanding contributors on this forum who could put together a how-to on setting gain.  What becomes stickied is up to the admin and moderators, but I, for one, would love to see a post that we can point to as an authoritive treatment on the subject of setting gain.  Until then, it's the same ol' "search for gain".

I talked about this here, too.

realmofexcursion=good, but not the best choice unless you can't get a hold of tones on CD. Most tones DLed from the internet is in MP3 format and loses some harmonics in the tones, so it may not be a pure tone. It's close enough to use, but for precision and to keep the tones as clean as IASCA, it's best to get a CD.

If you have a DMM with oscilloscope abilities, play your music at the level you usually like to hear it. Without changing the volume, put the tone in your head unit and meter the output. What you will see is a sine wave on the screen. Increase the gain bit by bit until you see a flat section on the scope. Back down on the gain until the flat area is gone. Then go next in line (line driver, amps etc) until you get to your speakers. You're gain set.

Tip: Disconnect your speakers after you get your sound to where you like to hear it. Then set the gains.

DYohn] wrote:

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Inductance in any wire goes down as frequency goes up (it's generally a logarithmic rate of change, not linear.) The amount of change is generally so small within the audio frequency band that it can be considered constant, however.

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