In order to find voltage output of an amp what 2 variables do I need?

[forsellb 1]

I am just wondering, how do you calculate the voltage output of an amp? Also how do you calculate the amperage output?

[///M5 2,833]

You don't calculate, but measure.

You'll need a DMM for the voltage along with a current clamp for the current.

[forsellb 1]

You don't calculate, but measure.

You'll need a DMM for the voltage along with a current clamp for the current.

so even if I know the input voltage, and the battery supply voltage theres no way to figure out the voltage output of the amp other than a DMM? And I know there are some way to get amperage through calculation.. Im just not 100% sure how.

current and ohms calculated here

[KU40 173]

You would have to know the exact efficiency of the amplifier as well as the exact input voltage and current to be able to calculate output power that way.

Since you wouldn't have to know the efficiency of the amplifier if you measured at the outputs instead of the inputs, why not do it that way.

[forsellb 1]

You would have to know the exact efficiency of the amplifier as well as the exact input voltage and current to be able to calculate output power that way.

Since you wouldn't have to know the efficiency of the amplifier if you measured at the outputs instead of the inputs, why not do it that way.

Im just curious, I like to know everything.. So how do you measure eff? and if I do just test the outputs do I just hook the DMM up to the speakers + and - or where?

Edited October 7, 2009 by forsellb

[///M5 2,833]

Search is your friend.

You need to know the voltage and current on the input and the output.

Let's ask a better question. Why are you trying to figure this out and how are you going to apply it?

[forsellb 1]

Search is your friend.

You need to know the voltage and current on the input and the output.

Let's ask a better question. Why are you trying to figure this out and how are you going to apply it?

Im trying to figure it out because if I do test with a multimeter then I can just double check and Id apply it when installing my amps and batteries and what not

[killa101 0]

Search is your friend.

You need to know the voltage and current on the input and the output.

Let's ask a better question. Why are you trying to figure this out and how are you going to apply it?

Im trying to figure it out because if I do test with a multimeter then I can just double check and Id apply it when installing my amps and batteries and what not

If you are trying to simply figure out what voltage you should have when you adjust your gain with a DMM you do the calculation below....

V^2 = P x I^2

Where V = voltage, P = power, I = impedance

An example would be....

You have a 4ohm DVC sub that is 500w RMS that you wire to a 2 ohm load. You also have an amp that is 500w RMS @ 2 ohms. You would do the formula...

V = sqrt( 500w x 2 ohms ) = 31.6 volts

So you would set the voltage to 31.6 volts using your DMM.

Edit: JL Audio Guide

Edited October 7, 2009 by killa101

[forsellb 1]

Search is your friend.

You need to know the voltage and current on the input and the output.

Let's ask a better question. Why are you trying to figure this out and how are you going to apply it?

Im trying to figure it out because if I do test with a multimeter then I can just double check and Id apply it when installing my amps and batteries and what not

If you are trying to simply figure out what voltage you should have when you adjust your gain with a DMM you do the calculation below....

V^2 = P x I^2

Where V = voltage, P = power, I = impedance

An example would be....

You have a 4ohm DVC sub that is 500w RMS that you wire to a 2 ohm load. You also have an amp that is 500w RMS @ 2 ohms. You would do the formula...

V = sqrt( 500w x 2 ohms ) = 31.6 volts

So you would set the voltage to 31.6 volts using your DMM.

Edit: JL Audio Guide

That is some very interesting info.. I just like knowing stuff like that, so when I do get my stuff I can tune it perfectly and help my friends whos systems are lets say lacking a bit..

also I just did the math and a BTL ran at 2ohm(DVC 1ohm) @2000wrms would equal a voltage of 63.25volts? Does that even seem right?

Edited October 9, 2009 by forsellb

[killa101 0]

That is some very interesting info.. I just like knowing stuff like that, so when I do get my stuff I can tune it perfectly and help my friends whos systems are lets say lacking a bit..

also I just did the math and a BTL ran at 2ohm(DVC 1ohm) @2000wrms would equal a voltage of 63.25volts? Does that even seem right?

That is correct from my calculation.

I should point out that you will only get this voltage at higher volumes. So you would only set your voltage to this level at the highest volume you are going to listen to your system at.

This link as well as this link will explain setting the gain with a DMM more in depth.

Using the method of using a DMM is fairly accurate and much more accurate then setting it by ear for most people but it is not perfect. Since impedance is different then resistance using ohms law will give you a little bit of error. However, this is a fairly good method and you should use it over using your ear to set the gain on your amp.