Power vs. Ohm load vs. Voltage?

[Skip01 5,000+ posts]

I think I know the answer but just wanna double check.

First , I believe voltage and amp draw is all relative to the power it puts out regardless of ohm load. That's what I think , but here's some examples to help me get a clearer picture.

3 amps here, all put out 2000 watts max power but:

Amp A does it at 2ohm

Amp B at 1ohm

Amp C at .5 ohm

Now they should all draw the same and have the same voltage drop since they put out same power regardless of ohm load correct?

Also what about effcientcy and how clean the power is?

Like would you say Amp A puts out a cleaner signal, which in turn might put up a better score ?

Appreciate the answers, or explanations too why I'm wrong ha

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[pr-festiva 10+ year member]

power draw should be the same as long as the only difference is ohm load to get said power.as long as the amps are designed to do 2k at those respective loads sound quality should be the same too. but im no expert mind ya

 

[Lakota 5,000+ posts]

I think that you're asking about what would happen if you did all of this with the same amp model? For example, are you asking if like a Sundown 3000d would have the same current draw and efficiency when doing 1000w @ 2 ohms, 1 ohm, and .5 ohm?

From experience, I would think that the ohm load does matter, even when the the amps are doing the do the same output power. I dropped a US Amps USA-400 (class ab) to 1 ohm bridged(double the ohm load it's rated for), and that ***** got really hot at low volumes...

Now, we all know that class d's will continue to lose efficiency as the amp is dropped to lower loads driven near clipping. There's a point to where dropping the amp's load will not give much more power because of saturation and efficiency.

 

[tymoto21 10+ year member]

no

amp c will draw alot more current.

the power is all the same, but power is voltage squared/ resistance. or power * resistance = voltage squared. so if you have 100 watts @ 1ohm you voltage should be 10v. now the current goes in there as power = voltage * current. so if your power is 100watts @ 1ohm, then your voltage is 10v, then divide power / voltage and get 10amps.

at 4ohm your voltage should be 20v, 100*4= squaroot of 400. 100watts / 20volts =5amps. 1/2 the current draw of at 1ohm.

 

[pr-festiva 10+ year member]

i took it as if the amps were designed to hit max at each load respectivly

 

[Lakota 5,000+ posts]

If the amps are different models then the current draws and efficiency will defiantly be different.

 

[Skip01 5,000+ posts]

All same amp and brand and everything.

Max power of each is 2000 watts but they make it at diff ohm loads

 

[Lakota 5,000+ posts]

noamp c will draw alot more current.

the power is all the same, but power is voltage squared/ resistance. or power * resistance = voltage squared. so if you have 100 watts @ 1ohm you voltage should be 10v. now the current goes in there as power = voltage * current. so if your power is 100watts @ 1ohm, then your voltage is 10v, then divide power / voltage and get 10amps.

at 4ohm your voltage should be 20v, 100*4= squaroot of 400. 100watts / 20volts =5amps. 1/2 the current draw of at 1ohm.

The problem with this is that V=IR is the equation for something that acts as a linear, passive/resistive element. Amps lose their linearity as they continue to produce more power.

 

[midnightg35x 10+ year member]

P=V^2/R or P=I^2*R only applies for DC power. If you are using a sine wave, P=V^2/(2*R) or P=I^2*R/2.

The rule is that for the same amount of power, if you drop the resistance, you decrease the voltage and increase the current. Conversely, if you increase the resistance, you increase the voltage and decrease the current.

I would say the lower impedance amp would draw more DC power due to the fact that it would output more current, more current means more heat, and more heat means less efficiency. Less efficiency means more DC current draw.

Also, in theory, less efficient amps are "cleaner". This is a pretty hefty generalization though because all amps can be designed crappy or great. I know people will come up with examples that contradict that statement, but I am coming from the direction of amp classes. Class A amps are by definition linear amps, but have horrible efficiency. Class AB amps are less linear than class A, but also have better efficiency. Class D is a separate animal. Modern electronics have allowed class D to even exist for audio use, but they are not a "traditional" type of linear amplifier.

 

[gunz4me 10+ year member]

Kind of like what some do not understand on here about the old school High Voltage/High Impedance amplifiers. I was always amazed that a Linear Power with 25 amps of fusing could produce 500 watts RMS @ 8 ohms. Of course, one must make sure they disconnect the power before pulling that bottom cover to move the taps near the power supply. If you touch something while dinking around in there, you will get a slight tingle