Hey Swez I a good peice of input that will allow people to figure out their RMS if it is not told. It is a pretty accurate formula which will give a very very good estimate to how much you really have as RMS power, Where could I put this information to show everyone? IDEA
Replies (9)
swez on 05/29/2006 16:57:31
Just link it to your next post and we'll have a look.
Swez
Zach1989 on 05/29/2006 17:55:21
It wasn't a link just some knowledge I picked up along the way, well here it is:
You can't get something for nothing. An amp cannot give out more power than it draws from it's power supply. Here is the formula for you to memorize: Watts=Amps X Volts. Base volts on 13.4, the average voltage of a running vehicle. Now, if your amplifier has a 10-amp fuse in it, then the absolute most power your amp can draw is 134 watts... Get it? (10 X 13.4). If your amp has 2 10-amp fuses in it, your maximum input power is 20 X 13.4, or 268 Watts. This figure is the total wattage input, so divide it by the number of channels the amp is, and then don't forget two more things to consider: First, this is the absolute maximum before blowing the fuse, not the normal running wattage, and Second, the heat your amp gives off is part of that number! Most amps give off at least 10% of their power in heat.. So here's the formula one last time: Max fuse amps X 13.4 divide by # of channels, and multiply by point 9 (.9). That's a very good guess of your per channel true RMS power.
ttocs on 05/29/2006 18:09:29
dude, most amps other then maybe class d are not anywhere near that efficient..... also remember that rms is normally half of the max power output. The number that you are solving for is the max output IF there was an amp that was %90 efficient, which there is not.
If you really want to get specific RMS stands for root means squared, or it is equal to (PI/2)/2=.707. In normal electronics circuits(not amplifiers) you would take the peak output voltage (Vp)times .707 to get the rms power out. so if you have a peak output of 100 watts peak, you would 70.7 watts rms.
Victor on 05/29/2006 18:37:33
by the way zach, that formulae you mentioned is age old knowledge in electronics.. and what scott sait is very true, in the Car Audio real world, 90% efficient amps are very rare, and those that are 90% efficient are costly beyond your imagination..class T, H, etc...even the best of class D are not more then 85% efficient..
Read this to gain better knowledge in this area..
http://www.clubknowledge.com/Car_Audio_FAQ/?t24
Victor...
swez on 05/29/2006 20:50:59
Let the fellow learn at his own pace and level. Grumpy... did you fall off the bike again this weekend???
The formula is actually correct in theory. However, in reality the formula is actually more complex. A lot depends on the type/class of amp circuits used, (A, A/B, D, G, H & T classes)
A typical Class A/B amp is about 50-60% efficient. That means, for every 100 watts it comsumes, we get up to 60 watts output. The rest is lost to heat and transistor biasing.
Class D amps are between 80-88% efficient. However, they are limited to low frequencies of 300 Hz., or lower. (Great for subs)
Class T amps can be as high as 90% efficient when using "Tripath" amplification circuits. This amp is very good for full range and sub applications.
Class G & H are not typically found in Car audio applications I am aware of. They too, are high efficiency and use multi-stage amplifiers and voltage rails when high output is needed. These are typically found in Pro Audio amplifier circuits.
Finally, the RMS (Root-Mean-Square) formula applies when we look at continous output power to a given load. As noted, the RMS = Peak Power x 0.707. However, most amps compensate for several load impedences and respective output power changes in ratio and proportion to a given load impedence. The higher the impedence load, the lower the RMS value will be. (Ie: 4 ohms VS 2 ohms)
Hope that helps,
Swez
MrBrownstone on 05/29/2006 21:32:04
Thought I'd chime in here.
Concerning amplifier efficiency, 90% efficient amps are just that...at 100% clipped signal!!!
Most class Ds run 70-75% at max CLEAN power (~1% THD). ABs, the same thing...about 40% efficient, 50% @ 100% THD. As, 25% efficient, and 33% @ 100% clipped signal.
Zach1989 on 05/29/2006 21:58:18
My bad I never knew all that until today, I figured you guys would know that, btu wasn't sure about begginers or if it was anywhere(i am a novice) and at the time the info seemed logical, and was pretty accurate in my case. I wasn't sure if you had the formula posted anywhere, so I figured I'd check.
Victor on 05/30/2006 02:50:31
Well actualy its good that you are trying to figure out thigns on your own, and sharing your findings here with us,
Its always good to make efforts to learn, We have a lot of study material in our "Article" and "How to" sections...
Also the "link" contains links to many many informative car audio site.
browse through all this immense treasure or knowledge at your will, and feel free to ask questions if any, we have very knowledgeble and experienced members and golds here, they have expertise in varied fields and make a nice mix on CK.
Also keep all such findings flowing in, even if we know it , its always useful to refresh such information.
Have fun COFFEE..
Victor...
ttocs on 05/30/2006 10:43:26
man I was having a REALLY REALLY bad day at work yesterday, didn't mean to jump ya.... I'm sorry.
Besides that I was thinking about the formula I spouted off and realized I was giving bad useless info. RMS is equal to the square root of 2, divided by 2. 1.414/2.
Swez is right there is alot of good info and good people here, don't let my reaction keep you from posting questions in the future.
Replies (9)
swez on 05/29/2006 16:57:31
Just link it to your next post and we'll have a look.
Swez
Zach1989 on 05/29/2006 17:55:21
It wasn't a link just some knowledge I picked up along the way, well here it is:
You can't get something for nothing. An amp cannot give out more power than it draws from it's power supply. Here is the formula for you to memorize: Watts=Amps X Volts. Base volts on 13.4, the average voltage of a running vehicle. Now, if your amplifier has a 10-amp fuse in it, then the absolute most power your amp can draw is 134 watts... Get it? (10 X 13.4). If your amp has 2 10-amp fuses in it, your maximum input power is 20 X 13.4, or 268 Watts. This figure is the total wattage input, so divide it by the number of channels the amp is, and then don't forget two more things to consider: First, this is the absolute maximum before blowing the fuse, not the normal running wattage, and Second, the heat your amp gives off is part of that number! Most amps give off at least 10% of their power in heat.. So here's the formula one last time: Max fuse amps X 13.4 divide by # of channels, and multiply by point 9 (.9). That's a very good guess of your per channel true RMS power.
ttocs on 05/29/2006 18:09:29
dude, most amps other then maybe class d are not anywhere near that efficient..... also remember that rms is normally half of the max power output. The number that you are solving for is the max output IF there was an amp that was %90 efficient, which there is not.
If you really want to get specific RMS stands for root means squared, or it is equal to (PI/2)/2=.707. In normal electronics circuits(not amplifiers) you would take the peak output voltage (Vp)times .707 to get the rms power out. so if you have a peak output of 100 watts peak, you would 70.7 watts rms.
Victor on 05/29/2006 18:37:33
by the way zach, that formulae you mentioned is age old knowledge in electronics.. and what scott sait is very true, in the Car Audio real world, 90% efficient amps are very rare, and those that are 90% efficient are costly beyond your imagination..class T, H, etc...even the best of class D are not more then 85% efficient..
Read this to gain better knowledge in this area..
http://www.clubknowledge.com/Car_Audio_FAQ/?t24
Victor...
swez on 05/29/2006 20:50:59
Let the fellow learn at his own pace and level. Grumpy... did you fall off the bike again this weekend???
The formula is actually correct in theory. However, in reality the formula is actually more complex. A lot depends on the type/class of amp circuits used, (A, A/B, D, G, H & T classes)
A typical Class A/B amp is about 50-60% efficient. That means, for every 100 watts it comsumes, we get up to 60 watts output. The rest is lost to heat and transistor biasing.
Class D amps are between 80-88% efficient. However, they are limited to low frequencies of 300 Hz., or lower. (Great for subs)
Class T amps can be as high as 90% efficient when using "Tripath" amplification circuits. This amp is very good for full range and sub applications.
Class G & H are not typically found in Car audio applications I am aware of. They too, are high efficiency and use multi-stage amplifiers and voltage rails when high output is needed. These are typically found in Pro Audio amplifier circuits.
Finally, the RMS (Root-Mean-Square) formula applies when we look at continous output power to a given load. As noted, the RMS = Peak Power x 0.707. However, most amps compensate for several load impedences and respective output power changes in ratio and proportion to a given load impedence. The higher the impedence load, the lower the RMS value will be. (Ie: 4 ohms VS 2 ohms)
Hope that helps,
Swez
MrBrownstone on 05/29/2006 21:32:04
Thought I'd chime in here.
Concerning amplifier efficiency, 90% efficient amps are just that...at 100% clipped signal!!!
Most class Ds run 70-75% at max CLEAN power (~1% THD). ABs, the same thing...about 40% efficient, 50% @ 100% THD. As, 25% efficient, and 33% @ 100% clipped signal.
Zach1989 on 05/29/2006 21:58:18
My bad I never knew all that until today, I figured you guys would know that, btu wasn't sure about begginers or if it was anywhere(i am a novice) and at the time the info seemed logical, and was pretty accurate in my case. I wasn't sure if you had the formula posted anywhere, so I figured I'd check.
Victor on 05/30/2006 02:50:31
Well actualy its good that you are trying to figure out thigns on your own, and sharing your findings here with us,
Its always good to make efforts to learn, We have a lot of study material in our "Article" and "How to" sections...
Also the "link" contains links to many many informative car audio site.
browse through all this immense treasure or knowledge at your will, and feel free to ask questions if any, we have very knowledgeble and experienced members and golds here, they have expertise in varied fields and make a nice mix on CK.
Also keep all such findings flowing in, even if we know it , its always useful to refresh such information.
Have fun COFFEE..
Victor...
ttocs on 05/30/2006 10:43:26
man I was having a REALLY REALLY bad day at work yesterday, didn't mean to jump ya.... I'm sorry.
Besides that I was thinking about the formula I spouted off and realized I was giving bad useless info. RMS is equal to the square root of 2, divided by 2. 1.414/2.
Swez is right there is alot of good info and good people here, don't let my reaction keep you from posting questions in the future.
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