Amplifier current draw

[bocco]

Does the current draw for amplifiers increase with volume or remain constant. Trying to figure out how quickly some amps can kill a battery.
Thanks
Gary

[thmper321]

An amplifiers current draw will increase as the volume on the radio is increased. Some amps draw more than others and keep in mind a class D amp draws just as much current as a class AB at the amps full output with the same rated power. Most amps are pretty close to eachother as far as current draw versus power. Alipne PDX Amps are more efficient and Rockford amps tend to be the least efficient.

[Just Be]

If you like the sub. Keep the amp down unless you want to kill the battery. The low end will draw more current than the high or mid frequencys. It take's more current to move the sub low frequency's.

[thmper321]

All good points except comparing current draw of class d and class a/b amps. Class D amps are typically 80-85% efficient, while Class A/B amps are 50-60% efficient. It's just simple math. Two amps producing the same power at greatly different efficiencies will draw substantially different amounts of current to make that output. It's not voodoo people, it's math.
It is math but for some reason the Rockford Fosgate 3000 Watt Power amplifier requires 400 amps of current to produce that 3000 watts. That is not 85% efficient. By the way the fuse in that amp is rated at 250 amps. That means anybody who purchased this amps is not going to see 3000 watts. I have seen other 3000 watt amplifiers pull 290 amps of current to create their specified power. All Class D amps. Class D amps are more efficient than A/B amps at lower volume levels but at full volume there is not much difference other than Impedance capabilities and the shape of the wave on the output. Class D amps have a square wave type of output rather than a sine wave or rounded wave. This is why Class D amps also abuse woofers more than an A/B. The woofer is witness to what looks somewhat like a clipped signal. I have seen the tests on the Alpine PDX Amps and they are 85% effecient but if you run a pure sine wave through them and push them the power supply will give up. Not too many people will be running pure sine wave through PDX amps in a real word environment. Amps do not relay completely on the output stage for efficiency. The power supplies also play a part. SWB, do you have any theories to this? I would love to see tests on all the amps in the industry to truely see how efficient they all are.

[rivercrazy]

Class D amps are chitty by nature, that's why they destroy subs. Plus, people play them into clipping.
Huh? A class A/B amp is much more likely to clip than a class D amp.

[thmper321]

Class D amps are chitty by nature, that's why they destroy subs. Plus, people play them into clipping.
Every test I have ever seen shows that Class D amps make more power with the same input current. It only makes sense, they're not running full range and making power above 1000 hz is much harder than making power below it.
Don't forget that making power below 30Hz is very hard to do as well. Class D amps make more power because they can run down to 1 ohm. Class A/B amps typically are stable at a 4 ohm mono load. This is where the mathmatics come into play. We can't cheat Ohm's Law.
Alpine actually didn't figure out how to make digital work at full range. They licenced the technology from another manufacturer. It works better than the Tripath chit they used when I worked there.

[thmper321]

No, Class D amps make more power because they're more efficient, because they're only producing output through a very narrow frequency range. It's time to go back to amp school. ;)
Actually Class D amps have more efficient output stages than A/B amps put the power supplys are the same running at 65% efficiency so the overall efficiency is not that different at full output. We have always been told that Class D is 85 to 90% efficient but I have never seen a Class D amp play in that range especially at full output simply because of the power supply that provides the voltage to the rails. I have seen it first hand on an Audio Precision test machine.
Class D amps are more efficient because they convert an analog signal into pulses. These pulses then go through "chokes" to help round off the wave before going to the speaker. The reason why Class D amps only play at low frequencies is because they are terribly noisy. So yes the output section is more efficient but not the amp as a whole unit. Try it on your Audio Precision and see for yourself...;)
And as far as school is concerned, I have been thinking about going back to get my Masters in Electronics Engineering. :D

[Beer-30]

To get back to your question - YES the more throttle, the more juice. The more juice needed, the sooner your battery(ies) will fail.
No matter how big you go, please put an isolator on the starter battery.

[HitIt]

Class D amps are more efficient because they convert an analog signal into pulses.
To go down to the next level...
After the the analog signal is converted into a series of pulses, these operate the output transistors in either an "on" mode or an "off" mode. Transistors that are very effiecent when all the way on or all the way off are used in class D amps. When transistors are operated somewhere in between on and off, they are not efficient and end up generating a lot of heat. This is what is done is class A/B amps. They do sound cleaner because they can provide a better electrical representation of what the speaker is supposed to do to make sound than the bang on-bang off control the class D's provide.
The reason they are used with subs is that the electrical and mechanical characteristics of the speaker will filter the pulse train from the class D amps.

[HitIt]

No, Class D amps make more power because they're more efficient, because they're only producing output through a very narrow frequency range. It's time to go back to amp school. ;)
Class D amps are being used on MANY portable devices now. Cell phones, mp3 players, etc. They dont play a narrow frequency range. See my post above for why they are more efficient.

[thmper321]

To go down to the next level...
After the the analog signal is converted into a series of pulses, these operate the output transistors in either an "on" mode or an "off" mode. Transistors that are very effiecent when all the way on or all the way off are used in class D amps. When transistors are operated somewhere in between on and off, they are not efficient and end up generating a lot of heat. This is what is done is class A/B amps. They do sound cleaner because they can provide a better electrical representation of what the speaker is supposed to do to make sound than the bang on-bang off control the class D's provide.
The reason they are used with subs is that the electrical and mechanical characteristics of the speaker will filter the pulse train from the class D amps.
And that is taking it to the next level. Good info. I was trying to not get over too many heads.

[ROZ]

And as far as school is concerned, I have been thinking about going back to get my Masters in Electronics Engineering. :D
You'll make more money as an EE in technical sales....

[thmper321]

You'll make more money as an EE in technical sales....
I'm actually making more money now in car audio sales than I was as an R&D engineer for Alpine. I was making the crap that the sales guys were selling and they were making more money than me.

[ROZ]

I'm actually making more money now in car audio sales than I was as an R&D engineer for Alpine. I was making the crap that the sales guys were selling and they were making more money than me.no no... I mean selling semiconductors and assisting in design to companies like Alpine, bose, Denon, YAmaha, Apple,etc... Real technical sales :D

[thmper321]

no no... I mean selling semiconductors and assisting in design to companies like Alpine, bose, Denon, YAmaha, Apple,etc... Real technical sales :D
I understood what you were getting at. I used to be in meetings all the time with Texas Instruments, Harris, and Tripath in regards to buying their semiconductors for projects I was working on.
I think sales positions just make more money overall. It helps to have tech experience to go along with it.

[warlock]

I failed amp class...I've got 2 old school punch 30's and a punch 150 and they seem ta' kill my amp quicker then shizz...What "class" are these juice suckers?

[orange peel]

punch is everyday store bought stuff maybe B class. Ill deal with D-class amps all the time you dont need a D-class amp in your boat. But if you want one you can get one easy>You have to know what ohms you need to run the speakers you have 1-2-4-8? The higher the ohms the less power it will make,
but You can also get a compacater it looks like a big AA batter it stores the power the amp needs to make the bass this will help the life of your battery
for the day and over all. Just remember with the right box and air space you dont need so much power some 6x9s can sound as good as some tens.THE KEY IS RESEARCH WHAT YOU HAVE!!!!!!!!!!!!!

[warlock]

punch is everyday store bought stuff maybe B class. Ill deal with D-class amps all the time you dont need a D-class amp in your boat.
Not EVEN close:eek: ...The OLD SCHOOL punch amps aren't EVEN close to an everyday store bought stuff...Name how many amps put out the power of a punch 150HD at the same size? New punch sucks but the old school shizz ya' can beat!:D

[HitIt]

Ya, the old Punch is pretty solid. I would guess it is class A/B. Efficiency is probably around 50-60% or so. I remember those old Punches getting so hot you could cook on them. They sure could move a sub though.

[thmper321]

You could cook eggs on them and they never shut off or blew up. The difference between american made semiconductors and overseas made. Linear amps back them were amazing also. There was no such thing as class D and they could move woofers like nothing else.

[KREGER]

Would this be a reasonable answer to the original question?
Amps Draw = Watts/14 Volts??
2000Watts /14Volts = 142.86 Amps of current.
Take the Apms and divide the AMP hours on the specific battery to get an estimate of how long it would take to drain a battery?

[HitIt]

Well, sort of. First off, I am assuming that since you are talking about the battery draining, the boat is not running and the alternator is not charging the battery. The voltage fo the battery will be lower than 14V, especially towards the end of the battery's charge. Second, a 2000W system will only draw 2000W in very short bursts (like when the bass hits). What you are looking for is not the peak (2000W) draw but the average draw. That can be a little hard to figure and depends on the volume of the music and type of music you are listening to. Also, a 2000W system will draw more than 2000/14 amps since the amps are not 100% efficient. That is why they get hot.
You did get all of the math right though :)
P=I*V (Power = Current * Voltage)
and
Battery capacity (in amp-hours) = current draw (in amps) * time (in hours)

[thmper321]

Good Points. Music current is definitely different from sine wave current which is used to measure the continuous current of an amp.
Also the comment about the amps not being 100% is also correct. I remember watching the techs at Audiobahn measuring an amplifiers output with a current clamp over the power wire while running a sine wave through it and saying the amp make the power it was spec'd at. My comment was yes but how much is being used to heat the amp? :idea: