Car amps vs "home" based amps

F

FNG212

Audioholic
What are the differences between amps used for cars and amps we use in home theater/music applications? It seems that car amps have higher power ratings with similar tolerances in THD and S/N but are much cheaper. Why not use something like http://www4.shopping.com/xPF-Rockford-Fosgate-Power-1500bd (purely as an example not specifically this) for home based subs?

I'm sure there is a reason or more people would do it; I'm just curious what the reason is.

Thanks.
 
M

markw

Audioholic Overlord
Home amps have power supplies, which are the ultimate limitation to what they can produce.

Auto amps draw from a battery which can provide virtually unlimited current for a limited amount of time. Search out "amp hours".

Here's a start : http://www.windpowerunlimited.com/batteries/Amp_Hours.htm

IOW, to get that performance from an auto amp in home usage, you're gonna need a ginormous power supply.
 
M

markw

Audioholic Overlord
Not a dumb question.

Got it.

Dumb question.

Thanks.
And not a mistake either. It was a good, valid question that is brought up fairly often.

Betcha a lot of lurkers/future newbies learned from it as well.
 
S

sparky77

Full Audioholic
Plus a lot of car stereo amps would need a powersupply like this if not something bigger, and much bigger than that, they usually require a 240v outlet.
 
Seth=L

Seth=L

Audioholic Overlord
Only thing is, 25 amps at 12v is nothing for a car audio amplifier of the magnitude you posted at the top, even if the amplifier is class D. We use a 60 amp at work to test amplifiers, but most amps can actually drain the power supply to where I can't give anymore power.

What you need is one of these.:D

http://cgi.ebay.com/Sorensen-DCR-500A-DC-Power-Supply-0-20-Volt-500-Amp-_W0QQitemZ250403515520QQcmdZViewItem

That's more than enough power for all the amplifiers you could think of ever connecting. Good investment if you ask me.;)
 
B

bigvag

Audioholic Intern
When the local curcuit citys where going out of bussines my friend picked up one of the power supplies they used to run their car equipment with, and even with it connected to a battery then to the amp it still couldn't keep up with the power draw, you would need a few batteries to do this.
 
R

redass

Junior Audioholic
And not a mistake either. It was a good, valid question that is brought up fairly often.

Betcha a lot of lurkers/future newbies learned from it as well.
yup. :D

-former lurker/current newbie
 
WmAx

WmAx

Audioholic Samurai
A very high quality, very low noise, reliable PS, with 50-60 amps current continuous, will cost around $300 roughly.

Sort of makes this option of using a car amp in the home a little bit more expensive than intended...

The best true value is using professional audio amplifiers. They have identical SQ and high SNR to audiophile home amps these days.


-Chris
 
H

Highbar

Senior Audioholic
DC current and the car alternator are wonderful things for car amps. Homes don't have either :( Back before I got my Jeep I had an old civic that I put the biggest alternator that would fit in it in, I kept killing factory ones trying to power my amps.

I wonder..... put a little 4 cylinder engine in the basement and hook it up, that might power some car amps:D:D
 
highfigh

highfigh

Seriously, I have no life.
What are the differences between amps used for cars and amps we use in home theater/music applications? It seems that car amps have higher power ratings with similar tolerances in THD and S/N but are much cheaper. Why not use something like http://www4.shopping.com/xPF-Rockford-Fosgate-Power-1500bd (purely as an example not specifically this) for home based subs?

I'm sure there is a reason or more people would do it; I'm just curious what the reason is.

Thanks.
Ratings tend to be, shall we say, generous. In the past, we used to consider car amps to be rated in Watts JBF (just before fire) and WLS (when lightning strikes), because what was stated never happened in real life. Also, you would need a pretty beefy power supply to adequately run a car amp unless it's Class D. If you look at Rockford amps, they tend to have very high headroom, which means they draw a LOT of current because their power supplies don't tend to be highly regulated. I wouldn't recommend using a car battery inside unless it's truly sealed, can't possible leak and is made for high current discharge. High current power supplies are expensive and would negate any savings you would see just when comparing amp vs amp. Optima isn't what it was but if you look in some of the car audio forums, you will definitely get some ideas about which ones are better than others. The reason car amps need a beefy supply is that cars work with 12VDC and the output devices often need 60VDC or more. You can't just take 12V and make it into 60VDC but 60V is a piece of cake on a 120V AC line because a transformer can be used to step voltage up or down. In a car, the 12VDC needs to go to an oscillator for creating an alternating voltage that can be transformed into a higher voltage, then rectified into DC voltage, regulated for stability and filtered. All of this happens before the audio is even considered.

It's not a dumb question, by any stretch. It can be done but you need current and as I mentioned, a truly sealed battery set up so it can't leak (acid or hydrogen) is needed. Storage batteries work well for this and if you think a bit outside of the box, it's not hard to charge it, especially if you're in an area that allows devices on/near your house that a homeowner's association or zoning doesn't.
 
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highfigh

highfigh

Seriously, I have no life.
Plus a lot of car stereo amps would need a powersupply like this if not something bigger, and much bigger than that, they usually require a 240v outlet.
That power supply won't do much for an amp that puts out much more than 150W/ch unless it's not driven hard. Most high power car amps have at least one 25A fuse and many have two 40A fuses. A car battery can deliver 800 CCA on demand and an amp can draw a lot more than 25A for a long period.
 
highfigh

highfigh

Seriously, I have no life.
Only thing is, 25 amps at 12v is nothing for a car audio amplifier of the magnitude you posted at the top, even if the amplifier is class D. We use a 60 amp at work to test amplifiers, but most amps can actually drain the power supply to where I can't give anymore power.

What you need is one of these.:D

http://cgi.ebay.com/Sorensen-DCR-500A-DC-Power-Supply-0-20-Volt-500-Amp-_W0QQitemZ250403515520QQcmdZViewItem

That's more than enough power for all the amplifiers you could think of ever connecting. Good investment if you ask me.;)
Tha' 'll do, lad. Tha' 'll do.
 
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