DIY amp quiestion. car audio power amp?

[cooptroop123]

I am planning on building a smaller practice rig, nothing fancy just something small and light. anyways i as looking at power amps and saw some really cheap car audio power amplifiers. I was wondering if these could be used to power a speaker cabinet. i would have a preamp also for tone controls and equalizer and stuff. so would this work okay? doenst need to be the best but as long as it works.

[3506string]

Making an amp out of a car amp + a cab.
Using a car amp/sub as a bass amp.
car amplifiers for bass?
Using a Car Amp?
Car amp

[T-Bird]

Hi.

There's been plenty of threads and debate about this lately .

Edit: And the links 3506string kindly dug up proves that.



Most of us DIY old-timers have tried it.

For purposes other than busking, ie running the rig off a battery, the car amp approach just isn't feasible if You have to buy any of the components.
However, if the components are free, try it, it'll make a sound and You may even like the result.

50W or so is about the absolute maximum wattage You can get from a setup like that without breaking the bank. And even that usually means having a 2 or 1 Ohm load.

Regards
Sam

[billfitzmaurice]

Originally Posted by cooptroop123

I am planning on building a smaller practice rig, nothing fancy just something small and light. anyways i as looking at power amps and saw some really cheap car audio power amplifiers. I was wondering if these could be used to power a speaker cabinet.

Sure, so long as you do all your practicing in your car. Otherwise, no.

[cooptroop123]

well i would use a power converter to go from 120V ac to the 12V dc that is needed for the car amp. except the price on one that is rated for the kind of current that is needed is a little high.

[JimmyM]

Originally Posted by cooptroop123

well i would use a power converter to go from 120V ac to the 12V dc that is needed for the car amp. except the price on one that is rated for the kind of current that is needed is a little high.

and now you get why it's not recommended.

[pi_r_squared]

I thought about this, dug out my old nakamichi subs, and my old pro-spec 7 band eq/amp.

I think it's 45w rms, uses a 7 amp fuse, and never blew it in all the years I used it in 4 or 5 different cars.

Would a laptop power supply be clean dc power?

They have 14v 6 amp units on ebay for $23 delivered

Don't most car batteries measure 13.5v or so? If so, you might want to think about something slightly more than 12v. Someone else might want to confirm or refute that before you take my word for it and let the blue smoke out of something.

Might be a fun project

[Rick Auricchio]

Originally Posted by pi_r_squared

I think it's 45w rms, uses a 7 amp fuse, and never blew it in all the years I used it in 4 or 5 different cars.

Would a laptop power supply be clean dc power?

Sure, if the amp was 100% efficient. And it isn't.

A laptop supply would sag terribly under the varying load of an amplifier. And, since most are switching supplies, they depend on the roughly constant load for which they're designed; it would shut down with a wildly varying load.

Even worse, it doesn't need to provide clean power, which would make an amplifier sound horrible.

[T-Bird]

Hi.

Originally Posted by pi_r_squared

I think it's 45w rms, uses a 7 amp fuse, and never blew it in all the years I used it in 4 or 5 different cars.

40 or so into 2 or 1 Ohm sounds about right.

Originally Posted by pi_r_squared

Would a laptop power supply be clean dc power?

No.

Originally Posted by pi_r_squared

They have 14v 6 amp units on ebay for $23 delivered

Cool, if Your laptop needs a new PSU

Originally Posted by pi_r_squared

Don't most car batteries measure 13.5v or so? If so, you might want to think about something slightly more than 12v. Someone else might want to confirm or refute that before you take my word for it and let the blue smoke out of something.

An automotive lead-acid battery in good condition reads about 12.4V to 12.8V without load. The in-use pole voltage depends on the voltage regulator, obviously, and can be as low as 13.5 in warm climate, but if there's a heavy electrical load, and/or the vehicle is operated in cold climate, 14.2V to 14.8V regulator is used.

Originally Posted by pi_r_squared

Might be a fun project

That is true. Especially if You don't have any high expectations and you do have some free time.


I guess it's like the age old (at least Mayans did it) alcohol soaked feminine hygiene products in certain body openings that every generation has to try for themselves. Because they were the first to invent it .

Regards
Sam

[Ken Baker]

All it takes is power and the money that buys the power.

I went to Alpine's site and looked at specs and instructions (PDF) for one of their mono power amps, the MRP-M500. The little one in their line. You might have an amp on hand, but this is a reasonable example.

You'd need to be able to feed it with automotive-style DC, and the circuit would need to be fused for 60 amps. Your supply wiring would need to be at least 4ga - 0.2043". Realistically, you'd need a car battery or two and a way to keep them charged. And you'd need to keep them in a well ventilated area because they outgas hydrogen when charging and discharging.

Then there's the question of what you're going to drive the power amp with. Preamp of some sort with a line level out will be needed. You might get by with a powerful active bass. Or not. Depends on the bass and the power amp.

You'll probably need to keep things on a cart. The amp will be small and light. The speaker would be as manageable as any bass cab. But the power supply would be hefty.

Fun project? Sure! OTOH, you might just be tilting at windmills.

Ken...

[seamonkey]

If you have 8 ohm cabs then you can just use a prebuilt ready to go module
Dayton Audio DTA-100a Class-T Digital Amplifier 50 WPC Provides Power To Computer Speakers, Bookshelf Speakers, Headphones, And More!
Lepai Tripath TA2020 Class-T Hi-Fi Audio Amplifier