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Old 25th August 2004, 01:29 AM   #1
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Default small single channel car amp

Im posting here cause it looks like people are very knowledgable about this sort of thing here

I been thinking how a small single channel amp for car use would be very handy.

I have a small truck, and room is very tight, so i dont want giant amps taking up all kinds of room, tempting people to break in, and ruin the look of the interior.

Something small enough that it could be mounted on the back of a speaker, or near the speaker in the door panel, or hidden somewhere, so it would probably need to be somewhat water proof, and be able to function in tight spaces that lacks airflow. Something in the 35-75 watt range.

here is a list of features i think would be needed:

Speaker level inputs
preamp inputs
gain adjustment

some frills if you really want to get fancy:

lowpass crossover
highpass crossover
subsonic filter


anyway, the main idea of the amp would be that is small, and sounds good. I was thinking normal car amps are getting so big cause they over build them for 2 ohm loads, 1 ohm loads and so on, this amp should only see 4 ohm loads.

let me know what you think, i think there are more people out there like me that want a normal looking audio system, that doesnt take up a ton of room, or weigh a lot, but want it to sound really good

thanks for your time

Tyler
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Old 25th August 2004, 03:18 PM   #2
jaycee is offline jaycee  United Kingdom
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No. The main reason car amps are this size is because half of them is a switch mode power supply that converts 12V to a more usable 30-50v symmetric. It's practically impossible to get high wattages straight from a 12V supply. If you see a head unit that says it's more than 50W per channel that works straight from 12V, odds on they're lying.

The other reason is that for 75-100W output you need some decent size heatsinking. The case of those car amps is the heatsink.
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Old 25th August 2004, 04:30 PM   #3
MikeB is offline MikeB  Germany
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Hi !

How "small" or big is your truck ?
If it's big enough, you might have 24 volts. In this case you could
build a small bridged amplifier. But with 12 volts, forget it, like jaycee said.
You might be able to make some 5watt into 8ohm...
A 24volt bridged amp should be able to deliver 50watts into 4 ohm.
(or 25watts into 8ohm)

Mike
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Old 25th August 2004, 10:13 PM   #4
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its a dodge dakota, so its 12volt, and no option to step up to 24 volt, but gives me an interesting idea, what about some kind of device that steps up the voltage to 24 volt (or higher if needed) and could be mounted in the engine compartment, then the 4 small amps (or more if needed) could recieve power off of that?

I didnt think it would be that hard to make a small amp cause the smallest amp I had seen was a Sony 20x2 amp that I installed in a friends car. it was about 1 inch high, 4 inch wide, and maybe 6 inch long. sounded pretty good too. I'll try to find a link to it if you want to see it, kinda wish I had a few of them, but i dont think they make them anymore.

would a class D amp still require a large heatsink?

Im just throwing ideas out, you might be able to tell i dont know what i am talking about

Tyler
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Old 26th August 2004, 01:35 AM   #5
Stocker is offline Stocker  United States
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That being the case, and since audio quality doesn't seem to be a large concern, go for...

hush everyone else, this is situation specific advice!

a...

Booster/EQ combination device.

They usually claim several tens of watts each, some will have the features you want and most all are tiny (1/2 or 1/4 -din size). Take the power output claim with a grain of salt. Ok a whole salt shaker full. Then have fun with the buttons and adjustments.

The power supply is done as required. The amp is built. Just slap it in.

The sound quality is NOT going to be the be-all-end-all, but as far as I can tell, that's not the goal yes?
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Old 26th August 2004, 02:18 AM   #6
jaycee is offline jaycee  United Kingdom
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Quote:
Originally posted by regcabdak
what about some kind of device that steps up the voltage to 24 volt (or higher if needed)
That device you mention is called a switchmode supply.. of boost topology, and that's what nearly every high power car amp contains internally. Making these work is not a simple business.

There is Class D amps, which I'm not familiar with much, but do seem to allow for high power outputs with lower voltages.
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Old 26th August 2004, 03:18 AM   #7
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sound quality would be a goal as i would hate to put a lot of effort into something that would sound worse then the factory sound system.

the sony amp i was talking about is the XM-3020 i think, its a bridgeable 30x2 mosfet amp, roughly 3/4"-1" tall by 4 inch wide, and 6 inch long. i couldnt find much info about this amp on the web.

maybe i should rephrase what i am asking...

How small do you think you could make a single channel car amp, in the 30-75 watt range, and still have close to the same sound quality as the bigger amps? and maybe some of the same features.
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Old 26th August 2004, 07:48 PM   #8
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I found a picture of the sony xm-2022 amplifier, 20x2, I dont have exact measurements, but you can see its pretty small by the size of the preamp inputs

I thought of something, do you trust the aftermarket headunit power ratings? they are showing 20x4, 22x4, 25x4 and even a little higher... These ratings are supposed to be RMS power.

would it be posible to remove the amplifier section of a "broken" headunit and bridge its output to 1 channel?

Tyler
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Old 26th August 2004, 08:01 PM   #9
Mr Teal is offline Mr Teal  Canada
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I'm not sure you'd get a diy project that small. In my (limited) experience, DIY amps tend to be large and overbuilt, much moreso than commercial gear. If you wanted to build a car amp, even of 50W, you'd need a switching power supply to get your rail voltages, and then your amp section. If you made something fairly efficient, you might still be able to throw a fan on the heatsink and get away with tucking it the sidepanels at the back of the truck or something.
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Old 27th August 2004, 12:25 AM   #10
Stocker is offline Stocker  United States
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If you want to, you can make the amp itself pretty small, but heatsinking might be the principle obstacle

If you put the heatsink (say) in the engine bay, the amplifier could be in a pretty small box through a hole in the firewall, or maybe just a hole for the output device(s) of the amp.
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