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Old 10th July 2007, 11:31 PM   #1
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Default Need Help With Small Stereo 4W 9V amp.

I am building some small, portable speakers. I have found some great speakers (8 ohm, 2-4W), but am having a lot of trouble finding a good amp for these speakers. I am planning on powering it with a 9V battery. I am going to be putting the amp and spaekers in a compact space, so I need a very small stereo ampl. I wish I could just design my own amp just for this purpose, but because I am very new with audio, that is not possible. If anyone knows of any amps, kits, schematics, or sites where I could learn to build my own amp, PLEASE inform me.
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Old 11th July 2007, 12:22 AM   #2
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Google is your friend

you could look into these but i am not sure how comfortable you are with building you own circuits. I just have links for schematics, someone else will have to help you with finding a kit, which may be a better idea for you.

http://www.discovercircuits.com/A/a-audioamp.htm

http://web.telia.com/~u85920178/use/afamp-4w.htm

Good luck

Dave
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Old 12th July 2007, 05:12 AM   #3
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Yeah, i am not advanced enough to build my own circuits, so a kit would be best. If anyone knows of any kits for good, small amps that can supply around 4W of power to my two speakers, please tell me.
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Old 12th July 2007, 05:47 AM   #4
impsick is offline impsick  United States
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well if you can etch your own board at home i will design one for you. (it very easy to etch)
or you can use perf board.
the tda2007 is a 6+6W amp that can run off 8v-something like 28 i think.
or check out the Dirty30 at the bottom of the DIY Projects link on Audiosquare.com (link below). it wont run off 9vdc i dont think but its a very small board. if you want i can make you something like the same for the tda2007.
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Old 12th July 2007, 07:51 AM   #5
Elorrum is offline Elorrum  United States
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I have built some amps from canakit that are stereo, 1.5W per channel. They fit inside an altoids box with a 9V battery and have been driving some rebuilt drive-in speakers nicely. I also built some boom (more a description of the style than sound) boxes with some small but accurate speakers I got from American Science and Surplus, self contained (plastic 1.5x4x3 with the front being the narrowest dimension, allowing a sort of bass port on the bottom) takeouts from old computer systems where the speakers hung on the sides of the monitor (I think) $2.00 a pair. They fit inside recipe boxes, with the amp and an MP3 player all inside. Without the recipe box, the two speakers and the altoids tin would be good for camping, very lightweight.

I just tried the little amps with some onkyo full range 4"speakers from a t.v. and they sound ok. I am going to put those speakers into some drive-in speaker cases. It's not very loud, so a dance party is out of the question, but it can get loud enough that I turn it down to answer the phone. It's not super fidelity, but it will be an improvement on the old oem paper cone speakers. Drive in speakers did not need very high power anyway.

I'm not well versed in the descriptive audiophile terminology, but with the little speakers, at not too high a volume, there is some spatial definition and imaging of the different instruments and voices. I was pleased enough with my first one that I made Christmas presents of three others.

I think the kit was CK122, but Canakit also makes a 7W x2 amp. I paid about 17.00 per kit and have gotten them from hobbytron, carl's electronics, see them on lots of online stores. The ck122 will run on 6V, 9V or 12V, maybe other powers(?) but I haven't tried them.
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Old 12th July 2007, 08:05 AM   #6
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I don't they they will run very long from a 9V battery..They have a pretty small capacity.Should be okay for a headphone amp though.
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Old 12th July 2007, 06:06 PM   #7
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A 9V battery won't have much capacity so a better option, if you can handle a larger supply, would be 4xAA NiMh batteries. This will give you about 5.5V which will allow about 2W of power. Or, if you can find a case, use more than 4 batteries for more voltage. You can get really high capacity NiMh AA now. But if you still want to run from 9V then check out National's LM4954, 9V part, simple to built. Need something like two resistors and a couple caps, give or take.

-SL
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Old 12th July 2007, 07:07 PM   #8
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Wow, thanks so much for all the help. Well I just took apart some pretty loud portable speakers, and they say they run off of 1W. I am pretty suprised they can get that loud with only 1W. My speakers are rated for 2-4W, so these should get pretty loud, right? Also, how do you etch your own pcb? Do you need certain equipment? I am going to look into some lower powered amps, because if 1W got that loud, I might not even need a full 4 watts. If anyone has any more ideas, please share.
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Old 13th July 2007, 02:44 AM   #9
BWRX is offline BWRX  United States
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A Sonic Impact T-amp or similar amp based on a TA2020, TA2021B, or TA2024 can work off of a 9V supply. I've tested the 2021B and it worked down to around 7V then shut off. The minimum supply voltage in the spec sheet is 8.5V though.
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