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Old 11th November 2011, 08:20 PM   #1
gio89 is offline gio89  United States
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Default boom box idea

I work at an elementary school and noticed that the p.e. teacher uses a small portable boom box, that sounds terrible, especially since it is outside and blasting through small cheap speakers.
So i thought i would build my own to bring and use for the children during p.e.
What i really want to build is a 2.1 channel system capable of being loud, but still clear and nice sounding with the .1 giving that extra bass.

Is this a good amp board to use TDA7294 2.1 Power Amplifier Board 80Wx2+160W Subwoofer $38.71 Free Shipping @GoodLuckBuy.com ?
I figured 80 watts per channel is much better than the 15watt boombox they are using now, and with the 160watt sub woofer it should sound great right? I don't know if the amp requires 4 ohm or 8 ohm but I'm assuming 4 ohm if you know that would be great.

My plan was to use 2 three way car speakers and 1 car sub woofer.
please give me some advice, i think it would be real neat to say that i have built my own boom box. Also, i don't have too much money to spend, but i would like it to last and perform. Any help is much appreciated.
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Old 11th November 2011, 11:34 PM   #2
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If its gonna run on batteries they better be big ones....too heavy. Is it too far away for a power cord?........you could use a normal P.A. Otherwise, sounds like it would be good in a car with the right speakers.

Interesting chip though!
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Old 11th November 2011, 11:38 PM   #3
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Damn! you can't build it for that......so that's one chip each for the 80w and two in bridge for the bass.....with controls. But two car batteries needed for operation out on the field, or a long power cord!
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Old 12th November 2011, 02:34 AM   #4
gio89 is offline gio89  United States
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The school just recieved a portable pa system, complete with ipod doc and mic inputs. But it is a 50 watt mono speaker system that is rather quiet and doesn't give great sound.

If anyone knows of any board that would give me great sound quality and still be loud enough for a class of students to hear, please let me know.

I wanted a 2.1 channel system because two 3-way car speakers would give good highs and mids, where the .1 would allow the bass to really be heard.
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Old 12th November 2011, 02:37 AM   #5
gio89 is offline gio89  United States
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Also, if it didn't have to be portable do you think that board is a good buy.

I'm fairly good with electronics, but no nothing about building my own electronics. That is why this board seems appealing. All i would have to do is get a power source, and hook up the speakers, correct me if i am wrong.
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Old 14th November 2011, 09:11 AM   #6
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You would need a heatsink and some sort of cabinet to house the board as well. It does look like a good buy and will do the job that you have in mind. Hopefully it comes with instructions on how to build a complete working system.

Another thing - you will need microphone pre-amplifiers too. One per mike. And a mixer. If the other PA system has a headphone output, you could use it to drive this setup.

If you want this shebang to be battery powered, you will need a deep cycle mobile home type of lead acid battery. Don't count on more than three hours or so on full blast. Might be more if you don't play too loud - this is just a guesstimate.

Last edited by ingenieus; 14th November 2011 at 09:15 AM.
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Old 14th November 2011, 09:49 AM   #7
RJM1 is offline RJM1  United States
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If you look at the data sheet for the TDA7294 page 6 figure 5 (output power vs supply voltage 4 ohms) you would need to have +-34 volts to get 80W output @ 10% distortion( 6 - 12V batteries). With +- 12V (2 - 12V batteries) you would only get 20W output @ 10% distortion or about 15W at .5% distortion.
Data sheet.
http://www.st.com/internet/com/TECHN...CD00000017.pdf
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Old 14th November 2011, 10:30 AM   #8
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The only options for your problem are
a) Big 12v battery and a car stereo with big booster amp and a mic input.

b) Look for an old 12v transformer coupled amplifier for PA work that were used in the 60's and 70's those used to kick ***! Distortion figures were not too good but with tubes or germanium outputs it didn't matter too much. With a couple of cheap column speakers, you will get quite acceptable sound for outdoor use.
Look up Boyer amplifiers, (they were really good) Geloso, even old Siemens or Philips jobs. The transformer coupling took a lot of handy short cuts for loud public use!
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Old 14th November 2011, 10:57 AM   #9
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You could use a switching power supply to convert the 12V from the battery to the +40V needed by the amp. I should have added that to the list. Easier to just use a car amp.
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Old 14th November 2011, 11:06 AM   #10
ODougbo is offline ODougbo  United States
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Default Anchor Audio

Check out Anchor Audio, they have cool (battery) stuff.

And they play loud!!

Anchor Audio,Inc.- Leader in Portable Sound Systems, Public Address Systems, Speaker Monitors, Intercom Systems, Conference Systems, Assistive Listening, & Lecterns.
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