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Old 30th January 2016, 02:29 PM   #1
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Default powering a 50 w amplifier by battery???

Hi everyone, first of all I would like to apologize for my poor english...
I was wandering if it's possible to power a tda7492p amplifier by battery. if it's possible, which kind of battery should I use in order to keep it working for 10 hours? thanks in advance for any answer

Last edited by ottotunz; 30th January 2016 at 02:58 PM.
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Old 30th January 2016, 02:48 PM   #2
Mooly is offline Mooly  United Kingdom
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The TDA7429 is an audio equaliser IC. Did you mean that ? or are you thinking of the TDA7294 power amp chip ?
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Old 30th January 2016, 02:56 PM   #3
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I do apologize... i wrote it wrong... I was talking about the TDA7492P
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Old 30th January 2016, 03:07 PM   #4
Mooly is offline Mooly  United Kingdom
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No problem. I see you've edited the first post

To deliver 50 watts (rms) into an 8 ohm speaker means that you need a DC supply of around 60 volts in total. That can be a single 60 volt supply or a split 30-0-30 dual supply.

You need a voltage that high so that the amplifier can put 20 volts rms (AC voltage) across the speaker. That figure corresponds to 50 watts rms.

To do that with batteries isn't really practical.

There are probably better options available. If your speakers are lower impedance (4 ohm) then you can get more power for a lower voltage.

Other options are Class D amplifiers (probably the best bet for battery use), or you could look at bridged 'chip amplifiers' a little like the TDA7294 but even here you would at least two 12 volt batteries. You would be probably be looking at VRLA types (valve regulated lead acid... like you get in alarm systems)

10 hours use on music shouldn't be such an issue.
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Old 30th January 2016, 03:17 PM   #5
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sorry if I ask you this question, but I'm new in the diy audio field... can you please suggest me an amplifier as powerful and cheap as the tda7492 but can work using a battery? I would have liked to use it with two 4ohm speakers. Another thing... how many amps should the battery be to make it work for 10 hours?
I do apologize again for my poor english

Last edited by ottotunz; 30th January 2016 at 03:33 PM.
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Old 30th January 2016, 03:34 PM   #6
Mooly is offline Mooly  United Kingdom
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The first thing I would do is try and decide just how much power you really do need. It might be much much lower than you imagine.

You can get a very good idea by trying this. All you need is a digital meter that can measure AC voltage, and to download the test files in the second post. Its fun to do and you might be surprised.

A Test. How much Voltage (power) do your speakers need?

Something like the TDA1558 might appeal to you. It would run off a single 12 volt battery (having multiple batteries to charge is inconvenient and messy). If you look at figure 4 in the data sheet then that shows a bridged amplifier.

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The battery capacity would probably be something like a 12 volt 7AH as a minimum capacity for typical music use.

There are many many chip amps available, but I'm afraid I'm not very well up on what is available in that line. It might be worth you asking for recommendations by posting a thread in the 'Chip amps' forum.

Your English is fine by the way
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Old 30th January 2016, 03:52 PM   #7
AndrewT is offline AndrewT  Scotland
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Buy an old car radio/amplifier.
Strip out all the radio stuff and use the two/four amplifier chips as your stereo amplifiers that will run from a 12Vdc battery.
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Old 30th January 2016, 03:59 PM   #8
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However you do it you will need a huge battery. Getting more than 12 or 24V is normally achieved with an SMPS but then the current required increases proportionally.

Just assuming a few details here.

If you want 50W x 2 = 100W.

Let's assume that the amplifier is 70% efficient, this will require a supply of 140W.

If the SMPS is 80% efficient this will require 180W.

If this is supplied from a 12V battery this will draw 15A.

So for 10 hours of operation you would need at least 150 A/Hr battery.

Last edited by KatieandDad; 30th January 2016 at 04:06 PM.
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Old 30th January 2016, 04:09 PM   #9
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I see... but I'm looking for a pre-made amplifier ahahah
I wasn't able to find one based on the tda1558... there is the tda1558Q, but it seems that no one sells it.
Can you suggest me any cheap pre-made amplifier?
sorry if I'm asking you al lot of questions, but i need to build a boombox and I don't have a lot of time to do it ahahah
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Old 30th January 2016, 04:32 PM   #10
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I see... may I know if you know some 30W pre made amplifier that can be easly powered by battery? (and possibly with a low battery drain)
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