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Old 1st March 2006, 03:54 PM   #1
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Exclamation please help with 2x12w 12 V portable audio amp

im building amplifier that will be powered by 12v ~10Ah battery.

i choosed TDA2006 integrated amps which produce
12watts of power at 4 ohm (drivers are from car stereo)
i will use their reccomended diagram

Click the image to open in full size.

can anyone give me some other diagrams, or some ideas to improve
amp, because idea of this amp is to play constantly for longer period of time
when i go on long outdoor trips.

i need to spare as much current as i can(because i want that amp
plays for a longer period of time)

i dont know how to built in stand by / mute circuit..

i'll use 2 amps to have stereo, and 2 of them are a lot easyer to cool, and are more reliable, if one channel burns other will be still usable

please help

thx
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Old 1st March 2006, 07:47 PM   #2
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If you want less current draw, either use higher impedance speakers, or turn up the volume less.

Instead of 4 ohm, if you went 8 ohm, you would save battery life, even at high volumes, because you would only use half the power.
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Old 1st March 2006, 11:17 PM   #3
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i can connect those two speakers in series too and use 1 amp or 2 bridged, i know, but thats optional... i wanted some kind of mute/ STANDBY switch if nothing is connected on input, but amp is turned on

i wanted to built bass cut circuit to save some power(then i f i want i can guide bass signal to 3rd amp, optional, but this amp is required for use on field so i dont need that for now).

which is best way to mute/standby this amp?
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Old 6th March 2006, 03:22 PM   #4
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i connected this amp on test board and i have measured about 2 volts on input and 5 volts at output, without anything connected. how is thah possible?
then i connected one speaker and discman on input, but i heared a lot of bzzzzzzzzzzzzzzzz and chip was over heating. why is that? amp was powered by computer power supply and discman was powered by another ac/dc adapter, was that creating buzz?
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Old 6th March 2006, 04:14 PM   #5
Eva is offline Eva  Spain
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This circuit is intended to operate in +-12V symmetrical supplies. This means that it doesn't only require a +12V rail and ground, but also a -12V rail. Don't try to use the -12V output of the PC power supply for that, as it's only rated at 100mA !!

You should look for single supply arrangements, and for BTL (bridge connection). There are thousands of car-radio ICs readily available that would fit your needs, for example TDA7375.
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Old 6th March 2006, 06:07 PM   #6
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but in data sheet is given application circuit for single power supply
http://www.st.com/stonline/books/pdf/docs/1452.pdf

shouldn't that work too?

tda 7375 is more expensive
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Old 6th March 2006, 07:06 PM   #7
Eva is offline Eva  Spain
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The single supply arrangement should work in your application.

TDA7375 does the same job as *four* TDA2006.
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Old 7th March 2006, 12:30 AM   #8
cpemma is offline cpemma  United Kingdom
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There's also the TDA2005M, a bridged mono designed for car use, 20W from 14.5V into 4R, and the TDA2004, a 14W mono bridged/4W stereo chip amp. I made 4 of the latter bridged amps many years ago for a portable mini-PA system, surprised me to find RS Components in the UK still do the "evaluation" PCB for it (434-598).
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Old 7th March 2006, 07:38 AM   #9
sangram is offline sangram  India
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Yeah but the 2005/2004 power ratings are at 10% THD. I have those datasheets and at a max of .1 THD you can get about 2 watts from the amp. Even at 1% THD AFAIK it's about 4 watts or so, after which the distortion ramps rapidly.

And those ratings are into 2 ohm loads at 12 volts.

Unfortunately you can't realistically get more power than that from a 12V supply. Philips had launched a class-H chip which used two large capacitors to boost rail voltage and get some more power at realistic distortion figures, I don't remember the chip number though.

The circuit diagram shown will work fine - it has a rail splitter for half-supply generation, but it needs more voltage, a single 12V battery means it's only getting 6V per rail, which is really low. According to the info it should work, but two batteries will be better.

For a 12V supply the best bet is unfortunately Class-D amps, with an SMPS, or a voltage doubler/SMPS and a good linear amp.

Why do you have to use one battery only?

By the way, you were getting a buzz because of a ground loop between the computer PSU and the discman power adapter. If you have a battery use the battery to power the amp.
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Old 7th March 2006, 12:18 PM   #10
cpemma is offline cpemma  United Kingdom
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Quote:
Originally posted by sangram
Philips had launched a class-H chip which used two large capacitors to boost rail voltage and get some more power at realistic distortion figures, I don't remember the chip number though.
a 70-watt class-H audio amplifier module based on the Philips TDA1562Q power IC...This ground-breaking IC uses special techniques to deliver up to 70 watts from a 12V battery and does away with the need for a DC-DC inverter.
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