Can it work?

[Mukhalled]

hi
Can this circuit work at 12V input?
http://www.electronics-lab.com/projects/audio/027/index.html

Thanx :)

[audioguru]

Hi,
This amplifier is designed for a 32V supply, so certainly won't give much power output with only a 12V supply.
10W into 8 ohms is a voltage swing of a little over 25V peak-to-peak.
So the voltage loss in the circuit is a little more than 7V. If you have the same voltage loss with a 12V supply, the output is only 5V peak-to-peak. That is only 391mW into 8 ohms or 782mW into 4 ohms at clipping.
Since the output voltage swing is reduced, the output current will also be reduced, so the voltage loss will probably be only 4V. The resulting 8V peak-to-peak will give 1W into 8 ohms or 2W into 4 ohms at clipping.

[Mukhalled]

Thank you :)

[Mukhalled]

but how can I do if I want to connect this amplifier to a car stereo I mean you know the car battery has 12V so shall it give a bad output power?

I need your help :)

[audioguru]

Hi again,
You can't use this amplifier in a car unless you also use a DC to DC step-up converter to get plus and minus 18V. Most very high power car amps do it this way, and use many strong output transistors so that they can drive a very high current into a very low impedance (1 or 2 ohms). Since Power = Voltage X Current, they increase the voltage and the current and therfore have a high output power.

A trick that many "ordinary" car amps use to increase the voltage is to use 2 amps for each speaker, wired as a bridge, with each amp driving 1 wire of its speaker, out-of-phase with the other. This results in nearly 4 times the output power. Most car amps are also rated to drive a 4 ohm speaker, into which they can deliver nearly 2 times the power than an 8 ohm speaker.
Some car amps even use low-loss Mosfets to increase their output power.

The most output power that an "ordinary" car amp can deliver to a 4 ohm speaker is about 25 Watts, at only 1 middle frequency, at 10% distortion and with a 14.4V supply. They are usually advertised as "50 Watts maximum power" (per channel, the 4-channel amps are advertised as "200 Watts").
I am sorry that I can't find a good car amp for you now. Maybe another of our members can help you or maybe you can find a car-audio forum on the web.

[audioguru]

Look what I found:
A car radio amplifier IC that gives 24W into a 4 ohm speaker:
http://www.semiconductors.philips.com/acrobat/datasheets/TDA1516BQ_1.pdf

[Mukhalled]

Thank you so much for your answers :)

[Giuflex]

U can search a schematic for a car amplifier with tda 1562q. this circuit should give U 70watts RMS (thet's what the manufacturer says)

This link should help U a little http://www-us.semiconductors.philips.com/acrobat/datasheets/TDA1562Q_ST_SD_2.pdf

[audioguru]

Hi Giuflex,
That's a tricky IC that uses a supply voltage-doubler. Its channels are internally out-of-phase so that mono bass doesn't load down the voltage-doubler too much, another neat trick.

Watch out about what the manufacturer says about power output. They guarantee only 45W at clipping, for a low-spec one that may have been made late on a Friday. Some ICs might produce 70W, but at a horrible-sounding 10% distortion (turned-up too much giving square-wave output). The power ratings are with a 14.4V supply, which is too high for a normal car battery, and without the voltage losses of a fuse and supply wiring.