more powerful, portable amp

I was messing around with some op-amps, building variations of the CMoy amp, etc. But I became depressed quickly -- these ICs' data sheets say that at the safe maximum of 15 volts, they can only pump out around 1/4 watt of power on a single channel! Well, i have a full range driver that really needs more power to sound decent. I was wondering what the normal way of constructing an amp would be if I were looking for 5 to 10 watts of power. *edit*: i'm not looking to run this thing off of batteries... i'm sure at 10 watts, a couple of D cells would get drained rather quickly... I recently cracked open an old 4.1 computer sound system (by microlabs) and scrapped the 5 drivers (4 satellites and a 5 inch sub), two big 3700 uF caps, and two JRC4558D dual op-amp ICs from the amplifier. I read up on the JRC chip (actually, just the data sheet from the RC5448D, the texas instruments flavor, i guess the JRC is discontinued) and it seems that this thing only puts out a max of 200 mW per channel, and typically around 90 mW. Ok i know those speakers didn't get THAT loud without distortion, but i am CERTAIN it was more than 800 mW for those 4 satellites. I am a new computer engineering student, so i can understand the physics behind the electronics, but i am nowhere near the level to start reverse-engineering that amp board. So how did these speakers get driven so hard? THANKS for reading!!!!!

gmoon10 years ago
Here's a TDA2005 datasheet, if you need 20 watts from an IC ...

By itself, an opamp is more precision than power (although it is often the basis of audio amps, mixers, etc.) So there's usually a power amp section after (transistors and other supporting stuff.) The transistors operate on the audio signal just the same way they would for a digital transistor switch. They take the signal (shaped by the opamp) but can handle much more current. Only the signal applied to the transistor is analog and not digital.

If it's a large amp you'll find the power transistors easily, as they'll have heatsinks attached...