I have a pretty good base in electronics, well I used to. I have gotten pretty rusty. Anyways, I am looking to build a home audio amp using the tda86571j quad amp chip from NXP. I have the chip, and the datasheet. But I am having trouble trying to figure out the supporting hardware needed, and how to bridge the circuit from 4 channel to 2 channel. The datasheet says its possible, but I'm not sure how.
What i would like to accomplish:
A simple 2 channel audio amp with a line in for mp3 players. Maybe a digital volume control. I have the speakers, amp chip, and power supply.
I am hoping to build this with parts from my junk bin. Cash is short, so I cant just go out and purchase an ots (off the shelf) version.
What i would like to accomplish:
A simple 2 channel audio amp with a line in for mp3 players. Maybe a digital volume control. I have the speakers, amp chip, and power supply.
I am hoping to build this with parts from my junk bin. Cash is short, so I cant just go out and purchase an ots (off the shelf) version.
Well , the datasheet shows a typical application that only uses about 6 extra components so it should be pretty easy to figure out , there is even a PCB layout in the datasheet for this chip .....
As for bridging the 4 channels into 2 , I don't really think it is possible , The chip it"s self actually has 8 amplifiers in it that are already bridged to get 4 outputs so they can"t be bridged again for a 2 channel output , though you might be able to parallel the + outputs of 2 channels and the - outputs of 2 channels to get a 2 channel output but would need to add a low value(0.22R) but closely matched resistor to each output leg ....
Cheers
As for bridging the 4 channels into 2 , I don't really think it is possible , The chip it"s self actually has 8 amplifiers in it that are already bridged to get 4 outputs so they can"t be bridged again for a 2 channel output , though you might be able to parallel the + outputs of 2 channels and the - outputs of 2 channels to get a 2 channel output but would need to add a low value(0.22R) but closely matched resistor to each output leg ....
Cheers
I saw the circuits supplied in the datasheet. I thought there should be more involved in an audio amp. So, I can insert power supply and audio in, and call it done? Other than a heatsink. Is it safe for the amp to ignore two of the channels?
Yes you can ignore the other 2 channels if you wish though you should short the inputs of the 2 unused channels to ground ....
Most of the circuitry is inside the chip , like the feedback network that would normally be set with external components with an opamp or power amp is already built into the chip .....
Most of the circuitry is inside the chip , like the feedback network that would normally be set with external components with an opamp or power amp is already built into the chip .....
Explains why the parts count is so low. Any suggestions for volume control? Is the 4 vcc inputs tied to the 4 channels? Should I power all of them? or only the ones being used?
Safest to connect all the VCC pins to begin with. If you were really worried about quiescent current then you could experiment with disconnecting the ones you didn't need.
Thanks for all the help/info. We will see how I fare. If its worthwhile, I may post the completed project here for "peer review."
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