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View Full Version : Chossing the right opamp for teensy 3.2 DAC audio output



tly
01-24-2016, 06:01 PM
hey guys :)

i bought a teensy 3.2 some time ago and i (like almost everyone :D) started a little audio project. Im using the DAC as an output and I would like to drive some small speakers with an amplifier. Im currently using a LM258 opamp as a small bit of amplification for headphone output. The output is reasonably loud and clear, but only for amplified speakers or headphones, small speakers like old PC-Beepers (http://assets.overclock.net.s3.amazonaws.com/7/7d/7d411b8b_vbattach158175.jpeg) cannot be driven by the amp, let alone bigger speakers.

The opamp is configured for a gain of roughly 3, supplied by a 12V DC adapter. I attached a picture of the circuit (drawn in mspaint :cool:)

My question is: Is it possible to drive bigger speakers with my configuration, or do i have some kind of impedance/level problem? If anyone used an opamp for the DAC output, could you recommend a good one for audio output?

PaulStoffregen
01-24-2016, 07:12 PM
These would be good ones to consider. These are very modern parts, with the ability to drive the speaker without a huge series capacitor, but they are designed for 5V power supply.

http://www.ti.com/product/lm4871
http://www.ti.com/product/lm4991

For 12V power, perhaps use LM1877.

http://www.ti.com/product/LM1877

PaulStoffregen
01-24-2016, 07:27 PM
Or if you want more power, you could step up to something like this:

http://www.ti.com/product/lm4950

tly
01-25-2016, 05:51 PM
thanks :) ill try the lm4871.

tly
02-20-2016, 12:18 PM
Just wanted you to know, I bought the lm4871 and it works really nice :) and i can make it really loud :cool: