Hi,
I would like to get started with a small audio project and Arduino, but not sure where to start. I have a nice 8-bit DAC which could take binary data from the digital pins.
But after the DAC, not sure. I would need an OpAmp probably to amplify the signal to something loud? How would I power the amplifier (5V ? or more? ) and, what are cheap/good loudspeakers to start with?
Any pointers to simple audio projects with Arduino would be great.
Thanks!
But after the DAC, not sure. I would need an OpAmp probably to amplify the signal to something loud? How would I power the amplifier (5V ? or more? ) and, what are cheap/good loudspeakers to start with?
What's the output voltage of the DAC?
It's probably approximately [u]line level[/u] and the easiest thing to use is regular active/powered computer speakers. Your soundcard, your CD/DVD player's RCA outputs, your TV's RCA audio outputs, etc. are all line level. The headphone-output on your laptop or iPod or phone is also approximately line-level, maybe a little high for line level with the volume turned-up. But, headphones are lower impedance so you can't drive headphones from a line-output.
If the DAC is powered by a single 5V supply (no negative supply), it will need to be biased at half the output voltage so the audio signal can swing negative relative to the bias and you'll need a capacitor to filter the DC bias from the output. You'll need to check the DAC's datasheet for how to bias the output, and you may need to bias the digital data. (i.e. Since it's 8-bits, you'd bias the data by adding 125 to the digital audio data before sending the data to the DAC.)
If the output swings from 0-5V (-2.5 to +2.5 after biasing and filtering with a capacitor) that's slightly "hot" for a line level signal, but that's OK as long as you have a volume control. And, it's usually better to have a signal that's a little loud than a signal that's a little weak.
A standard op-amp can't put-out enough power/current to directly drive a speaker. You need a power amplifier chip such as the LM380 or LM386. You can also plug the line-level signal into an input on your stereo receiver.
Thanks, the chip I have is: TLC7528, see http://www.ti.com/lit/ds/symlink/tlc7528.pdf
Interesting points about the signal swing and "line out" specification. So, using an active loudspeaker makes sense to act as a power amplifier. Also good to know that the OpAmp probably would not have provided enough power.