How to Connect a 8Ohm Speaker to MCP4821 DA-IC?

Hi

For a small project, I would like to use a MCP4821 D/A IC for a good quality sound output. I have the following parts which I would like to connect:

  • Arduino Uno
  • MCP4821 with SPI
  • Speaker, 8 Ohm, 0.2W

To connect the MCP4821 with SPI to Arduino is very simple, I already did this. But now I would like to connect the speaker to the output of the MCP4821. I’m unsure about the specs of this D/A chip: http://ww1.microchip.com/downloads/en/devicedoc/21953a.pdf

Is it possible to directly connect the speaker to the output of this chip? Or what do I need to connect the speaker to the output of this D/A chip?

You can't directly connect a speaker. The output is rated for 25mA maximum. (From Ohm's Law, Current = Voltage/Resistance.)

You need a "power amplifier". If you want to build one yourself, the [u]LM386[/u] is a popular low-power power amplifier chip, and it's fairly easy to use. Or, there are [u]other power amplifier chips[/u].

Or, you can plug it into an "Aux" or "Tape" input of your stereo system*, or even your TV. Or, you can get a small amplifier something like [u]this[/u].

If you have a desktop/tower computer you can connect to the line-input on your soundcard. (The mic input on a laptop is too sensitive for regular line-level audio). If you use your soundcard, test your computer's configuration by plugging-in a CD player or DVD player, or something that you know is working before you connect your "unknown" DAC.

  • If you have a good high-power hi-fi system, be careful when experimenting! An unexpected blast of sound could damage your woofer or tweeter.... It's possible to fry a tweeter with high-power high-freqency test-tones that you can't even hear. A 100W speaker is generally designed to handle music with occasional 100W peaks, and can usually be damaged with constant 100W test-tones. The tweeter in a 100W speaker system can usually be burned-out with 10 or 20W test tones!

DVDdoug:
You can't directly connect a speaker. The output is rated for 25mA maximum. (From Ohm's Law, Current = Voltage/Resistance.)

Using an amplifier is a solution, but if you don't need a lot of volume, you can put a resistor in series with the speaker as well.

Voltage/Current=resistance.
6.5V(max voltage)/0.025A(max current) = 260 ohms.
You probably won't find a 260 ohm resistor but you can use the closest next one, 270ohm, to stay under 25mA.

Thank you very much for the helpful replies!

The LM386 seems really to be a good solution, it seems it was built with a 8ohm speaker in mind.

Simpson_Jr:
Using an amplifier is a solution, but if you don't need a lot of volume, you can put a resistor in series with the speaker as well.
Voltage/Current=resistance.
6.5V(max voltage)/0.025A(max current) = 260 ohms.
You probably won't find a 260 ohm resistor but you can use the closest next one, 270ohm, to stay under 25mA.

That would be a good starting point for some tests at least.
So if I use 5V as voltage from the Arduino board, it's 5V/0.025A = 200Ohm - 8Ohm = 192Ohm. So I use the next from e.g. a E12 series, a 220 Ohm resistor. This will keep the current at 22.7mA. Is this correct?

It might be interesting if you were to explain the conjunction of an Arduino UNO with "a good quality sound output".

I don't see a connection there. :astonished:

ZVe69:
So if I use 5V as voltage from the Arduino board, it’s 5V/0.025A = 200Ohm - 8Ohm = 192Ohm. So I use the next from e.g. a E12 series, a 220 Ohm resistor. This will keep the current at 22.7mA. Is this correct?

Yes.
I personally might choose an bigger resistor to keep current lower as 60-70% of the maximum. I recently used a 1k resistor with a similar speaker, simply because a smaller resistor resulted in too much noise.

But your calculation is within specs of the chip and should work fine.