Arduino Due DAC output to powered speakers

I am trying to output sine waves to some powered speakers. I am aware that I need to do some sort of impedance matching but I'm not entirely clear on what I need to do to achieve that.

The measured input impedance of the speakers that I am using (an old boombox, with RCA inputs) is 53kohm. I ruined one of the DACs on another board trying to hook up the DAC directly to one of the channels through the RCA input so I am a little hesitant to connect it now. Could someone please provide some guidance?

I need to do some sort of impedance matching

No you don't. Use resistor divider to bring signal down to 0-2V level, then run it thru a capacitor so the powered speaker input sees +/1V signal.

Look at my post "piano tones micros" to see how I did the same with a '1284P chip. The cap to provide AC coupling between the devices is the important part.

http://forum.arduino.cc/index.php?topic=179761.0

I used 10uF polarized caps, experiment and see what sounds good to you.

CrossRoads:

I need to do some sort of impedance matching

No you don't. Use resistor divider to bring signal down to 0-2V level, then run it thru a capacitor so the powered speaker input sees +/1V signal.

Look at my post "piano tones micros" to see how I did the same with a '1284P chip. The cap to provide AC coupling between the devices is the important part.

http://forum.arduino.cc/index.php?topic=179761.0

I used 10uF polarized caps, experiment and see what sounds good to you.

Thanks for your quick response. So I do not need to impedance match? Could you maybe explain why? I thought the output impedance of the Due's DACs is low and would need to match the high input impedance of the boombox?

Also, I assume the capacitor is to get rid of the DC sent to the speakers? The Due seems to already provide 0-2V range (but not +/-1V due to DC).

The Due is basically driving an open circuit with a 53K ohm load. 3.3V/53K is microamps of current. Signal to 5K/10K to Gnd resistor divider to bring level down to 0-2.2V will be all the "matching" needed. If it's already 0-2V, then perhaps just a 10K to Gnd to make sure the signal doesn't float during resets or similar.

Yes, cap gets rid of DC and makes it a +/- signal with 0V ground.

CrossRoads: The Due is basically driving an open circuit with a 53K ohm load. 3.3V/53K is microamps of current. Signal to 5K/10K to Gnd resistor divider to bring level down to 0-2.2V will be all the "matching" needed. If it's already 0-2V, then perhaps just a 10K to Gnd to make sure the signal doesn't float during resets or similar.

Yes, cap gets rid of DC and makes it a +/- signal with 0V ground.

Ok, that seems to make sense. I tried hooking up a 0.1uF cap in series to the DAC and tha got rid of the DC. I am still hesitant to connect it to the speakers because I seemed to ruined one of my DACs on a previous board by connecting it to the boombox without anything between the DACs and RCA inputs. Was it the DC that ruined the DAC?

Thanks for your help.

Was it the DC that ruined the DAC?

Probably yes.