Rather than blow one up which tells you little why not look in the data sheet.
The SAM3X/A datasheet:
45.5.3 Conversion Performances
- For performance and electrical characteristics of the DACC, see the product DC Characteristics
46.2 DC Characteristics
I(OH) (ISource) for pins in Group 2 (which include the DAC), is -3mA.
I(OL) (ISink) for pins in Group 2 (which include the DAC), is 6mA.
Pins in Group 2:
PA[1-6], PA8, PA[10-13], PA[16-17], PA[20-24], PB[4-7], PB9, PB[12-13], PB[15-21],PB[25-31],PE[10-14], PE16, PE22,
PE24, PE26, PF[3-5]
Group 1 (most other) pins have limits of -15/9mA.
The minimum allowed load (by spec, conservative) is 3.3V/.003A =1100 ohms. Personally, I would never intentionally come close to this low of a load for this chip.
The information in this thread: http://arduino.cc/forum/index.php/topic,132130.0.html applies to everyone, even us audio guys.
(not an audio guy)