Short answer: No.
Arduino Unos and Megas have PWM (Pulse Width Modulation) output, which rapidly turn the output on and off with a varying "duty cycle" (The ratio of on time to off time.) That is not the same thing as an analog output voltage.
If you have a constant load you can build a low pass filter that will smooth the output to a slightly dirty DC output based on the PWM output.
You're better off using an external DAC (Digital to Analog Converter.) You send that a digital value and it converts it to a clean, filtered analog output. Most modern DACs are fast enough to output complex waveforms like music.
The Arduino zero apparently has a built-in DAC with up to 10-bit resolution. you could use that to output a low current DC voltage. However the zero is a 3.3V device.