I checked the voltage it is around 2.5V, varies a little bit because I am playing a cd.As you appear to realize but others may not, 2.5 volts is the specified **maximum** output voltage of the DAC, that will only occur when the digital data corresponding to the instantaneous volume of the music is at its greatest possible value. Most of the time that voltage will be much lower, especially on recordings having wide dynamic range. And to be completely precise, that voltage is defined on the basis of the RMS (root mean square) value of a presumed sine wave, as opposed to the peak or peak-to-peak voltages of the waveform.
Also, John Atkinson’s measurements of the DA-06 indicate 2.36 volts, rather than the specified 2.5 volts:
www.stereophile.com/content/luxman-da-06-da-processor-measurements
Good luck. Regards,
-- Al