Standard output voltage for RCA line-outs DAC/CD/Streamers, etc?

Not sure there really is a standard, esp. w respect to DACs.  As I understand it, traditionally, line level for consumer equipment is typically about 0.5-1 volt. 

I was under the impression that most CD players and DACs had a 2V output, though there was no standard.  Your Chord does sound high.  If you're running it directly into an amp, you might consider using some kind of passive attenuator between the DAC and the amp.

Although I haven’t ever looked at the actual document, my impression is that the Sony/Philips "redbook" spec for the cd medium, that was originally issued ca. 1980, specified a "full scale" (maximum) output for cd players of 2 volts. That would be for unbalanced outputs, and would correspond to 4 volts balanced. Those numbers are much higher than had been (and usually still is) the case for analog sources.

Nevertheless it is common for many digital sources to exceed those numbers by up to around 25%. The 3 volt/6 volt numbers for your Chord DAC, though (which John Atkinson measured as being closer to 3.1/6.2 volts) are the highest I’ve ever seen.

As rcprince suggested, a pair of inline passive attenuators, such as the Rothwells which are offered in both unbalanced and balanced form, may be a good solution. As I mentioned in one of your other recent threads some users (including me) have had positive experiences with them, while others have reported that they compromise dynamics to some degree. The low output impedance and apparently hefty drive capability of the Chord, as well as the high input impedances of the amps you indicated in the other thread that you were considering, would seem to work in the direction of favoring a positive outcome with them.

Another approach, if applicable, might be to drive balanced inputs of the integrated amp or preamp with the unbalanced outputs of the Chord, via an adapter such as this one. That would cut the voltage seen by the amp or preamp in half, compared to a balanced-to-balanced connection. Whether or not there would be adverse sonic consequences resulting from that approach is equipment dependent and probably unpredictable.

Regards,
-- Al