Digital voltage?

AES/EBU is currently called AES3.

There are a number of differences between the formats AES3 and S/SPDIF.

Voltage, impedance, max length of cable run, etc.

There is also a slight difference in the data stream.

The voltage in the AES3 case helps with the max cable length you can use.

For more information these articles are interesting:
http://www.rane.com/note149.html
http://www.proav.de/index.html?http&&&www.proav.de/data/aes-ebu.html

"Would a higher voltage digital output level bump up the analog output level?"

No ... the detection process to recover the 1s and 0s compensates for the different levels. For example if the levels were 0v and 10v I might set my decision threshold at 5v. If the levels were -1v and +1v I'd set the decision threshold at 0v.

"Are there big 1's and 0's and little ones?"

Kind of. There's really no such thing as digital, since all digital signals must ultimately be modulated onto an analog waveform. The choice of analog waveform can make a difference in the noise immunity of the transmission mechanism and can reduce the number of bit errors. This is why balanced (AES) is considered superiod to SPDIF, especially for longer cable runs.

It's much clearer now, thanks for the responses!