I don't think that's physically possible, at least not with the current hardware.

Yes, the mods confirmed this once that this is not possible with the SL1.

ok but i was thinking more of a software solution.

A simple decreas in the Db level output would work.

the two types of equipment:
Balanced: +4 dBm (cd players and other line level equipment)Unbalanced: -10 dBV (Phono)

There's a difference of 11.8 dB between +4 dBm and -10 dBV

So a simple software filter that lowers the output level by 12 Db would work fine

Actually there is a third. The -10dBV level you referred to as 'phono' is actually one of two 'line' levels. +4dBm is also sometimes referred to as 'line' level, but this higher level is not used anywhere on the Serato interface (if you have a mixer with XLR (3-pin) connectors on the master output this is what is present there).

The term phono in this regard refers to the RCA 'phono' plug used- confusing indeed because true 'phono' level also uses the same connector. Phono level from a turntable is actually -40 to -50 dBm (or so) and if you understand the dB you know that this it is an infinitesimally smaller voltage.

In theory the SL1 output can be run at this lower level but you would lose significant sound quality- I explain why here scratchlive.net