The 1089 is the same circuitry inthe EQ and preamps sections. THe only difference is in the line section where the gain starts opposite from the 1073.. so it starts @ -20dB -> +10dB instead of the +10dB ->-20dB
The 1099 if you can find them cos they are pretty scarce from what i have seen in my short travels is a 1073 without the line section. These were used in custom 8024's and they had a seperate line section houses int he meterbirdge module over the EQ module itself. This line switching section house the switches to switch the 1099 between MIC & LINE modes and has additional gain trims for the line inputs into the console itself.
The line section to drive the 1099 inthe 8024 is driven by either a 3415 or 1272 depending on what was ordered.
hope this helps
PEACE
Wiggy