In many of the 2600 V's presets the ADSR input into the VCA module has exponential sensitivity, as in the original synth. However, in some of the presets the ADSR input has linear sensitivity. I'm just curious if there is a setting somewhere in the synth that lets you choose the sensitivity for this input.
Take a look at the connections for the ADSR and AR to the VCA and the VCF.
As you can see in the VCA then both the AR and the ADSR is pre connected to input with tags "LIN" (Linear) and "EXP" Exponential.
If you for instance connect the ADSR to the VCA input tag "LIN" then you get a linear VCA for the ADSR.
As you can see, then the ADSR has a pre cabled connection to the VCF - but you can for instance connect the AR instead.
Different combinations of connections give different results. Take a look at how the presets are connected.
You can for instance also use the AR as a pre envelope for the ADSR and for instance delay the ADSR this way.
You can connect the outputs and inputs in many more ways than i mention here. This is just trying to answer your question not being and expert.
Hope this was what you asked for and this will help you.