I don’t have time to type right now, but here are the images from the analysis for a 2 Channel Orange, 3 Channel Vintage on ch 2, and 3 Channel Vintage on ch 3. The responses of the 2 Channel Orange and 3 Channel Vintage on ch 2 are very close. Other factors could influence the differences between them.
2 Ch Orange
2001 Recto, Ch 2 Vintage
2001 Recto, Ch 3 Vintage
The top line is the low pass filter after the tone stack. The next filter is the Presence control being rotated at 20 points. The difference between this and the original plots is the inclusion of the circuitry after the tone stack. Had I included the tone stack, it would be different still, but this illustrates the actual effect on signal vs. the presence in isolation.
One note: Ch 3 is a bright channel and the graph shows this, particularly in the phase graph.
warpedmusician 