The picture on page 13 of the Clarinet manual appears to show a two gang set of RCA
output jacks that have red atop red on the right and white atop white on the left. Given
that they are mounted such that the foot of the module is to the top of the chasis, the picture
you show would seem to agree with what appears in that picture on page 13. I refer to
the picture, not having had built a Clarinet myself. And, I don't have a PCB board with
which to check the traces. However, should be easy enough to do given the jack's schematic,
http://www.cui.com/pdffiles/RCJ-41XX.pdfThe manufacturer's part number is RCJ-412233. Referring to the above data sheet,
pins 1 and 4 should be going to ground. So the question then is, are pins 2 & 3 tied
to the same trace and pins 5 & 6 tied to the same trace? If so, then the left jacks are
indeed the same signal and the right jacks are both the other signal.
Or, simpler yet, if you have an multimeter with continuity (or failing that, resistance),
you can simply check and see: do the two inner pins on the left hand jacks have
continuity (near zero resistance like 0.2 ohms -- the typical resistance of the test
leads, etc.). If so, they are the same channel.
Dan