Nobody knows very much about Robben Fords amp, but the myth has it that Robben Ford used a Rivera Combo for the actual song 'talk to your daughter'

IMO the secret about Robben's sounds is that it's in his hands. 

Something about that amp, like it's wound up like a spring and just explodes at the right time. Just leaps right out at you.

Hopefully you wouldn't need a Dumbleator-Kleinulator whatever if the effects loop wires are 18 inches or less.  Another simple solution is balanced connectors and cables for effects hookup?

You guys are really starting to scare me with the effects loop, something I've taken for granted on other amps for decades.

I'm sure I could wire up a Kleinulator in less than an hour's time. Afterwards I'd  need +15VDC and -15VDC.  Counting the Kleinulator itself, that's 2 to 3 wallwarts for an effects loop that most companies include within the amp.  All to power an 8 pin, dual op-amp chip that might cost a quarter.

Sometimes I think I'd settle for an internal reverb and spare myself the agony of dealing with such an effects loop and goofy external boxes.

Suffice it to say, I've done my time with breadboard circuits, op-amps, filters, power supplies.

The Boss Line Selector is good for matching impedance? No degradation of tone? Is it passive or active?
Sounds like a simple solution if the cost is right.

I still say there's room for another 12AX7 in the OTS chassis for an effects buffer.