How to hook JL F112 sub to both preamp and pre/pro

Srosenberg, thanks much for the input. I actually did have an email exchange with Barry at JL and he confirmed what you said, its perfectly fine to run both inputs, LFE/RCA out from pre/pro and balanced/XLR out from preamp.
Not surprised your calypso was better, as I have heard great things about that unit, but VERY surprised about the W4S being so good. What gear are you running? Wondering if there is a certain threshold of gear quality above which such distinctions become more pronounced. I'm running B&W N803 as mains (HTM1 ctr and DS7 surrounds), with Sunfire TGA5200 amp ( a very good and underappreciated amp) and a Sunfire TGP5 pre/pro fed by both a modded Denon 3930ci and a Sonos-BelCanto Dac2 combo. Although not heavy high end, would assume its good enough to hear a difference?

The below is from the JL Audio F112/3 manual. As you can see, they specify NOT connecting 2 sources to one sub, as the tech at JL Audio told me previously. I don't know who Barry is, but I would check for clarification. I don't think you can do this with a JL Audio, I think it could fry the crossover and amp, unless they have changed the electronics significantly. Look again at the last sentence of the setup from the manual below.

SYSTEM CONNECTION DIAGRAM 1:
One Fathom to
Home Theater Receiver or
Home Theater Preamp/Processor
Most home theater receivers and
preamp/processors provide a single
(mono) subwoofer output. When
connecting a mono subwoofer output
to your Fathom, you will only use the
Fathom’s “Left or Mono” input.
Two connection types are available
for connecting the Fathom to your home
theater system: balanced (XLR or 1/4-
inch TRS connector) and unbalanced
(RCA-type connector). Balanced
connections provide superior noise
rejection and ensure proper grounding
between components. If your receiver or
processor has balanced outputs, we highly
recommend that you use them.
In the connection diagram at left ,
balanced connections are shown as solid
lines, unbalanced connections are shown
dotted. You will only use one of these
input connection methods (not both).

texas,
that's really odd that the manual is SO explicit on this point, while their technician is clearly telling end users something different. point taken, thanks for your comments - perhaps the OP should bring this up with JL.

Jeff,
my rig isn't the final word in high end, but i've spent the last several years going through several different amps, preamps, sources, DACs, speakers, etc to get to a point now where i'm comfortable evaluating gear IN MY ROOM to MY PREDILECTIONS. those are important to note, as we all listen for different things, and my gear might sound dramatically different in another room.

i'm currently running Wilson speakers and VAC monoblock amps. the aforementioned DAC2 serves as DAC and preamp and is surprisingly capable in that role. that piece was really something of a surprise, as i never expected it to better my Weiss Minerva, and certainly never thought I'd be running it as a preamp.

Mac:

Barry Ober is a technical consultant for JL. Check out his own personal website at soundoctor.com ( a wealth of audio info and white papers). This guy has an uber-impressive resume, he's an audio engineer and has built recording studios. A very knowledgeable dude.

I think he's credible, to say the least.

Srosenberg, thats a mighty nice system, and certainly more high end than mine by a longshot. As I stated earlier, I wonder if I'll be able to hear as much of a significant difference with preamp changes as you would in your system. Guess the only way to find out is try it! The W4S Dac seems like a real giant killer based on your experience, so I may give that a shot at some point. By the way, Classe just came out with the CP-800 a killer preamp/dac/async USB all-in-one unit that also has sub-out. $6k pricetag, but thats pretty reasonable for everything it does (as long as it sounds good of course)