Hey all,
I would truly appreciate some advice regarding this subject. I have read previous posts but I have definite knowledge gaps re: OTB vs ITB. My original objective was to stick a compressor, probably the FMR RNC 1176, between an ISAOne and a Profire 610 interface, primarily for treating the signal going in. No previous thoughts re: using the unit in Mixdown, using a comp/Eq for color, etc., just taming the incoming signal a bit. That is when I learned about the Warm WA76 Comp and their Pultec-like EQ and the G.A.S. reared its head.  I was aware and have read about external inserts, but never used before. 
 
So, I originally "figured" that I could run the ISA One into the WA76 in to the EQ in to the Line Input of the Profire 610. Then I read in the manual, " The external gear’s audio input must be connected to one of your audio interface’s output ports and the external gear’s audio output must be connected to one of your audio interface’s input ports." Does this mean the ISA/WA76/EQ "chain" won't work? I'm lost in the terminology, me thinks.
 
And, finally, would I be able to use the outboard gear on the Master Buss when mixing, or quasi-mastering? Or would this require a mixing board? Am I missing something entirely? Any direction would be very appreciated.
 
TIA, and please hurry. This G.A.S. is really starting to hurt :-)

If your goal is to control the analog signal before it hits the input, you'll need to just put all the FX in front of your interface's Input as you already described. External Insert is intended to be used to process already-recorded tracks with external gear. Nothing ITB can get at the signal until it's been digitized so it's not possible to use External Insert to control the analog signal before it hits the A/D converters.

Thanks for your reply. Love me some Manitou Springs. I realize I may not be asking the right questions, or phrasing my intentions correctly. The original goal was *just* to control the analog signal. Then I got G.A.S. for the Warm devices and recalled reading about External Insert, which I've not used before. I assume I can color the signal with those devices when tracking, which is a good thing, but I'm wondering if my current setup is capable of also inserting the devices and monitoring their effect on already recorded tracks when mixing. I'm hoping the answer is yes - if the answer is no, I would like to know what I need to do to make it so.

External insert works like a vst plug-in in the FX bin...you will need to set it up with sample latency in order to keep the audio aligned, but I use it all the time with my outboard gear...so yes what you want to do is possible...you will need to tie up an input and output channel of whatever audio device you are using (M-Audio profire 610 I assume)...
 
the best way to do it is first set up a device loop running an output into an input of your device using cables an check the latency, after that plug-in whatever external gear you want to use, put it in bypass mode and check the latency again (ping box in External insert) enter in the latency sample numbers it gives you into the lower box and you're set...

Thanks for your comments, Psychobillybob. I'm jazzed that I have the capability to use the outboard gear. At this point I get that External Insert is only effective AFTER the signal is in the DAW and that there is a latency measuring/calibration process. I am chagrined to say that right at the moment I am at a loss what, "you will need to tie up an input and output channel of whatever audio device you are using" means. I get that INPUT>>ISA ONE>>COMP>>EQ>>PROFIRE LINE IN will color the incoming signal when tracking. 
 
Here is the point of my disconnect. Is the Profire Line In the "In" I'm tying up? I'm ignorant to what it means to "tie up an output channel".  So then what do I do with an output channel? I have a feeling the answer is very simple and I will exclaim "DOH!". Man, I love this stuff.

What I mean is that in order to use external insert you are basically sending an analog signal OUT of your audio interface---->INTO external gear------>back INTO audio interface...
 
So in the case of what I think you are using it would look like this:
 

 
Where instead of "Lynx Two PLAY-B"(SEND) you would have an output from your Profire 610 (left side of image)
And instead of "Stereo Lynx Two B RECORD"(RETURN) you would have the input channel of your Profire selected...
 
Obviously making sure the channels correspond to what you are actually using as In and Out for the external device...
 
You are converting your audio back to analog via your audio device (Profire)sending it out to the external device, processing it then bringing it back into the DAW and converting it to digital again via your audio interface (Profire)...
 
(This is where I prefer to keep things digital if at all possible because you are converting from D to A and back again...if you have a digital reverb/eq/like a Kurzweil Rumor or something that will allow AES/Spdif in/out then you eliminate a conversion process but frankly most people cannot hear the difference...)
 

That's it?? DOH! I can't thank you enough. 

Yep, that's it :-)

Only other thing to watch is the levels going out to the interface and back in again. The output from the interface is probably line level, and might overload/overdrive the input of whatever hardware it's connected to if that hardware expects mic/guitar level inputs. Similarly, if the hardware effect adds volume remember to keep an eye on the level of signal that's hitting the interface input and adjust things as required to avoid clipping.

Oh, and Sonar generally gets the returned audio time aligned with the already existing tracks pretty well, but it can be a little off at times. Usually only a few samples, which might or might not make an audible difference, but you may need to manually nudge the recorded audio returned from the external insert a little.

tlw
Yep, that's it :-)

Only other thing to watch is the levels going out to the interface and back in again. The output from the interface is probably line level, and might overload/overdrive the input of whatever hardware it's connected to if that hardware expects mic/guitar level inputs. Similarly, if the hardware effect adds volume remember to keep an eye on the level of signal that's hitting the interface input and adjust things as required to avoid clipping.

Oh, and Sonar generally gets the returned audio time aligned with the already existing tracks pretty well, but it can be a little off at times. Usually only a few samples, which might or might not make an audible difference, but you may need to manually nudge the recorded audio returned from the external insert a little.

Drove me bonkers a while ago, I was calibrating a SSL compressor I had built with a cloned drum track using UAD's SSL Comp to compare ratios and attack times (makes it easy yo set up the meter this way, the digital meters are way better accurate than the real thing) and when I auditioned the tracks together it was off just a hair and I could not really see which one it was, my gear or the UAD track...

Also your output will take up a paired set of channels eg 1,2 of your audio device even if a mono signal and your return/ input will do the same so it will be eg 3,4