Logic Mics, Aggregate Devices and The Input Issue

Question

There is a lot of discussion about Logic's inability to accept simple microphone inputs, and I ran into this for two frustrating DAYS of trying all the things in the Logic Express 8 Docs to fix it—to no avail.
But now it is solved, so I'm trying to create a DEFINITIVE list of steps and principles here so others may quickly blast past this issue.
The equipment I have seems to be emblematic to the problem. The Blue Snowball is one of those USB mics that simply doesn't automatically show up in Logic's Preferences > Devices > Core Audio >Device list. The fix for this is never mentioned in the Logic manual or Getting Started docs that I can find. There is a passing reference on page 100 that is virtually zero help, and does not bother to mention how this Prime Gotcha can bring you to your knees.
Principle #1: Logic uses the Preferences > Devices > Core Audio >Device (list) process to identify which microphone you can record with. The list has to have in it an entry that makes sense for both the incoming audio and the playback path that Logic uses to feed earphones or an external monitor.
Normal items on that list look like this:
Built-in Output/Line Input
Built-in Output/Digital Input
Built-in Line Output/Input
Built-in Line Output/Digital Input
Built-in Digital Output/Line Input
Built-in Digital Output/Input
The Built-in Output is the computer’s inner speaker or headphones. The Built-in Line Output is the computers stereo jack for feeding to an amplifier. The Built-in Digital Output is the fiber optic feed that can also feed an amp with up to six parallel audio channels (okay, 5.1 channels).
Nothing on that list will show a fully functional USB microphone that is being viewed on the computer’s System Prefs > Sound > Input page, even though the metering dots there show that the computer sees a live, active microphone.
Selecting the Mic in the Sound prefs page does nothing to pass it on to the Logic > Preferences > Devices > Core Audio >Device list of selectable items. This is frustrating, since GarageBand sees the live mic without any problem, but GB is a simpler program that has fewer options while Logic has many other potentials, so a one-size-fits-all solution may not be its best default setting.
To get the mic into Logic, you have to go into the Audio MIDI Setup utility program where a peculiar option appears that is called “Aggregate Device”.
This keyword is not found in the Mac docs, and understanding it seems to be a big secret. Even the Audio MIDI Setup help page will show you how to find it, but not how it works or how to use it for Logic. Ahem.
You open Audio MIDI Setup and under its header bar Audio is only one item, sure enough, Open Aggregate Device Editor. That opens a window that has two sections, an upper window with Aggregate Devices / In / Out across its top, and a lower window that shows all the options that the computer is aware of. The lower window is called “Structure:” and columns show Clock / Use / Audio Device / In / Out / Resample.
A default item “Aggregate Device” shows in the top panel, and you can add others and double click on one to change its name. You can make many variations here.
By default these will be present:
Built-in Line Input
Built-in Digital Input
Built-in Output
Built-in Line Output
Built in Digital Output
At the bottom of this list any other audio input devices that are plugged into the computer should show up. If they can be seen in the System Prefs > Sound > Input page, they’ll be here, too.
When I plug my Blue Snowball USB mic into the computer, it shows up here as Blue Snowball.
You create an Aggregate Device by clicking on your sound source, in my case, the Blue Snowball, then adding one or more other options.
When you click the Use check box for any entry, it pops to the top of the list.
Principle #2: An Aggregate Device is used by Logic to “see” both an audio input and an audio output path at the same time. The Device you’re creating at this point must include an input Audio Device AND at least one Output item to be fully functional for Logic. A Help page in Audio MIDI Devices called “Combining multiple audio devices” explains this in bare bones, but you can’t see that help page unless the Audio MIDI Devices utility is open.
In my case, I’ve checked the Blue Snowball and Built-In Line Output, so I can use that combo in Logic to define where the mic is coming from and where the Logic audio output should go to my line-input amp and speakers.
In the Audio MIDI Setup utility, simply selecting the Blue Snowball as the “Default Input:” device and/or the “Properties For:” options shows that the Audio Output area of the page has this cryptic message: “Output is not supported.”
At this point, you’re almost ready to go, and you can close the Audio MIDI Setup utility. But there is at least one more “gotcha” to conquer.
Principle #3: Logic ONLY looks for its list of usable Core Audio Devices when it starts up. If you have it open right now, all the choices made for Aggregate Device will not show up as selectable. Save any work in Logic, shut it down, then boot it up again.
Now you can use Logic's Preferences > Devices > Core Audio >Device list to see your Aggregate Device. I’ve named mine “Snowy Line Out” to trigger my recognition of what it contains. Another one is called “Snowball + Line + Digital” and it has both line and digital outputs aggregated to the Snowball mic input.
You can make one in the Aggregate Device Editor that combines a microphone plus earphones (Built-in Output) plus Line and/or Digital Outs, too. You'll have to switch among them in Logic as you work, but each will carry the live mic direct to recording.
I hope this gets you through the frustration of not knowing what to do when confronted with the lack of clear docs and complete steps to get a USB mic or other seemingly opaque input issue. Feel free to add to this so others in my former state of bewilderment can gain understandings.
If Steve Jobs were to encounter the level of opacity, ambiguousness and frustration that setting up a simple USB microphone can create in Logic, you can bet that the several programs and their intimate interdependency would be either automated or fully explained in the documentations that followed his fiery analysis of the issue.

Answer 1

I don't know of another way to get the Blue Snowball USB mic to show up in Logic. If you can do it without having to go through the Aggregate Device route, feel free to post here how to get that to happen.
I didn't have a different mic available when I started trying to do what seemed to be the simplest of things -- record and play back an audio track -- and nothing else seemed to work.
There are a lot of Aggregate Device threads around here, many associated with Blue Snowball, Blue Snowflake and other things, but none of them laid out the principles of how Aggregate Device Setup needs to work or what to do to force it into compliance.
As I said, the clues in the Logic docs and in-mac docs are minimalist, at best, none of them bringing instant head slaps of success readily.