I bought a Logitech Extreme 3.5mm Supra-aural PC Gaming Headset.  I later picked up a Behringer EURORACK UB1204-PRO for $90 new.  Having already been using my headset, I plugged it into my new mixer, and to my surprise, I could not get any sound out of the microphone.

After a bit of research today, I found out that computers don't use dynamic microphones.  They use electret microphones.  I didn't even know these things existed.  I only knew about dynamic and condenser microphones.  So now I have a headset that I can't even use with my soundboard. 

Here are two pages I found to be very informative:
http://www.hobby-hour.com/electronics/comp..._microphone.php
http://www.epanorama.net/circuits/microphone_powering.html <- this one has schematics for using 48V phantom power with electret mics
Wikipedia only has a short summary of electret microphones (surprising, they usually have a lot more information)

I have been unable to find any adapters being sold to go from 48V XLR (male) to 5V 1/4" (or 3.5mm) TRS (female).  Does anybody know of anywhere to get such a thing

(or am I stuck building my own)?  Or external power supplies?

My current solution is to just plug my soundboard into my main soundcard's input, and plug the mic into a different sound card, then send that card's output back to the soundboard.  Although annoying, this isn't the worst thing, since I can't live without having two soundcards anymore anyways.

I am currently using a Creative Sound Blaster Audigy SE 7.1 Channel card.  To put it simply, it fails to properly output 5 channel sound (5.1 is fine) and instead downmixes to stereo or up-mixes it to every other channel.  I had to go back to my cheap USB 5.1 sound card just to be able to listen to voice chat with the L/R channels and music on the center/SL/SR channels.  My onboard sound has similar up-mix-what-I-don't-want-it-to problems.  The Audigy's -10dBV output is fine, but it doesn't support +4dBu input (got past that by using the control room output lowered, I have the levels matched to -14dB[digital] to 0dB[analog]).  Unfortuately the mixer I have doesn't have a switch to change it to -10dBV.

I've just lost patience with overpriced, featureless (or just has useless features) junk.  I would really like configurable up-mixing, perhaps similar to the matrix mixer found in ffdshow.  Even though I'm a gamer, EAX doesn't impress me, so it isn't a mandatory feature.

One possibility looks like the M-AUDIO Delta 1010LT 24-bit 96KHz PCI Interface 10-In-10-Out PCI Virtual Studio, but I'm not sure if it will allow me to upmix from stereo to 7.1 IF I want to.

So much for packaged consumer solutions... ;-)

I have a couple of 101LTs, and they are what they are. They are desgned for use with audio production grade multitrack editing software, and rely on it to do whatevery mixing you desire.

I think you really should not try to mix consumer/prosumer grade hardware with professional hardware.

Also, forget about asking professional hardware to have consumer grade features.