Deane,
Eddie hit the nail on the head--there is no single setup that fits all. However, there are lots of great options available and none take a lot of time to setup.
First and foremost, I try to use the least amount of equipment as possible, thereby decreasing the possibilities of equipment failure to just a scant few.
I don't use a mixer, my mic is fed directly into the TC Helicon M and it is fed directly into the keyboard's Mic/Line In connection. This allows you to get the full benefit of the keyboard's vocal processor, plus provides the best available vocal harmony when needed. If you don't use an external harmonizer, then the mic is plugged directly into the keyboard.
On the Bose L1 is fire the keyboard's outputs directly into channel 1 and 2. Channel 3 of the L1 is used for the audio output of the Laptop, which is where I run MP3s during breaks. Winamp seems to work best for this. Channel 4 of the L1 is reserved for guest mic situations, which this time of year seems to be more prevalent because of corporate Christmas parties where someone wants to make lots of announcements. I use an inexpensive, high-gain mic for announcements, which fires directly into the channel withing the need of a powered mixer.
If I were doing a duo job, which is extremely rare, I would likely run the second mic through my Alesis 6FX mixer and then run it into channel 4, thereby providing the effects and control of the mixer without effecting my standard setup.
The presets will vary depending upon venue configurations, crowd density, and ambient noise level. Some days 05 work, while on others you may find that 12, 55 or 57 work best.
I set the L1s remote EQs at the 12-O'clock position and channel 1 & 2 remote volumes at the 12-O'clock position. The Master volume, however, rarely exceeds the 9-O'clock position, while the keyboard's master volume is usually set at about the 1-O'clock position.
As I've said so many times in the past, BE SURE to set the gain staging exactly as it is outlined in the instruction manual.
If at all possible, set up everything in a large hall while setting the Gain Staging, and making the various other L1 setup adjustments. This is really important. If I set up my L1 in the office, which measures 15 X 18 feet, has a 7.5-foot drop ceiling, and carpeted floor, there is almost no bass and the L1 doesn't seem as if it has enough power. However, when set up in a large venue, the bass can be overwhelming and with the master volume just set at 25 percent, I can blow the walls down. It's the nature of the beast. If you get into a bind, give me a call and I'll do what I can to help you out.
Good Luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)