As I may have mentioned before I work for a company that does some show/events work and a lot of rental type work. The "flagship" of our rental audio equipment at our company and just about every other like it is the Mackie SRM-450 powered speaker and Mackie 14, 16 and 24 channel mic/line mixers. These powered monitors have pre-amps built into them that enable you to plug a dynamic mic (like a Shure SM58) into them and just start talking. Thanks to Mackie in designing some versitility into their products, the mixers have an XLR output that allows you to choose line or mic level. These facts all line up and point out that as a set-up tech, you have a choice to make. Do you drive the output at line level and back off the pre-amp on the speakers, or put out a little mic level signal and let the monitors do the major amplification in the final gain stage? There is some debate within my company and between those of us on one side and those of us on the other. Here are some arguments that I've thought up for both sides... I fall on the "drive signal line level to the speakers" because: -the higher nominal voltage is less susceptible to voltage drop over long cable runs. -similarly, the higher nominal voltage of a line level signal is more immune to interference from electrical and magnetic fields, and RF interference. -the pre-amps on the mixer already did the work of getting the mic level signals up to line level where the filters and other electronics in the board can do their job at optimal parameters. -There is more head-room in the final gain-stage if SPL levels need to be increased. -If you translate the scenario to passive speakers and amp racks, almost every professional amplifier I've ever seen has taken a line level signal as an input...why should amps bolted onto the back of speakers cabinets be any different? -If you want to use outboard gear in "loop though" mode the signal is the right level and everything would work as it does inserted on a channel or bus (if you wanted to run a mains EQ between the mixer and the speakers) Those who argue for the mic level scenario say: -There is more gain before feedback when using open mics in close proximity (this seems counter-intuitive except than with electronics you find out quickly that every component in a circuit has a sweet spot where it operates the most efficiently and in audio this translates directly to frequency response and sensitivity...my theory is that the electronics in the amps are configured in such a way that frequencies that typically ring and feed-back in a live room are attenuated out of coincidence because of the behavior of the electronics involved.) -Easier to interface with house systems as most rooms have XLR "mic" jacks (this is valid but more of a point of convenience than anything else) So with all of this I had the following thought...the SRM-450s level knob has a "unity" setting in the middle exactly in-between mic and line level. Perhaps setting the mixer to mic level and driving the master faders a little harder (or even the pre's) could take advantage of the parameters involved on the amp side while still allowing for headroom and slightly less voltage drop / noise susceptibility. You could also set this knob at unity and drive the mixer at line level but attenuate the master faders, but you would loose some of the functionality of the meters on the board. All of this seems like a way to engineer around a problem that is much better addressed with more gear (a graphic of parametric EQ). For me, I like to start with the mics and go foward to the speakers in setting up my gain structure...that way the pre-amps are in optimal range, the faders are optimal and the output stage is optimal (with the masters at or around unity). I know this was kind of a brain dump but I've been thinking about this for a while and have been raring to have a technical discussion about it ... so go to it!