Sonic Maximizers are way misunderstood and mostly over-used when they are used. If they are still true to the original BBE designs, they are a dynamic high-frequency eq, meaning they boost highs when there are highs present to be boosted, but they do not boost highs when there are no highs, or no signal, so they don't enhance hi-end noise like a 'static' hi frequency eq would. They also react dynamically, meaning they boost highs more or less depending on much high frequency action there is in the signal. If you are already using your amp or an outboard eq to boost your highs, then you should set the maximizer so it is just slightly brightening things overall, and pull back on your other eq so things don't get too bright. But if it is making a night-and-day difference when you switch it on and off, I promise you are WAY over-using it and you will wear your and the audiences ears out with it. They are a MAJOR source of listening fatigue. I personally agreee with CL400Peavey - they suck - but if some people get what they want from them, then it's all good.
+1