Look on the [Invalid or Expired Link Removed]. Notice the 2 graphs? The top one is the graph showing you how much the bass and treble controls can be boosted or cut. The second one shows you how much the mids can be boosted or cut. The reason there are two curves is because they show the boost/cut levels for the minimum and maximum frequencies that the Mid Q (same thing as the varimid on old Ibanez basses) allows you to to select from. You can select any frequency between those two curves and boost or cut that specific frequency.
The switch allows you to turn on and off the EQ so you can be in either active or passive mode. But the battery may be required still, not sure. Depends on the preamp design inside.
On the [Invalid or Expired Link Removed] you'll notice the same scenario; HOWEVER, the switch is only somewhat like the Mid Q in that you can choose different frequencies to boost or cut, but you are limited to only 2 (400Hz and 800Hz) instead of being able to select from a wide range of frequencies with the Mid Q. This seems like a serious drawback, but some players like being able to switch their tone on the fly at the flick of a switch rather than having to turn a knob precisely to one spot to get a desired tone.
The SR 505 doesn't have that on/off switch and so it's always active.
Could you modify the wiring in each bass? Sure. you could replace the entire electronics or depending on the design of the preamps, you might be able to put a switch in the SR4005E or a Mid Q in the SR 505.
Btw, Style Sweeper is not a Mid Q. This is a feature on lower lever SR basses that EQ's every frequency at once for slap or fingerstyle. It's kinda like when a car stereo has preset EQ's for Funk, Rock, Country, etc
A monorail bridge is different because each string basically has its own bridge piece. They are NOT connected at all and so the idea is there are less sympathetic vibrations thus providing a clearer sound. I've never had a bass with them so I can't tell you, but the people on youtube who have Monorails on their bass say they can definitely tell a difference
EDIT: Hey man, check this thread out
http://www.talkbass.com/forum/showthread.php?t=717521 the OP asked the same question almost haha
