By this I meen that (and I want the forum gurus to clarify) a normal eq section on an amp only cuts (basicly you have the base signal with the knobs at 10 and then you cut B/M/T/P as you roll down the knobs but the eq of the MP-1 adds and cuts in the freqs that its eq section is made (so it works like an eq pedal/unit). This also meens that on a normal eq of an amp the center freq points actually shift around deppending where the other knobs are at and on the MP-1 as other eq pedal or units those points are fixed.
So can the gurus chime on this?
Yes most tube heads have a passive tone section,passive means it can only cut.Very simple design with a few caps,a resistor and 3 pots.Now the presence is different and is actually sort of active since it works in the feedback circuit of the amp.Same goes for the resonance knobs on the more modern amps,but these can also be installed on older amps.
Now some tube amps did have an active EQ section,what comes to mind is the marshall major 200W also called the pig which had only 3 controls,vol,bass and treble which were active.Another example is the JCM800 bass head which also had an active bass and treble EQ.
Now the passive eq even if everything is on 10 isn't actually flat,there will be some eq'ing going on due to the design.
Here is a nice site with some more info,there's even a emulator so you can "see" how it works in the freq domain.
http://www.duncanamps.com/technical/tonestack.html
So EL i hope this answers your question?