I was just wondering what frequencies make the Marshall or Plexi tone? Why is there such a definitive Marshall sound that is rich in tone (treble) but not really a fizzy tone. A tone that allows for some massive gain (maybe not hi-gain) but still sound musical. Aside from some other very important engineering decisions by Marshall, what are the important frequencies that a Marshall tone sits at...800Hz, 1.2Khz, 3.5KHz etc. I really don't know and wish I did. I want to play with an EQ in my FX Loop of my amp to get as close as I can. I have played around and it sounds really good (will never sound as good as a Marshall), but I am still working on understanding what specific frequencies are crucial to a Marshall tone. I use a parametric EQ. I have increased 100Hz by 4dB using a .5 octave. I then decreased 200Hz by 4dB with a .5 octave and then increased 5Khz by 2dB with a 4.0 octave...almost a shelf of the highs. In the front of the amp I use an RC booster as a clean boost and set my Radial Switchbone JX-2 to a 10dB boost of 800Hz. Some day I will be able to afford adding Marshall amp. Something Plexi or very close with just a pinch more gain available, but for now I am just trying to fake it I guess. I can say that my tone is much more rich. It is more musical and when I play chords the notes are all identifiable and not mush. I only use half of the available gain for a classic sound. And I notice that pick rakes and harmonics and sustain of single notes is greatly improved by ten fold. My tone before was just too dark. I started checking out Henric Hermmanson and Freidman and Landry and it dawned on me...I need a freak'n Marshall. I love the Brown Sound and so that led me to where I am now. Anyway, thanks for any helpful tips on what frequencies you feel would benefit me.