The EQ is the most important part of any guitar amp.
Why?
For most other instruments is it the goal of an amp to make the signal of the instrument 'just louder'.
For an electric guitar almost no one is keen of this.
Check it out - by using your (linear) stereo system and connect your e-guitar directly to it - or switch off amp, eq and cab blocks in the KPA.
If we use a clean guitar sound - then it makes not a big difference were to place the EQ.
E.g. some tube amps work like this:
input --- pre amp --- EQ --- power amp
others like this:
input --- EQ --- pre amp --- power amp
if you change the EQ settings - it makes not a big difference where it is places - before (pre) the preamp or after (post) the pre amp.
In reality does the pre amp consist of more then one amplifier stage - each preamp tube consist of two amp stages - there are preamp stages in the input section and there are even some 'pre amp tube' in the power stage.
e.g.
Type 1)
input --- preamp stage1 --- EQ --- preamp stage2 --- power amp
This is very similar to many fender type amps.
Type 2)
compare this to a Marshall type amp:
input --- preamp stage1 --- preamp stage2 --- EQ --- power amp.
Amps of type 1) do not distort this easy (nobody wanted an amp to distort when the amps were first produced in the 50').
The reason for less distortion is that the EQ reduces a lot of the signal amplified by preamp stage 1 - so preamp stage2 will distort not this easy.
Type 2) amps distort easier because the output of stage1 will drive stage2 with much more strength.
Some modern amps look like this:
input --- stage1 - stage2 - stage3 - stage4 --- EQ --- power amp
Off course these amps can create much more distortion then the old ones with less gain stages.
What will this all tell us if we use the KPA and profiles?
For most modern amps (EQ at the end of the pre amp stages) it is enough to profile the amp with neutral setting of the amp tone stack - since we can always place a KPA EQ after the KPA amp stage to adjust the sound.
For amps of the 'old' (type 1) style will the tone stack settings (use during the profile process) not only change the overall sound - but the kind of distortion the amp produces.
In general:
If the amps EQ is at front of the preamp - it changed the kind of distortion the amp produces.
If the amps EQ is at the end of the preamp - it changes 'just' the overall sound (more bass, less treble or whatever).
Some amps have both types of EQ e.g. most Mesa Boogie Mark amps - incl. the latest one the JP 2C
These amps work like this:
input --- EQ1 - preamp stages --- EQ2 --- power amp
EQ1 are the tone controls bass, mid , treble = Pre EQ
EQ2 is the Mesa 5 band graphical EQ = Post EQ
So EQ1 will be used to shape the tone to get the desired kind of distortion - while EQ2 will be used to change the overall sound.
So to get good profiles of such a kind of amp it's important to have a variety of settings of EQ1 and the EQ2 is not this important - since an EQ block after the KPA amp stage can simulate this EQ2 very good.
I hope this helps some of you - and you start to use more and more the KPA EQ knobs and EQ blocks before and after the AMP block.
Enjoy!
