Mark V:25/35 tone knobs
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Rob9874
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I found that too with my Mark V 25. I get much more response with the EQ sliders. Didn't notice much tonal difference with the tone knobs on channel 2, except for the bass knob. I just posted in the V 25 tone thread that on Channel 2 with gain turned up past 12 o' clock, having the bass knob any higher than 9 o' clock makes it sound muddy. Almost like the speaker's blown. So I've been keeping the bass knob low, and adding bass with the EQ slider.
The Lead channels on the Mark series amps are not like other High Gain amps.
Most High Gain amps are laid out "Marshall style", with a bunch of gain and drive stages with some internal shaping to get the distortion tone, then an EQ section after the drive to do shaping of the final result. Most High Gain amps have their BMT (Bass Mid Treble) controls here.
However, Mesa's Mark series started life as modded Fenders, and thus use more of a "Fender style" topology, where your input goes straight to an EQ (BMT) then gain and drive.
This means the BMT controls are the first thing your signal sees inside the amp, and it's shaping work happens before the gain and distortion, leading it to do less overall shaping and instead just affect the character of the overdrive by modifying what's hitting it to actually overdrive. You can simulate this on other amps by putting an EQ pedal in front of it, or even changing pickups, etc.
This is why Mesa became such fans of the 5-band Graphic EQ: That GEQ acts at the place where most other high gain amps do their tone shaping with BMT controls, giving you back the sculpting ability lost by keeping the BMT so early in the circuit.
This is also why they're so flexible, because on most amps the BMT and other early signal shaping are all locked at whatever the designer chose, and you only get to shape the final result, but on the Mark series you get to tune in the input signal and the output signal.
But it also means the BMT on their own don't seem as effective, instead offering Bass - tightness, fullness, flub, Middle: kind of texture/fullness/stiffness, Treble - Gain and bite.
The Owners manual actually goes through a lot of this in detail, including the recommendation to keep the Bass low as the Gain increases, because the bass knob is still a fender style one that is very powerful for clean signals but quickly gets out of hand under gain.
TL;DR: The BMT controls are before the gain, so they shape the signal being overdriven, and therefore adjust the character of the sound more than the overall shape and EQ itself.
Most High Gain amps are laid out "Marshall style", with a bunch of gain and drive stages with some internal shaping to get the distortion tone, then an EQ section after the drive to do shaping of the final result. Most High Gain amps have their BMT (Bass Mid Treble) controls here.
However, Mesa's Mark series started life as modded Fenders, and thus use more of a "Fender style" topology, where your input goes straight to an EQ (BMT) then gain and drive.
This means the BMT controls are the first thing your signal sees inside the amp, and it's shaping work happens before the gain and distortion, leading it to do less overall shaping and instead just affect the character of the overdrive by modifying what's hitting it to actually overdrive. You can simulate this on other amps by putting an EQ pedal in front of it, or even changing pickups, etc.
This is why Mesa became such fans of the 5-band Graphic EQ: That GEQ acts at the place where most other high gain amps do their tone shaping with BMT controls, giving you back the sculpting ability lost by keeping the BMT so early in the circuit.
This is also why they're so flexible, because on most amps the BMT and other early signal shaping are all locked at whatever the designer chose, and you only get to shape the final result, but on the Mark series you get to tune in the input signal and the output signal.
But it also means the BMT on their own don't seem as effective, instead offering Bass - tightness, fullness, flub, Middle: kind of texture/fullness/stiffness, Treble - Gain and bite.
The Owners manual actually goes through a lot of this in detail, including the recommendation to keep the Bass low as the Gain increases, because the bass knob is still a fender style one that is very powerful for clean signals but quickly gets out of hand under gain.
TL;DR: The BMT controls are before the gain, so they shape the signal being overdriven, and therefore adjust the character of the sound more than the overall shape and EQ itself.
.
