JustPassingThrough
Well-known member
I was perusing the schematics of the F series amps for possible mods this week and something caught my eye.
Namely, the contour switch on the F series amps and what it does to the sound. I was initially investigating whether it could be put on a pot for a sort of blend control and may have stumbled across something better.
Here's the F series contour circuit:
You'll see it's 4 inductors and a network of caps and resistors, in other words these are gyrators boosting specific frequencies, the resistors above the inductors can basically be seen as a fixed resistance, or a pot hard-wired at one point.
Compare that to the graphic EQ Mesa use on the mark series amps and others:
Barring the 240hz control and the funky parallel resistors that's the exact same thing more or less.
I posit that the F series contour section can be modded to a 4 band graphic EQ by changing the fixed resistors to pots and matching the mark series schematic with regard to ins and outs.
Has anyone tried this? There's an F-30 amp I was looking at that led me down this road of homework and I haven't seen anyone do this online, despite it initially looking like quite an obvious change.
Namely, the contour switch on the F series amps and what it does to the sound. I was initially investigating whether it could be put on a pot for a sort of blend control and may have stumbled across something better.
Here's the F series contour circuit:
You'll see it's 4 inductors and a network of caps and resistors, in other words these are gyrators boosting specific frequencies, the resistors above the inductors can basically be seen as a fixed resistance, or a pot hard-wired at one point.
Compare that to the graphic EQ Mesa use on the mark series amps and others:
Barring the 240hz control and the funky parallel resistors that's the exact same thing more or less.
I posit that the F series contour section can be modded to a 4 band graphic EQ by changing the fixed resistors to pots and matching the mark series schematic with regard to ins and outs.
Has anyone tried this? There's an F-30 amp I was looking at that led me down this road of homework and I haven't seen anyone do this online, despite it initially looking like quite an obvious change.
