Mark 7 Mod
- Thread starter Reiby
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Without a schematic, it would be rather difficult to mod.
Considering how the Mark 7 makes use of the lead drive circuitry associated with CH3, it gets reconnected to follow the first gain stage by use of relays. Not exactly sure if the tone stack remains on V1A or if it is moved to follow the lead drive circuitry. Mark VII mode uses the full lead drive circuit and crunch drops the last gain stage of that particular circuit. It is unclear if the Mark 7 alters the presence circuitry like the Mark V90 does for extreme mode.
If you ever looked inside the Mark VII, there are far more relays used on that amp in a smaller PCB footprint that that associated with the Mark V90. If there was an easy way to make use of reprogramming the onboard midi controller, assuming the tone stack and gain controls are switched with a different outputs than the other relays, it would be assumed it could be done. This is just speculation. If the switching logic was done to simplify the design, I doubt this would be possible.
If you wanted to have two channels for the IIC+ mode, the JP2C as far as I know is the only way to get that. Sure, CH3 does have more gain pulled in based on some changes with relays but it does not re-map the location of the lead drive circuit relative to the tone stack. CH2 is as close to the IIC+ and the CH3 is on the Mark IV side. As for the Mark VII, they seemed to cater to those who want more use of the clean, fat and IIB modes. CH1 (Crunch), CH2 (VII), CH3 (IIC+ or IV) modes are the only combinations unless you wanted to use crunch on CH2 as well. Perhaps that is why some have called it a Dad amp and not Heavy Metal. Too bad they did not include a dual GEQ like the JP.
I can see having two IIC+ or IV modes on separate channels. Having two fats is pointless from my perspective. If there was a possible way to manipulate one of the circuits or reconfigure what gets switched on CH1 or CH2, there is a very slim chance it would be easy. Way too difficult to make assumptions without the full schematic (must include the switching circuits and perhaps the program or firmware loaded into the midi processor).
Considering how the Mark 7 makes use of the lead drive circuitry associated with CH3, it gets reconnected to follow the first gain stage by use of relays. Not exactly sure if the tone stack remains on V1A or if it is moved to follow the lead drive circuitry. Mark VII mode uses the full lead drive circuit and crunch drops the last gain stage of that particular circuit. It is unclear if the Mark 7 alters the presence circuitry like the Mark V90 does for extreme mode.
If you ever looked inside the Mark VII, there are far more relays used on that amp in a smaller PCB footprint that that associated with the Mark V90. If there was an easy way to make use of reprogramming the onboard midi controller, assuming the tone stack and gain controls are switched with a different outputs than the other relays, it would be assumed it could be done. This is just speculation. If the switching logic was done to simplify the design, I doubt this would be possible.
If you wanted to have two channels for the IIC+ mode, the JP2C as far as I know is the only way to get that. Sure, CH3 does have more gain pulled in based on some changes with relays but it does not re-map the location of the lead drive circuit relative to the tone stack. CH2 is as close to the IIC+ and the CH3 is on the Mark IV side. As for the Mark VII, they seemed to cater to those who want more use of the clean, fat and IIB modes. CH1 (Crunch), CH2 (VII), CH3 (IIC+ or IV) modes are the only combinations unless you wanted to use crunch on CH2 as well. Perhaps that is why some have called it a Dad amp and not Heavy Metal. Too bad they did not include a dual GEQ like the JP.
I can see having two IIC+ or IV modes on separate channels. Having two fats is pointless from my perspective. If there was a possible way to manipulate one of the circuits or reconfigure what gets switched on CH1 or CH2, there is a very slim chance it would be easy. Way too difficult to make assumptions without the full schematic (must include the switching circuits and perhaps the program or firmware loaded into the midi processor).
GEQ is after the FX loop. I checked for that when I got mine by slaving into another amp (FX send to the return of another amp). Discovered that the volume controls are also after the FX loop.
I am curious what Mesa says. Doubt they will reveal anything though. That would be cool to have channel cloning on the IIC+ or IV instead of fat and crunch. I have been able to get some good tones from the Mark VII mode on CH2, think of it like a Rectifier, dial out the midrange and add it in to taste. One of these days I will have to try the sample settings in the manual. For now I am still exploring the overall characteristics of each channel and mode.
I am curious what Mesa says. Doubt they will reveal anything though. That would be cool to have channel cloning on the IIC+ or IV instead of fat and crunch. I have been able to get some good tones from the Mark VII mode on CH2, think of it like a Rectifier, dial out the midrange and add it in to taste. One of these days I will have to try the sample settings in the manual. For now I am still exploring the overall characteristics of each channel and mode.
The Mark VII mode is not your typical Mark circuit. Neither is the Crunch. I have been exploring the Mark VII for some time and still going through the process. I am getting a better understanding by comparing this amp to some others like the Badlander, JP2C, and even the Mark V90. I have yet to bring out the TC100 or TC50 but probably will not do that as they are more Brit Voiced in tone.
CH2 IIC+ and IV are basically your traditional Mark circuits. The same can be said for the IIB mode. I looked up the schematics for the IIB to see if it is similar to the IIC+ but with one triode taken out of the lead drive circuit. Yep. The tube task chart is not easy to follow as there are several things that take place with the different modes. I did not include the clean and fat in this graphic as it just simply bypasses the lead drive circuit completely. I was more interested in how the things are arranged in the other modes. I did contact Mesa and asked if the tone stack is shifted in its location for Crunch and VII modes. It was confirmed that the tone stack for those two modes will get pushed and become a post-gain set of controls. This would be similar to the Badlander but without the cold clipper or cathode followers. Think of dialing out some midrange and make use of the GEQ and you can basically match the Badlander in most respects with the crunch and VII modes. Even the clean mode you can push the gain to get a very similar characteristic to the clean mode of the BAD, but only with the gain at noon on the bad with the gain at 3pm on the MK7. I tried to experiment with the FAT, nope, it has too much bottom bloom for that to work. The MK7 crunch is similar to that of the Mark V90, it brings in an extra gain stage in front of the tone stack. However, that required an additional tube (V2). for that design, the lead drive circuit shown in red remains in the same location. With the Mark VII, it was all about keeping the design compact. I would almost dare to say this is based off of the JP2C but with additional features and many more relays. Not sure if there are any changes to the plate and cathode resistors when the lead drive gets inserted before the tone stack.
Having a firmware change to the Midi controller is just a long shot idea. I doubt that is possible. Perhaps if the MK7 had two GEQs like the JP2C, that would have allowed for better use of the VII and Crunch modes in combination of the IIC+ or IV. What was the target for this amp? If there was duplication of the IIC+ and IV modes rather than fat and crunch or if there was some means to switch between IIC+ and IV modes on the fly (footswitch controlled or Midi controlled) that would be much better.
This is what is for the Badlander. Not the same thing but sounds very close to the crunch and MKVII modes. The blue color represents the cold clipper circuit, what is in purple represents the cathode followers. Badlander is based off of the Rectifier circuit, just with different components. I always felt the BAD sounded close to the JP2C when using the crush mode. Different but close. Now the Mark VII is a better match for both crunch and VII modes. Still different circuits but they do seem to achieve the same tone characteristics. The Badlander has a bit more low end.
CH2 IIC+ and IV are basically your traditional Mark circuits. The same can be said for the IIB mode. I looked up the schematics for the IIB to see if it is similar to the IIC+ but with one triode taken out of the lead drive circuit. Yep. The tube task chart is not easy to follow as there are several things that take place with the different modes. I did not include the clean and fat in this graphic as it just simply bypasses the lead drive circuit completely. I was more interested in how the things are arranged in the other modes. I did contact Mesa and asked if the tone stack is shifted in its location for Crunch and VII modes. It was confirmed that the tone stack for those two modes will get pushed and become a post-gain set of controls. This would be similar to the Badlander but without the cold clipper or cathode followers. Think of dialing out some midrange and make use of the GEQ and you can basically match the Badlander in most respects with the crunch and VII modes. Even the clean mode you can push the gain to get a very similar characteristic to the clean mode of the BAD, but only with the gain at noon on the bad with the gain at 3pm on the MK7. I tried to experiment with the FAT, nope, it has too much bottom bloom for that to work. The MK7 crunch is similar to that of the Mark V90, it brings in an extra gain stage in front of the tone stack. However, that required an additional tube (V2). for that design, the lead drive circuit shown in red remains in the same location. With the Mark VII, it was all about keeping the design compact. I would almost dare to say this is based off of the JP2C but with additional features and many more relays. Not sure if there are any changes to the plate and cathode resistors when the lead drive gets inserted before the tone stack.
Having a firmware change to the Midi controller is just a long shot idea. I doubt that is possible. Perhaps if the MK7 had two GEQs like the JP2C, that would have allowed for better use of the VII and Crunch modes in combination of the IIC+ or IV. What was the target for this amp? If there was duplication of the IIC+ and IV modes rather than fat and crunch or if there was some means to switch between IIC+ and IV modes on the fly (footswitch controlled or Midi controlled) that would be much better.
This is what is for the Badlander. Not the same thing but sounds very close to the crunch and MKVII modes. The blue color represents the cold clipper circuit, what is in purple represents the cathode followers. Badlander is based off of the Rectifier circuit, just with different components. I always felt the BAD sounded close to the JP2C when using the crush mode. Different but close. Now the Mark VII is a better match for both crunch and VII modes. Still different circuits but they do seem to achieve the same tone characteristics. The Badlander has a bit more low end.
I looked up the schematics for the Dual caliber online, DC5B does use the lead channel in this manner, gain stage in addition to the primary in front of the tone stack. The actual gain control follows the tone stack so it is a little different. The Mark V90 also does this in Channel 2 with an extra gain stage V2 which is not used anywhere else. I have no experience with the Dual Caliber amps or the other amps that are similar.
If I had the schematics for the Triple Crown or even the Royal Atlantic, they would be similar as there are no DC coupled cathode follower tone stack drivers used. Tone stack is plate driven. Perhaps that is whey Mesa referenced that amp in the manual for the Mark VII in reference to the crunch mode as well as the Mark VII mode.
The Mark lead drive circuit is unique to the Mark amps. All of them have the same topography with some changes over the years. However, to see it inserted between V1A and V1B is not a common thing. Understanding where the tone stack sits may help one understand the amp better. Or is it more confusing? In other words, using the same tone stack settings as one would do for the IIC+ or IV modes may not work as good with the crunch or VII modes. However, I doubt there are any rules how to dial it in. What works for you is all that matters. Some have stated they do not like the VII mode but it could be due to the difference in the circuit and having a post gain tone stack vs a pre gain tone stack.
I can say for one thing, the Badlander crunch and Crush are very close to the Mark VII crunch and VII modes but you still need to use the GEQ to get it there. I did try to compare the Mark V90 Extreme to the VII mode on the MK7 in a video. It is similar but not quite the same.
The Mark VII is a new tool to make use of. It is different than its predecessors, so there will be some adapting to it. As for the IIC+ and IV modes, yeah, those are really good. The VII mode is just different.
If I had the schematics for the Triple Crown or even the Royal Atlantic, they would be similar as there are no DC coupled cathode follower tone stack drivers used. Tone stack is plate driven. Perhaps that is whey Mesa referenced that amp in the manual for the Mark VII in reference to the crunch mode as well as the Mark VII mode.
The Mark lead drive circuit is unique to the Mark amps. All of them have the same topography with some changes over the years. However, to see it inserted between V1A and V1B is not a common thing. Understanding where the tone stack sits may help one understand the amp better. Or is it more confusing? In other words, using the same tone stack settings as one would do for the IIC+ or IV modes may not work as good with the crunch or VII modes. However, I doubt there are any rules how to dial it in. What works for you is all that matters. Some have stated they do not like the VII mode but it could be due to the difference in the circuit and having a post gain tone stack vs a pre gain tone stack.
I can say for one thing, the Badlander crunch and Crush are very close to the Mark VII crunch and VII modes but you still need to use the GEQ to get it there. I did try to compare the Mark V90 Extreme to the VII mode on the MK7 in a video. It is similar but not quite the same.
The Mark VII is a new tool to make use of. It is different than its predecessors, so there will be some adapting to it. As for the IIC+ and IV modes, yeah, those are really good. The VII mode is just different.
The Dual and Triple Rectifiers have the tone stack post gain, which is one of the features that differentiates them from the Mark series and makes them similar to Marshalls, as you know.
Knowing this made using the VII mode much easier on the MK7 since the manual states the VII mode is a hybrid between MK and Rectifier. I basically use the settings that I would use with my Triple, a bit more bass and mids, a bit less treble. For chug rhythm, I use the EQ in the typical way, and for leads I turn off the EQ. This works really well. I get two sounds from one mode by switching the EQ in and out. The VII mode is one of my favorites on the amp.
Knowing this made using the VII mode much easier on the MK7 since the manual states the VII mode is a hybrid between MK and Rectifier. I basically use the settings that I would use with my Triple, a bit more bass and mids, a bit less treble. For chug rhythm, I use the EQ in the typical way, and for leads I turn off the EQ. This works really well. I get two sounds from one mode by switching the EQ in and out. The VII mode is one of my favorites on the amp.
I rechecked the Badlander circuit again. I must have read the cathode resistor incorrectly on the last gain stage. I though I saw 15k but it was 1.5k. I have two of these now. So I rechecked all of the resistors on the tubes (plate and cathode) as this may reveal what is what in the Badlander. To my surprise, the Badlander does not have a cold clipper circuit. After taking resistance measurements on two different revisions of the Badlander board Rev 5 (pre-100 build) and Rev 7 (post-1100 build) it was interesting to note one thing, both Badlanders have your typical first gain stage (V1A), the second and third gain stages (V1A and V3A) are the same as that used in the Mark Lead Drive circuit and the last gain stage (V3B) is like the first. Yeah, this one does have the DC cathode follower circuit as a tone stack driver (V2). V4 probably is a cathode follower as well for the FX loop. I did not poke around to check it for that. No schematic on this available to the general public, so I have not seen it. Considering that the Badlander is more of a Mark VII hybrid.
This is the Mark VII. Look at the last two rows, the Mark VII crunch and VII modes are similar to the Badlander. So the trapezoid TS block is a plate driven tone stack. There still may be some error in this once the schematics get leaked out. It was based off of the tube task chart. I did ask Mesa about where the tone stack sits for the crunch and VII modes, it is after the gain circuit. In red is the basic Mark lead drive circuit. The V3B will have an 82k plate resistor and 1.5k cathode and V4A has a 270k plate and 3.3k cathode resistor. I measured the same values on V1B and V3A on the Badlander. In other words, my first thoughts that V3B was a cold clipper were wrong. V2 is confirmed to be the Recto tone stack driver since the control grid of V2B was connected to the plate of V2A.
When comparing the two amps side by side. I found the BAD crush to be more in line with the IV mode on the Mark VII. That was the closest match. Crunch vs Crunch were similar with both amps. If you really listen to the Mark VII modes, there is not much of a difference from VII, IIC or IV modes. Feel or gain structure may differ a bit. IIC is just a hair less gain, IV is a bit more saturated. I did not have to max out the gain on the Bad to get that sound, I simply left the gain controls at noon on both amps. I am sure there is more gain control with the Mark VII though. Interesting enough, the tone stack of the Bad does have a much better response than say a MWDR. I found it closer to the JP2C characteristic. Single note detail of the Bad is on par with the JP2C. The Mark VII did not retain that characteristic with the STR445 green bias color tubes. I dropped down to the yellows and that made a huge improvement not only in single note detail but at gig levels it did not lose composure as I was getting with the green bias color tubes.
This is the Mark VII. Look at the last two rows, the Mark VII crunch and VII modes are similar to the Badlander. So the trapezoid TS block is a plate driven tone stack. There still may be some error in this once the schematics get leaked out. It was based off of the tube task chart. I did ask Mesa about where the tone stack sits for the crunch and VII modes, it is after the gain circuit. In red is the basic Mark lead drive circuit. The V3B will have an 82k plate resistor and 1.5k cathode and V4A has a 270k plate and 3.3k cathode resistor. I measured the same values on V1B and V3A on the Badlander. In other words, my first thoughts that V3B was a cold clipper were wrong. V2 is confirmed to be the Recto tone stack driver since the control grid of V2B was connected to the plate of V2A.
When comparing the two amps side by side. I found the BAD crush to be more in line with the IV mode on the Mark VII. That was the closest match. Crunch vs Crunch were similar with both amps. If you really listen to the Mark VII modes, there is not much of a difference from VII, IIC or IV modes. Feel or gain structure may differ a bit. IIC is just a hair less gain, IV is a bit more saturated. I did not have to max out the gain on the Bad to get that sound, I simply left the gain controls at noon on both amps. I am sure there is more gain control with the Mark VII though. Interesting enough, the tone stack of the Bad does have a much better response than say a MWDR. I found it closer to the JP2C characteristic. Single note detail of the Bad is on par with the JP2C. The Mark VII did not retain that characteristic with the STR445 green bias color tubes. I dropped down to the yellows and that made a huge improvement not only in single note detail but at gig levels it did not lose composure as I was getting with the green bias color tubes.
