Mesa Boogie Mark III Simul-Class modded to be non simul

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Jordan1990

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Hello all this is my first post to the board, I've just ordered my first mesa and I'm stoked. It's a red stripe "simulclass" that the techs at mesa say has been modded to a non simul. My question is why and how? I called mike at mesa to see about it getting switched back but could I benifit more from this?
 
easy to get Simulclass , just add or reconnect central tubes pin 8 to switch open/ground
 
sotosprince said:
Welcome to the board man! I am Sotiris aka #ios4ever# ;)
thanks man I've saw ya here a time or two.
BlackBoxy said:
easy to get Simulclass , just add or reconnect central tubes pin 8 to switch open/ground
And that's it? What if the hacked the transformer out? I shpuld have it in my possession in 3 or 4 days so I'm not sure what has happened to it
 
Mesa called and left a voicemail saying if a amp was born there simul class and switch over here"I hope" and to be switched back here "I hope" then yes it can be done. Those are the exact words. I'm going to call him back tomorrow. But yes I would think that too about the transformer but mesa acted like it was a quick easy change. I hope easy enough for me to do cause thats cutting my cab funds all up Lola. Thanks guys!!
 
JOEY B. said:
To truly change from a Simulclass to a 60/100, a different output transformer is used, I believe.

nope,

its the same OT , and as all Mark III are 4 amp tubes powered as simul class, it can easily be revesed to class A/simul class , i don't see what are advantages to mod a class A to permanent simulclass , OT delta voltage is around 5 volt between both pairs of tubes output!
 
Simul class uses an "ultra-linear" OT,that has seperate taps that would be for the screens in a 2 tube output.These taps are used for the plates of the inner pair of tubes for simul class.Delivers a couple less volts to the inner pair.
 
stokes said:
Simul class uses an "ultra-linear" OT,that has seperate taps that would be for the screens in a 2 tube output.These taps are used for the plates of the inner pair of tubes for simul class.Delivers a couple less volts to the inner pair.


an ultra linear OT coil? what is that ?
 
Look at the schem for a simul class.You will see a winding tap on each side just short of the plate tap at the end of the winding.Before Mesa came up with their simul class scheme these transformers were used as "ultra linear output trannies".That extra tap was connected to the screen of the output tube on that side,with the longer tap connected to the plate.It delivered a few volts less to the screens.In simul,Mesa uses these taps for the inner set of tubes plates.
 
Well you all have lost me lol. I'll wait and see what transformer it has and try to get pics up. I'm doing this on a phone so I'm not sure if I can. Thanks guys

Jordan
 
stokes said:
Look at the schem for a simul class.You will see a winding tap on each side just short of the plate tap at the end of the winding.Before Mesa came up with their simul class scheme these transformers were used as "ultra linear output trannies".That extra tap was connected to the screen of the output tube on that side,with the longer tap connected to the plate.It delivered a few volts less to the screens.In simul,Mesa uses these taps for the inner set of tubes plates.


thanx alot, i know about the taps, schematics are clear on this, it was just the linearity of a a signal through a solenoid .

regards
 
Jordan1990 said:
Well you all have lost me lol. I'll wait and see what transformer it has and try to get pics up. I'm doing this on a phone so I'm not sure if I can. Thanks guys

Jordan


you do think they changed the OT ? so yes it could be problematic
 
The transformer is the key ingredient in simul,but it doesnt mean the transformer was changed.A simple re-wire of the plate taps may be all they've done.The switch on the cathodes of the inner tubes isnt so much a simul switch as it is a "class A" switch.In order to have simul you need 4 power tubes connected,in these amps there is no way to have 4 powertubes active without being in simul.......except to re-wire the plate connections or change the tranny.If the tranny is not blown,I can see no reason to change out the tranny,so it is likely someone did the simple mod.
 
Thank you all so much for your help. In still waiting on the **** thing and I can't wait. My next question is why they did this? I know you all don't know their answer but if you all did this why would you? Volume? Are the 60/100 more aggressive from the extra power? Thanks again


Jordan
 
Jordan1990 said:
Thank you all so much for your help. In still waiting on the **** thing and I can't wait. My next question is why they did this? I know you all don't know their answer but if you all did this why would you? Volume? Are the 60/100 more aggressive from the extra power? Thanks again


Jordan


hi Jordan, don't worry, you just have to check if inners tube pin 3 are still connected to the OT, and other tap wire than external tubes! and check the mesa part number of the OT to be the good one

it could be just connecting class A swtch after all ! good luck
 
No telling why it was modded.I have never modded an amp as you describe,but I have done an adjustable bias mod to a few MkIV simuls and I can tell you its a royal pain in the ***.It becomes more of a compromise bias control since there are different voltages going to the inner pair and the outer pair of power tubes,get the inner pair biased where you want and the outer pair may be too hot,so if someone wanted to set up the 4 power tubes to run "balanced" I could see doing it,but it might be more work than someone would want to do.I am not a fan of simul,for numerous reasons,so if I owned a simul amp,I might mod it,but I wouldnt buy a simul amp to begin with.
Could also be that the amp had a bad OT and someone replaced it with a standard OT.Who knows,wait til you get it and see just what someone did.Oh,and just FYI,"60/100" isnt necessarilly "simul".
 
Ok guys wait is over. I hope everybody sees this so I won't have to quote everything. I got the amp and barely saw it has a Simul-Class OT. When I got home from work I yanked it out of the headshell and the inner tubes pin 8 are connected together and running to the half power switch on the front. And pins 3 on the inner tubes are goin to the OT that says Simul-Class. So WTF lol.
JOEY B. said:
It brings me back to the original question. Why in the HELL would anyone do this, unlless the OT had a problem?
I hear that the 60/100 have more punch to em. If this is modded to 60/100 I might keep it over here for a lil bit before o witch back over.
 

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