None simul class Mk3 to simul class mod?

[dwman3]

So I sent my Mk3 to boogie to get some major work on it done and found out that it’s not a simul class even though it was labeled a simul class. So my question is, has anyone had a none simul class modded to a simul class or is it even possible?

[Markedman]

I have heard of it, you can search here on the BB and you'll find something like this - https://forum.grailtone.com/viewtopic.p ... +class+mod

[dwman3]

Wow lots of info in that thread, I think a call to Boogie is in order. Thanks!!

[woodbutcher65]

I've been doing some reading on simulclass. It took some time to find the information and read it and digest it. Sorry we didn't have any answers for you within 15 minutes.


There are those who have dissected output transformers from simul-class amps and found that there's nothing different about them vs. the "regular" variety output transformer from a non-simul-class amp. But I don't know if that's ALWAYS the case.

However, if it IS, then all that's really happening is that the outer two tube sockets have added resistors that function as a voltage divider on the cathodes, to change the bias points on the outer tubes so they run closer to class A.

BUT....there are multiple schemes Mesa has used. It may be that there ARE different output transformers, and I tend to think that there actually are, since simply rebiasing the tube to run in class A means it's going to run a lot hotter. Unless you reduce current which requires reducing plate voltage, which would require a different wind on the output transformer.

[Authorized Boogie]

I've been doing some reading on simulclass. It took some time to find the information and read it and digest it. Sorry we didn't have any answers for you within 15 minutes.


There are those who have dissected output transformers from simul-class amps and found that there's nothing different about them vs. the "regular" variety output transformer from a non-simul-class amp. But I don't know if that's ALWAYS the case.

However, if it IS, then all that's really happening is that the outer two tube sockets have added resistors that function as a voltage divider on the cathodes, to change the bias points on the outer tubes so they run closer to class A.

BUT....there are multiple schemes Mesa has used. It may be that there ARE different output transformers, and I tend to think that there actually are, since simply rebiasing the tube to run in class A means it's going to run a lot hotter. Unless you reduce current which requires reducing plate voltage, which would require a different wind on the output transformer.

This requires a different transformer, and more.

[dwman3]

Well I called and confirmed that it can be done so no worries there.

[woodbutcher65]

Before you send your amp in for that work, please make a note of the part numbers on your transformers. Then when the amp has come back after the upgrade, check the part numbers on the transformers again.

If you really feel frisky, remove the chassis and make good detailed photos of it before and after the surgery, too, so we can see what's really getting changed.

[s-fresh]

Before you send your amp in for that work, please make a note of the part numbers on your transformers. Then when the amp has come back after the upgrade, check the part numbers on the transformers again.

My Mark I was converted to simul-class at Mesa and I can confirm the output transformer was swapped.