The Boogie Board

Discussion Forum for Mesa Boogie Products
It is currently Wed Aug 15, 2018 5:42 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: MARK III + + mod
PostPosted: Tue Feb 06, 2018 9:35 am 
Offline
Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 87
That makes a lot of sense thanks! Is there any chance you could PM me any schematic stuff you have? I'm drawing up some schematics at the moment and getting a comparison between the IIC+ and the different stripe versions of the III as they're all great in their own unique way.

Eventually I'd love to get a full wiki on the Mark IIA, B, C, C+ and III (all different stripe revisions) along with parts, PCB board layouts and some general parts knowledge base, plus MAYBE some official mods but understand these are still closely guarded by Mesa for competition reasons.

I'm still not 100% sure what the ++ mod is but as mentioned one of my best friends has a Red Stripe III++ modded by Mike B. All I know is it has a crazy amount of gain and the clean breaks up at a much lower gain setting. Maybe one day he'll finally agree to let me take the chassis out and I'll let you know!

INFO ON THE ++ MOD:

According to this: /viewtopic.php?f=27&t=48193

"the ++ mod adds another 20 or 26 db of boost to both channels. From what I have heard, the ++ mod also sacrifices the clean channel and makes it dirty. Channel 2 is in your face high gain" - that basically sums up what my friend's III++ sounds like. Not sure how this is achieved though and wasn't the biggest fan - far too OTT for me


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Wed Feb 07, 2018 5:50 am 
Offline
Mark II

Joined: Fri Jul 28, 2006 5:58 pm
Posts: 104
Location: Europe
Well, if the gain is raised in both modes I guess the ++ mod also involves the 3M3 - 470k voltage divider which is in parallel to the drive channel. Probably the 3M3 resistor is reduced to 2M2 (that is what is in the Blue Stripe already) or even lower, and the 470k to ground is increased to 680k (like in the II C+). This increase would be more noticeable in the Blue Stripe than in the Red Stripe as it would be in parallel with a 470k to ground (instead of a 100k), making it 235k vs. 278k - still not a big difference though.

A further possibility is that the 0.47uf cathode cap on V2a which is normally only engaged in the R2 mode is wired in permanently. That would give more gain to this stage from 225 hz upwards. R1 and R2 would get closer to each other, and the Lead mode would get more push.

Cheers Stephan


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Mon Apr 02, 2018 4:54 am 
Offline
Mark I

Joined: Mon Dec 08, 2014 2:00 am
Posts: 22
Really very interested for the III++ mod.

Can some one post pics and what caps to mod to make it III++

Thanks all.


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Thu Apr 12, 2018 9:45 am 
Offline
Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 87
See here for a IIC++ schematic. https://forum.grailtone.com/viewtopic.php?f=27&t=74680&p=505315#p505315

I've done some research and we can be pretty sure of darkbluemurder's assumptions about the ++ mod are pretty much correct. There are actually two versions of it done to the C+. So the ++ Mod is as follows:

Version 1. Replacing the 3.3M resistor between V1 and V2 with a 2.2M OR adding an additional 2.2M and 20pF over the existing ones (unsure which of these if used). The second seems to be confirmed by Boogiebabies who is basically THE guy when it comes to the IIC+ apart from Mike B: http://forum.grailtone.com/viewtopic.ph ... 15#p437196

Most likely the second of these was used and incorporated into the III as R133 and C28, although their values ended up as 3.3M and 250pF in the III.

OR

Version 2. 0.47uf or 10uF cathode cap on V2A (technically V2B on IIC+) (unsure which but it's most likely a 10uF from researching.). This was done to 12 Factory C++s as a switchable ON/OFF version controlled by the Middle Pot having a Push/Pull. Version 2 on the C++ was incorporated as part of the R2 channel in the Mark III but ended up as 0.47uF in the III: http://forum.grailtone.com/viewtopic.ph ... 15#p469289

I imagine what Mike B does is mod a III to a III+ by changing the everything in the lead circuit to IIC+ specs, matches the main bits in the preamp to IIC+ specs. I think he leaves the EQ stock though. Then he does one of the ++ mods above. The second of which is already the R2 channel though but you could experiment with a 10uF cap instead.

Send it to Mesa if you can :) Unfortunately this is difficult for some like me being outside the USA.

Thanks,

Jon


Last edited by jrb32 on Thu Apr 19, 2018 10:01 am, edited 3 times in total.

Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Fri Apr 13, 2018 1:13 am 
Offline
Mark II

Joined: Mon Dec 10, 2012 3:44 pm
Posts: 94
Location: Mile High City
I have a loaded 3+ red stripe head, and it rips. Identical lead tone as my upgraded SRG IIC+ that mike B did too. If you need any more gain, I’d throw a Precision Drive in front and get the benefits of the noise gate vs the ++ mod. IMO


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Fri Apr 13, 2018 3:54 am 
Offline
Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 87
Big Block wrote:
I have a loaded 3+ red stripe head, and it rips. Identical lead tone as my upgraded SRG IIC+ that mike B did too. If you need any more gain, I’d throw a Precision Drive in front and get the benefits of the noise gate vs the ++ mod. IMO


Yeah or just engage the R2 channel! III++ is a bit ridiculous and OTT for me but each to their own!


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Tue Jun 05, 2018 10:13 pm 
Offline
Bottle Rocket

Joined: Mon Feb 21, 2011 7:43 pm
Posts: 18
I have 2 of these and it does not involve some of the changes mentioned in this thread. Mine came from Mike B at MB. They are switchable via the mid pot pull out to switch the mod on. Not going to divulge the specific changes, but much of what’s been mentioned here so far is off base. The + mod is something different altogether.


Top
 Profile  
 
 Post subject: Re: MARK III + + mod
PostPosted: Sun Jun 10, 2018 11:43 am 
Offline
Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 87
Wizard of Ozz wrote:
I have 2 of these and it does not involve some of the changes mentioned in this thread. Mine came from Mike B at MB. They are switchable via the mid pot pull out to switch the mod on. Not going to divulge the specific changes, but much of what’s been mentioned here so far is off base. The + mod is something different altogether.


Thanks for the info. So to clarify you have 2 III++s and the mod is switchable via the mid pot when pulled? Was this a special request? The only reason I ask is my friend has a III++ from Mike B and it definitely still has the R2 channel AND the ++ mod so the mod is not switchable on that. Once we pull the chassis (it's in a custom shell at the moment making that more difficult) I'll check what was changed.

Also you're saying the III+ mod is something completely different to the III++? The assumption here is that the III+ involves changes to shape the tone close to a IIC+. If you could clarify without divulging anything specific that'd be great. The idea is that the III++ mod adds a db or gain boost to that but if we're definitely wrong thanks for clarifying!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group