MARK III + + mod

[paulyc]

So I have a fully loaded MARK III blue stripe head with graphic EQ, reverb and Simul Class. I'd LOVE to get a combo cab for it as I have lots of great Mesa (and other) heads but no small portable rig. I would also love to have a + or a + + mod done by Mike B. I'm a hard rock and metal player (so think tones from 80s Sunset Strip hard rock to Metallica). Which mod (+ or ++) is the way to go ? Also, in a combo, what speaker would be a good choice (leaving the EVM out of it, too heavy !) ? I'm leaning toward C90 or a G12 H or K 100 ? What about the old Eminence 150 watt from the half back days ?

Thanks !

 

[thediavlo]

So I have a fully loaded MARK III blue stripe head with graphic EQ, reverb and Simul Class. I'd LOVE to get a combo cab for it as I have lots of great Mesa (and other) heads but no small portable rig. I would also love to have a + or a + + mod done by Mike B. I'm a hard rock and metal player (so think tones from 80s Sunset Strip hard rock to Metallica). Which mod (+ or ++) is the way to go ? Also, in a combo, what speaker would be a good choice (leaving the EVM out of it, too heavy !) ? I'm leaning toward C90 or a G12 H or K 100 ? What about the old Eminence 150 watt from the half back days ?

Thanks !

I didn't know there was a ++ mod. I would love one for my Blue stripe if there is one. I personally prefer the organic timbre speaker in my blue stripe, Great response and similar in sound to the EVM but with more Roll off on the upper treble frequencies. Bandit made a great comparison with it in his MKV.

 

[paulyc]

Organic timbre ? IDK what speaker you're talking about, can you explain please ?

I've seen a clip on YT of someone playing psychodave's Mark III ++ and it sounds glorious. MB has confirmed the ++ mod exists...

 

[thediavlo]

Organic timbre ? IDK what speaker you're talking about, can you explain please ?

I've seen a clip on YT of someone playing psychodave's Mark III ++ and it sounds glorious. MB has confirmed the ++ mod exists...

http://www.organictimbre.com/store/p1/Rhapsody_G12F.html


Oh cool. So the Organic Timbre Rhapsody 12 is a speaker that has recently come to light on this board and I have heard great things about it, link is above.

 

[thediavlo]

I just looked up the mod on youtube and it sounds pretty over the top and ridiculous. Definitely gonna look into sending mine off for that.

 

[Stevie C]

paulyc, where are you located? I might be looking for a head shell for my mark iii.....if I decide to go that route, mine's loaded in a combo shell that's in great shape.

 

[paulyc]

New England.

 

[jack s.]

So this ++ mod has even more gain than a regular Mark III? I thought Mark IIIs already have a bunch more gain than the Mark IIC+ amps.

 

[paulyc]

The Mark III May have a bit more gain than a IIC+, but there is a + and a ++ mod for the Mark III that makes it awesome. The ++ mod is like 26 db more gain than stock.

 

[jack s.]

Oh nice

 

[Stevie C]

New England.

Still considering looking for a combo shell?

 

[paulyc]

Yes, PM sent

 

[Stevie C]

Yes, PM sent

PM sent

 

[jrb32]

I'm pretty sure the initial III+ mod essentially turns a MkIII into a Mk III Red Stripe with added IIC+ circuitry to make it close to the IIC+sound but not identical. The Red stripe was the closest of the Mk IIIs to the IIC+.

The ++ mod then adds a crazy amount of gain on top of that. My friend has a III++ modded by Mike B so it definitely does exist!

A blue stripe already has a stupid amount of gain. I've not compared it to a normal Blue Stripe but a stock coliseum Blue Stripe had way more gain than the III++

So if it's gain you're after, a + or ++ mod wouldn't add much but would change the overall sound of the amp.

Hope I am correct in this?

 

[darkbluemurder]

Red stripe lead mode is indeed very close to Mk II C+ lead mode - only one capacitor (C30 - 500pf in the red stripe, 1000pf in the II C+) and one resistor (470k to ground before V2b in the red stripe vs. 680k in the II C+) is different. The cap difference has the bigger impact. The shunt resistor will affect the clean tone more than the lead tone because in lead mode it is in parallel with the 100k shunt resistor, thereby resulting in approx. 82k in the red stripe vs. approx. 85k in the II C+. This would not make any audible difference to the lead tone.

From comparing the schematics it is clear why the Blue stripe has more gain than the red. Red has the voltage divider of 220k to 100k (caps ignored for this purpose) whereas Blue has 470k to 470k. So in the red stipe 31% of the signal gets to the grid of V2b whereas it's 50% in the blue stripe. The tonal change you mentioned comes from the caps in parallel to the resistors - if the resistors are bigger the caps have a more noticeable effect.

In another thread where the III ++ was mentioned I posted some ideas on how to increase the gain in a Mk III. Still don't know what the ++ mod is.

Cheers Stephan

 

[jrb32]

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

 

[darkbluemurder]

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

 

[charleonthronez]

Really very interested for the III++ mod.

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

Thanks all.

 

[jrb32]

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.php?f=27&t=48193&start=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.php?f=3&t=68218&start=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

 

[Big Block]

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