Information regarding the "Mark III+ mod"

[revgsmall]

I read a few folks mention this but the search box did not reveal what this mod does specifically to a Mark III. I just bought a III, and have a IIC+. One person said it would voice the lead channel closer but that is all the info I have at this point. Can any amp tech do it or is this something best done by Mesa?

Thanks in advance!!!

 

[revgsmall]

okay I found this via google but the results are not nesessarily what I am looking for:

1) C27 : 10 pf should be stock - replace it with a 20 pf capacitor.

This mod is quite common and already known here i think. It smooths out the clean channel and affects all other channels as well. I like that mod, because you can turn the treble knob at about 7 or even 8 without the clean sound sounding too snappy,

2) C30 (near V3) : 500 pf should be stock there - replace it with 1000 pf to smooth out the lead channel.

3) C516 (In presence control circuit) : 0.01 microfarat should be stock - replace it with 0.005 microfarat. The presence control works different afterwards. I set it normally around 3. At 5 it is still usable for distortion. And at 7 it starts sound really bright.

These mods do change the amp a lot - but you can still make it sound bright if you want to. Raise the eq on the treble side and or set the presence higher. The difference is mainly that distortion sounds in general more vocal and not as trebly.

I had this modification done to a mesa mark iii simul class red stripe. When i called Mike B. i told him that i wanted to get better smooth high gain sounds (like Petrucci or Vai ...).

I now use the amp with an engl 1x12" (v30) cab and i have to say that although i thought sometimes about a change in equipment i have not found an amp that i really liked better. It is more versatile and sounds more organic than an old two channel dual recitifier of a friend of mine(Although bouth can be dialled in to sound similar). It a bit more vocal than my second amp, an engl thunder head (A really simple and very good amp!). The only amp i liked somewhat more so far is a mark IV i played at a store in Denmark. It is more versatile for live use and sounded similar and good on the distortion channel. However - it is quite expensive here in Germany

 

[revgsmall]

Soooooo I sent this email off to Mesa, chirp in with any suggestions, will let you know their response:

Hi Boogie folks. Long time user of your fine amps. I hear tale of your Mk III+ mod and would like to know if it is for me. I've been using my MKIIC+ head since 2000, 100 watt, no graphic, no simulclass, reverb (which doesn't work, I put a digital reverb in the loop).
I recently picked up a MKIII purple strip combo, (reverb, simulclass, graphic EQ,EV speaker) I a/b'd the two together. Both through EV12's. I am very much in the Santana school of tone and I live on these settings on the MkIIc+: V1 on 7 pulled, Treble 6 1/4 pulled, Bass 2-3 pulled, Mid 8 pulled, Master 2-3, Lead drive 7, Lead Master 2-3 pulled, presence on 1. Almost always with a PRS Santana III guitar. I ride the volume knob heavily, using 8-10 for sustaining notes mainly, treble knob usually rolled off a little too.
If you'd like a sound sample of how I use it here it is: https://www.youtube.com/watch?v=tRY3X_vqLoc

When I a'b'd them this was my comparison results: The III is much darker in the lead channel and has substantially more gain, I had to reduce the pre-amp volumes down to 6 to approximate the same gain levels to make the two amps somewhat comparable. I guess the simulclass circuitry adds to the darker tone: the III had brand new Mesa 6L6's and EL34's in it. A little boxier sounding clean.

My IIC+ was bold, more open and less gain. However the III was more controllable at lower volumes which is my only complaint with my IIC+.. The EV speaker in it was one of the older non-boogie stamped EV's. I ran it through my newer Boogie labelled EV and it sounded more open and less boxy on the clean setting.

So all that being said, and in the way I use the IIc+ will this III+ mod pull these amps closer together? What is the cost if you think it would be a good move?

 

[MrMarkIII]

I may be wrong (I was, once), but the label on the EVM just means it was in a combo where you could see the back of the speaker. EVM's in closed cabs weren't labeled 'cause you wouldn't see it anyway. So if you have a Thiele cab with a labeled EVM, most likely it didn't come that way from the factory.

 

[revgsmall]

I may be wrong (I was, once), but the label on the EVM just means it was in a combo where you could see the back of the speaker. EVM's in closed cabs weren't labeled 'cause you wouldn't see it anyway. So if you have a Thiele cab with a labeled EVM, most likely it didn't come that way from the factory.

My Mark IIc+ came with no label in a combo, and this Mark III shows no nicks or marks that it has been switched out. Not absolute proof as I didn't buy either brand new. I would surmise that Mesa didn't have their label on the EV's until further on down the line. But I've been wrong once too. I am almost positive that the label has a big effect on the tone as well

Seriously, it was just likely the difference in which, what speaker was played through the most and possibly what climate a thirty something year old speaker spent it's time in that made the two speakers in question sound differently.

 

[loylo69]

Hi,

As you may already know, the IIIs differ slightly from stripe to stripe.
According to the purple stripe schematic I have, it seems that C30 and C516 are already 1000pF and 5nF respectively.

But I'm not convinced this schematic is 100% accurate, so it may be wrong. And the purple may have more differences relatively to the IIC+ than the red stripe has. The mods you posted earlier is for the red stripe. According to the Mark series history's article, the red stripe is supposed to be closer to the IIC+ than any other mark III, at least in the lead circuitry.

I'm sure Mesa will give you all the information you need to make a good choice.
But would you mind posting detailled pics of the circuit board of your purple stripe? Sothat I can confirm the assumptions above, or correct the schematic of the purple stripe.

 

[revgsmall]

Hi,

As you may already know, the IIIs differ slightly from stripe to stripe.
According to the purple stripe schematic I have, it seems that C30 and C516 are already 1000pF and 5nF respectively.

But I'm not convinced this schematic is 100% accurate, so it may be wrong. And the purple may have more differences relatively to the IIC+ than the red stripe has. The mods you posted earlier is for the red stripe. According to the Mark series history's article, the red stripe is supposed to be closer to the IIC+ than any other mark III, at least in the lead circuitry.

I'm sure Mesa will give you all the information you need to make a good choice.
But would you mind posting detalled pics of the circuit board of your purple stripe? Sothat I can confirm the assumptions above, or correct the schematic of the purple stripe.

I 'll try and get you those pics over the weekend. I'm not a amp guy but I'll photograph the whole thing.

 

[revgsmall]

just got an email from MB regarding the Mark III+ mod:

I can duplicate the values of the 2C+ in the mk3, there are small differences all thru the amp to change. One other thing to try and make them the closest would be to know the exact value of the treble pot in the 2c+. These can have a very noticeable effect if they are very different
There still always seems to me to be a difference in the dynamic sense of the amps once all I can do has been done. I say the C+ will always win here, bigger wider deeper "bolder". Tone wise they can be very much the same.

The 3+ mod also adds an Rhythm 2 master on rear in the place of the direct (SLAVE ) output if you wish.

 

[loylo69]

I 'll try and get you those pics over the weekend. I'm not a amp guy but I'll photograph the whole thing.

Thanks in advance.
But I don't want to force you to do so, if you don't feel confortable enough to pull out the chassis. No worry. :wink:

There are several intersting points in MB's answer. I'd try to develop without being to technical.
First, circuit wise, there is just a slight discrepancy between the purple stripe (and all Mark III in general) and the IIC+, as the mark III is a revision of the IIC+. Just like the mark IV is a revision of the III, etc.
Small changes, like caps and resistors, could be done to bring the III closer to the IIC+. As far as I know, that is the III+ mod done by MB.
But there is more than just small differences on the circuit, that MB don't / can't mod. Those differences are in the power supply and in the circuit board layout. Those are responsible for the difference in the dynamic sens between a III+ and a IIC+, which remains "bigger, wider, depper, bolder".
The power supply modification can't be done because Mesa don't have anymore the big power transformer of the IIC+ production.
And the rest of the power supply implies a circuit board modification to adapt the voltages in the preamp. In my opinion, this modification would have very little to no tone improvement, that doesn't deserve the hassle.
The circuit board layout can't be altered neither for obvious reasons. On the Mark III the lead circuit is on V3 preamp tube and the reverb is on V4. On the IIC+, the reverb and the lead circuit are shared with the 2 halves of both V3 and V4.

Secondly, it is intesresting to note that MB implies the treble pot of the IIC+ could be different from the traditional 250K log value. This confirms that there had also been small discrepancy during the production of the IIC+. During those old days of artisanal production, Mesa would have used different components depending on the supply.
Of course, he's right saying it has a noticeable effect. A different treble pot value changes the response of the tonestack and so the general tone of the amp.
To find out for sure what is the treble pot value in your IIC+, could you read the code stamped on this pot?
It should be stamped on the metal chassis, as you can see on this pic:

 

[revgsmall]

I don't mind pulling the chassis for you, it would be my pleasure for you chiming in with your good information.

You gave me a piece of info here regarding V3 and V4 sharing reverb. My reverb on the IIC+ stopped working some time ago. I'll replace those pre-amp tubes temporarily with the Mark III pre-amp tubes in V3 and V4 to see if the reverb comes back. I prefer a digital reverb in the loop but it would be good to have it working again, should some dummy leave his reverb unit behind. I may as well photograph the Mark IIC+ as well.

Hopefully I can see the value code on the treble pot, hopefully I can read it without it having to be loosened. Me not being an amp guy, I would not feel comfortable loosening it, but my friend in town is an amp guy and he lives just five minutes away. I thought Mike was referring to measuring it with a meter or something like that.

I spent close to 3 hours yesterday trying to match tones on the amps and I actually have it very close in tones with the help of the 5-band eq on the III. A slight difference in response to my fingers but again not too big a difference. I play music in the Bob Marley/Carlos Santana vein. I did the same thing with my first Mk III around 2002 and I had dismal results trying to get that III to match. I didn't know about the various color codes back then so I'm not sure which III it was, but it was brittle, and raspy compared to my IIc+ so I sold it. The III actually belonged to a member of Little Feat, can't remember his name but he sang for them for a while.

I'm starting to question whether this slight difference is worth chasing. The Mod is $200 minimum and likely another $100 in shipping, but I would get the R2 volume control out of the deal.

I also had a cool happy accident, I started a/bing the amps with an old Alesis Microreverb II in the loop. I got tired of swapping out the reverb over and over again. I noticed that the reverb had two inputs and two outputs so I plugged each Boogie in to the unit. One time I left the stand by on, and some of the signal came through whatever amp I was not playing on. It was beautiful!!!!!! Best reverb sound I've ever gotten!!!!!! Spacious, wide and just amazing!!!!

 

[loylo69]

I don't mind pulling the chassis for you, it would be my pleasure for you chiming in with your good information.

Thank you so much, Gary.
It's my pleasure if I can be of any help.

You gave me a piece of info here regarding V3 and V4 sharing reverb. My reverb on the IIC+ stopped working some time ago. I'll replace those pre-amp tubes temporarily with the Mark III pre-amp tubes in V3 and V4 to see if the reverb comes back. I prefer a digital reverb in the loop but it would be good to have it working again, should some dummy leave his reverb unit behind. I may as well photograph the Mark IIC+ as well.

According to your description, I don't think your reverb problem lies in the preamp tubes.
Half of V3 is for the reverb recovery stage, and the other half is one the second gain stage of the lead circuit. It goes the same for V4: half of it is the reverb driver, the other half is the first gain stage of the lead circuit. It is rare that only one half of preamp tube fails. So if it's a V3 or V4 preamp tube problem on your IIC+, not only the reveb would stop working, but it would also affect the lead channel.
You may have to search somewhere else, like the cables between the amp and the reverb tak that can get oxydised and loose contact.

Hopefully I can see the value code on the treble pot, hopefully I can read it without it having to be loosened. Me not being an amp guy, I would not feel comfortable loosening it, but my friend in town is an amp guy and he lives just five minutes away. I thought Mike was referring to measuring it with a meter or something like that.

Well, I had a look at my IIC, and it is quite impossible to read the codes without loosening the pot. So my advice is not so good. :?
The problem is that measuring the pot while it is connected to the circuit wouldn't give direct measure. It needs to be isolated from the rest of the circuit, because the volume pot and the 2 other pots of the tonestack (bass and mid) will interfere with the measure.
Luckily, the volume pot value is high enough, so the meter would read an approximative measure of the pot. For example, I've just measured my IIC and the treble pot reads approx 215k for a standard 250k. To see if it is a log or a lin one, you should take a measure between the wiper and either of the 2 outer lug while the pot is on 5/10. If it reads half of the total value, it's a lin pot. If it's closer to one of the extrem (0k or 250k depending of the outer lug you've choosen), it's a log pot.

I spent close to 3 hours yesterday trying to match tones on the amps and I actually have it very close in tones with the help of the 5-band eq on the III. A slight difference in response to my fingers but again not too big a difference. I play music in the Bob Marley/Carlos Santana vein. I did the same thing with my first Mk III around 2002 and I had dismal results trying to get that III to match. I didn't know about the various color codes back then so I'm not sure which III it was, but it was brittle, and raspy compared to my IIc+ so I sold it. The III actually belonged to a member of Little Feat, can't remember his name but he sang for them for a while.

Yeah, I find the EQ is a powerful tool which can help to further adjust your tone.

I also had a cool happy accident, I started a/bing the amps with an old Alesis Microreverb II in the loop. I got tired of swapping out the reverb over and over again. I noticed that the reverb had two inputs and two outputs so I plugged each Boogie in to the unit. One time I left the stand by on, and some of the signal came through whatever amp I was not playing on. It was beautiful!!!!!! Best reverb sound I've ever gotten!!!!!! Spacious, wide and just amazing!!!!

Nice! I'd like to hear that!

 

[revgsmall]

Update: I did send the Mark III back to Mesa for the III+ mods. They have had it approximately two weeks now. I likely will get a phone call soon with the prognosis.

 

[loylo69]

Hey Gary, I'll look forward to your report.
I'm curious to see what magic would MB do to this purple stripe. It seems already quite close to IIC+ circuitwise, closer than the blue stripe for example.

 

[revgsmall]

Update II: Mike called regarding the Purple Strip III and informed me it had a few issues that should be addressed. Evidently the "Our Tech went through this amp and it's in great shape" sales pitch was a bit inaccurate..... not too happy at the moment with that store.

However, Mike is going to get it up to tip-top condition and also do the III+ mod. The amp is shipping back to me this monday. I bought the Mk III as a back up to my IIC+ and I am way over budget considering this was to be my back-up amp.

Who knows, it may out perform my Mk II since it is getting the best tune up that likely can be given. Will report again soon.

 

[megavoice]

Evidently the "Our Tech went through this amp and it's in great shape" sales pitch was a bit inaccurate.....

To all of you out there !!!!!!!!!!!!!
Never trust words like these, even more if you`re young ones !!!

Also when you want to buy a new unit:
".........We`ve got 5 or 6 items of this model and we`re going to select the best for you before shipping, and we`ll tell our tech to go over before to make everything sure........."

HA ! HA ! HA !.................................

 

[revgsmall]

Evidently the "Our Tech went through this amp and it's in great shape" sales pitch was a bit inaccurate.....

To all of you out there !!!!!!!!!!!!!
Never trust words like these, even more if you`re young ones !!!

Also when you want to buy a new unit:
".........We`ve got 5 or 6 items of this model and we`re going to select the best for you before shipping, and we`ll tell our tech to go over before to make everything sure........."

HA ! HA ! HA !.................................

There was a bit more to it than that, but I'm giving the short and sweet version. The Boogie shipped back today so I'll likely see the results monday or tuesday of next week.

 

[loylo69]

Update II: Mike called regarding the Purple Strip III and informed me it had a few issues that should be addressed. Evidently the "Our Tech went through this amp and it's in great shape" sales pitch was a bit inaccurate..... not too happy at the moment with that store.

However, Mike is going to get it up to tip-top condition and also do the III+ mod. The amp is shipping back to me this monday. I bought the Mk III as a back up to my IIC+ and I am way over budget considering this was to be my back-up amp.

Who knows, it may out perform my Mk II since it is getting the best tune up that likely can be given. Will report again soon.

Hey Gary,

As far as I can remember from the pics you sent to me, your mark III seemed pretty clean to me, from the outside and the inside.
I can remember some "tweaks" on the circuit boards, such as some grey filter caps added above the regular blue ones on the preamp section, and some protection diodes added on the EL34 sockets. Those tweaks are no "state of the art" mods, but they aren't "issues" neither.

That being said, there may be more issues that I just can't see from the pics. That is why it is a good thing you had sent the amp to Mesa or any a tech you can trust. They can have a better look and test the amp during operation.

Let's see the results next week! :wink: