Mark IIC++ Hetfield mod

[Audiokill]

GuitarPlayer, I just finished replying to you over the same topic on another thread. Didn't see this one here until afterwards.

Anyway, so your C++ has a push/pull on the mid pot? Interesting. I too own a factory C++ which has been directly confirmed by Mike Bendinelli to be legit. However, my C++ does not have a push/pull on the mid pot, nor is my amp able to switch between C+ mode and C++ mode in any way, as previously stated. Mike B also specified to me over the phone that in all of the C++ mods he ever performed, never did he add a push/pull on the mid pot or a hidden switch or anything like that. With the exception of the duplicable ++ marking above the power cable (by no means indisputable proof), a real C++ will appear externally identical to a regular C+. Even a well trained eye couldn't make a determination with any certainty until getting a good look at the internals.

However, let me clarify that I do not doubt the awesomeness of your amp. I'm sure the mid boost you got there sounds plenty good. And you may very well be the proud owner of a mark IIC++. But you should know that your mid boost is not what makes your amp a C++... and this is from the horse's mouth at Mesa/Boogie. So, whether or not your amp is a true C++ or just a regular C+, an additional (non-factory) mod has indeed been done to your amp to give it that mid boost push/pull feature.

I don't know how to post pics either, but please feel free to PM me if you'd like to compare notes. By the way, there's a particular way that your ++ should be written that makes most forgeries easy to spot.

 

[Audiokill]

Also, keep in mind that the mighty Mark IIC+ is really nothing more than a factory mod of the original IIC, with the C+ mod providing a somewhat different voicing and slightly increased gain. But wait, the IIC already had plenty of gain and sounded killer.

The IIC+ is actually very different from a IIC. I had a IIC. After much playing and after tracing out the schematic, I knew that amp pretty well. I then sent it to Mike B for him to mod it to turn it into a IIC+. The amount of work that is necessary to do the upgrade is pretty impressive...circuit elements have to be swapped, gain-stages have to be re-ordered, and the effects loop put later in the signal chain so that it doesn't screw up the cascading overdrive. When I got the amp back, I traced out the new circuit and (obviously) I've played it extensively. In circuit, in sound, and in feel, the IIC+ is quite different from the IIC, especially in the lead channel.

I think that a major source of confusion is in the name "IIC+", which implies more relation to the IIC than actually exists. No one would confuse a IIB with a IIC(+), and no one should confuse a IIC with a IIC+. So, in my opinion (and I'm not alone), it should NOT have been called the "Mark IIC+"...it really should have been called the "Mark IID".

Chip

Despite all the work it takes to do the C+ mod/upgrade, any IIC can still be converted to a bona fide C+ thanks to all the common parts they share, which includes the all-important preamp motherboard. On the other hand, a IIB can never be upgraded to a IIC. Also, if I'm not mistaken, even the first C+ ever built was a IIC that Doug West and Mike B tinkered and experimented with until they finally got the tone they were looking for. Therefore, I see it more as a mod than as a completely different design, but I understand your perspective, too. There's a big gray area there. You may disagree, and that's cool, but continued mass debating from here would only beg the question; At what point does a mod become a whole new design? By then, though, we'd have already started asking similarly unanswerable philosophical questions, like; If a tree falls and no one hears it...blahblah? Then we'd all be dirty hippies who just want to smoke weed and get high. Hippies piss me off.

Of course, I say all this as a relative layman when it comes to the technical aspect of electronics, and I totally defer to anyone on that playing field who knows their stuff. However, I personally don't confuse the C and C+ simply because they share the same letter in their name. I know they're different...or perhaps I don't fully know the full extent of how different they really are. You tell me, would it be safe to say that a IIC is more closely related to a IIC+ than a IIB? I'm inclined to answer yes.

 

[chipaudette]

Have you played a IIB or a IIC for any length of time? What style of music do you play? I'm curious to know what experience is informing your thoughts on the IIC...

Also, as someone with experience with circuits, amp building, and amp modification, I will also offer my opinion that the IIC pre-amp is unlike any other Mark series amp. IMO, it was a freak. The effects loop is before the lead circuit! The reverb is in parallel with the lead circuit! Who does these things? It was a weird time in the early 80s...they were inventing the architecture of channel-switching amps...and they made some bizarre choices in the IIC. Many of the unique circuit features of the IIC were abandoned when going to the IIC+.

Chip

 

[Audiokill]

I have played a friend's IIC, but it really wasn't a fair A/B comparison as he was likely using completely different tubes than me. Never heard a IIB in person. I hear you on the IIC's placement of the reverb and effects loop, but I'm sort of a plugguitarstraightintotheamp type rhythm metal guitarist. I never use effects at all.

By the way, since you're familiar with the preamp circuitry of these amps, I would be highly interested in picking your brain regarding the functions of V1 through V5 in the C+. Mesa's website has a downloadable copy of the IIC's owner's manual which includes this info, but nada for the C+. The IIC preamp tube layout looks like this according to the manual;

V1a: Input Amplifier
V1b: Tone control

V2a: Effects Return
V2b: Mixer Amplifier

V3a: Reverb Return Amp
V3b: 1/2 Lead Drive Amp

V4a: 1/2 Lead DriveAmp
V4b: Reverb Driver

V5a: Phase Inverter
V5b: Output Driver

In what order are these arranged in the C+? And what is a mixer amplifier?

 

[chipaudette]

The thread where I discuss the development of the schematic for my IIC is at:

http://forum.grailtone.com/viewtopic.php?f=27&t=37463&hilit=schematic

Towards the end, we get to the best schematic that I was able to do before sending it off to Mesa for the IIC+ upgrade. The last schematic that I did can be seen directly at:

Page 1: https://picasaweb.google.com/lh/photo/6SNBfcfYmpCM1ydhaRW1ANMTjNZETYmyPJy0liipFm0?feat=directlink

Page 2: https://picasaweb.google.com/lh/photo/9QM-EPHkmLAlrHPsJOHS8dMTjNZETYmyPJy0liipFm0?feat=directlink

Since my amp has now been upgraded, I cannot go back and confirm the wackiness that is this schematic compared to the IIB or IIC+. Even at the time, though, I realized that this circuit was a bit weird, so I spent some time making sure that it was right. Given that, without being able to go and check it again and again and again, it's tough to remain convinced that they would have chosen to design the circuit this way given where they were for the IIB and where they went with the IIC+.

With this schematic, we can now walk through the roll of each tube stage in the IIC. This will inform one's understanding of the changes that went into the IIC+. (As a smidgen more background, if you're not already aware, each pre-amp tube contains two sections...the "A" side and the "B" side...each can be used independently of the other as a gain stage. so, when we say "V1A", we're talking about the "A" half of preamp tube #1.)

V1A: "Input Amplifier". Good name. Boosts the guitar's signal prior to the tone knobs. This stage is basically the same between the IIC and the IIC+.

V1B: "Tone Control". An OK name, but not totally great. It actually boosts the signal back up after all the losses that occur in the tone controls (the potentiometers, resistors, and capacitors) that are between V1A and V1B. So, V1B itself isn't the tone control...it's just an amplifier after the tone controls. Therefore, I would call this "Post Tone Control Amplifier". This stage is very similar between the IIC and the IIC+...it performs the same function at the same location, but is implemented a little differently.

V2A: "Effects Return". On the IIC this is an OK name, but on the IIC+ it's totally wrong. The reason for the difference id that the location of the effects loop is different in the two amps. So, on the IIC, the effects loop is between V1B and V2A, so V2A does receive the signal returning from the effects loop and boosts it up (effects loops require low-level signals and so always need amplification, even if nothing is plugged into the loop). On the IIC, this isn't the only thing happening here, though. On the IIC, V2A also receives the signal from the reverb and from the lead circuits and mixes it all together with the direct signal passing through the effects loop (even with nothing in the loop). So, a better name on the IIC would have been "Effects Return and Mixer Amplifier". On the IIC+, the effects loop and the reverb are later, so this stage is only a signal mixer for the direct (rhythm) and lead circuits. On the IIC+, therefore, I'd call this simply the "Mixer Amplifier".

V2B: "Mixer Amplifier". On both the IIC and IIC+, I feel that this is the wrong name. My schematic could be wrong...but I don't think so. On the IIC, this stage just provides additional signal gain...for both rhythm and lead channels. So, I'd call it "Final Amplifier" or something. On the IIC+, they stuck the reverb and effects loop between V2A and V2B, so this stage is providing all the make-up gain. On the IIC+, therefore, I'd call this "Effects Return Amplifier". FWIW, this is also where the "Pull Gain" or "Pull Deep" knob does it's thing.

V3A: "Reverb Return". Good name. True for both the IIC and IIC+. It amplifies the signal returning from the reverb tank.

V3B: "1/2 Lead Drive Amp". Again, good name. It is the 1st gain stage in the lead circuit. True for both the IIC and IIC+.

V4A: "1/2 Lead Drive Amp". Yup, good name. It is the 2nd gain stage in the lead circuit. True for both the IIC and IIC+. It doesn't exist at all in the IIB (see "Reverb Driver" below).

V4B: "Reverb Driver". Yes, good name. This amplifier drives the reverb transformer, which drives the reverb tank itself. True for both the IIC and the IIC+. As an aside, in the Mark IIB, the reverb driver requires two gain stages instead of one. So, in going from the IIB to the IIC (and IIC+), they redesigned it to only need one gain stage, thereby freeing up the 2nd stage for other duties. In the IIC (and IIC+ and later amps), they used that extra stage in the lead circuit...and, once they finally got it right in the IIC+, a legend was born. The IIC+ configuration became the standard lead circuit configuration for the III, the IV, and V.

V5A: "Phase Inverter". Yes, good name. True for both the IIC and IIC+.

V5B: "Output Driver". Um, in my opinion, there is no explicit "output driver" at the end of the pre-amp. In my view, a phase inverter actually needs two gain stages working together. So, in my view, both V5A and V5B are the "phase inverter" and there is no explicit "output driver". Maybe others have differing opinions.


So, this is probably more info than you were looking for. Sorry. Note that the info regarding the IIC is based on my own derivation of the schematic for the IIC and there are no other independent sources of info on the IIC's schematic. Anyone familiar with Mark amps will say that what I show for the IIC weird...especially for what happens after V1B and and what happens between V2A and V2B. It's just plain bizzare. For someone to accept my extraordinary claims, they should expect extraordinary evidence. I checked my circuit pretty carefully when doing the schematic, so I feel pretty confident that it's right...but one man's schematic is probably not sufficient evidence. All that I can say in my defense is that the "loop test" for telling the difference between a IIC and a IIC+ is correctly predicted based on my schematic of the IIC. So, that's a little bit of independent evidence, at least.

Chip

 

[Audiokill]

So, this is probably more info than you were looking for. Sorry.

Not at all. Your breakdown and job description of each tube stage was highly informative and is exactly the information I was looking for. Your explanation for V5b is puzzling to me, though. As a layman, I was under the impression that phase inverters generally necessitate only one side of a preamp tube to produce both signals. In addition, I previously imagined that V5b's supposed output driver in the Mark IIC(+) is 1.) either sort of a "final amplifier" to boost the signal back to an appropriate level before it hits the power tubes, or 2.) simply as part of the output stage, separate from the rest of the preamp (I'm sure you'll forgive me if any of this sounds nonsensical). However, from what I could gather from your description of V5b, neither of my speculations seem like they could be correct.

At any rate, though, thank you. I really appreciate you taking the time to lay all this out. This is more than helpful.

 

[chipaudette]

Your explanation for V5b is puzzling to me, though. As a layman, I was under the impression that phase inverters generally necessitate only one side of a preamp tube to produce both signals.

The Mark series amps (like most tube amps that are more than 10W) use a "Long-Tail Pair" phase inverter to take the single-ended signal running through the pre-amp and to generate the separate positive-going and negative-going signals required by the class AB power amplifier. A long-tail pair phase inverter is usually implemented (must be implemented?) as using both halves of a single tube. I don't claim to understand all the details of how it works, but I have seen enough tube amp schematics to know that it is very, very common. Maybe you'll have a better chance of figuring it out...

http://www.aikenamps.com/LongTailPair.htm

Note that the schematic in the link above is not exactly the same as used in a Mark amp...but it's got the same overall architecture.

Looking at the phase-inverter drawn this way, one could say that the "in phase" output is the same as what came in from the preamp, so maybe you could call that half of the tube ("V5A" in a Mark IIC or IIC+) as the "Output Driver". The inverted signal is coming off the other tube stage ("V5B" in a Mark IIC or IIC+) so you'd call it the "Phase Inverter". In my opinion, though, both halves are necessary to create the two signals together at the right amplitude and phase to drive the push-pull power amp. Therefore, in my mind, they're both the "Phase Inverter". Just my opinion.

Chip

 

[Boogiebabies]

No you're not. You'll be stone dead in a moment.

For all you tinkerers, try a 2.2M and 20pf cap over the existing 3.3M 10/20pf and
Call me in the morning.

 

[discostu29]

Does anyone know how to get hold of Mike B. from Mesa?

Stu

 

[Boogiebabies]

Does anyone know how to get hold of Mike B. from Mesa?

Stu

Call Mesa.

 

[4406cuda]

THe IIB might be completely different than other Mark amps. Two of my favorite hard rock guitar sounds are:

Mark IIB - Brad Gillis on Ozzy Osboune's Speak Of Devil. I believe he had a pair of them with a chorus in between

Mark III - John Sykes- 1987 White Snake and Blue Murder

Amazing guitar tones from both of those guys!!!

:mrgreen:

 

[themisfit138]

Necro bump!
I just had to add my 2 cents. I talked to Mike B and Rich Duvall about the C++ mod, today. Mike said there was less than 15 real ++ mods done. Also, there is no added knob or push pull in the middle. It is just a C+ with much higher gain. Mike B said it was a "Metal Machine" and to not get it done if you don't play metal, because it is not switchable. Hope that clears up a few things.

 

[DaveP]

I actually owned one of the factory produced C++ and it does in fact have a push pull middle.
When I purchased the amp I wasn't aware it was a C++ nor even knew it existed. I found out when I sent the amp in for service at Mesa.
Mike B called me with the information. He told me I had one of the original C++'s that were factory produced.

 

[themisfit138]

I actually owned one of the factory produced C++ and it does in fact have a push pull middle.
When I purchased the amp I wasn't aware it was a C++ nor even knew it existed. I found out when I sent the amp in for service at Mesa.
Mike B called me with the information. He told me I had one of the original C++'s that were factory produced.

OK, I was just going off of what I was told on the phone the other day.

 

[JD]

I also own a C++ with a pull switch on the middle knob and also a jack to switch it on the back where the reverb control would be.
Mine doesnt have reverb.

 

[decker]

Hi,

I've got several question :

1/ Why is this mod called "Hetfield mod" ? Did James Hetfield ask for it first ?

2/ When did James Hetfield used it ? What year, what album, in live ?

Thanks

 

[themisfit138]

Hi,

I've got several question :

1/ Why is this mod called "Hetfield mod" ? Did James Hetfield ask for it first ?

2/ When did James Hetfield used it ? What year, what album, in live ?

Thanks

1/ not sure if Hetfield had it done first, but he is probably the most well known user.

2/ albums pretty much everyone Puppets and after. Live, Puppets and Justice tour maybe Black tour also. Best heard on the Seattle show in the Binge and Purge box set. On a side note, I am watching the San Diego show from '92 and it also has awesome tone.

 

[decker]

Tanks for your answer.

Do you think James used it on the black album ?

 

[decker]

?

 

[themisfit138]

I am pretty sure I saw some pictures of them in the studio from then, and also a picture of them in his live rack with a Mark IV. Also James talk about the C+ as a ”thickener" on Classic Albums, if I remember correctly.