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PostPosted: Thu May 10, 2018 4:48 am 
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Mark II

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 52
I think I get it now that I've seen the pictures; basically set up like that it just goes to ground regardless of what's been selected.

The EQ cap in the Mark V was the one from non-EQ IIc+ models, I can imagine it making a difference although I've already got similar orange drops to a IIC+. I'll think about it as I have to make instructions for these mods since I don't want to risk damaging the board by doing it myself. You're always welcome to have a go instead next time you're down this way. :lol:

And yeah as has been said, simuls are brighter, but paradoxically the component changes in the preamp were an attempt to brighten it as it was felt to not be bright enough. I can't see letting more treble in at c27 ruining anything, or deleting C30, since it's already deleted in the stock blue stripe (which also lowers the unnamed V3 grid cap to 500pf along with the 2m2 reistor and the voltage divider revoicing) and a lower value in the red stripe.

What's the difference to tone and attack on yours since modding? If your attack is more pronounced I'll probably hold off, if it's around the same I'll probably go for simulclass specs. I also need to verify that 20pf will let more treble through compared to 10pf! I'm guessing that's what the 0.1 cap in the II is doing compare to the 0.047 in the III too.


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PostPosted: Thu May 10, 2018 6:30 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 82
From the Mark V manual "In our endless comparisons of many original II C+’s - both EQ and non-EQ samples - alongside this golden reference, we discovered
that I wasn’t just Tone-dreaming. There was actually a difference between the EQ model and those non-EQ models. It all came
down to a coupling capacitor at the end of the EQ circuit that feeds the driver. In the EQ model, it was a great big cap that let a lot
of sub-low pass, slowing down the sound and making it fatter. In my amp - a non-EQ version - this cap was smaller and didn’t let as
much sub-low through - which speeds up the sound and makes everything tighter and more urgent. There it was, a simple part…but
it made all the difference in the time domain."


Ah yeah thanks for clarifying. Looking at the Mark V schematic theres a .22uF cap used instead of the 10uF axial cap in IIC+ mode (M7 channel 3) in the EQ circuit. It also looks like the 10K resistor off the 10uF cap is changed to 100K in IIC+ mode. I don't think it's anything to do with the 0.1uF orange drop after that but I could be wrong (If you have any more info regarding this that'd be great thanks!)

Assuming boogie have taken these values direct from the IIC+ non EQ they traced, and I will until anyone can say otherwise, I'll add this to my IIC+ schematic as a list of potential mods. I doubt this is the only the secret to the non EQ IIC+s being preferred by many players but anything is possible! Apparently the 60W reverb models are the nicest.

Quote:
yeah as has been said, simuls are brighter, but paradoxically the component changes in the preamp were an attempt to brighten it as it was felt to not be bright enough


Seems weird! Lowering the value of C30 brightens the amp right, but then why does increasing the value of C27 also brighten the amp? I would have thought increasing value = brighten, reduce value = darken but I'm not an expert. Maybe increasing C27 is to counter balance C30 being reduced? If that's the case though I don't know which way (higher or lower) has the effect on brightening or darkening!! Or I'm completely wrong all together - need's some experimentation done I think to find out.


------------------------------------------------------------------------

Also in other news, speaking to Boogie and xdg999 sending me some pics it seems the Black Dot (the earliest III) uses a different kind of R2 channel and different circuit board (CP1D) to the others. It only has 1LDR for R2 and doesn't have C214 anywhere.

So anyone looking for a +/++ switchable III > IIC+ the best candidates are probably the purple stripes or black stripes with the CP1E circuit board which have two LDRs for R2 and engage both R130 and C214 in R2 mode as well as causing a slight ground shift on the tone stack. The earlier the transformer date on them the better (so black stripe preferred). 1985 dated transformers or earlier ideally.

CP1F and higher (Red Stripe onwards) seem to add another LDR to engage treble shift on all the time when R2 enabled, but from reports from lions and others this causes a graininess factor when treble shift pulled in lead mode regardless of R2 being enabled. It should be able to be removed but requires some modding work (until I can trace one I won't be able to give instructions on modding those but lions is looking at doing this at the moment for his blue III>IIC+ conversion).

You could also probably still mod a CP1D board in adding C214 (10uF cap preferred to .47uF!) and making that on/off switchable if you wanted but it's gonna be more tricky.

Just some useful info hopefully if anyone is reading through this.


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PostPosted: Thu May 10, 2018 11:40 am 
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Mark II

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 52
jrb32 wrote:
Ah yeah thanks for clarifying. Looking at the Mark V schematic theres a .22uF cap used instead of the 10uF axial cap in IIC+ mode (M7 channel 3) in the EQ circuit. It also looks like the 10K resistor off the 10uF cap is changed to 100K in IIC+ mode. I don't think it's anything to do with the 0.1uF orange drop after that but I could be wrong (If you have any more info regarding this that'd be great thanks!)

Assuming boogie have taken these values direct from the IIC+ non EQ they traced, and I will until anyone can say otherwise, I'll add this to my IIC+ schematic as a list of potential mods. I doubt this is the only the secret to the non EQ IIC+s being preferred by many players but anything is possible! Apparently the 60W reverb models are the nicest.


I've been taking a look at Triaxis schematics recently, and it looks like their "Mark III" mode on the Triaxis has little in common with the III schematically, although I suspect it's doing something similar electrically, so those values might not necessarily represent a schematic lineage from the IIC+ non-EQ versions, but hey they probably do, just something to consider. I'm pretty sure my amp has that 60w transformer! That or something pretty analogous.

Quote:
Seems weird! Lowering the value of C30 brightens the amp right, but then why does increasing the value of C27 also brighten the amp? I would have thought increasing value = brighten, reduce value = darken but I'm not an expert. Maybe increasing C27 is to counter balance C30 being reduced? If that's the case though I don't know which way (higher or lower) has the effect on brightening or darkening!! Or I'm completely wrong all together - need's some experimentation done I think to find out.


That's why I'm trying to verify it. :lol: I've seen people say 20pf makes things darker and brighter, so I'm totally lost. I think I'll do the mods I have planned incrementally so we can use the information on which changes affect the sound, so no C30/C27 changes for now, just the III circuitry, LDR6 etc removal. I would be surprised if LDR6 was causing the graininess, unless it's that 360 resistor in the LDR6 circuit causing it, but we'll find out soon enough.

So if anyone who actually understands amp circuitry has any info on the difference in effect between 10 and 20pf at C27, and whether just removing LDR6 and its associated components would work without causing any issues that would be super helpful. The last thing I want to do is remove it and find it permanently enables treble shift on R2 or something!


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PostPosted: Mon May 28, 2018 9:16 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 128
Location: Boogieville
The Mark lll+ is back home and it sounds fantastic. Everything about the amp is improved. It’s quieter and smoother. The reverb is better. The touch response is awesome and the R2 mod makes it the perfect amp for me. I had Mike B. reduce the brightness so now I can set the presence at 5 or 6 instead of 2. I’ll definitely be sending the Black Dot to Mesa for the lll+ mod.

_________________
Mark llc+ (HR x 3, DR x 2, HR upgrade, DRG upgrade)
Mark lll+ DRG Black Stripe (x101), Mark lll+ DRG Black Dot (105)
Mark V 25
1994 Dual Rec Rev G Black Chassis
1994 Dual Rec Rev G Chrome Chassis
Mini Rec

How many guitars and amps do you really need?


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PostPosted: Sun Jun 10, 2018 4:12 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 128
Location: Boogieville
The Black Dot is on it’s way to Mesa for lll+ mod and service. I almost wanted to keep it stock. It’s a very fast and aggressive amp. Mike B. said it should still be more aggressive than the Black Stripe lll+ because of the 105 transformer.

_________________
Mark llc+ (HR x 3, DR x 2, HR upgrade, DRG upgrade)
Mark lll+ DRG Black Stripe (x101), Mark lll+ DRG Black Dot (105)
Mark V 25
1994 Dual Rec Rev G Black Chassis
1994 Dual Rec Rev G Chrome Chassis
Mini Rec

How many guitars and amps do you really need?


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PostPosted: Sun Jun 17, 2018 6:46 pm 
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Mark II

Joined: Fri May 04, 2018 10:36 pm
Posts: 67
I'm considering doing (or having done) a IIC+ mod done to my black dot Mark III DRGX.

But, while instructions have been posted here concerning the mod for a black stripe version, I guess I need to know how a black dot and a black stripe are different first.

I'm also seeking more information about whether or not this tonal mod is the direction I really want to go in.

Knowing full well that I'll never have the talent or skill to even get on the same continent with Steve Lukather, I would like to get the sort of tonality he got out of his late 80s Mesa based rig, knowing full well that a large part of his sound was due to his Bradshaw rack and of course a lot of his tone comes from his fingers. As I understand it, he was using a IIC+ as the basis of his tone, but yet that's also the same thing that is the foundation of the Metallica tone, too. And these two examples are dramatically different in their overall sound, so that's the part that's confusing me. Is it really the case, that a single type of amp can sound as different as Hetfield's tone AND Lukather's tone?

They just seem so fundamentally different to me that I have to find out before I commit to modding anything, so I don't end up doing a mod with expectations that have nothing to do with the final reality.


Oh...micro rant. I really do wish that Randall Smith had learned to draw schematics the "Standard" way, that being, inputs on the left, outputs on the right. Supplies on top, grounds on bottom. Most of his schematics are backwards, with inputs on the right and outputs on the left, and it's like trying to read a Japanese book. Read it in a mirror! It'd make comparing the IIC+ and III schematics a LOT easier.


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PostPosted: Sun Jun 17, 2018 9:59 pm 
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Mark II

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 52
Supposedly Black Stripe = Black dot. I would imagine there may well be some small differences but you could open your amp up and take a look for yourself. Resistors are colour coded!

The Metallica sound is in the IIC+, but it takes a lot of EQing to get to the album sound, you can get ballpark tones out of a IIC+ though easily.


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PostPosted: Mon Jun 18, 2018 5:43 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 82
Quote:
I'm considering doing (or having done) a IIC+ mod done to my black dot Mark III DRGX.

But, while instructions have been posted here concerning the mod for a black stripe version, I guess I need to know how a black dot and a black stripe are different first.


I should clarify, the instructions I gave turned out to be for a really weird Jan '86 Black Stripe. It was kind of a crossover between a Black Stripe and a Purple Stripe Mesa made for a few months with the new production board (CP1E). I think it retains a lot of the values from the Black Stripe but has the Purple Stripe CP1E board! Not the CP1D board of the Black Dot and Black Stripe.

xdg999 sent me some pics of his black dot and black stripe but one was done post III+ mod so I cannot verify that they were the same to begin with. They both have the CP1D board but they could have different components. I would imagine it's pretty unlikely though most likely scenario is Black Dot = Black Stripe for all amps up to those with the CP1E board made from around 1986 shortly before the purple stripes. My serial is 163XX for reference.

So my instructions on here don't really apply to a 'traditional' Black Stripe/Dot I'm afraid!

Quote:
Oh...micro rant. I really do wish that Randall Smith had learned to draw schematics the "Standard" way, that being, inputs on the left, outputs on the right. Supplies on top, grounds on bottom


I actually redrew the schematics for the IIC+ and III the correct way round as it was annoying me too! I added any extra info I've found as well.

https://mega.nz/#F!HZAAgRLS!g1V-9NWuStE3uW2O7MKZKA

The III is 100% correct for my weird black/purple crossover amp, and the Mark IIC+ schematics are accurate but I've not traced one myself, just from pictures I've seen and info I've been told from reliable sources. Component values can differ slightly though as they used what was on the shelf at the time. The more info I get the more I'll stick on my schematic.

I will hopefully draw up a black stripe CP1D schematic from the pics xdg999 sent me when I get some time. I'm currently doing a IIC+ RP11 board layout and schematic from other pics he sent me (thank you so much again for those!)

Cheers,

Jon


Last edited by jrb32 on Wed Jul 11, 2018 9:56 am, edited 1 time in total.

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PostPosted: Mon Jun 18, 2018 6:06 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 82
Quote:
Knowing full well that I'll never have the talent or skill to even get on the same continent with Steve Lukather, I would like to get the sort of tonality he got out of his late 80s Mesa based rig, knowing full well that a large part of his sound was due to his Bradshaw rack and of course a lot of his tone comes from his fingers. As I understand it, he was using a IIC+ as the basis of his tone, but yet that's also the same thing that is the foundation of the Metallica tone, too. And these two examples are dramatically different in their overall sound, so that's the part that's confusing me. Is it really the case, that a single type of amp can sound as different as Hetfield's tone AND Lukather's tone?

They just seem so fundamentally different to me that I have to find out before I commit to modding anything, so I don't end up doing a mod with expectations that have nothing to do with the final reality.


Your III should be able to do this already though as it's very similar to a IIC+. They're both VERY versatile amps. The main difference is feel and brashness. If you can't get close to the sound your after, then no amount of modding will get you there. It's not a night and day difference after doing the + mod, it's more a 'tone shaping' of what was there originally.


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