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PostPosted: Wed Mar 14, 2018 4:50 pm 
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Mark IV

Joined: Fri Jul 01, 2011 4:09 pm
Posts: 865
Location: Looking over the shoulder of the guy who lost his apples - not that he really ever had any to lose.
jrb32 wrote:
I’m pretty sure you could modify the preamp of a III to a IIC+ without much problem and get 95% close to a IIC+ easily enough. They’re not some mythical creature that have a hidden mystery component inside and some are definitely better (and worse!) than others in that they vary a lot in resistor and cap type. They also vary a lot in values and different components if they were an original factory C+ or an upgraded C. It will take some minor PCB mods on a III to do this, at the least disconnecting some components and maybe running wires to other bits of the board but it's definitely possible! I’m planning on doing this though to my recently aquired III Early Black Stripe and will report back. I would imagine the reason the III+ mod doesn’t replicate this turning the III into a clone of the IIC+ preamp because the III+ mod is more simple component value changes or cap additions rather than any PCB mods which would be time consuming and costly for Mesa.

For as close a conversion as possible, the more difficult bit to sort is the output transformer and the power voltage rails which are different on the III vs IIC+. If you have an early Black Stripe III with the IIC+ transformer I don’t see this as impossible though. You’d need to add a filter cap and mod the PCB slightly for the different voltage rails but it’s certainly achievable.

It wouldn’t be a ‘verified’ IIC+ but would be near enough identical. I’ll try it out and see what happens :) give me a few weeks though with work commitments at the moment though.

Jon


Oh God here we go again.... :roll:
Jon your intentions might be noble but seriously if it was as simple (or "minor") as you describe it'd have already been done.


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PostPosted: Thu Mar 15, 2018 5:03 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 97
gts wrote:
Oh God here we go again....
Jon your intentions might be noble but seriously if it was as simple (or "minor") as you describe it'd have already been done.


I know I know! But hear me out. Are we at least in agreement that the Red Stripe is at least similar in sound to the IIC+ but not the right 'feel'? The preamp section of the Red Stripe is almost identical to the IIC+ apart from:

R226
R223
R105
C506

Which have different values. Change these (simple component changes with no PCB mods) and you have exactly the same preamp as a IIC+, but it still isn't 'right'. I agree,
However, imagine you could put this preamp through a IIC+ power amp? It would be pretty much there in my opinion. Add the additional voltage rail for some of the preamp valves and it would be identical.

This is EXACTLY what you would be doing if you modded an early Black Stripe to Red Stripe specs, then changed R226, R223, R105, C506, added the additional voltage rail and changed the C516 presence cap to 5000pF. The only difference is the slightly different tolerances of having a different PCB layout in the IIC+, and the V3 and V4 valves being separate.

If you wanted to go a lot further you could make up a PCB clone of the IIC+ and swap the components over, but obviously that's crazy advanced for most people.

My point is that when you say it is 'impossible' it's not. You just need the right amp to begin with. So modding a purple stripe and later stripes to IIC+ specs can definitely be done, but it will never have the right feel unless you get hold of some IIC+ transformers. That I’ll definitely agree with you on.

Thanks,

Jon


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PostPosted: Sat Mar 17, 2018 3:15 am 
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Mark II

Joined: Tue Sep 08, 2015 3:35 am
Posts: 62
Given that my two IIC+s sound and respond differently enough to reliably tell them apart blindfold; and given that everyone else's various IIC+s all sound different from each other in a variety of ways.... and given that we all like different things about these amps anyway; and further given that a modded amp is an uncertain proposition versus a known outcome:

if you picked a great sounding MkIII (presumably you wouldn't start with a bad-sounding one - that'd be a recipe for yet more uncertainty before you even began), and modded it to get to some approximation of a MkIIC+.... you might end up losing something that is really good in its own right. Trey's red stripe sounded pretty good (on the half-power setting I think) on a lot of live material IMO. Not to mention that MkIII Colis are among my favourite of all the Marks, and I think that modding a good one of those would constitute an actual crime!

All to gain something that, try as you might, will never actually become a IIC+.

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MkII eh?


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PostPosted: Mon Mar 19, 2018 8:00 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 97
Wyzard wrote:
if you picked a great sounding MkIII (presumably you wouldn't start with a bad-sounding one - that'd be a recipe for yet more uncertainty before you even began), and modded it to get to some approximation of a MkIIC+.... you might end up losing something that is really good in its own right. Trey's red stripe sounded pretty good (on the half-power setting I think) on a lot of live material IMO. Not to mention that MkIII Colis are among my favourite of all the Marks, and I think that modding a good one of those would constitute an actual crime!


Definitely agree! Just because you can do something doesn't mean you should!!! There's no substitute for having a great amp or sound you like to begin with, so if you don't like the feel/sound of your III look at getting a different amp! So yes it is possible to mod a III to a IIC+ but DON'T unless you really know what you're doing and are seeing it more as an experiment than a 100% reliable result. As stated before if you don't like the sound of your III then this will not transform it into something amazing, just shape the sound slightly, maybe for better maybe for worse!

That said, if you want to experiment change components one at a time and always keep the originals secure, labelled and make a note of where they go! But the main things to change to shape a III to a IIC+ (for a black/no stripe) would be:

C506 change from 0.047uF to 0.1uF
C502 change from 0.047uF to 0.022uF
Replace 150K resistor from V3A Grid to Cathode with 470K
Add 120pF 1KV ceramic disc or mica between V3A Grid and Cathode
Change C30 from 2000pf to 1000pf 1Kv ceramic disc or mica
C215 replace .22 cap with .22 Kemet T110 or equivalent military spec
C516 replace 0.01uF (10000pf) presence cap with 0.005 (5000pf). Closest you can get is a 0.0047uF cap

The other component differences between the two are minor I would say but can be done.

Also make a note that the IIC+s use 715ps and 225p capacitors, plus carbon and metal film resistors in random arrangements which I think is one of the reasons for the huge differences you get between different IIC+s. Others have left over components from a IIC to IIC+ conversion and differ as well!

All III stripes vary as well! Trace your own stripe version yourself, compare to the IIC+ schematic I put up (check earlier post where someone linked to it) and know exactly what you're doing first before continuing! As mentioned the Red Stripe is basically a IIC+ preamp already and still doesn't feel like a IIC+, so this is what you can expect if you modify a Purple or Later I would think. The early Black Stripes with the same transformers would get you there but are rarer and are a great amp in their own right. Anything more, as mentioned, you'll be looking at sourcing IIC+ transformers from a IIB and then we get into the butchering amp territory! So if you love your III sound great! If not, sell it and get another one until you do, or get a different amp if the sound is not what you're expecting :)

Wyzard wrote:
Given that my two IIC+s sound and respond differently enough to reliably tell them apart blindfold; and given that everyone else's various IIC+s all sound different from each other in a variety of ways....


Saying that are there any IIC+s out there that people don't really like? Just curious as they differ so much!


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PostPosted: Mon Mar 19, 2018 10:30 am 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
I like the 6 that I own. :) I just don’t get to spend enough time with them. :(

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Tue Mar 20, 2018 11:22 am 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
I bought a really clean Mark lll black stripe wide head online this morning. Don’t know if it’s a DRG or HRG yet. It has an x under the power cord, 1/2 power switch on the front, x101 transformer, and a quad of 415’s. I plan on keeping it stock for now.

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Tue Apr 03, 2018 3:34 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 97
xdg999 wrote:
I like the 6 that I own. I just don’t get to spend enough time with them.


I'll happily take some off your hands!! Here the UK it's hard to even find one IIC+ let alone six!

xdg999 wrote:
I bought a really clean Mark lll black stripe wide head online this morning. Don’t know if it’s a DRG or HRG yet. It has an x under the power cord, 1/2 power switch on the front, x101 transformer, and a quad of 415’s. I plan on keeping it stock for now.


Fantastic! Let me know how you find it in comparison to other IIIs and your IIC+s out of interest.


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PostPosted: Tue Apr 03, 2018 8:34 am 
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Mark II

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 62
jrb32 wrote:
xdg999 wrote:
I like the 6 that I own. I just don’t get to spend enough time with them.

I'll happily take some off your hands!! Here the UK it's hard to even find one IIC+ let alone six!



Seconded :lol:


Last edited by lions on Tue Apr 03, 2018 1:12 pm, edited 1 time in total.

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PostPosted: Tue Apr 03, 2018 12:48 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
My c+'s ain't goin' nowhere! :) I didn't plan on owning 6 of them. I just can't resist buying one for a good price. The Mark lll I bought was the same kind of thing. I found it online at a Music Go Round and my curiosity got the best of me. I'll post a review of the Mark lll later today after work.

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Tue Apr 03, 2018 9:22 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
I'm glad I bought the Mark lll. It's an awesome amp. I like it as much as my c+’s. I’ve already talked to Mike B. about modding it to a lll+. Does it sound and feel like a c+? I think it’s about as close as you can get. It has the elastic, bouncy feel of a c+. It’s not as smooth but I’m hoping the lll+ mod will take care of that. I think it had been sitting idle for a long time. The more I use it, the better it sounds. I can’t wait to hear what it will sound like after Mike B. gets done with it. The 2 c+’s he upgraded for me sound fantastic. I’ll be shipping it back to Mesa in a week or two. I’ll post an update as soon as I get it back.

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Wed Apr 04, 2018 8:46 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 97
Quote:
I'm glad I bought the Mark lll. It's an awesome amp. I like it as much as my c+’s. I’ve already talked to Mike B. about modding it to a lll+. Does it sound and feel like a c+? I think it’s about as close as you can get. It has the elastic, bouncy feel of a c+. It’s not as smooth but I’m hoping the lll+ mod will take care of that. I think it had been sitting idle for a long time. The more I use it, the better it sounds. I can’t wait to hear what it will sound like after Mike B. gets done with it. The 2 c+’s he upgraded for me sound fantastic. I’ll be shipping it back to Mesa in a week or two. I’ll post an update as soon as I get it back.


Tell me about it the early black stripes are great!! Really overlooked amp. Let us know how the III+ mod sounds once Mike B does his magic. One day I hope to own a similar collection but for the moment I'm very jealous!!

In theory the III+ mod on a black stripe with the X101 transformer would basically turn it into a IIC+ with an R2 section which is how the amp was initially intended I think? Unless there's something else hidden which we're missing to the mystery! I'd also recommend the R2 volume mod done while it's there - really helps with channel switching and levels :) Anyway let us know would be very interested to find out how it sounds.


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PostPosted: Wed Apr 04, 2018 9:46 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
Mike B. said he automatically does the R2 mod. I asked him what the x under the power cord meant. He said the amp was built right before the Purple Stripe. I won’t argue with anyone but to me this amp is already a c+. It’s the first amp besides a c+ that passes my half hour test. It makes me want to keep playing longer than a half hour. It’s different than my c+’s but not in a bad way. Just like the difference between a Simul and a 100 watt or a 105 and a 100 transformer. As for my collection, I ain’t done yet!

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Thu Apr 05, 2018 4:35 pm 
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Mark II

Joined: Tue Sep 08, 2015 3:35 am
Posts: 62
I sold all my MkIII blue stripes, as I mentioned a while back, and bought an X101 black X/dot instead.

I still prefer my IIC+s, but it's undeniably a really great amp, and one that can be got for very reasonable money.

_________________
MkII eh?


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PostPosted: Mon Apr 23, 2018 8:32 pm 
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Donating Member

Joined: Tue May 05, 2015 9:07 am
Posts: 143
I finally got around to calling Mesa today to get an RA# for the Mark lll. I had been going back and forth about keeping it stock or modding it. It just sounds so good as is. I can get really good British tones with the current Mesa 12ax7’s and EL34’s in class A. If I load it with nos Chinese military 12ax7’s and Sovtek 5881’s, probably my favorite tube combination, it gets really close to my simul c+’s. Ultimately my curiousty got the best of me and with the R2 mod this is probably as close as I can get to a 3 channel c+. With shipping and shop time I’m guessing it’s going to be 4 to 6 weeks before I get the Mark lll back.

_________________
Mark llc+ (HRx4,DRx2,HRG,DRG upgrade,HRG upgrade,HR upgrade)
Mark lll+ (DRG 105,DRG X101,SRG)
Mark V 25
50/50
Studio Preamp
Dual Rec (1994 Rev Gx2)
Mini Rec
D-180
4x12 Half Back x3
1x12 Open Back x5


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PostPosted: Tue Apr 24, 2018 4:50 am 
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Mark II

Joined: Wed Jan 31, 2018 8:32 am
Posts: 97
Quote:
Ultimately my curiousty got the best of me and with the R2 mod this is probably as close as I can get to a 3 channel c+


It'll be worth it don't worry!! The + mod should mainly apply to the lead channel (R153 changed to 470K - more gain, C502 changed to .022 - less bass, C30 changed to .001 - slightly more treble but this might be left stock at .002) and it's in the best hands possible! Mike B should retain the character of the amp while giving it some extra oomph! So with the R2 channel (did you know this was originally used as a +/++ switch on 12 factory C+s that later developed into the R2 channel on the III) it should be an absolute monster!

Really curious to hear how it will turn out too! Cant wait!

In the meantime I'm almost done with my full III to IIC+ conversion experiment on my black stripe. I'm worried about it changing the character of the amp but I've kept all original components and have a background in electronics repair so it's no hassle to swap back for me 8) I wouldn't worry about this happening to yours as mine is a pretty major overhaul rather than some minor tone and gain shaping.

We've also found that there is a later board change in the IIIs to do with the LDR switching for the treble shift and R2 channel (PCB board change from CP1E to CP1G). We think this starts with the Red Stripe onwards but haven't confirmed for a Purple stripe yet but it seems to very much change the character of the amp and it's not confirmed whether this can be reversed yet or what the function is. If anyone's curious it involves an additional LDR stacked on top of LDR1, an addition of D212 and a 360 Ohm resistor in that area and seems to link the R2 channel to the tone stack via the treble shift pull. It is definitely present from the Red, Blue and Green Stripes but cannot be sure for the Purple Stripe. In theory that would have a CP1F board unless this was omitted and went straight to CP1G in production but will need someone with a Purple Stripe to confirm!

Anyway let us know how you get on! Maybe you'll love it so much you'll sell me one of your C+s :lol:


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