Anyone convert their MKIII to a MKIII+ (IIC+)

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Hi!
I would also want to hear from someone who has done this mod to their mark III. I am letting a local tech that has done superior work on my vintage Vox AC30 do the R2 mod on my Boogie. I really want to hear if this mod is worth it regarding the tone. Since I am very happy with the lead sound of my Boogie I would like to hear more of what character you get after the "+" mod.
DrBazooka
 
can't you always just mod it back if you dont like it? (i'm referring to the 3 cap replacements for clean, lead, and presence. not referring to the 3+).

edit: tho i guess you could mod that back too, it would just be hella expensive. seems like a local tech could do those 3 cap replacements and clean up the amp for cheap.
 
keep in mind that every version of the mark III is different. i talked to mike b today about the mods ahoi listed and it turns out that my blue stripe has no cap at c30 and already has a .005 mf cap in the presence circuit. no 500 pf cap in c30 makes the blue one of the brighter stripes. he also suggested changing another 500pf cap to 1000pf that runs off of pin 7 on v3. i'm gonna try these out tomorrow and report back.
 
Hmm, now this has got me thinking. To me it seems that the IIC+ is the most sought after but all this talk about mods to a III has got me thinking about maybe picking one of those up and modding it if needed. Needless to say, the III's seem to go for pretty cheap. Thanks for the info.
 
did the C30 mod and wow what a difference. the high end is so much more flexable now and the amp is alot more vocal as others have said. i'm probably gonna leave it be now.
 
timjtitus said:
did the C30 mod and wow what a difference. the high end is so much more flexable now and the amp is alot more vocal as others have said. i'm probably gonna leave it be now.
Click to expand...
Can you go into a little depth about what you did. I have a red stripe and my only complaint is I want a little more clarity and defintion.
 
i took the chasiss out and located the space where C30 should go. most of the caps on the board are labled. my blue stripe didn't have a cap in the C30 spot and so i called mike B as mesa/boogie and he told me in the blue stripe they left it out to make it brighter. he suggested that i put a 1000pf cap in that spot and i wouldn't say it's made clearer but it's rounded it out and i can run it with reasonable amounts of treble where before i was cranking down the top slider to smooth it out.
 
timjtitus said:
i took the chasiss out and located the space where C30 should go. most of the caps on the board are labled. my blue stripe didn't have a cap in the C30 spot and so i called mike B as mesa/boogie and he told me in the blue stripe they left it out to make it brighter. he suggested that i put a 1000pf cap in that spot and i wouldn't say it's made clearer but it's rounded it out and i can run it with reasonable amounts of treble where before i was cranking down the top slider to smooth it out.
Click to expand...

That is good info...I also own a blue stripe and I run the presence WAY lower on that amp than on any other amp I own. Whereas on most amps I set it around 7 or so, I'm running at 2 or 3 on the Mark III. This mod might be just the ticket for me.
 
yeah, the best thing about it i you don't have to remove anything, just solder it in there and if you don't like it, take it back out.
 
Is there an added amount of 'smoothness' to the gain channel aswell as what you've described?

I'm pretty keen on doing this mod to my purple stripe.
 
Hi - I am new here. I have a green stripe Mark III. I just performed the mod on my amp and the difference is amazing. There were some harsh high frequencies I could not seem to dial out because the amp was so incredibly bright so the mod was perfect for me. It now has a smoother, rounder tone with the perfect amount of highs and no harsh frequencies.

Like the guy with the blue stripe, mine already had the presence cap changed and was missing the cap @ c30. I believe it also has the correct cap for the mod already in place for the clean channel.

For those people who like the way the Mark III cuts through in a mix this mod may not be for you!

Now my next project will be to replace all the electrolytic caps since its almost 20 years old!
 
Hey guys, just wanted to verify a few things before I dive into my first amp mod.

First, I can confirm that C30 is indeed absent in the blue stripe, as seen in this pic.
And also C516 is already 0.005uf.
1004641f.jpg


Second, what's going on with C27?
I'm a tube noob so I'm not sure if that round tab is indeed the capacitor, and if it is, I'm not sure what value it is as all I can read from the print on its surface is "100 1KV", is this the one I should swap to 20pF?

1004645.jpg
 
Hi Silentrage,

Your "tab shaped" C27 is what a ceramic capacitor looks like. Ceramics are very common for these small valued capacitors. They also have a very high voltage tolerance (not that it's need here), which is why it says "1000V".

The reading of "100" describes the value of the capacitor. For ceramic caps, the "100" label should be read as a "10" followed by a "0", which is then interpreted as "10" x 10^"0" picofarads (pF). Since 10^"0" equals 1, your cap value is 10 x 1 = 10. So, this is a 10 pF cap.

This would contrast to a label of "102". A label of "102" would be "10" x 10^"2". Since 10^"2" equals 100, your cap value is 10 x 100 = 1000, which makes it a 1000 pF. This is the value being discussed for the mod to C30 (not C27).

Going back to C27, your 10 pF value is pretty standard. To raise it to 20 pF per the mods being discussed above, you could just solder another 10 pF cap in parallel with the existing 10 pF cap. That way, you don't have to unsolder anything from the board.

Note that tube amps have large capacitors inside that can store a tremendous amount of electrical energy. So, even with the amp off and unplugged, you can still get a massive shock if you don't know what you're doing. Your Mesa could actually kill you.

Chip
 
Thanks!
I spoke to Mike B just now and he said 10pf for C27 is definitely smoother.
He also says replacing the 2 Caps coming off of Pin 6 and 7 of V3 will smooth away some more fizz.
For those who're interested, Pin 6 cap is in parallel with the 270k plate resistor, this is labeled C30 on the board and is missing from the blue stripe,
and pin 7 cap is in parallel with the 68k grid resistor, this is a ceramic disc cap labeled "k 501" on the cap.

I'll be doing the R2 volume and the above mods today, wish me luck!
 
Did the R2 mod, pulled it off without a hitch, it actually adds gain to R2 when you crank it! But when cranked it kind of offsets the channel balance.

Put a 1000pf carbon film cap in C30, got a noticable mellower sound on the lead channel.
I put it in very lightly because I'm not very experienced with a soldering iron, and when I was testing it after I wasn't sure if there was a difference.
Then I noticed there was a crackling sound on the lead channel, so I took some pliers and prodded the new C30 a bit, and BAM, it turned mellow.
I love this, now I can bring up the presence and have the same brightness as before with less fizz, just as Mike B said!!
I'm putting in the Pin 6 cap later, but can't play as it's too late, so I'll report back tomorrow. I don't think either of these affect the R2 channel though, anyone got a mod to mellow that out?
 

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