Studio Premp w/ MKIIc+ mod

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mboogman

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Posted this in the announcements section, but I figure it should be in here too, since, it's about a rack piece, so here ya go.

I just got done doing a little work on my Mesa Studio Preamp. When I bought it, the reverb tank was not working, so I replaced it with a tank from MojoTone. Sounds great! While I was at it, I went ahead and set it up for the MKIIc+ tone stack. I think it made a huge difference in the overall feel of the lead channel.

Here's a quick recording I did one morning before heading off to work.

http://soundclick.com/share.cfm?id=11184795

I normally would have an SM57 on the cabinet, but all I had on hand at the time was one of my AT4040's. No FX, just straight into the preamp, then into my VHT 2:Ninety:2 power amp, into my Peavey JSX cab, which is less than ideal, but you'll get the idea.
 
Sounds awesome, though without a 'before' clip to hear how the stock version sounded on your particular setup, it's difficult to know exactly how much of the sound to attribute to the mod.

I have a couple of schematic images regarding a IIC+ mod to the Studio Preamp, one of which is apparently just for the lead circuit and involves changing some resistor and cap value, and the other of which is for bass shift and deep modes. Did you do just the lead mod, or the others as well? Or is it a different mod you worked from?
 
Whoopysnorp said:
Sounds awesome, though without a 'before' clip to hear how the stock version sounded on your particular setup, it's difficult to know exactly how much of the sound to attribute to the mod.

I have a couple of schematic images regarding a IIC+ mod to the Studio Preamp, one of which is apparently just for the lead circuit and involves changing some resistor and cap value, and the other of which is for bass shift and deep modes. Did you do just the lead mod, or the others as well? Or is it a different mod you worked from?

It was just the Lead mod. I'd be interested in seeing your schems for the bass shift and deep mode too though.

I agree that I should have done a before clip. I just got excited to get the mod done, and jumped the gun a little.
 
my studio pre never get that clean, if i do get it that clean, i sacrifice the lead channel. I havent changed tubes and i bought it used so there is a good chance that the tubes are all stock. what would you suggest to be able to get my stupre sounding like that? oh, and was the mod hard to do?
 
toolshed said:
my studio pre never get that clean, if i do get it that clean, i sacrifice the lead channel. I havent changed tubes and i bought it used so there is a good chance that the tubes are all stock. what would you suggest to be able to get my stupre sounding like that? oh, and was the mod hard to do?

New tubes would allow you to determine if the old ones sound.... old.
If they sound fine then you have backups : )
What are your current tone settings?
 
682091492_2438934403_0.jpeg


as far as old tubes, I have changed them in other amps and it's made a world of difference, as far as the setting
here is an awful pic of the rig but you get the idea. the settings are
gain4.5,volume 2,high 9,low 1,mid 7.5, reverb 1,gain9, 4lead volume all switches are up except the bright rhythm channel
i'm running a eq pedal on the lead channel via switcher but the clean is breaking up even with the settings like 2 on the gain and almost all the way up on the volume. then the lead channel needs more gain...
 
mboogman said:
It was just the Lead mod. I'd be interested in seeing your schems for the bass shift and deep mode too though.

I agree that I should have done a before clip. I just got excited to get the mod done, and jumped the gun a little.

Just realized I never posted my schematics. Here are both:

http://maxcrowe.co/img/lead_C+mod.jpg
http://maxcrowe.co/img/bass_shift_&_deep_MOD.jpg
 
Hi mboogman,

Can you please describe the tonal difference's you noticed after doing the mod?


Thanks!

Shane
 
Shane C said:
Hi mboogman,

Can you please describe the tonal difference's you noticed after doing the mod?


Thanks!

Shane

Before the mod, I had a hard time getting a nice, round clean sound while also getting a cutting, tight rhythm/lead sound. Now, the upper mids cut a little better, some of the bottom end flub has been trimmed out of the lead mode, and the useable gain increased just a hair. The graphic EQ also seems to complement the lead channel a little better without having to use the typical "V" settings.
 
mboogman said:
Before the mod, I had a hard time getting a nice, round clean sound while also getting a cutting, tight rhythm/lead sound. Now, the upper mids cut a little better, some of the bottom end flub has been trimmed out of the lead mode, and the useable gain increased just a hair. The graphic EQ also seems to complement the lead channel a little better without having to use the typical "V" settings.

Hey great work man, my vote for post of the year. The circuit diagrams, tone samples, it's all good and the Studio sounds great.

This very week I was thinking, "hmm, it's amazing how my C+ just hangs together and both channels 'just work' even though there's all the shared dials "...

And to be honest I never understood what the + mod was really all about, I've never had IIC so I couldn't work it out for myself but I'm guessing the motivation was to make both channels happy and work better together. Maybe gain, the loop or something else changed in the process but I'll bet that's what it was mainly all about.

Cheers.
 
mboogman,

I want to do the C+ mod on my Quad. Im just in the planning stage, I have figured out most of it but I need a little help please:

1m = the lead drive pot correct? The only part I cant figure out is where to put the 680k before the 1M/lead drive, I could post some close-up shots of my Quad's board and label everything I can see for the mod if you or anybody can help me out?


Any info would be greatly appreciated.


Shane
 
A_Ryder said:
mboogman said:
Before the mod, I had a hard time getting a nice, round clean sound while also getting a cutting, tight rhythm/lead sound. Now, the upper mids cut a little better, some of the bottom end flub has been trimmed out of the lead mode, and the useable gain increased just a hair. The graphic EQ also seems to complement the lead channel a little better without having to use the typical "V" settings.

Hey great work man, my vote for post of the year. The circuit diagrams, tone samples, it's all good and the Studio sounds great.

This very week I was thinking, "hmm, it's amazing how my C+ just hangs together and both channels 'just work' even though there's all the shared dials "...

And to be honest I never understood what the + mod was really all about, I've never had IIC so I couldn't work it out for myself but I'm guessing the motivation was to make both channels happy and work better together. Maybe gain, the loop or something else changed in the process but I'll bet that's what it was mainly all about.

Cheers.

Those are very kind words. The more time I get to spend with the SP, the more I'm loving it these days. In fact, last night, I was mentioning to the other guitar player in my band that I was really missing the "idling diesel engine" clean sound you hear on a bunch of recordings, and then I simply flipped over to the Studio clean side, no comp, no effects, just clean, and wow! There it was! I didn't need change a thing on the front panel to get there either. Win-win!
 
Shane C said:
mboogman,

I want to do the C+ mod on my Quad. Im just in the planning stage, I have figured out most of it but I need a little help please:

1m = the lead drive pot correct? The only part I cant figure out is where to put the 680k before the 1M/lead drive, I could post some close-up shots of my Quad's board and label everything I can see for the mod if you or anybody can help me out?


Any info would be greatly appreciated.


Shane

I'd be glad to help any I can. I haven't seen the insides of a quad before though. I can send you some pics of the inside of my Pre after the mods if you like.
 
Hey sorry to interrupt, but I am very iterested in doing the IIc mod to my
Studio preamp!

MBoogman, Any pictures you could share with me would be greatly appreciated! Thanks in advance and have a Merry Christmas!
 
Howdy guys,

I hope you all had a great Xmas and all that jazz. Ive been doing a little research and I'd like to share.

I think the 170k resistor shown on the C+ modded Studio schematic is incorrect, the original MKIIC+ schematic is nearly unreadable and another version shows the resistor as being 1k. Also 170k is a non standard value which means its highly unlikely that it would be used. Here are the MKIIC+ schem's:

http://tubefreak.com/mk2c2.gif
http://tubefreak.com/mk2c.gif


The schematic's of the Studio, Quad, Mk3, Mk4 and MKV (IIC+ Mode) all show a 270k value for that resistor, also the MK4's lead circuit schem is IDENTICAL to the C+ modded Studio schem with exception to the 170k resistor in question.

I have read that the MK4's lead circuit is meant to be the same as the MKIIC+ and based on the component values shown, this appears to be 100% true. This leads me to believe that the stock 270k resistor is the correct value and does not need to be changed. Compare the C+ modded Studio schem to the MK4 lead circuit:

http://genitalhercules.com/~mcrowe/img/lead_C+mod.jpg
http://tubefreak.com/mk4-2.gif


Here is a link to the same Studio C+ Mod drawing that someone edited with some instructions, it might be helpful to anyone interested in doing the mod, but just ignore the 170k and keep the stock 270k:

http://voices.yahoo.com/converting-mesa-boogie-mark-iic-studio-preamp-3858698.html?cat=33#comments




mboogman said:
I'd be glad to help any I can. I haven't seen the insides of a quad before though. I can send you some pics of the inside of my Pre after the mods if you like.

Pics would be great thanks, maybe some close ups of the changed components? I have located all the parts to be changed on my Quad but just wanna make sure.


Cheers!

Shane
 
Forgive my ignorance, but does the deep mod and bass shift require a push/pull pot to be installed or is it a permanent "shift"?
 
The 170k is indeed incorrect. I forgot to mention that. I'm trying to remember what I used, but i think it was a 470k. I'll have to give the 270k a try to see if it works better.
 
Caligulus Boogie said:
Forgive my ignorance, but does the deep mod and bass shift require a push/pull pot to be installed or is it a permanent "shift"?

Hey Caligulus, yea the idea is to make the studio have switchable options so its more like a standard Mark Head.



mboogman said:
The 170k is indeed incorrect. I forgot to mention that. I'm trying to remember what I used, but i think it was a 470k. I'll have to give the 270k a try to see if it works better.

Hey mboogman,

Didn't you have the 270k in there as stock? Bigger resistor = less gain and this will affect the tone slighty as well. Also you might want to try 1000pf instead of the 500pf off the top of V3b. That cap is basically interchangeable and Mesa played with it a lot!! Here are the most common values used by Mesa Boogie throughout the mark series amps (that I know of) for that particular ceramic cap:

No Cap (Blue & Green Stripe MK3, Quad Preamp - Lead 1, Studio Preamp)
500pf (MK4)
500pf (Red Stripe MK3)
1200pf (Quad Preamp Lead 2)
2000pf (MK3 Black Dot)



Shane
 
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