Triaxis Undoing the Fat Mod (Guide)

Triaxis, Quad Preamp, Stereo Power series, Recto Preamp

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Inkomodo.Dragon
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Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Wed May 23, 2012 5:13 pm

Introduction

I'm not what you would call an active member of the forum but since I got most of the information for this mod from here I thought it would be nice to give a little back to all of you. Let me start by saying that this mod is really simple but the Triaxis is not. As a matter of fact it's a fragile and complex unit. This is why I don't encourage anyone without previous soldering experience to perform the mod.

The other thing to say would be that you should pay attention while working on any tube device since there may be lethal voltages and all that crap. But if you are confident enough to work on a Triaxis you probably know what you’re doing and if you don't maybe you shouldn't be such a cheap bastard and send your unit to Mesa.

Now that we got that out of the way...let's fire up that soldering iron and start taking out the bazillion screws this thing has :?


Initial information

I've seen two pieces of information regarding this mod one is this picture and the other one is a little text saying pretty much the same. I've also read that it seems to be some degree of inconsistence between boards so I took this schematic from tubefreak.com and opened up my unit. I checked every part of the hand written schematics and it was almost exactly like it was on my Triaxis. The only difference was the order of C12 and R46 but since they are in series it doesn't matter. So from what I could gather the instructions for the mod make sense.

The mod takes place within the TX4 board which is the one Mesa added specially for LD1 Red and doesn't alter the other modes in any way.

I can tell my unit is V2 because it shows 2.0 all over the display on startup, the serial number is 62XX and it has MIDI continuous control capabilities.

I can tell is a Fat mod because, aside from sounding like poop on that mode, the factory presets are as follows:

Preset 10: 6.0 6.0 7.0 8.0 2.0 0.0 5.5 2.0 0.0

Preset 11: 6.0 6.5 7.5 7.0 5.5 0.0 4.5 5.0 0.0

I should mention that it's impossible to get a decent tone from LD1 Red as it is. Yes, it sounds fat, but it’s a loose and undefined kind of low end. So if you find your unit to behave this way on that mode you probably want to get rid of the Fat mod.


Sound Differences

Before you even consider performing the mod I would like to state that after I did it to mine it sounded amazingly tight and focused but there is an overall fizz factor that's hard to tame. I think this is the stuff that made them create the fat mod in the first place. It is the same kind of fizz that you can find on a JCM800 and it’s not that easy to eliminate. Either way I think Mesa’s “solution” was quite poor. I’ve worked on a lot of Marshallesque designs so I know a thing or two about this kind of distortion and there are a couple of improvements I will be trying out in order to make this mode fully controllable but for now let’s focus on undoing the Fat mod. If you still want the original "Recto" sound keep reading. My opinion is that it is way more usable than the Fat mod but you may differ.


Mod Details

The mod can be separated in three parts, the first one changes the filtering between the first and second gain stages. The second one alters the tone stack section and the third one change the effect of the mid and bass EQ settings.

Since the unit is crammed inside and the TX4 Board is really close to the top cover you should make sure the new caps don't stand up too tall.
There's no need for measuring, just compare their height with the existing components. That alone will ensure proper clearance.

These are a couple of pictures of my unit's TX4 board as it was when stock.
Image Image

Looking at the first picture, locate the three places where the mod is done. Part one is on the top left corner of the board. Part two is on the top right corner and Part three right in the center of the board.


PART ONE
  • Replace R45 with 330k
  • Replace C22 with 47p
  • R46 = 82k
  • C12 = 1n
The following schematic shows the difference between my unit and the Recto version.
Image

These pictures show the steps...
Image Image Image


PART TWO
  • Replace R9 with 120k
  • Replace C6 with 1n
  • C5 = 1n
  • R44 = 33k
C6 was 1n on mine but that's not the case with all the units. I removed it anyway to show where it is.

Difference between my unit and the Recto version.
Image

Steps...
Image Image Image

Notice I used a 3k3 resistor for R44 instead of the correct 33k value. The original value is 33k.

PART THREE
  • Replace R33 with 1M
  • Replace R34 with 10k
Just two pictures for this one...
Image Image

THATS IT! :mrgreen:

I was going to make before and after sound bites but I got carried away and forgot to record the before one...sorry guys :)

Hope this info helps
Last edited by Inkomodo.Dragon on Tue Oct 01, 2019 10:23 pm, edited 3 times in total.

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daveg62
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Re: Triaxis Undoing the Fat Mod (Guide)

Post by daveg62 » Fri Jul 13, 2012 8:54 pm

Just finished doing this mod tonight, plugged it in just to make sure everything is working. Seems good, will have to wait until tomorrow to really see if I like the change. I really didn't like the lead 1 red channel at all with the fat mod so I figured it's worth a try to see if I like it any better reversed. It's definitely different, I will report back when I get a chance to really audition it.
Thanks for the great instructions!
my current rigs:
86 Mesa Mark III blue stripe simul-class limited maple combo - mesa thiele EVM12L 1x12
Mesa Triaxis - Matrix GT800 power amp - EarCandy Buzzbomb 2x12
Digitech gsp1101 w/ Control2 footcontroller

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Inkomodo.Dragon
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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Sat Jul 14, 2012 6:37 am

daveg62 wrote:Thanks for the great instructions!
You're welcome Dave!

Let me say you'll not regret it.

At first I was a bit skeptical as you may have seen from my first post but now that I've had time with it I find LD1 Red to be one of my favorite modes. There is no other mode for metal rhythms period.

One thing I forgot to add is that you should pay attention to the height of the new components. If you use big caps you may have a problem closing the unit after you are done. I'll add that to the first post just in case.

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by daveg62 » Sun Jul 15, 2012 7:19 am

Well there is no question, LD1 red is now much, much better. Before I didn't like it at all, it seemed way too different than all the other modes and just was not my cup of tea. Now it seems to fit in with the other modes much better. I will definitely be using LD1 red now. I'm 100% satisfied and glad I did the mod.
As far as the mod, I would not recommend this to anyone who does not feel comfortable soldering small components or have the right tools. Please take it to a tech to have it done. This mod is not for the inexperienced. I didn't have a problem but it's not something that just anyone can do.
my current rigs:
86 Mesa Mark III blue stripe simul-class limited maple combo - mesa thiele EVM12L 1x12
Mesa Triaxis - Matrix GT800 power amp - EarCandy Buzzbomb 2x12
Digitech gsp1101 w/ Control2 footcontroller

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by rascarvalho » Sat Aug 04, 2012 6:51 pm

Dear,
First of all, thanks a lot for your project.
I made it and I like the result too much, but i have one question: The Cap C12 (1n) must be poliester or can be ceramic? This is the only difference I saw between my mod and yours. I use a ceramic capacitor on C12 and all resistor is 0,25W.
After mod complete, when I use gain 10 and Lead 1 drive 10, the sound cut off (like a clip). There are some that a need to change to lead 1 red channel don't clip like this?
Thanks again and sorry for my english.
Ricardo.

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Inkomodo.Dragon
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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Sat Aug 04, 2012 7:14 pm

You're welcome Ricardo,

There's no problem if you use a ceramic cap for C12. Some guys will say they prefer poly types for those applications but the difference is barely noticeable. I wouldn't worry too much about it.

As for your clipping problem, I've never had the need for that amount of gain so I never tried both levels on 10.From the way you describe it I think it might be blocking distortion due to the amount of gain you're using but I can't be sure if I don't hear it so if you want to record a little sample that would be very useful.

-------UPDATE---------

I've just tried my unit with every control at 10 and I can hear it's starting to have some blocking distortion but it's not that bad. If you are using higher output pickups than mine it may be a lot worse. There are ways to overcome this by changing some resistor values but I wouldn't suggest you do that. I think you should lower the Gain control to around 6.0 (since that's the value Mesa suggests for that mode) and adjust your overall "gain" from Lead 1 Drive. I also suggest you take a look at the manual since there is a lot of info on how to dial the different modes.

Hope this helps

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by rascarvalho » Sat Aug 04, 2012 8:10 pm

Inkomodo.Dragon wrote:You're welcome Ricardo,

There's no problem if you use a ceramic cap for C12. Some guys will say they prefer poly types for those applications but the difference is barely noticeable. I wouldn't worry too much about it.

As for your clipping problem, I've never had the need for that amount of gain so I never tried both levels on 10.From the way you describe it I think it might be blocking distortion due to the amount of gain you're using but I can't be sure if I don't hear it so if you want to record a little sample that would be very useful.

-------UPDATE---------

I've just tried my unit with every control at 10 and I can hear it's starting to have some blocking distortion but it's not that bad. If you are using higher output pickups than mine it may be a lot worse. There are ways to overcome this by changing some resistor values but I wouldn't suggest you do that. I think you should lower the Gain control to around 6.0 (since that's the value Mesa suggests for that mode) and adjust your overall "gain" from Lead 1 Drive. I also suggest you take a look at the manual since there is a lot of info on how to dial the different modes.

Hope this helps
Well... again, thanks!
Really, I won't use gain 10 and drive 10, i was just testing and I observe this!
My cap is a Dimebucker, and a know this have a very high output. With gain on 6 or 7, the sound was great!
I bought my triaxis one week ago (used one), and i already made this mod.
I have a rocktron piranha too, i comparing with triaxis, I observe this one have more noisi than rocktron. The rocktron has a hash mode (like a noise gate), and the sound is so good. What can I do with triaxis to have something like this? I don't have a gate stomp box, just a gate on my g-system, and, to eliminate the noise, i need to put a lot of gate. There are another way to do this?
Thanks again!

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Sun Aug 05, 2012 10:35 am

Well, noise can come from various sources. If the noise you hear is a bit of hiss then there is no problem because it is normal. If the noise has a pitch it may be ground or wire related. What I would do is turn of the Hush on the Piranha before making a comparison.

Sound clips would really help.

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by retnuH » Sun Feb 10, 2013 3:45 pm

Thanks for all the good info on the mod. I had a Triaxis many years ago with the Fat mod and I didn't like it. I am getting ready to buy another Triaxis when the right one comes up on eBay and expect to do this mod. Since I don't have one handy to see what they are, can you tell me the resistor wattage I need to order? It's hard to tell from the pics and I want to go ahead and order them in before I actually get the Triaxis. Also any other info about the parts list would be helpful. Thanks!
Hunter

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Mon Feb 11, 2013 8:07 am

retnuH wrote:can you tell me the resistor wattage I need to order?
No problem, 1/4W carbon or metal-film would be fine.

I used metalized polyester caps except for C22 (48p) that was ceramic. I wouldn't suggest using high mojo (Mallory, Sozo, Sprague Atom, etc) caps as they are huge and they will not fit. Besides the Triaxis never used those kind of components.

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by SigiZ58 » Sun Mar 23, 2014 5:12 pm

Thank you for this reverse mod.

I wanted to start this, but during collecting parts and preparing work something did not seem to be correct.
Sorry, but I will describe.

Step 2 - when you compare you schematics with the fotography
In The schema, FAT Mod, C6 & R9 have parts. In the corresponding photo, R9 and C6 are empty (same as on my board)

Does this mean we have no FAT Mod ? What is wrong ?

Other question: When looking in the internet (and examining several fotos with TX4, the resistor for R44 seems Triple orange what would mean 33k and fits with an other description for making fat mod undone...

Can you explain ?

Nevertheless - great work and many thanks

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Mon Mar 24, 2014 9:33 am

I forgot to take the picture before I removed C6 and R9, my bad.

But they where there, R9 was 2k7 and as I said C6 was 1n on mine but that's not the case with all the units.

As for R44, I checked my notes and it was supposed to be changed to 33k but I lowered it to 3k3 because it sounded better to me. I clearly forgot to tell you all that. The lower the value the less high freq you get.

Hope that helps!

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by SigiZ58 » Mon Mar 24, 2014 6:01 pm

Hi,

thanks for your reply. But what I mean with step 2 is following:

schema FAT Mode: C5 & R44 empty, R9 is 2k7-C6 is 1nF
Foto FAT Mode: R9 & C6 is empty, R44 is 2K7-C5 is 1nF
You see what I mean ? The discrepancy foto/schematics with R9/R44
The point is, that this becomes only important when you want to have the phat mod again :-)
That phat mod needs R44 (2k7) and C5(1nF).

BTW the foto is exact the status that is on my board also.

schema Recto Mode: C5 is 1nF, R44 is 3K3, R9 is 120K

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Re: Triaxis Undoing the Fat Mod (Guide)

Post by metropit » Sun Apr 03, 2016 10:58 pm

Non-fat mod R44 seesm to be 33k (instead of 3k3) from the photo, anyone can confirm this?
MK V Combo + Rectifier 2x12 Cab
Lonestar Classic 2x12 Combo
Express 5:50 1x12 Combo
Triaxis v2.0 w/TX4-D Fat Mod
Quad Preamp
JP2-C Head
Maverick Head
Subway Rocket
High Gain Amp Switch

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Inkomodo.Dragon
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Re: Triaxis Undoing the Fat Mod (Guide)

Post by Inkomodo.Dragon » Tue Oct 01, 2019 10:41 pm

Just bumping the guide as I re-uploaded the pics. Better late than never :roll:
metropit wrote:
Sun Apr 03, 2016 10:58 pm
Non-fat mod R44 seesm to be 33k (instead of 3k3) from the photo, anyone can confirm this?
The original value for R44 is 33k, don't pay attention to what I soldered there as I was just testing different values.

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