Mark IV mod to get closer to III?

Looking for some additional info on mod options for a Mark IV that get it closer to the III's relatively more aggressive, raw, and tight characteristics. I read a ~14 year old post on another forum about someone who worked with Mike B to have this done, but the details were next to nothing. So I am curious to see if anyone had any more details.

The IV is one of my favorite amps of all time. But I recently started to take more notice of the Mark III and really like the even more raw, aggressive, and tight characteristics of it, especially the Blue and Green Stripes. If I could get a IV modded to adopt some of these characteristics I would pretty much have exactly what I want. Can anyone shed any light on this?

Also, I am wondering if there are any mod options for the second channel. If I could have it my way, I would mod this channel to be closer to the second channel on the Mark V. The Crunch, Mark I, or even the Tweed voicings on the V are significantly more useful for me, but I prefer the IV over the V.

I wound up sending a RMA request to Mesa asking the same question about these mod options. I am in talks with a seller of a Mark IV rev a that will need some servicing, so I am looking to send the amp direct to mesa for this work and modding at the same time.

I'll plan to follow up with any feedback that I get for others to reference. Below is a copy of the question for reference.

I am looking to mod the IV’s lead channel to adopt some of the characteristics of the Mark III Blue or Green Stripe. It would be ideal if my IV could have more of the raw, aggressiveness, less compression, and tightness of the III. On the other hand, I tend to prefer the slightly more pronounced mids of the IV compared to the III, so I would prefer not to lose that. I also like how the IV seems to be relatively easier to saturate and get a bit looser tone out of, when desired, so it would be ideal if that could be retained to some degree while moving away from the IV’s relative smoothness and compression compared to the III.

Additionally, I would really love to tweak the Rhythm 2 channel too, if possible. I would be happy with a variety of alternatives depending on what was possible, and I am not that worried about any mods affecting channel 1 if that was a trade off. I am basically looking for channel 2 to be relatively thicker, warmer, and have some more gain on tap. I absolutely loved channel 2 in the Mark V 90 watt that I owned for 5 years. The Crunch voicing was incredibly useful and the Mark I voicing was great too. I was also a big fan of the Tweed voicing in channel 1. Some other inspirations would be the Blues voicing from the tremo verb, any of the mid gain voicings from the Roadster/Roadking, pushed clean from the new rectifiers, etc. For this particular amp, I would also greatly welcome channel 1 becoming an additional variation of a low to mid gain, overdriven channel if that could be part of the mod process too.

Is it fair to interpret the lack of replies as either 1) Mark IV mods do not exist for the most part, at least in regards to going "backwards" into Mark III territory or 2) this might have been attempted before and the results were just not so good? Mesa has not responded to my question either.

FYI my goal here was to have kind of the best of both worlds hybrid III/IV with a modded IV. i.e. the raw, aggressive, and less compressed character of the III coupled with the additional boldness and somewhat different midrange grind of the IV.

If a modded IV is probably not a good way to accomplish this, the next thought I am starting to toy around with is to still get a Mark IV Rev. A as well as a Quad Preamp and find a way to blend both preamps signals (primarily using the Mark III channel 2 mode from the Quad) into a single channel that is then fed through the power amp of the IV. I recall seeing ABY amp head switchers that can blend the signal from two full power amps into one cab, so I don't see why this would not work with preamp signals.

I was also starting to look into a Mark III green stripe and doing some mods to that instead (at a minimum a pentode/triode switch). In fact, I was going to buy one from a guy off of Craigslist yesterday, but it was jacked up in too many different ways after a seemingly botched servicing job so I passed.

Tiger1016,
I can't speak to any mods for the Mk IV. You might try some different, i.e. lower gain, preamp tubes to try and tame the compression. Whether or not that would get you into Mk III territory I don't know. I do know it is absolutely possible to feed two preamps into one power amp. I do that with my Mk III and a Diezel VH4 preamp pedal. I split the signal in front of the amp using a Suhr buffer.
https://www.suhr.com/electronics/tone-tools/suhr-buffer/
One output goes to the Mk III, the other to the Diezel. Use the phase switch, if necessary. The output of the Diezel then gets patched into the effects loop return using a Y cable like this:
https://reverb.com/item/32704632-hosa-technology-y-cable-1-4-in-ts-to-dual-1-4-in-ts-5-ft
I think it sounds great!

skelt101 said:

Tiger1016,
I can't speak to any mods for the Mk IV. You might try some different, i.e. lower gain, preamp tubes to try and tame the compression. Whether or not that would get you into Mk III territory I don't know. I do know it is absolutely possible to feed two preamps into one power amp. I do that with my Mk III and a Diezel VH4 preamp pedal. I split the signal in front of the amp using a Suhr buffer.
https://www.suhr.com/electronics/tone-tools/suhr-buffer/
One output goes to the Mk III, the other to the Diezel. Use the phase switch, if necessary. The output of the Diezel then gets patched into the effects loop return using a Y cable like this:
https://reverb.com/item/32704632-hosa-technology-y-cable-1-4-in-ts-to-dual-1-4-in-ts-5-ft
I think it sounds great!

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Great info and good to hear. **** a VH4 + Mark III. Sounds like you are going all out on some raw, aggressive, and in your face kinds of tones. Bet it sounds awesome and something I would enjoy as well.

I had nearly forgotten that I could use the Axe Fx III that I have to function as my channel switcher and blender for the two preamps. I plan to replace that with a Neural Quad Cortex once they are available, but that should also be able to serve the same purpose.

Have you ever considered getting a Mark III and doing the "+" mod?

From samples posted, it seems to have more smoothness than a stock Mark III (and slightly more compression), but more rawness/aggressiveness/openness than a Mark IV.

Perhaps III+ owners could talk more about it.

erickompositör72 said:

Have you ever considered getting a Mark III and doing the "+" mod?

From samples posted, it seems to have more smoothness than a stock Mark III (and slightly more compression), but more rawness/aggressiveness/openness than a Mark IV.

Perhaps III+ owners could talk more about it.

Click to expand...

I have been actively looking into the III+/++ mod options. Definitely interesting, but the preliminary conclusion I have come to is it is probably not for me. I was wanting to push a IV closer into III territory, because I like the III's rawness and aggression, instead of pushing a III into IV territory by making it relatively smoother and more compressed. And I would still want to run both this modified IV and a III or Quad preamp together.

However, I got a call back from Mesa yesterday evening and Chris confirmed that they do not have any supported mods for the IV and that there would probably not be much to try to tinker around with it to make it closer to a III because there are too many differences between the amps. So other than some preamp tube rolling and pre and post EQ magic, there is nothing else to do to try to adjust a Mark IV in any particular direction.

Soo... It looks like the idea I had to pair a Mark IV Rev. A with a Quad preamp and get creative with blending the two preamps together in an Axe Fx III would be the only way to get the hybrid III & IV that I am really interested in trying to create.

The problem is trying to find a used Quad in the first place. Seems like I will likely have more luck with finding a III first. But I just got spooked on buying any of these options used without being able to try because I went to check out a Mark III Green stripe two days ago from a local Craigslist seller, and the amp was all sorts of messed up. It had been serviced by an unlicensed repair shop, and I could not even get the thing to flub out with the bass and gain dials on 10 (it still sounded like a light and bright crunch like this) and the freaking reverb dial acted as an additional, third volume knob on all 3 channels.

Now why would you wanna do that? When I sold my red stripe III and bought a IVb i never looked back. The biggest difference was recording. The IV records really well and sounds very professional, the III on the other hand was a pain to record and always sounded cardboardy and harsh. It just didn't like to be recorded. I think the IV is the best Mark series amp besides the IIc+. It also stayed tighter at band volumes with a more pleasant top end to it. While the III can be fatiguing on the ears at high volume. IMO you should Keep the IV the way it is.

rgx612a said:

Now why would you wanna do that? When I sold my red stripe III and bought a IVb i never looked back. The biggest difference was recording. The IV records really well and sounds very professional, the III on the other hand was a pain to record and always sounded cardboardy and harsh. It just didn't like to be recorded. I think the IV is the best Mark series amp besides the IIc+. It also stayed tighter at band volumes with a more pleasant top end to it. While the III can be fatiguing on the ears at high volume. IMO you should Keep the IV the way it is.

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I wound up going with a IIC+ HX with EQ in the loop and various drive pedals in the front and parametric EQ after IRs. I am shaping my way to the exact tone that I want with the awesome feel that the IIC+ brings to the table.

And the second amp I got to pair with the Mark was a Wizard Modern Classic I MCI 100 watt.

I am 100% with how everything has turned out so far.

The Mark IV can't be modded or it would become unstable. That's according to Mike B. himself. I basically wanted two ch.3's. He and I went back and forth on this subject. No contest, he won.
The Quad pre amp I have, I would like to even out the channel volumes, it can't be done without sacrificing tone, so I'm told. I believe it.