Mesa MarkV / Saturation 'mod'

[bandit2013]

Why the JAN/Phillips 12AT7 works in the Mark V90W and does not in the older models. The Mark V uses two different tube positions for the drive (V5A) and high gain stage (V4B) that follows in addition, there is an additional gain stage in the works (V3A). Mark V has a total of six gain stages before the FX loop (V1A, V1B, V5A, V4B, V3A and V6A. The older models (IV, III, IIC+) only have 5 gain stages before the FX loop. IIC+ is V1A, V1B, V3B, V4A, V2A and the III and IV have similar topographies V1A, V1B, V3A, V3B, V2A Unfortunate for the IV and III that the drive and high gain stage share the same tube position V3 so the side effect of installing the 12AT7 into V3 probably will not result in the same effect. Comparable to the Mark V you would need to use a 12AT7 in V5 and V4. The IIC+ (original) does have separation and uses V3B as the drive and V4 as the high gain circuit. I did try the 12AT7 in V4 of the JP-2C (assuming it has the same topography as the IIC+) and the end result was less than enjoyable. Other than the separate circuits in different tubes, it is V3A that adds that additional grit before the final gain stage of V6A that has the intricate works for defining IIC+, IV and Extreme voices. There are some JFETS that pull in two different cathode bypass capacitors and I am uncertain if this is used on the lead channel or CH1 and CH2.


Other uses for the 12AT7 when it comes to the older versions would be better served in the Phase Inverter. I did try that in the JP just for kicks as it shares similar topography to the IIC+ and in some respects the Mark III and Mark IV. It added a bit more bottom punch and little effect on the top end response. It is not a dramatic change (at least in the JP) but notable.


I thing that most do not understand the effects of using the 12AT7 in place of a 12AX7 in their Mark V 90W. "Oh, that has lower gain, I want more gain not less" is the common comment I have read in Facebook where the 12AT7 mod is mentioned. Perhaps some of those that state the 12AT7 mod are followers here or came across this thread by sharing. I have gone back to the 12AX7 only to return to the 12AT7 as I enjoy the characteristics that tube swap provides. I know I have referenced the JP-2C on several occasions. I really cannot claim which is better. I also had a Mark III and Mark IV both of which are great amps too. The Mark V does have a unique tone on the lead channel using the stock complement of preamp tubes that sets itself apart from the predecessors. The 12AT7 mod in V4 of the Mark V will give you similar characteristics of the amps from yesterday but only better. In my opinion, I believe the Mark V has more gain on tap than the previous models. IIC+, MKIV and Extreme never sounded better. I used to think the Roadster had the most gain/ distortion level, yeah different family of amp but the Mark V is definitely robust in its grinding ability. I would agree with other statements regarding how I dial in the amp. I am learning new tricks on dialing in the lead channel to the point that this amp is very impressive. Now that is covered, I only wish I had a means to select IIC+, IV and Extreme on the fly vs the toggle switch shared on one channel.

 

[Markageddon]

Seems to me that people saying it has 'less gain' haven't experimented with dialling.
With higher preamp dialling on EQ dials and gain: its a case of 'more usable gain'.
More solid, gutsy and smooth yet searing in all the right ways.
And thats blatantly obvious in My V, V:25, III, and my friend's IV and another's V:35, plus like 10 or so other people who I've helped online who have a fair mix of the aforementioned models.

Could also be that their V1 is standard and/or worn and probably not SPax7 or Tungsol gold.
Thusly its all deducting from a weakened source in the 1st place.

Also who knows what else is affecting it...? Choice of pickups/quality of axe wiring etc
The marks are sensitive to these factors and of course the biggest commonly ignored factor: The playing technique involved.
Also some might just prefer Rectos or a Framus Cobra or may even just love quasi white-noise levels of distortion.
The marks just not that kind of amp. It gives back what you put into it.

 

[Wayno]

I agree whole-heartedly with you two.

The Mark V has has more than enough gain for ANY genre. True heavy is not a Line 6 Spider on the insane channel! Can't think of anything worse to be honest. True heavy is setup and technique, just think of how many bands still to this day use Jcm 800's! Nowhere near a high gain amp by todays standards. I remember seeing Sepultura in 1999 at Milton Keynes bowl and it was the heaviest live tone I've ever heard still to this day. And im 99% sure they used Jcm 800's. If it wasn't for the fact Metallica headlined therefore Big Mick had them louder than everyone else, Sepultura would have blown them off the stage. And that's from a full on Metallica fan boy, I'm not in the slightest bit ashamed to admit.

This saturation mod evolution has taught me many things.

The Mark series are iconic, but iconic for their specific tone. Which is not to everyone's taste. Using the AT7 to reduce the gain in specific places allows me to dial in MY tone, which is a variation of the stock core tone of this amp. Previously you had to follow the rules, gain up = bass down etc. I have iiC+ mode gain at 4 o'clock, bass and middle at nearly 1 o'clock. Treble around 2 o'clock and a barely there smile on the graphic. No flub, just dirty thick grind. No piercing highs present here. Sure, its not the amp for everyone, it is for me.

As for Newysurfer and his perfect out of the box Mark V...

Bully for you, the interwebs littered with complaints about Mark V uncomfortable highs. I stand by my statement.

 

[guijs]

Hello,

I have read the first 6 pages of this thread and just ordered a GE 12AT7 (could not find a Jan Philips in my country) to try in V4. I currently use a V30 speaker but i'll also try the C90 that came stock with the MKV combo (I converted to head).

Does this mod is equally audible in all 10-45-90w modes or more prominent in 90w mode? I usually play at home in 10w and 45w settings.

 

[mace]

Hi,

Good luck with the tube rolling! The V4 tube swap affects all channel 3 modes on all power settings. It doesn't affect channel 1 or 2.

This thread should be condensed and stickied to the top of the forum.

 

[guijs]

Thanks Mace! The AT7 is already in V4 and the results are excellent as expected!

As for speakers, are guys enjoying more the V30 or C90 with this mode?

 

[dlpasco]

I thing that most do not understand the effects of using the 12AT7 in place of a 12AX7 in their Mark V 90W. "Oh, that has lower gain, I want more gain not less" is the common comment I have read in Facebook where the 12AT7 mod is mentioned. Perhaps some of those that state the 12AT7 mod are followers here or came across this thread by sharing. I have gone back to the 12AX7 only to return to the 12AT7 as I enjoy the characteristics that tube swap provides. I know I have referenced the JP-2C on several occasions. I really cannot claim which is better. I also had a Mark III and Mark IV both of which are great amps too. The Mark V does have a unique tone on the lead channel using the stock complement of preamp tubes that sets itself apart from the predecessors. The 12AT7 mod in V4 of the Mark V will give you similar characteristics of the amps from yesterday but only better.

(strongbad voice) I am not an electrographist, so my grasp of what is going on internally with the 12AT7 substitution is pretty poor, but it definitely works.

I haven't looked at the master volume level or output levels I gravitate towards when using AX7s vs AT7s but I'm pretty sure the amp volume drops a bit with the AT7s in place. Maybe we're just cranking the volume on the lower gain tone more and getting an overall improvement in the final gain structure as a result? (more power section gain, etc).

 

[Markageddon]

It does have that fat organic thing that that offers, for sure... but theres a quality to it that suggests its something other than simply turning down the preamp gain on a stock V. It feels like 'the same amount of gain, but smoother', to me..especially on the V:25. Pre-swap I used the less preamp gain trick to stand out in metal bands with with the other guitarists playing with real high gain..... and it worked in a similar way, but you still had the undesirable higher frequency thing in the sound.
The tubeswap completely eradicated that and left nothing but full fat goodness.
The tungsol V1 variant of this mod is legendary level good for live and recording perhaps making sure that the amount going in the front was fuller/more somehow frequency spread wise in the first place before deduction, im guessing...? And the way the power stage then acts on these different set of frequencies could be the difference?

Been getting really good results with the V, V:25 and III all with these tubesets. I've never been happier, and neither has my recorded tone.

Happy new years guys.

 

[Wayno]

Happy new year all :twisted:

 

[ehehat]

I'm new to the MK V and just stumbled upon this thread. There's a TON of information here! Can i please just get a down and dirty update? Maybe update the OP? Not looking to do anything but the AT7 swap. Is it just V47? Just V6? Both?

Thanks!

 

[mace]

I'm new to the MK V and just stumbled upon this thread. There's a TON of information here! Can i please just get a down and dirty update? Maybe update the OP? Not looking to do anything but the AT7 swap. Is it just V47? Just V6? Both?

Thanks!

If you have a single AT7, try it in V6 for a while, then in V4. If you have a couple of AT7s, try them in both V4 and V6. See what you like best! I stuck with the AT7 in V6 and have been running that way for quite some time. I’m not the OP btw.

 

[ehehat]

I'm new to the MK V and just stumbled upon this thread. There's a TON of information here! Can i please just get a down and dirty update? Maybe update the OP? Not looking to do anything but the AT7 swap. Is it just V47? Just V6? Both?

Thanks!

If you have a single AT7, try it in V6 for a while, then in V4. If you have a couple of AT7s, try them in both V4 and V6. See what you like best! I stuck with the AT7 in V6 and have been running that way for quite some time. I’m not the OP btw.

Thanks for the input. I have 2 on the way and will play around when they get here. Does this improve overall sound or only when the loop is on?

 

[Markageddon]

V4. V7.

That is all.

 

[Eevil]

I'm new to the MK V and just stumbled upon this thread. There's a TON of information here! Can i please just get a down and dirty update? Maybe update the OP? Not looking to do anything but the AT7 swap. Is it just V47? Just V6? Both?

Thanks!

If you have a single AT7, try it in V6 for a while, then in V4. If you have a couple of AT7s, try them in both V4 and V6. See what you like best! I stuck with the AT7 in V6 and have been running that way for quite some time. I’m not the OP btw.

I tried the AT7 first in V4 and it did not work at all but then I swapped the AT7 to V6 and it really was magical cure for cold and stingy high end the amp was putting out. I was (and still am - haven’t tested with today’s ears) struggling with channel 2 pointy high mid but it’s not so prominent anymore.

In the end this was cheap mod with great results I may revert to stock at some point but let’s see.

 

[jp1seattle]

V4. V7.

That is all.

AT7 in the V7?

I also got a couple Jan AT7’s after reading this thread.

Now that it’s dialed in, this amp (90 combo) is really great.

 

[Markageddon]

Yup. In the Phase Inverter. Try it.
The V4 one does the typical AT7 drive perfomance, the Phase Inverter one appears to enhance that massive 3d sounding vintage Markness across all channels. Ive had all my amps in 'this-config-or-similar-to' for a year and a half. Never looked back.

I also use Tungsol 12AX7s for the 1st stages of the preamp too to keep it coming in well in the front end in the first place.

 

[Thaymz]

Yup. In the Phase Inverter. Try it.
The V4 one does the typical AT7 drive perfomance, the Phase Inverter one appears to enhance that massive 3d sounding vintage Markness across all channels. Ive had all my amps in 'this-config-or-similar-to' for a year and a half. Never looked back.

I also use Tungsol 12AX7s for the 1st stages of the preamp too to keep it coming in well in the front end in the first place.

Didn't know about this v7 enhancing 3d. Excellent to know, I have a spare Jan Philips so look forward to giving it a go.

 

[Markageddon]

Yeah it definitely sounds that way to me. In my III, V and V:25.

Good man. Let us know what you thought!

 

[psihiatros]

Yup. In the Phase Inverter. Try it. The V4 one does the typical AT7 drive perfomance, the Phase Inverter one appears to enhance that massive 3d sounding vintage Markness across all channels.I also use Tungsol 12AX7s for the 1st stages of the preamp too to keep it coming in well in the front end in the first place.

Hi, great info there!
If you were about to get new tubes for the Mark V (for all positions), would it be possible to give us a quick rundown so that we could get the most out of it? Like,
Position/tube type/tube manufacturer/supplier?
I live in Europe btw.
Thanx in advance

 

[Markageddon]

V1) Tungsol 12AX7 Goldpin
V2) Tungsol 12AX7 Silver
V3) Tungsol 12AX7 Silver
V4) Mesa 12AT7
V5) Tungsol 12AX7 Silver
V6) Mesa 12AX7
V7) Mesa 12AT7

Try that config. It sounds/feels awesome on my V.

Ive got an equivalent setup in the V:25 and Mark III too.

Its worth noting that the Mesa SPAX7 is also good for V1, but the its sounds like it has like a more modern/selective frequency thing happening compared to the Tungsol Goldpin. Both are good for introducing high sound/power-to-noise ratio. (All the sound, less of the hiss.)