Mesa MarkV / Saturation 'mod'

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APEMAN
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Re: Mesa MarkV / Saturation 'mod'

Post by APEMAN » Tue May 23, 2017 2:30 am

Giz-Tone wrote:Forgive my lack of knowledge on this topic; but wouldn't using a different pre amp tube than a 12AX7 in the Mark V damage the amp?
As far as I know, from a technical side nothing speaks against a 12AT7 as a substitute for a 12AX7 - compared to 12AX7s gain (100%) you get less gain with the 12AT7 (70%).

But you can NOT always substitute a 12AT7 against a 12AX7 because the 12AT7 can handle more current.... but this is off topic here.


Hey bandit, I was offline for a view days... Just listened to your recordings. I think it captures the audible impact in front of the speaker quite well - but we both know there is more happening in the room that is hard to catch with the mic. The overall difference is far bigger if you stand in front of the amp - the rock-solid bass fundament that you get with the 12AT7.

What 12AT7s does Mesa use? I got a JJ ECC81 flying around somewhere... I think I give it a try. But overall, I'm still very happy with the Vs CH3 now. To me, CH2 crunch was perfect - now CH3 starts where CH2 ends and goes beyond - they fit together perfectly. Actually, it sounds so good I don't care anymore if it is MarkIIC, MarkIV or JP - fact is, I love it! :)

bandit2013
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Re: Mesa MarkV / Saturation 'mod'

Post by bandit2013 » Tue May 23, 2017 6:13 am

Mesa is using a Shuguang 12AT7. It can be found on the RA100 for the FX Loop, same tube used in the TC-50 for the same purpose. It look like the following but with the Mesa logo:

http://www.thetubestore.com/Tubes/12AT7 ... uang-12AT7

I had my doubts on the substitution of the 12AX7 with the 12AT7 in terms of maximum applied plate voltage. 12AX7 maximum rating is 330V where as the 12AT7 is 300. However, I do not believe an amp designer will run the tubes at their maximum plate voltage unless they want them to have a short life. I did look at the schematic to calculate the maximum currents if the tube was shorted and then looked at the operating point to determine the applied plate to cathode voltage with assumed current flow to be half of the short circuit current. It does not appear that V4 will pose any issues for the 12AT7 based on standard specifications for the tube and rough analysis. I would have to work out load lines and perhaps take voltage measurements to determine the impact. Also the other half of V4 is the driver circuit for the reverb that is pulling the current through the reverb transformer. Voltage would be easy to measure across the tube that I may do this weekend so I can get a better idea if the 12AT7 is at its limit based on idle conditions. I would like to know for myself what if any critical condition may result.

As for the recordings, may have to run it again with some other mics (perhaps over mic the amp) and see what the result will be. I could also use the attenuator and push the amp to the sweet spot, at least I will not be clipping the mics or the mic preamps. Not sure what the SPL is with the JP-2C but I had to adjust everything to record and I was not running the amp where I like it. Mark V on the other hand about the same so the attenuator may have to be used. No big deal as I am working out a project and will have to do this anyway so may as well find out what works now.

bandit2013
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Re: Mesa MarkV / Saturation 'mod'

Post by bandit2013 » Thu May 25, 2017 9:20 pm

Now I am even more impressed. All this time I have been using pentode on CH3, sounds even better on triode. Just for kick I swapped the MC90 in the combo with an EVM12L just to hear the difference. Nothing wrong with the MC90 as it was a new replacement I bought since my combo was a conversion. Sweet. Also had to swap the Mesa (JJ) tube with the old Mesa Chinese in V2 to get that monster tone. Mark V is all set. Interesting when you push the gain all the way up in CH2 crunch it is similar to the Mark IIC mode in CH3 if you use the sliders for CH3 and the preset for CH2 with EQ active of course. Too bad no tube fix for the send level on the FX loop (that is supplied by the EQ circuit). Can't win them all I suppose.

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Re: Mesa MarkV / Saturation 'mod'

Post by elpingua » Sat May 27, 2017 9:28 am

Can anyone recommend a good place (in US) to Jan GE 12AT7 tubes? I see some on ebay they appear used.

Perhaps?:
https://tubedepot.com/products/12at7wc- ... AkZx8P8HAQ

Im a noob when it comes to tubes. Should I select any options such as high gain or low noise? Or can someone else just recommend where to buy.
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bandit2013
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Re: Mesa MarkV / Saturation 'mod'

Post by bandit2013 » Sat May 27, 2017 6:57 pm

That is the Jan/Phillips 12AT7, same tube I am using. Good price too. The GE version may cost a bit more. I see they also have other varieties in the JAN category, Sylvania RCA and Tung sol. I should shop at tubedepot than the other place...

mace
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Re: Mesa MarkV / Saturation 'mod'

Post by mace » Sun May 28, 2017 8:38 am

I've had good luck getting tubes from dougstubes.com. They also offer "sets" of tubes for different amps.

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Re: Mesa MarkV / Saturation 'mod'

Post by IronSean » Mon May 29, 2017 9:16 am

elpingua wrote:Can anyone recommend a good place (in US) to Jan GE 12AT7 tubes? I see some on ebay they appear used.

Perhaps?:
https://tubedepot.com/products/12at7wc- ... AkZx8P8HAQ

Im a noob when it comes to tubes. Should I select any options such as high gain or low noise? Or can someone else just recommend where to buy.
The JAN-Phillips tubes are no longer in production, like most classic tubes these days. (In fact, there are only three remaining tube factories, Shuguang in China, JJ's factory in Slovakia, and New Sensor in Russia (which makes all the new/remake version of Sovtek, Tung-Sol, Mullard, EletroHarmonix, etc. because they bought a bunch of the trade names). (Then Groovetubes, Ruby, and Mesa buy those tubes, test them, and rebrand them, but that's a whole other story)

But this means for many of the classic tubes you only have two options: Used, as you've seen on Ebay. And NOS, or New Old Stock, which are are leftover boxes of brand new tubes from when they were still being made. Now, since many of these tubes haven't been made since the 30s-80s, obviously true New, never used, old stock, is getting rarer. But some of the specialty tube shops (Doug's Tubes, The Tube Store, maybe Tube Depot) would be as trustworthy as anyone on them at least being tested and working.

For High Gain or low noise, it really depends on your uses. High gain can be helpful for a tube in a gain generating position where you want to get a bit more gain, but in the Mark V I think you've got enough on tap to not worry. And Low noise can be helpful especially for the first tube in the chain (V1) because any noise there gets amplified with every other tube it passes through. For the late stages this thread is talking about I also wouldn't worry.
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APEMAN
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Re: Mesa MarkV / Saturation 'mod'

Post by APEMAN » Tue May 30, 2017 9:13 am

Giz-Tone wrote:Forgive my lack of knowledge on this topic; but wouldn't using a different pre amp tube than a 12AX7 in the Mark V damage the amp?
http://www.mesaboogie.com/tubes/pre-amp ... 12AT7.html

"... but the 12AT7 can also be substituted in 12AX7 gain stages where users are seeking lower gain response from higher gain positions in the preamp string. ..."

"... The lower gain output of 12AT7s can expand the range of clip and overdrive potential of higher gain amps for truly authentic roots and traditional styles. ..."

You have to know in general I'm not that illuminati-conspiracy type of guy, but the more I think about this 'mod', the more i doubt this being a lucky accident. RS builds this amps for quite a while and I think he knows exactly what he is doing. Maybe he gave those who search for the old school mark sounds this kind of backdoor to reach it. Could be, who knows...

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Re: Mesa MarkV / Saturation 'mod'

Post by barryswanson » Thu Jun 01, 2017 5:24 am

So I got me one of these tubes. Does it go in V4 or V6?

APEMAN
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Re: Mesa MarkV / Saturation 'mod'

Post by APEMAN » Thu Jun 01, 2017 5:45 am

http://forum.grailtone.com/viewtopic.ph ... 30#p496987

...in V6 the effect is more subtle and just removes the ice pick.
...in V4 changes the 3CH gain structure what almost makes an another amp (- more like the JP2C).

Give it a try!

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Re: Mesa MarkV / Saturation 'mod'

Post by bandit2013 » Thu Jun 01, 2017 6:00 am

I prefer the 12AT7 in V4 as this puts the Mark V on par with the JP-2C.

Hijack attempt, not intentional..... I also use an old Mesa tube in V2 as this alters the CH2 character just a bit. Still sounds about the same but eliminates that nasal tone I was getting with the current Mesa 12AX7 (re-branded JJ ECC83S, don't forget they are also sorted per Mesa standards). From late 80's to early 90's I had accumulated a few of these from my Mark III days. Note that I sold that amp in October 2012 just before I got the Mark V. The old Mesa Chinese tube has a dimpled square foil getter along with the triple mica spacers and typical metal plate clips. There are new versions of this tube and they are not as good for what ever reason (those have a round halo getter). Doug's tubes has some of the old tubes available. Not sure how they stack up to the Mesa branded versions as those were sorted to Mesa specifications. I may have to get a few to see for myself.

http://www.dougstubes.com/preamp-tubes/ ... -90-s.html

Here is what the original Mesa 12AX7A tube from the late 80's to early 90's looks like:

Image

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Re: Mesa MarkV / Saturation 'mod'

Post by barryswanson » Fri Jun 02, 2017 12:07 am

Wow! The tube in the V4 position fixed a problem I wasn't really sure it had, until I made the swap. It takes away that sterile kind of sound and makes it come to life with a really warm character. It's like it's alive now and cranking the mid knob on channel 3 yields awesome results. It gave channel 3 the balls it was missing. Very glad I did this.

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Re: Mesa MarkV / Saturation 'mod'

Post by dlpasco » Fri Jun 02, 2017 12:09 am

APEMAN wrote:Hey there,
over the past days I was able to deepen my tests with 12AT7 in V4 vs V6. Here are my thoughts about it:

In V6 (with IV mode engaged) it is the pure and cleaned IV mode - just without the ice pick (the overall effect is more subtle). FX and Solo work very well without sound degration. It has that special drive in the upper mids that makes the sound very big and chunky, perfect for heavy rythm, but you might fight those upper mids for leads. Unfortunately, I found the total amount of gain in the crunch mode in CH2 suffers a little bit - which is sad because I totally love this mode.

In V4 (with IV mode engaged) it is all what I wished the IIC mode would be. It sounds and plays phantastic. There is a certain amount of low mid girth that the V couldn't do before. No ice pick at all and Solo and FX work very well again without sound degration. Those upper mid harmonics I talked about before in the V6 configuration get lost with the 12AT7 in V4 - but it is possible to compensate that with the channel eq pots so it is just a little different. Everything sounds more organic and musical. After all this years with the V (in the IV mode) it feels a little like a new amp and settingwise I have to get used to it. The Extreme mode makes that even more expressive with a very musical mid bump. CH1 and CH2 stay original which is perfect. I will run my V with the V4 config for at least a while. Tomorrow with the band I will see if it cuts as good as the V6 config.

In conclusion, it is very nice to have the ability to choose! Some MarkIV lovers might like the V6 config more, some more lead orientated players might become addicted to the V4 config. So it is up to your personal feel as a player.
One final thing, I never had more fun to experiment with the triode/pentode switch and the multiwatt features together with the full power/variac selector then now with the V4 config.
Just wow! Unbelievable what this amp has to offer! This amp is so highly adaptable, it covers any stage from small club to stadium.

Cheers!
Wow. I just got the chance to try this today (right now I have 12AT7's in both V4 and V6).

This really does close the distance between the Mark V and the JP-2C. IIC+ has an amazing crunch now, too.

Thanks for sharing this, guys.
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Re: Mesa MarkV / Saturation 'mod'

Post by dlpasco » Fri Jun 02, 2017 3:06 pm

I did a quick play test again this morning to make sure that I wasn't hallucinating yesterday.

First off, this amp has never sounded this good with the fx loop on. Period.

IIC+ mode sounds and more importantly, *feels* fantastic. There's a crunch and a tear to it that it didn't have before, and some real authority to the chunk of it when you palm mute the low E string.

It sounds bigger, in the same way that the JP-2C sounds big.

I got the fever, so I got a V going on the eq. Then I added another eq pedal to the fx loop and scooped the mids out even further. TOTAL MASTER OF PUPPETS LAND.

I got lost in that for quite a while.

I haven't really played with Mark IV mode yet, but I flipped that amp to Extreme on a whim and oh my god it's *usable*. I've always hated extreme mode but this was fantastic. I could feel the sound physically shift forward (can't really describe it any other way). I immediately lowered the bass on the eq, it's got a lot more thump to it.

Uh. I'm going to be playing with extreme for awhile. Wow. Holy crap. Dang.
Last edited by dlpasco on Sat Jun 03, 2017 7:46 am, edited 1 time in total.
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bandit2013
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Re: Mesa MarkV / Saturation 'mod'

Post by bandit2013 » Sat Jun 03, 2017 6:33 am

Yes it is. Now I am having difficulty which I like more. JP or V. Both is a good answer. Not identical but very much in the same league.

If you want that true Mark experience. Run both the V and the JP in stereo mode. Use CH2 on the JP, and switch between IIC and IV on the Mark V. I am completely blown away. Also best if you have an isolated splitter to separate the ground loop. I recently got one. Now I am after another that will do a stereo out. I can combine both of them so I can drive up to three amps at the same time. Left Center Right is my goal. I have to know what it would sound like driving the JP, Mark V and Roadster at the same time. 8) I just might s :shock: t my pants.

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