Mesa MarkV / Saturation 'mod'
- Thread starter APEMAN
- Start date
Help Support The Boogie Board:
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-ECC81-Tube-Types/Shuguang-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.
http://www.thetubestore.com/Tubes/12AT7-ECC81-Tube-Types/Shuguang-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.
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.
elpingua
Well-known member
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-jan-philips?gclid=Cj0KEQjwx6TJBRCWtsiXpI7bhOYBEiQA1en3FxA4_UtE6RUHYU_SXMKPr7p2YVejUSBl1z_45llhV8MaAkZx8P8HAQ
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.
Perhaps?:
https://tubedepot.com/products/12at7wc-jan-philips?gclid=Cj0KEQjwx6TJBRCWtsiXpI7bhOYBEiQA1en3FxA4_UtE6RUHYU_SXMKPr7p2YVejUSBl1z_45llhV8MaAkZx8P8HAQ
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.
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...
I've had good luck getting tubes from dougstubes.com. They also offer "sets" of tubes for different amps.
Mace
Mace
elpingua said:
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.
barryswanson
Well-known member
- Joined
- Aug 21, 2012
- Messages
- 359
- Reaction score
- 0
So I got me one of these tubes. Does it go in V4 or V6?
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/12ax7-ecc83-7025/nos-chinese-12ax7-80-s-90-s.html
Here is what the original Mesa 12AX7A tube from the late 80's to early 90's looks like:
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/12ax7-ecc83-7025/nos-chinese-12ax7-80-s-90-s.html
Here is what the original Mesa 12AX7A tube from the late 80's to early 90's looks like:
barryswanson
Well-known member
- Joined
- Aug 21, 2012
- Messages
- 359
- Reaction score
- 0
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.
APEMAN said:
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.
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.
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.
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.
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.
barryswanson
Well-known member
- Joined
- Aug 21, 2012
- Messages
- 359
- Reaction score
- 0
I really like how it makes the mid knob behave on channel three. I'm running the mids at like 1:00 on Iic+ and it's making me gooey in the fork.
barryswanson said:
I know. I dimed the mids last night and pulled a slice back out with the eq and it roared.
I'm supposed to be sleeping but I'm honestly too excited.
Bandit, I have no conflict here: my Mark V just blew past my JP-2C. I don't think I'm going to look back, either.
It'd be interesting to know if there's anyone out there with a IIC+ and a Mark V that can compare them after doing this mod. It's definitely good enough that it's worth trying out.
Pretty sure this is the end for my JP.
Pretty sure this is the end for my JP.
APEMAN said:dlpasco said:
I knew you would like it if you give it a try
In the moment I'm stuck on extreme. I learnt to dial it in properly, settings look similar to my lead2 red settings on my triaxis. gain 2:00 treble 4:00 mid 10:00 bass 11:30 presence 3:15 bright to normal. Chunky, heavy, fast, tight, organic, dynamic, saturated but cristal clear - almost unreal.
Yeah, I am stuck on extreme, too. Wow.
