REISSUE Rumor: Mark IIC+ and 2ch Recto

Came across this today and had to laugh out loud... although it is over the top and not 100% based in reality, IMHO. But the fact that some dude went to this level of effort to write and record this catchy tune about such an esoteric topic was pretty funny. Hopefully you folks can appreciate at least the silliness of stuff we sometimes take too seriously (myself included!).

And for the record, the non-metal tones dialed in by Mr. D sounded good to me, good meaty rock and roll tones. The Sweetwater video was kind of hard to watch, though.

The same channel also has a good song about appreciating your amp tech!

Mesa did state the IIC+ reissue was suitable for EL34 in the Class A sockets. Even Mike West stated it is best to use the older NOS EL34 tubes. This is more of a quality issue regarding current production EL34 tubes not holding up under certain conditions. STR450, STR442, STR416 would be suitable. The STR447 or others may be questionable. Bottom line, Mesa/Gibson decided not to include any mention of the EL34 as alternative use in the Class A sockets as this could be an issue as most NOS tubes with Mesa branding (yeah it has to have the Mesa logo printed on them to be acceptable to meet warranty requirements) may lend to issues as the STR447 or the STR446 may not do well in the reissue. Whatever the case may be. I do not have the reissue yet. Still waiting and waiting, and well not sure it will come this year. Perhaps by April, I may see it. That did get upgraded to March then to February. If everyone drops off the list I may see it sooner. This has nothing to do with supporting the heater current. This is not 1960. I doubt they skimped on the windings to support the heaters. Perhaps KT88 or 6550 tubes may pose some issues. It is more of the bias voltage at the control grid of the class A sockets. Is it low enough to support EL34 effectively or is it too high (in magnitude) that ends up with cold tubes?

If you want that 6CA7 effect with 6L6 tubes, just leave the STR445 in the Class A sockets and change what you place in the Class AB sockets. The STR445 do have some 6CA7 characteristic sound to them. Actually, I am curious to find out how the reissue will sound with the stash of Mesa tubes I have. NOS STR415, NOS STR454, NOS STR440 (they became NOS when the company closed shop due to fire), current STR441, STR443, STR448. Since it is Simul-Class, you do not have to run the same tubes in the amp. Blending STR415 in Class AB with the STR445 in Class A may be interesting. I actually like the blend of the STR448 with the STR445 in the Mark VII but that runs full pentode at 90W. the triode/pentode thing may be different with the EL34 in the Class A. At this point, I no longer care. Mark III DRG sort of lost its flavor with all 6L6GC tubes. The EL34 were ok but not as nice as the 6CA7 STR416 tubes. I am sure some remember the 90's when you could not find any Mesa power tubes. Nothing but Groove Tubes or Sovtek tubes of unknown origins back then. At least in PA/NJ the tube availability was rather scarce in most shops that carried Mesa amps.

bandit2013 said:

Mesa did state the IIC+ reissue was suitable for EL34 in the Class A sockets. Even Mike West stated it is best to use the older NOS EL34 tubes. This is more of a quality issue regarding current production EL34 tubes not holding up under certain conditions. STR450, STR442, STR416 would be suitable. The STR447 or others may be questionable. Bottom line, Mesa/Gibson decided not to include any mention of the EL34 as alternative use in the Class A sockets as this could be an issue as most NOS tubes with Mesa branding (yeah it has to have the Mesa logo printed on them to be acceptable to meet warranty requirements) may lend to issues as the STR447 or the STR446 may not do well in the reissue. Whatever the case may be. I do not have the reissue yet. Still waiting and waiting, and well not sure it will come this year. Perhaps by April, I may see it. That did get upgraded to March then to February. If everyone drops off the list I may see it sooner. This has nothing to do with supporting the heater current. This is not 1960. I doubt they skimped on the windings to support the heaters. Perhaps KT88 or 6550 tubes may pose some issues. It is more of the bias voltage at the control grid of the class A sockets. Is it low enough to support EL34 effectively or is it too high (in magnitude) that ends up with cold tubes?

If you want that 6CA7 effect with 6L6 tubes, just leave the STR445 in the Class A sockets and change what you place in the Class AB sockets. The STR445 do have some 6CA7 characteristic sound to them. Actually, I am curious to find out how the reissue will sound with the stash of Mesa tubes I have. NOS STR415, NOS STR454, NOS STR440 (they became NOS when the company closed shop due to fire), current STR441, STR443, STR448. Since it is Simul-Class, you do not have to run the same tubes in the amp. Blending STR415 in Class AB with the STR445 in Class A may be interesting. I actually like the blend of the STR448 with the STR445 in the Mark VII but that runs full pentode at 90W. the triode/pentode thing may be different with the EL34 in the Class A. At this point, I no longer care. Mark III DRG sort of lost its flavor with all 6L6GC tubes. The EL34 were ok but not as nice as the 6CA7 STR416 tubes. I am sure some remember the 90's when you could not find any Mesa power tubes. Nothing but Groove Tubes or Sovtek tubes of unknown origins back then. At least in PA/NJ the tube availability was rather scarce in most shops that carried Mesa amps.

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@bandit2013, curious to know if you're an EE. Your level of tube expertise is impressive and inspirational.

@Doug Doppler yeah, I am an Electrical Engineer. I work in the HVAC industry; it is far removed from audio engineering. I did not venture into understanding the triode until after I got my hands on a Mark V90 back in 2013. It had issues so why not use it as an experimental tool to learn what I can with the associated tube circuits. Tube circuits and associated physics of the vacuum tube triode are not subjects taught in college these days. It was not in the 90's. Most of the theory developed during the tube era is still applicable to silicon equivalents. Just different. As for my knowledge on tube circuits and the like, I am a novice at best. I am still learning so I have room to grow in that aspect.

bandit2013 said:

@Doug Doppler yeah, I am an Electrical Engineer. I work in the HVAC industry; it is far removed from audio engineering. I did not venture into understanding the triode until after I got my hands on a Mark V90 back in 2013. It had issues so why not use it as an experimental tool to learn what I can with the associated tube circuits. Tube circuits and associated physics of the vacuum tube triode are not subjects taught in college these days. It was not in the 90's. Most of the theory developed during the tube era is still applicable to silicon equivalents. Just different. As for my knowledge on tube circuits and the like, I am a novice at best. I am still learning so I have room to grow in that aspect.

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Yeah, had a feeling and do recall seeing something about the HVAC. I commend your all-in tube mania - in all honesty if you're a novice, I'm not sure what that makes me. I'm a replace a replace the stock tubes with the stock tubes guy and while that works (and really well) the NOS and deep dive tube thing is like a gentle voice going, "You know you want to..." Thanks for all your contributions here - appreciated

bandit2013 said:

Mesa did state the IIC+ reissue was suitable for EL34 in the Class A sockets. Even Mike West stated it is best to use the older NOS EL34 tubes. This is more of a quality issue regarding current production EL34 tubes not holding up under certain conditions. STR450, STR442, STR416 would be suitable. The STR447 or others may be questionable. Bottom line, Mesa/Gibson decided not to include any mention of the EL34 as alternative use in the Class A sockets as this could be an issue as most NOS tubes with Mesa branding (yeah it has to have the Mesa logo printed on them to be acceptable to meet warranty requirements) may lend to issues as the STR447 or the STR446 may not do well in the reissue. Whatever the case may be. I do not have the reissue yet. Still waiting and waiting, and well not sure it will come this year. Perhaps by April, I may see it. That did get upgraded to March then to February. If everyone drops off the list I may see it sooner. This has nothing to do with supporting the heater current. This is not 1960. I doubt they skimped on the windings to support the heaters. Perhaps KT88 or 6550 tubes may pose some issues. It is more of the bias voltage at the control grid of the class A sockets. Is it low enough to support EL34 effectively or is it too high (in magnitude) that ends up with cold tubes?

If you want that 6CA7 effect with 6L6 tubes, just leave the STR445 in the Class A sockets and change what you place in the Class AB sockets. The STR445 do have some 6CA7 characteristic sound to them. Actually, I am curious to find out how the reissue will sound with the stash of Mesa tubes I have. NOS STR415, NOS STR454, NOS STR440 (they became NOS when the company closed shop due to fire), current STR441, STR443, STR448. Since it is Simul-Class, you do not have to run the same tubes in the amp. Blending STR415 in Class AB with the STR445 in Class A may be interesting. I actually like the blend of the STR448 with the STR445 in the Mark VII but that runs full pentode at 90W. the triode/pentode thing may be different with the EL34 in the Class A. At this point, I no longer care. Mark III DRG sort of lost its flavor with all 6L6GC tubes. The EL34 were ok but not as nice as the 6CA7 STR416 tubes. I am sure some remember the 90's when you could not find any Mesa power tubes. Nothing but Groove Tubes or Sovtek tubes of unknown origins back then. At least in PA/NJ the tube availability was rather scarce in most shops that carried Mesa amps.

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It does not add up. When Mesa released the user manual for mk3 they specifically stated only el34s shall be used for the outer sockets. Dont know which revision this was as they did not have version control for the document nor date/year on the manual. My mark 2 simulclass did ship with quad of 6L6GC, which i believe were sylvania. So they believed those could take the abuse. Then they changed their mind, current 6l6s were not durable enough, el34 was recommended instead. At that point there was anyway only few sources of tubes left. Pretty much the same manufacturers we have today. Since then if the quality has changed, it has gone up. Now they recommend only nos el34. Why current production was ok with the mk3 but not anymore? Now 6l6 is the recommended type and el34 will void the warranty. The poweramp was the same with mk2 and mk3, only difference was the precense circuit, and even that was fixed to be the same around red/blue stripe. And that does not have any impact on the tubes.

It grinds my gears is that they have decided not to be honest and open. If they did make the changes for the simul-class, it’s ok, but i feel they are hiding something and that will come out sooner or later so why bother with this smoke and mirrors approach.

Hey Folks - per the whole EL34 Simul-class convo this just went up...


https://mesaboogie.zendesk.com/hc/e...amps-such-as-the-Mark-IIC-Reissue-or-Mark-VII

Mesa obviously has some concerns with current production EL34s and is trying to just fully cover their rears... I'm guessing similar to how they changed their tune with the Mark V and updated the manual to repeatedly state that when running EL34s you must not only flip the bias switch, but also only run in variac mode

When I had my first V that was not in the manual. and I also ran =C= El34s in that amp, never in variac mode. Never had any issues either, but I'm sure its a better safe than sorry thing

VisaL said:

It does not add up. When Mesa released the user manual for mk3 they specifically stated only el34s shall be used for the outer sockets. Dont know which revision this was as they did not have version control for the document nor date/year on the manual. My mark 2 simulclass did ship with quad of 6L6GC, which i believe were sylvania. So they believed those could take the abuse. Then they changed their mind, current 6l6s were not durable enough, el34 was recommended instead. At that point there was anyway only few sources of tubes left. Pretty much the same manufacturers we have today. Since then if the quality has changed, it has gone up. Now they recommend only nos el34. Why current production was ok with the mk3 but not anymore? Now 6l6 is the recommended type and el34 will void the warranty. The poweramp was the same with mk2 and mk3, only difference was the precense circuit, and even that was fixed to be the same around red/blue stripe. And that does not have any impact on the tubes.

It grinds my gears is that they have decided not to be honest and open. If they did make the changes for the simul-class, it’s ok, but i feel they are hiding something and that will come out sooner or later so why bother with this smoke and mirrors approach.

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This is all a frustrating thing. First Mesa stated yes, then they backed out at last minute, I assume that was a corporate stance and not based on it's overall design. As for the Mark III DRG, I had a blue stripe, Manual said to use 6L6GC tubes as an alternate for more headroom in the class A sockets. Mine came equipped with the STR416 in the class A and STR415 in the Class AB. Odd that it was always the Class A sockets that roasted the tubes. I was lucky to get 3 to 8 months of use with the EL34 tubes, that was after Mesa no longer offered the STR416 6CA7. Had to use groove tubes as you could not find any Mesa 6L6 or 6CA7 replacements. I believe the notice came out a short time after they were making the Green stripe version. They did change from triode to all pentode wiring with that model. That may have been some reason why the restrictions on using 6L6 tubes in the Class A positions. Bias voltage was probably too low or hot for the 6L6 tube. Original scratchwork schematic of the mark III lists -45V Class A and -51V Class AB for bias. The export version was different, it had -37V Class A and -46 on the class AB. Bring that bias voltage any more positive say to -39V and that is an EL34 bias. Too hot for 6L6GC tubes. That is for the triode wiring. Not sure what changed with the Green Stripe version. Heck the original design for Extended class A push-pull used early versions of the 6L6, 807 was the tube number. This was done in the 50's. The key to this was one pair at triode and the other at pentode. Randall took the design and modernized it for the Simul-Class Patent. It was not necessary to mix the EL34 and 6L6 but that was the key ingredient for smoother distortion characteristics. 6L6GC was fine as long as the tubes can handle a hotter bias voltage. Hotter meaning more positive as the more negative in voltage closer to -60V the colder the amp bias is for a 6L6 tube. -51Vdc is too cold to support EL34 as it may not have much bias current or idle current which is needed for the tube to work properly. Also have to consider the cathode is electrically connected to chassis ground which is 0V to the rest of the circuits. A small change in control grid voltage increases the current considerably. Since the Cathode is the emitter of electrons, a negative control grid will regulate the current flow to the plates. Make it more positive, say closer to 0V and you get instant red-plate. Some may think that 6L6 tubes have a hotter bias, they don't. They will draw similar idle currents at a more negative bias voltage than the EL34 tube with a control grid that is more positive.

Mesa warranty is more of a corporate document to support the reliability of their product. 5 years is long. Power tubes generally do not last that long if you are very active using the amp everyday for extended periods of time. When they fail, the amp's integrity should hold up to that without requiring servicing or repair. Hey, be happy it is fixed bias. Most amps that require a bias adjustment will void the warranty if tube replacement was not done by a qualified technician. Mesa branded tubes do fall within the bias range for their amps. Not sure if their matching is ideal but I have yet to burn up an amp (with the exception of the Mark V90, it was a dead horse when I bought it, thought it was new, but could have been a customer return due to a defect. Probably why I will never buy anything from Guitar Center again.)

Keep the STR445 in the Class A and experiment with the other Mesa 6L6 tubes in the Class AB sockets. You may be surprised how that will change a few things.

I can say this, the Mark VII 25W mode (STR445 6L6) in triode sounds really good. Sure, I did load up the EL34 (bias switch, ha-ha). The amp did not sound much different. No variac power mode either as it is not equipped with such. I had assumed the EL34 would be toast but that did not happen. No dramatic change in sound, volume and overall performance remained unchanged from the 6L6 tubes.

Why not bring up the other Mesa amps that support EL34 as their primary tube. Badlander, Triple Crown, Royal Atlantic, and the Stiletto. We an address the Stiletto first. No bias switch so it cannot run 6L6 as it is fixed at -39VDC. One would also have to consider that the output transformer is different as well. There also appears to be zener diodes in the screen resistor circuit to drop some voltage. Plate votlage is 480VDC on the A circuit (center tap on the OT) the choke also has 8 zener diodes in series for all modes except for clean so the B voltage drops to 452VDC. once that reaches the screens on the EL34, that screen voltage will be below the 450V threshold that usually results in premature tube failure. Always thought it was the older EL34 that had the issues and not the current production versions. Always seems to be a contradictory story. Royal Atlantic, quite different. Also has a bias for 6L6 tubes. 400VDC plate voltage, screens are at 396VDC which they call SCV node. That is the same as the B voltage. Have not seen the schematics for the BAD or the Triple Crown. I do know the TC runs at 450V plate. When I tried a pair of STR450 in the TC50, it blew the fuse on new tubes. It was fine with the STR447 but after the STR450 trial, I had to send the amp in for service. That is when I got the contradicting story about EL34 tubes not living up to their spec sheet with the screen voltage. So I was led to believe it as the NOS tubes and not current production. I get tired of the run a round routine. Sometimes I feel that technical service is totally clueless, and they have no clue how to be honest to the customer. Aside from that scenario, the case I am trying to make is the amps geared to the EL34 tube as its primary tube choice will not perform as well with the 6L6GC tubes even though it has a bias switch to use them. Mostly due to the screen protection and I assume the OT is different than it would be for a 6L6 based amp. Running the 6L6 in the Triple Crown seems to take a hit on output power. Same with the Badlander and Royal Atlantic. Sure, the 6L6 tube has a different impedance characteristic, it also has a higher power rating than the EL34. With that being said, I was surprised that there was no change in performance with the Mark VII with the EL34 (STR447) or the 6L6 (STR445). They sounded exactly the same. Ran one Mark VII with the EL34 and compared it to the other with 6L6. Considering the warning or caution in the manual on EL34 use and reliability, probably best to stick with the 6L6 tubes.

I am still waiting on the reissue. Nothing yet. Curious how it stacks up to the JP2C and the Mark VII. May even want to pit it against the Badlander. I doubt I will run the STR450 tubes in the reissue. Will save them for a rainy day after eating up the STR442 =C= tubes in the RA100. Too bad the STR450 sounds too much like the STR447. Nothing special about them.

I know, I know, I am draining as one put it. Sorry. I am drained too.

Doug Doppler said:

Hey Folks - per the whole EL34 Simul-class convo this just went up...


https://mesaboogie.zendesk.com/hc/e...amps-such-as-the-Mark-IIC-Reissue-or-Mark-VII

Click to expand...

OK, that also answers my question I posed earlier about when they started using EL34s in the IIC+ since nothing is in the manual as it was with the MKIII. The IIC+ all must have come with a quad of 6L6s because:

"Though the last few months of production in 1985 saw original Mark IIC+ amplifiers ship with robust Sylvania-made EL34s installed in the Class A sockets"

Again, here is what the MKIII manual says:

NOTE: In the past, MESA/Boogie advertised the "interchangeable power tubes" feature of the Mark III Simul-Class. We told players
that they could use either EL-34's or 6L6's in the outer (Class A) power sockets. However, in recent years we've observed a much
greater reliability factor with the use of EL-34's in these outer sockets, with much fewer incidents of tube failure. Therefore, today we
strongly recommend using EL-34's in the outer sockets and 6L6's in the inner sockets of your Simul-Class Boogie.

This is a bit confusing because these statements seems to contradict each other.

In the end, I don't really care. I don't feel my MKVII lacks something because I cannot use mixed tubes, and I probably won't care when I get the IIC+ RI that it can't use mixed quads either. However, it is nice to have the warranty information.

bandit2013 said:

Keep the STR445 in the Class A and experiment with the other Mesa 6L6 tubes in the Class AB sockets. You may be surprised how that will change a few things.

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yea I mixed 6L6 tubes up on my V:90, STR-441s GRYs in the outer sockets, STR-448 GRNs in the inner sockets. Simulclass saw a major tonal upgrade. Didn't do an exhaustive tube comparison with others variants, didn't need to as it sounded most excellent with this arrangement.

I don't know how different the VII power section is vs the V:90 but I'm with @bandit2013 on this one.

I wanted to take a moment and respectfully ask that we take a collective deep breath and chew over the following. The Mark IIC+ and Mark VII both leave the factory with a quad of 6L6s, which for the VAST majority of users is the common use case scenario. They've been proactive about replying, and while it took them a minute to define policy they did so pretty vigilantly considering it's the end of the year, they're busy fulfilling existing orders, and they have other releases they're working on for 2025. They're busy but have still put their best people on this trying to find the best solution so 'your' amp doesn't experience a tube failure on your gig. U.S. tech support that replies quickly, cares to research their answers and follows up if something changes seems like a sign that they care a lot

And they DO say this on the web site, "Disclaimer: In order to continually improve the design, quality and performance of our products and to use the best materials at all times, MESA/Boogie reserves the right to substitute or change specifications (including parts or coatings) without notice."

and this...
Mark IIC+

Power Amp Tubes​

4x 6L6

Mark VII

Power Amp Tubes​

4x Mesa 6L6 (or EL34)

These are really good people trying to do right by us. I know this can be frustrating, but I invite you to put yourself in their shoes and in so doing know how much they care - about us

Hope that came across with the love and respect intended

Hello! Just received the reissue a fews days ago. Great amp! Question about the input jack for the EQ/Reverb foot switch on the underside of the chassis: is there a “preferred” method of fishing the provided cable to this location so the heat from the nearby tubes doesn’t melt the cable’s outer covering? Thanks in advance!

I simply ran it straight down through the relief hole for the reverb tank and out the back under the amp.

Just got the amp! So far so good…and I did not care for the JP or the VII. I’m comparing to a loop modded IIb SRG (RP-9C) and a mk III+ (green). No direct C+ comparisons for me, but my IIb is amazing. This reissue is right there with it.

The VII was too boxy for me. I was afraid this would be the case with the RI, but it’s not. It seems to capture that open feel of the older amps. I haven’t swapped tubes yet (I have a new quad of 415’s) but I’m sure I will. Just learning the amp as it comes, but I’ll say I’m pretty pleased. One thing I’ve found so far is that I prefer the EQ on all the time. Seems like the clean needs it. On my IIb and III, I run auto. Personal preference of course.

I have some new 442’s that I was going to throw in the RI, but sounds like that’s a no. I run 442’s and 415’s in my III along w Mesa square getters (415’s and square getters in the IIb as well). I have a nice stock of classic Mesa tubes I’ll be swapping into the RI for fun. So far, it sounds great stock! It’s a keeper.

I cannot recreate the squeal btw…