Mark III power tube break up - doesn't seem possible

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Bross63

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I have a green stripe Mark III that I purchased new around 1989-90. For many years I ran the Master down very low so I could drive the preamp section for tube saturation and breakup in Rhythm 2. However along the way I learned the difference in preamp tube and output (“power”) tube saturation/overdrive/breakup/distortion. I have gone to running my Master much higher to drive my output tubes more which, at least to my ears, gives me a better tone. An example is 5 on the Volume and 3-5 on the Master for Rhythm 2 and Volume on 7 with Master on 5 in Rhythm 1. I dial back the volume on my guitar a little to bring the “loudness” (decibels) down to a manageable level.

That said, despite having even maxed out my Master at 10 and running the Volume at either 7 in Rhythm 1 or 5 in Rhythm 2 (and even going up to 8 in Rhythm 2 and 10 in Rhythm 1 - wearing earmuff headphones for hearing protection) I am unable to get any output tube clipping. The only breakup I get is from the preamp tubes. This is the same whether running in Class A mode or SimulClass (Class A is supposed to break up easier than SimulClass as I understand it yet it still will not break up in the power section). I have tried both 6L6 and EL 34 (Mesa 420 and 441 6L6, Electro Harmonix 6L6, and Mesa EL 34) tubes in the outer sockets, and even with the EL 34 tubes I still cannot achieve any output tube breakup.

Other "Master volume" amps like Marshall will break up in the power section, even with the (gain)Volume turned down lower, and allow the user to dial in preamp breakup, power tube breakup, or a combination of the two. Sadly with my Boogie I am only able to get preamp tube breakup no matter what I try. Has anyone achieved output tube saturation and breakup in your Mark III? Am I learning after all these years that my Mark III will only produce preamp tube saturation and breakup while the power section is simply there to amplify or make louder the tone sent to it without the possibility of providing its own tube character?

I do understand each iteration of the Mark III was different from the others, so is this something that is specific to the green stripe or is this the case with all Mark III amps and possibly other mark series amps?

I’m aware that I could simply use a pedal to create overdrive or distortion, but the whole point of a tube amp is the rich tonal character (and range of tones when an amp will clip properly) that cannot be produced by a pedal.

Last point for consideration or reference, I play blues, Grateful Dead, and a little classic rock, and am not at all looking for metal type distortion. I like an overdriven tone and up to a crisp, “classic rock” type of distortion and would like to get that out of my output tubes, or at least part of it. I can get as “dirty” or distorted as I want from the lead mode, but again that is pure preamp saturation/distortion and not what I’m seeking.

Thanks for any insight any of you may have.
 
I owned a MK III purple strip simul-power at one time and tried to do the same as you, turn it up to get power tube distortion. I could not get it to happen, it was just way too loud for any practical live playing situation, imho.

I never had the master above 3 to 4 for any of the gigs i was doing back in the day, mid 80's to mid 90's. And it was plenty loud. Very punchy, awesome clean headroom when needed, and of course that awesome boogie preamp distortion.

Never tried a power soak or those type of devices. Hopefully SOMEONE was able to get that power amp scream, live thru it and can chime in! lol!

peace.
 
Thanks Fernando. I agree that the Boogie preamp breakup is better than that of many other amps, I still want to tap into the different tonal characteristics of saturating the output tubes. Having pushed the amp almost as hard as it will go in rhythm 2 (8 on Volume with Master on 10) and totally maxed out in Rhythm 1 (10 on both Volume and Master) with no power tube saturation I’m beginning to think it isn’t possible without some modification. Maybe someone has found some 6L6 output tubes that saturate much easier and will then allow breakup even in the Boogie circuitry.

By the way, when I tried it on Rhythm 2 with Volume at 8 and Master at 10 (wearing headphone ear muffs for hearing protection) the vibrations blew pages off the music stand several feet away, and I could feel it in my whole body. Those were some powerful sound waves moving a LOT of air and quite forcefully ha ha.

I bought a used Weber Mass attenuator that will be here by early next week, so I’m looking forward to hearing how that will sound with the Master cranked high and the volume at higher levels on both Rhythm 1 and 2. As a side note, while I understand the tube breakup that occurs when driving Rhythm 2 at higher Volume settings is still preamp tube saturation, it has a more pleasing breakup sound to my ears than does the Lead mode. Don’t get me wrong, I like the range of tones I can get out of the Lead mode and can dial in some excellent tones from clean to mildly overdriven to full distortion. But the Rhythm 2 breakup has a different sound to it that I like.

The last thing I didn’t mention in my original post is that I have the EV 250w speaker in my Mark III combo cabinet. I may be able to go to a lower watt speaker and get some cone breakup also, but that would be a risky proposition because I might get to the point of blowing the cone.

I hope after all these years with my boogie I’m not forced to seek out a different amp to give me the rich 6L6 saturated sound I want.
 
lol, yea, that anecdote about the papers flying and "feeling" the sound wave are pretty intense. I still wish i had that amp, it also had an EV. i always have in the back of my head the thought of buying a used purple-stripe. But i don't think i would ever use it live again, since I have a MKV:35, Fillmore 50, TC-50 and LSS that are much lighter. I run 3 amps, less the lss, in a 3 amp rig that lets me dial in "many" tones of distortion and clean. And it's easier to control the volume at lower levels than it was with the MKIII.

I agree with you about that power amp grind. it would be cool to have as another sound. supposed to be more "touch sensitive".

Maybe if you have the option of contacting mesa/boogie directly, they might be able to give you "straight from the source" tips. Good luck with your sound search!

peace
 
I'm not the one that can give you all the tech insights, but yes you're right it seems the Mark series weren't designed for power tube break up.

Biasing warmer might help. I know my amp tech put a bias adjustment pot in ( I think he replaced R117 or R102 with a pot), Mesa biases them very cold. Once you do this you may be freer to try different tube types. You could have a hunt around for tube comparison charts like this one:
https://geargods.net/wp-content/uploads/2013/10/6L6GC-Comparison-2013.pdf

I was happy with the mod my amp tech did. The other thing is it might have something to do with the Phase Inverter/Driver tube (try different V5 tube types?). Or modding the surrounding circuitry, but then I suppose you're into a world of re-voicing the amps caps and resistors which may cause problems with oscillations, Output Transformer and biasing etc. As I said I don't know, since I'm not an amp tech. You could call Mike B. at Boogie.

Am I right you're after a kind of Tweed/Bassman style break up? You might be able to get there with more tweaking of the preamp (maybe utilise a low gain lead channel with a pedal in front). Maybe run some searches on what other players have done for that kind of tone. Does your Mark have the GEQ, if not you can run one in the FX loop? Have you done the R2 Vol Pot mod? https://forum.grailtone.com/viewtopic.php?f=3&t=18520

This was taken from this site (https://robrobinette.com/Tube_Guitar_Amp_Overdrive.htm#History_of_High_Gain_Amps), great info on tube amps:

"If you want to see a truly different circuit, check out Mesa's Mark series. They look very complicated because of all the switching options, but if you go back to the Mark IIC+ and ignore all the complicated stuff, you mostly get this: a blackface Fender (say a 60's Twin) with the reverb circuit replaced by a gain boost circuit. Look at it, you'll see it: first stage drives a tone stack via the plate, then is followed by a recovery stage (textbook Fender blackface), then you get the 3M3 resistor which is typically used to attenuate the signal to mix it with the reverb, but instead of a reverb circuit you get the "Lead" circuit which is a pair of triodes (aka one 12AX7) configured for high gain. What you get is basically trying to replicate a cranked to hell Fender: lots of distortion AFTER the tone stack instead of before it. Also the interesting thing is you get a bit of clean sound mixed in with the extra distortion (what makes it through the 3M3 resistor). The resulting sound however is very mid-heavy, hence the graphic EQ, which is a much more powerful tone shaper than the classic TMB tone stack (especially this one, which runs on much higher voltage than a pedal). This gives you a lot of power, the early tone stack can be used to shape the distortion (crank Treble, cut Bass for a very tight aggressive sound, go more moderate for that "fusion" lead sound), then the graphic EQ lets you do the final shaping. Boosting the lows late will not muddy up the distortion, that's how it can sound so massive while tight (the "Simulclass" power amp where 2 of the tubes run in Triode mode help here too)."
 
First thing said: Boogies are not made for powertube distortion. Also 6L6 are beam power tetrodes, which break up later and not so even than EL34 pentodes. It is possible to get breakup, but only at ear splitting volumes. You wont get power tubes to break up, if you back down the preamp volume and the guitar: If you really want to hear power tube distortion stay on the clean channel, open the master to 10 and slowly rise the preamp volume with the guitar wide open. Use enough speakers!!! even a 200W EV can get easily destroyed by a 100W poweramp when distortion appears. So use at least a 2nd EV cab...And wear Headphones. Good luck :lol:
 
The power amp is always running at 100% output. What makes it overdrive is how much volume you put into it.

With a Mark III I get poweramp overdrive with the master at 4 or 5. I'm running the preamp fairly hot also. I'm not going after vintage tones.
 
Most of Mesa’s amps run the output section cool and clean.

IMHO-
If it sounds good, feels good, and fits the band, why does it matter how much the power section is breaking up?

If you’re not happy with what you’re getting from the MKIII, maybe try a Fender?

Im not trying to be snarky, I’ve just learned over the last 30+ years not to get too hung up on things like that. I used to spend so much time (and $$) tube rolling, bias modding, having my amp modded, etc to chase a tone, to the point that it wasn’t as fun as it was frustrating.

For the last few years I’ve learned that I get more control of my tone from my fingers than the tubes. I haven’t even bothered to throw my bias meter on the TC-100, it sounds great as is, why do I need to know my plate current? I’m sure the power section is not breaking up, but who cares, it sounds great.

If the MKIII is not delivering what you need you might want to try other amps, rather than try to make the MKIII something it is not.

My $0.02
 
Red3 said:
Biasing warmer might help. I know my amp tech put a bias adjustment pot in ( I think he replaced R117 or R102 with a pot), Mesa biases them very cold.

Thanks for that input. I've been considering having my amp tech either change the fixed bias or put in a bias adjustment, so I'll talk to him about that and see if he thinks it will help.

The other thing is it might have something to do with the Phase Inverter/Driver tube (try different V5 tube types?).

I have tried quite a few different tubes for the phase inverter including new production and NOS but none have changed the response of the output tubes.

Am I right you're after a kind of Tweed/Bassman style break up? You might be able to get there with more tweaking of the preamp (maybe utilise a low gain lead channel with a pedal in front). Maybe run some searches on what other players have done for that kind of tone. Does your Mark have the GEQ, if not you can run one in the FX loop? Have you done the R2 Vol Pot mod? https://forum.grailtone.com/viewtopic.php?f=3&t=18520

As I stated initially I don't want to use a pedal for overdrive/breakup. I am able to get overdrive from Rhythm 2 by using the Volume and am able to get a wide range of overdrive and distortion in Lead with a combination of Volume and Lead Drive, but all of that is preamp saturation which is different than output/"power" tube saturation and breakup. I'm taking my amp in after the holidays to have the R2 Volume mod done by my amp tech.

Thanks for the links and for all the info in your reply. I appreciate it.
 
TiPiMods said:
First thing said: Boogies are not made for powertube distortion. Also 6L6 are beam power tetrodes, which break up later and not so even than EL34 pentodes. It is possible to get breakup, but only at ear splitting volumes. You wont get power tubes to break up, if you back down the preamp volume and the guitar: If you really want to hear power tube distortion stay on the clean channel, open the master to 10 and slowly rise the preamp volume with the guitar wide open. Use enough speakers!!! even a 200W EV can get easily destroyed by a 100W poweramp when distortion appears. So use at least a 2nd EV cab...And wear Headphones. Good luck :lol:

I have tried with the Master on 10, Volume on 10 in Rhythm 1/Clean and with my guitar volume on 10 also and never got any output tube saturation/breakup. I have even gone up to 8 in Rhythm 2 but never got anything different than the preamp breakup that was present at lower settings of the Master. So I have driven the power section as hard as the amp will drive it with no success in achieving output tube saturation. I believe what others have stated is the case - that boogie biases the power section very cool/cold. That makes sense also because when I called to order new output tubes and said I wanted to put 6L6 tubes in the outside sockets they said I needed the cooler rated tubes. That said, I also tried the 10/10/10 approach with EL-34 tubes in the outer sockets with no break up in them either. I have come to accept that even with a bias adjustment and running "hotter" tubes, whether 6L6 or El-34, I won't ever get output tube saturation out of my Mark III without it being dangerously (literally) loud. And that is assuming I might even be able to achieve output tube saturation after the bias adjustment and using hotter tubes.

I still like my Mark III. But I never truly understood it like I do now, and I asked the question to see if maybe I was missing something. They are simply preamp driven amps with a power section that is meant to always run crystal clear and merely make louder the signal sent to it. It creates some fantastic tones with the preamp saturation, so I'm not saying it sounds bad or that it sucks. I'm simply interested at this point in being able to tap into output tube saturation for an additional tonal texture or flavor. Sadly that will almost certainly require my purchasing an additional amp.
 
stephen sawall said:
The power amp is always running at 100% output. What makes it overdrive is how much volume you put into it.

With a Mark III I get poweramp overdrive with the master at 4 or 5. I'm running the preamp fairly hot also. I'm not going after vintage tones.

Which version of Mark III do you have (ie what color stripe)? I can't get poweramp overdrive even with the Master on 10, so hearing you are getting it on 4 or 5 makes me think you may have a different version of Mark III. Running the Master on 4 or 5 means you are only driving the output tubes at 40-50%, so if you are truly getting the output tubes to break up at that dramatically cut back signal then something must be very different about your amp or the tubes you are using. What tubes are you using in the outer sockets? Are you certain you aren't hearing preamp overdrive? I only ask because you stated you are running the preamp hot also, and doing so will cause preamp saturation in R2 and sometimes in R1 with certain preamp tubes.

Thanks for your reply
 
domct203 said:
Most of Mesa’s amps run the output section cool and clean.

IMHO-
If it sounds good, feels good, and fits the band, why does it matter how much the power section is breaking up?

I agree that if it sounds good and there is no potential tone available beyond what is being produced then it doesn't matter if that tone is being created by the preamp or poweramp sections. But with some amps, running very different circuitry of course, output tube saturation starts happening fairly early and becomes an important part of that amp's sound and the tones it can generate. I was only wondering if it is even possible to get a Mark III to break up in the power section, but I've come to understand that it really isn't and if it ever is, even with some mods to the amp, it will still be so ridiculously loud as to be unusable

If you’re not happy with what you’re getting from the MKIII, maybe try a Fender?

I'm considering getting another amp that will do output tube breakup, maybe a tweed or tweed clone type circuit

Im not trying to be snarky, I’ve just learned over the last 30+ years not to get too hung up on things like that. I used to spend so much time (and $$) tube rolling, bias modding, having my amp modded, etc to chase a tone, to the point that it wasn’t as fun as it was frustrating.

I definitely agree about going on a wild goose chase and the frustration that can result from it. That's why I've accepted I'll probably add another amp to my setup in the (hopefully not too distant) future.

For the last few years I’ve learned that I get more control of my tone from my fingers than the tubes. I haven’t even bothered to throw my bias meter on the TC-100, it sounds great as is, why do I need to know my plate current? I’m sure the power section is not breaking up, but who cares, it sounds great.

If the MKIII is not delivering what you need you might want to try other amps, rather than try to make the MKIII something it is not.

You are absolutely right. The reason I asked the question is because I wanted to learn if my experience is the same as other Mark III owners or if maybe I was missing something and could learn from the experience of others here. But as I stated above, I have come to understand my Mark III much better than I have before and now accept it as a preamp driven amp. That doesn't make it bad, it is simply the nature of the way it was designed. It still sounds fantastic in many ways and does a LOT of things extremely well. Part of this process has been not only understanding the amp better and accepting it for what it is and isn't but also appreciating it for what it is and not trying to make it something it isn't as you said. Your points are spot on, so thank you.

My $0.02
 
Bross63 said:
stephen sawall said:
The power amp is always running at 100% output. What makes it overdrive is how much volume you put into it.

With a Mark III I get poweramp overdrive with the master at 4 or 5. I'm running the preamp fairly hot also. I'm not going after vintage tones.

Which version of Mark III do you have (ie what color stripe)? I can't get poweramp overdrive even with the Master on 10, so hearing you are getting it on 4 or 5 makes me think you may have a different version of Mark III. Running the Master on 4 or 5 means you are only driving the output tubes at 40-50%, so if you are truly getting the output tubes to break up at that dramatically cut back signal then something must be very different about your amp or the tubes you are using. What tubes are you using in the outer sockets? Are you certain you aren't hearing preamp overdrive? I only ask because you stated you are running the preamp hot also, and doing so will cause preamp saturation in R2 and sometimes in R1 with certain preamp tubes.

Thanks for your reply

I ran various Mesa powertubes. Usually STR420.

Red Stripe....I sold it a long time ago. I played in all the different stripes and there is not a huge difference. They all sound like a Mark III.

I'm not sure if you or most people understand how a tube amp works. Guitar tube amp or any other tube poweramp are running at 100% all the time. What makes them overdrive is how much you put into the poweramp from the preamp. Basically it requires to be very loud to get poweramp overdrive. The master doesn't control how loud the poweramp is running....it controls how much of the preamp is being feed into the poweramp.

As for bias it really doesn't matter if it's hot or cold.... it's more like a idle point. Where you start when not playing.

If set too low you get crossover distortion. If too hot no focus and a blurry sound.

What having a cold bias does mostly is more dynamic range and more punch. If too low it's harsh because of the crossover distortion.

Most of my amps are NMV....I started playing in 1969 when virtually all amps didn't have a master volume. I'm very familiar with poweramp distortion.
 
which kind of guitar do you use? very weak pickups?
Maybe you should bring your amp to some good technician...looks as if there is something wrong. On both of my Boogie Mk amps even with a Stratocaster I get easily power amp distortion with volume on 9 (which is just before preamp breakup with a strat) and master levels more than 4-5. Great crunch sound, but loud.
You could have a bad tube somewhere, leaking caps (bad cathode bypass caps result in loosing a lot of gain on the corresponding tube)...also check your effects loop: plug in some short patch cable, it should sound the same without & with cable...

regarding your comments about output tubes:
1) bias has not very much impact on power tube saturation, hotter bias will make the amp a bit louder, but not necessarily breaking up earlier.
2) 6L6GC are 30W tubes, they are able to deliver clean power with little distortion up to their rated value, and like all beam power tetrodes they break up quite late...so you wont get power tube distortion at reasonable levels without a power soak. If you really want to use power tube saturation, get a 15-20W amp and crank it: it will be loud enough, in many clubs too loud.
3) regarding simul class: the inner tubes run class AB, traditionally quite cold on boogies (use only 6L6) the outer tubes are the class A sockets: use only EL34/6CA7 on a MK III, and try to get quite strong tubes with a lot cathode emmission, otherways they run also in something like class AB at about 60% dissipation. Mesa does NOT advise the use of 6L6 anymore, as they run really really HOT...I measured 115% dissipation on idle with a pair of normal 6L6GC in my amp. Thats way too much and not save with the amp. Worst case is a failure that destroys your output transformer.
 
stephen sawall said:
I'm not sure if you or most people understand how a tube amp works. Guitar tube amp or any other tube poweramp are running at 100% all the time. What makes them overdrive is how much you put into the poweramp from the preamp. Basically it requires to be very loud to get poweramp overdrive. The master doesn't control how loud the poweramp is running....it controls how much of the preamp is being feed into the poweramp.

On some other master volume amps such as Marshall it's possible to achieve:
a) preamp breakup with the preamp (Volume/Gain) turned up higher and the power amp turned down lower and running "clean"
b) poweramp breakupi with the preamp set lower and not breaking up but with the master volume turned up higher so the output tubes break up and provide the overdriven or distorted tone
c) a combination of preamp breakup and poweramp breakup by setting both the Volume/Gain high enough to induce preamp tube saturation and setting the master volume high enough that the output tubes saturate also which creates a blend of both preamp and output tube breakup in the tone

My amp tech, the owner of the premier tube amp repair, modification, etc shop in Nashville, also a Boogie certified repair center and tech himself, described the master volume to me as a limiter on the poweramp section so that with the Master on 10 the poweramp is running without limitation and any setting lower than that being a limitation on how hard the poweramp and subsequently the output tubes are being driven. Your description of the Master as controlling how much of the preamp signal is being sent to the power section doesn't change the fact that the preamp signal, whether clean or already overdriven, is a separate matter entirely from poweramp/output tube saturation and breakup. I'm not arguing your point at all and appreciate your information. But no matter the manner in which it is described (even if my wording was inaccurate compared to your explanation) the amount the poweramp is being driven is controlled by both the Volume and the Master with the Master being effectively a limiter on the poweramp section that controls how hard the poweramp and output tubes are being driven. My initial question was about the ability to achieve poweramp/output tube saturation and breakup in Mark III series amps and that being a different breakup that is separate and independent from preamp tube saturation and breakup. Obviously the harder the front end (preamp) is driven the stronger the signal that can be sent to the poweramp section, however I have been unable to achieve notable poweramp breakup even when driving the front end at maximum levels and running the Master at maximum levels also.

As I stated in previous replies I have come to understand and accept that Boogies in general and certainly the Mark III series achieve their tone primarily from the preamp tubes. The cascading gain setup is designed to elicit various degrees of potential preamp tube saturation and overdrive or distortion as a result while the poweramp section is simply designed to make louder the signal it is given with no intent for it to ever reach satuation/clipping and provide its own additional potential texture to the end tone as a result. The answers you and others have provided have helped me gain this new understanding and knowledge about my amp and Boogies in general, so for that I am very grateful.
 
TiPiMods said:
which kind of guitar do you use? very weak pickups?

My primary guitar is a 1970 ES-335, and I do have the pickups set on that guitar to produce a more articulate and stringy/woody tone. My other guitar is a 1985 Les Paul Custom, so there is no lack of gain being provided by that guitar for certain, yet I get no different response from the poweramp as compared to the 335. The Les Paul does drive the preamp section harder and produce overdrive and distortion at lower Volume settings in R2, and will even cause some breakup of the preamp section in R1 at 9-10

Maybe you should bring your amp to some good technician...looks as if there is something wrong. On both of my Boogie Mk amps even with a Stratocaster I get easily power amp distortion with volume on 9 (which is just before preamp breakup with a strat) and master levels more than 4-5. Great crunch sound, but loud.

Is this in R1 (the "Clean" mode)? I also assume you aren't describing being in the LEAD mode? Based on your description you may be getting what I would like to be able to achieve, but I can only imagine the decibel level to be insanely loud at your settings of V9/M4-5 unless your treble setting is well below 5

You could have a bad tube somewhere, leaking caps (bad cathode bypass caps result in loosing a lot of gain on the corresponding tube)...also check your effects loop: plug in some short patch cable, it should sound the same without & with cable...

I have changed out and tried various tubes in all the preamp and poweramp tube slots, so it's not a bad tube. Also no change in output tubes, brand or model of 6L6 had any impact on poweramp breakup. Putting EL-34 tubes in the outside slots did get a little poweamp saturation at exteme settings of V10/M9-10 in R1 and V6-8/M10 in R2, but the amount of poweramp breakup was very minimal and the loudness/debibel level was so high that I would have to have the amp in a separate, isolated room in order to run it that way. I'm taking my amp to Jeff, my amp tech, next week. He is going to go through the whole amp and check everything and swap out some things he knows to be helpful at smoothing out the icepick sound that can be a problem in Mark III amps. During that process he will identify anything that may be "bad" that needs replacing, so you may be right that there is something in need of repair that can be contributing to what I'm experiencing. To be clear, however, I don't have a lack of tone or a degraded sounding tone. My amp sounds great in all modes - R1, R2 and Lead. So while it's certainly possible something is amiss, the amp doesn't express any notable, apparent lack in the tone(s) it produces.

regarding your comments about output tubes:
1) bias has not very much impact on power tube saturation, hotter bias will make the amp a bit louder, but not necessarily breaking up earlier.
2) 6L6GC are 30W tubes, they are able to deliver clean power with little distortion up to their rated value, and like all beam power tetrodes they break up quite late...so you wont get power tube distortion at reasonable levels without a power soak. If you really want to use power tube saturation, get a 15-20W amp and crank it: it will be loud enough, in many clubs too loud.
3) regarding simul class: the inner tubes run class AB, traditionally quite cold on boogies (use only 6L6) the outer tubes are the class A sockets: use only EL34/6CA7 on a MK III, and try to get quite strong tubes with a lot cathode emmission, otherways they run also in something like class AB at about 60% dissipation. Mesa does NOT advise the use of 6L6 anymore, as they run really really HOT...I measured 115% dissipation on idle with a pair of normal 6L6GC in my amp. Thats way too much and not save with the amp. Worst case is a failure that destroys your output transformer.

Mesa has said for many years now that it is fine to run 6L6 tubes in the outer slots provided they are a "cooler" pair. When I called to order new tubes several weeks ago I told the tech I wanted to run 6L6's in my outer slots. He said there is no problem doing so and recommended either red or yellow color coded tubes since those are the two coolest ratings among their offerings.
 
Bross63 said:
stephen sawall said:
I'm not sure if you or most people understand how a tube amp works. Guitar tube amp or any other tube poweramp are running at 100% all the time. What makes them overdrive is how much you put into the poweramp from the preamp. Basically it requires to be very loud to get poweramp overdrive. The master doesn't control how loud the poweramp is running....it controls how much of the preamp is being feed into the poweramp.

On some other master volume amps such as Marshall it's possible to achieve:
a) preamp breakup with the preamp (Volume/Gain) turned up higher and the power amp turned down lower and running "clean"
b) poweramp breakupi with the preamp set lower and not breaking up but with the master volume turned up higher so the output tubes break up and provide the overdriven or distorted tone
c) a combination of preamp breakup and poweramp breakup by setting both the Volume/Gain high enough to induce preamp tube saturation and setting the master volume high enough that the output tubes saturate also which creates a blend of both preamp and output tube breakup in the tone

My amp tech, the owner of the premier tube amp repair, modification, etc shop in Nashville, also a Boogie certified repair center and tech himself, described the master volume to me as a limiter on the poweramp section so that with the Master on 10 the poweramp is running without limitation and any setting lower than that being a limitation on how hard the poweramp and subsequently the output tubes are being driven. Your description of the Master as controlling how much of the preamp signal is being sent to the power section doesn't change the fact that the preamp signal, whether clean or already overdriven, is a separate matter entirely from poweramp/output tube saturation and breakup. I'm not arguing your point at all and appreciate your information. But no matter the manner in which it is described (even if my wording was inaccurate compared to your explanation) the amount the poweramp is being driven is controlled by both the Volume and the Master with the Master being effectively a limiter on the poweramp section that controls how hard the poweramp and output tubes are being driven. My initial question was about the ability to achieve poweramp/output tube saturation and breakup in Mark III series amps and that being a different breakup that is separate and independent from preamp tube saturation and breakup. Obviously the harder the front end (preamp) is driven the stronger the signal that can be sent to the poweramp section, however I have been unable to achieve notable poweramp breakup even when driving the front end at maximum levels and running the Master at maximum levels also.

As I stated in previous replies I have come to understand and accept that Boogies in general and certainly the Mark III series achieve their tone primarily from the preamp tubes. The cascading gain setup is designed to elicit various degrees of potential preamp tube saturation and overdrive or distortion as a result while the poweramp section is simply designed to make louder the signal it is given with no intent for it to ever reach satuation/clipping and provide its own additional potential texture to the end tone as a result. The answers you and others have provided have helped me gain this new understanding and knowledge about my amp and Boogies in general, so for that I am very grateful.

If you look at the schematic you can see the Master is in the preamp.

https://www.google.com/search?q=mesa+mark+iii+schematic&oq=mesa+mark+III+sc&aqs=chrome.1.69i57j0l3.14811j0j8&client=tablet-android-hms-tmobile-us-noonebox&sourceid=chrome-mobile&ie=UTF-8#imgrc=r9Ep5iO3tDsQuM:
 
IMHO, the mark series amps were designed so that along with the EVM speaker there would be no change in character going from very low volumes to very high volumes. You hear people complain all the time about how this or that non master amp "sounds great but it's too loud" and then go down the attenuator rabbit hole. I would suggest that you try a low wattage speaker like a celestion G12M 25watt green back which will have a break up character of it's own when driven to it's power limit. Driving an EVM speaker to breakup could decimate the local bird population.
 
You can try using a higher gain but well balanced 12AX7 in the phase inverter. This will give more drive to the output tubes.


But ultimately, a Mesa Mark series amp is pretty nearly the polar opposite of a classic Marshall Super Lead. The Marshall is very clean and breakup happens mostly in the output stage when cranked way up. (Usually, and if in stock configuration with average gain preamp tubes)

A Mark is built for preamp overdrive and lots of it, and a power stage that isn't meant to distort at full rated output.

Don't ask a Mesa to do what a Marshall does, and vice versa.

If you want the sound of a dimed Plexi, get a Plexi and dime it.
 
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