Mesa MarkV / Saturation 'mod'

[bandit2013]

Try it with Pentode and Triode. Wow. I have lost complete interest in using the Mark V before this mod. Either Clean on fat or CH2 Crunch was the only selections that had any merit towards keeping the amp vs selling it. Now I am really liking the Mark V more than I ever imagined. This boogie now has the Mojo it was missing from day one. Actually it makes the Mark V CH3 a multi voiced JP-2C. Triode mode is amazing with all voices. Perhaps I am happy I held onto the amp as there was a solution for the Mark V icy blues (not regarding music style). I can blame this on my exposure with the Mark III and Mark IV and for some reason the Mark V was not living up to its reputation. Perhaps many who love the amp never had the privilege to play though the older amps that make the Mark series what it is. The Roadster was also the V killer as well as the RA100. Still, the CH2 with the gain maxed was the ultimate heavy metal chugger especially when running a quad of Gold Lion KT77 though a pair of 8 ohm EV speakers running on the 4 ohm output. The Roadster could not even come close to that sound. The JP-2C had the tone and gain character I have been searching for all this time. Now the Mark V is on Par with a few tricks up its sleeve. I can also run the amp though the V30 speakers and love what I am hearing. I could not stand the tone of the V30 before with this amp. Had always thought it be the speaker and not the amp. Wrong. The ice pick tone only gets worse with the EV as it is much louder. The Celestion Crème 90W ALNICO was one that did make a difference as it has more top end roll off.

I have played a newer Mark V when I was in NJ to try out the new TC-50. I did not notice it having the ice pick tone on CH3, it actually sounded really good but I was playing though it at a reduced volume level. However with the simple mod, my icy mark V is a monster that it should be at any volume setting. I normally use the FXloop active to use the master volume. I should try the FXloop off and see how that sounds. I could not tolerate it that way before, that may be different now. Change in V4 Still has plenty of bite with the bright switch off, adds a bit more with the bright switch on but not brittle and lacking the full midrange control. Seems that the 12AX7 in V4 tends to shelve the upper frequencies and harmonics and dampens the lower mids and sounds like you are playing though a tunnel or under a blanket. I have tried many 12AX7 tubes in this as well as in V5. The long plate Mullards did help a bit but still harsh in terms of top end character. JJ long plate ECC803s helped a little too but still not the same. The JAN/Phillips 12AT7 is the key in this solution due to its warmth compared to the Chinese verion that Mesa uses in the RA100 and TC-50 for the FXloop. There are other options if you are willing to pay the money, actually most are quite reasonable (except the Telefunken Diamond Bottom ECC801s as I could buy a new guitar for that price). I would personally stick with military grade for this application.

 

[Dreamtheaterrules]

Ok,ok, ok! I'm sold! Now to check the tube stash for a 12AT7. I do have a nice (EDIT!) Jan Phillips NOS 5751

 

[dlpasco]

The store by my house had JJ's and Tung Sol's. Tung Sol was okay in V4 but the JJ was better (for me) in V6.

I put the other Tung Sol 12AT7 in for the phase inverter on my Mark III and I think it's going to stay there.

 

[bandit2013]

I have one of those too. Have not tried the 5751 there yet. Out of my inventory I have three JAN/Phillips 12AT7, one RFT 12AT7 and a few Mesa Chinese 12AT7. The JAN/Phillips sounded the best to my ears in V4. The rest of the tubes are 12AX7. Mesa SPAX7 in V1. I should try the 5751 in V1 and see how that compares. Perhaps try it in V6 or go for a long plate 12AX7 (Mullard RI, JJ ECC803s or the sovtek LPS) which is what I have currently. Will also have to try the Mullard in V5 and see what happens. I was hoping to stay with majority stock tubes but I may be getting on the tube roll bug again with the Mark V since this is one of the amps that responds well to preamp tubes of different variety. I am thinking of pulling the STR440s from their sockets and install the SED =C= 6L6GC or the new quad of Preferred Series tubes that are similar to the TAD that has dual cup getters. Now that the brittleness has been reduced the other power tubes should sound much better.

 

[Wayno]

Back again,

I am so chuffed that all you guys are getting such great results with this simple mod too. I can't believe how much of an improvement it is. APEMAN, you are legend!

I always thought this amp was incredible from the get go to be truthful. I've not had many amps through my guitar playing life, first amp was a no name little 6W 6" speaker thing that had no tone to speak of at all. But it served a purpose, it allowed me to learn. Once my father had seen that I wasn't going to give up learning straight away he bought me a second hand Peavey Bandit. Very nice amp I thought, being my first proper amp. And, it allowed me for the first time to be able to keep up with my friends who all had marshalls and fenders etc. I loved the Peavey, could get great scooped 80's metal from it, even though it was solid state. I was gutted when it died, I had a local amp tech fix it but it was never the same, the distortion sucked after the fix. I then had left school and started work so I went and bought myself a Marshall AVT275. Clean channel was lush, both overdrive channels sucked though. Was gutted when I got it home and cranked it up, was so excited at the store when I bought it I never really listened to it properly. Gave all the channels a quick 5 minute run through and handed over my money. Fingers burnt, lesson learned! I struggled on with that Marshall for about 10 years, never could afford to improve it so just stuck with what I had. Then about 5 years ago my nan died and left me some money. Was supposed to be saving for a house with my girlfriend, now wife, but she agreed that this would probably be the only time I'd be able to afford a luxury "toy" so she agreed I could buy a Boogie. Now, what to get? Always wanted a Mark iV as a kid in the 90's, Didn't like the sound of any of my local bands pretty much all playing Dual Recs and Marshalls. Found a Mark V on Gumtree and went for it. I was blown away when I got it home. Every channel shined. My first real valve amp and it lived up to all the hype about tube warmth etc etc. Not perfect no, but still incredible. Now I thought to myself, surely all these people slating it for not sounding like a true iiC+ are either just butt hurt for some reason or just spouting off on the Internet about how great their iiC+ is. Same with the JP2C+. I've never played or heard in person either of those amps but have searched youtube comparisons extensively and listened to them through very good quality speakers on my hi-fi. I always thought the differences where so subtle that the cork-sniffers really where nitpicking over the slightest thing. And I still do hold that opinion to an extent.

Was i ignorant? Was i right? I don't know, what I do know now is that with this simple "upgrade" the Mark V is everything I always wished a high end amp would be if I could ever afford one. It was incredible to begin with, not perfect though. Ice was its only downfall for me. But now, holy **** balls! This thing absolutely smokes everything I've heard in the past. The iiC+ mode has turned me into a believer of how great those old amps must actually be. I could spend days getting lost in that mode if my wife and child would let me haha. iV mode is more of the same, just deeper and wetter if you know what I mean. Haven't had time to play much with extreme as I can't miss out on iiC+ and iV modes with the limited time I get to play. Hope I get enough time to really try it soon. I can honestly say I'll never be looking for another amp again, if this one, God forbid, goes south, I'll get another without a doubt. Untill that day, spare cash is going towards stocking up on my choice of preamp tubes to keep this dream alive.

I'm proper stoked that so many of you guys seem to be getting the same result as me. This last 2% of improvement is the difference between incredible and perfection I honestly think. Spread the word people so this amp can get the praise it truly deserves! Maybe Boogie themselves might stumble across this thread and consider it as an option?

Thank you again APEMAN, Bandit2013 and the rest of you guys, you rock.

Peace,

Wayno.

 

[Wayno]

Sorry about the ramble above, I'm just super happy 8) 8) 8)

 

[dcphillip]

Hey guys, just picked up a Mark V a couple weeks back and have been enjoying the hell out of it. Its my first foray into Boogie amps after playing Marshalls for years, so there's been a bit of a learning curve. I have noticed the icepick in the highs and hi-mids when running the gain/treble high in Ch3. Its my understanding that the treble influences the saturation on this channel. I ordered some Jan Philips 12AT7 grey plates, and am going to experiment with swapping them out in V4 or V6. APEMAN, can you explain how you're able to dial in more gain with the reduced gain of the 12AT7's? Is it because you're able to dime the gain and treble knobs without the high-end fizz?

 

[dlpasco]

My take on this is that these amps have a lot more gain on tap than is actually usable. Even if you have to turn the gain knob a little higher than you did before, it’s still going to be PLENTY brutal as it is.

To be clear, I am a detuned metal player. I like the brütez tones.

 

[Wayno]

My take on this is that these amps have a lot more gain on tap than is actually usable. Even if you have to turn the gain knob a little higher than you did before, it’s still going to be PLENTY brutal as it is.

To be clear, I am a detuned metal player. I like the brütez tones.

Spot on this, I have iiC+ mode gain around 4 -4:30 o'clock, treble to around just past 2, mids around 11, bass at 9 or 10. That's plenty aggressive enough for master of puppets era Metallica. When I want more bottom I switch to iV mode and drop the gain to around 1 o'clock. Pretty normal V on the sliders for both. More than aggressive enough for even the most brutal of music. Any more gain would probably end up as mush in a full band context. There's more than enough gain on tap in this amp to allow for the drop in gain from 12AT7's in either V4 or V6 I personally feel. Maybe both might be too much if your looking to really get the most saturated tones but that would only really be a problem at the extreme of the spectrum and you'd probably only need one in both spots if you're really trying to get as vintage possible therefore you probably won't be looking for insane levels of gain anyway.

 

[dlpasco]

My take on this is that these amps have a lot more gain on tap than is actually usable. Even if you have to turn the gain knob a little higher than you did before, it’s still going to be PLENTY brutal as it is.

To be clear, I am a detuned metal player. I like the brütez tones.

Spot on this, I have iiC+ mode gain around 4 -4:30 o'clock, treble to around just past 2, mids around 11, bass at 9 or 10. That's plenty aggressive enough for master of puppets era Metallica. When I want more bottom I switch to iV mode and drop the gain to around 1 o'clock. Pretty normal V on the sliders for both. More than aggressive enough for even the most brutal of music. Any more gain would probably end up as mush in a full band context. There's more than enough gain on tap in this amp to allow for the drop in gain from 12AT7's in either V4 or V6 I personally feel. Maybe both might be too much if your looking to really get the most saturated tones but that would only really be a problem at the extreme of the spectrum and you'd probably only need one in both spots if you're really trying to get as vintage possible therefore you probably won't be looking for insane levels of gain anyway.

Case in point: if you ever watch Ola England play on a Dual Rectifier, he's got the gain somewhere between noon at 1 o'clock. I don't think I've ever seen him get it past two, and it sounds insanely heavy.

 

[APEMAN]

-

 

[dcphillip]

Yeah, I think I'm currently running the gain at 1-2 o' clock right now. I'll take your guys word for it then. I was playing a Marshall Jubilee with a Maxon VOP-9 for metal before this, and that was plenty of gain for me. I think the Mark is a little deceiving because there's so much clarity even when the gain is cranked.

 

[dcphillip]

...can you explain how you're able to dial in more gain with the reduced gain of the 12AT7's? Is it because you're able to dime the gain and treble knobs without the high-end fizz?

Each gain stage comes with its own distortion characteristics, by using a 12AT7 you shift that's stage behaviour. In the v4 situation, by increasing the gain and treble you drive v1B and v5A harder while simultaneously decreasing the distortion contribution from v4B (12AT7). That results in a reduction of the overemphasized upper mid distortion aka ice pick.

More usable musical gain, less white noise.

Awesome explanation! Thanks for clearing that up for me!

 

[dlpasco]

...can you explain how you're able to dial in more gain with the reduced gain of the 12AT7's? Is it because you're able to dime the gain and treble knobs without the high-end fizz?

Each gain stage comes with its own distortion characteristics, by using a 12AT7 you shift that's stage behaviour. In the v4 situation, by increasing the gain and treble you drive v1B and v5A harder while simultaneously decreasing the distortion contribution from v4B (12AT7). That results in a reduction of the overemphasized upper mid distortion aka ice pick.

More usable musical gain, less white noise.

Awesome explanation! Thanks for clearing that up for me!

or possibly THAT could be it

 

[bandit2013]

that is good enough for me.

 

[Bankim]

This mod sounds very interesting. I can't wait to do this to my Mark V !!

 

[bandit2013]

In short: the 12AT7 used in V4 just sounds better due to the cascade circuit design. This may not work in other amps unless the top end is brittle and you would need to find out what tube is cascading into the other. It may be that both triodes form the cascade and in that case you are out of luck.

The long form: I had to compare the Mark IV schematics to the Mark V again. I did notice something missing on the Mark V cascaded common cathode circuit on V4, it does not have an cathode resistor bypass cap. This would introduce negative feedback in the gain stage. Also I figured out what the grid to cathode cap is doing, it is altering the Miller effect capacitance inherent between the grid and cathode by increasing it. That in itself will give the circuit a higher frequency response. To bad I am no tube expert and have not studied audio circuits in over 23 years. I am a bit rusty on that subject. Having the voltage gain of two 12AX7 circuits coupled with two gain stages that are tailoring the input capacitance of each stage will give way to improved higher frequency response. This will also support higher order harmonics adding to the brittleness of CH3. A reduction in the voltage gain on V4 with a 12AT7 will also have a different Miller effect capacitance associated on the pins of the triode should allow for change in the harmonic content. In layman's terms, a harmonic is a multiple of the fundamental frequency. 3k Hz would have harmonics at 6k, 9k, 12k, 15k, 18k and it goes on. Where the roll off begins may be higher than expected due to the design. This will result in a distorted signal that is more square wave in shape. The more harmonic content in the distorted signal the worse it will sound. Note that harmonics are a result of clipping the signal. If the efficiency of the cascade amplifier circuit is ideal like it is for transistors it will sound like poo. Tubes for audio are not inherently good for high frequency generation as they have more roll off due to the tube characteristic and associated Miller Capacitance. I am positive there is way more than I am digging into here.

An answer to a previous question: how can you dial in more gain if the overall gain is reduced? You can't but you can. All of the tone and gain controls are just a change in a voltage divider (for gain) or resistance value for some of the tone controls. The lower gain effect on the cascaded gain stage allows for larger range of control settings. With both V5 and V4 with 12AX7, lower settings on the controls will have the same effect as the case with one 12AX7 followed by the 12AT7. You think you are getting more but you are not. A higher setting on the gain with the 12AT7 will not be as effective as it would be with the standard tubes. In essence you increase the useable range to tailor you tone without sacrificing tonal quality. A 5751 will have a similar effect but will be closer to the original 12AX7 tube. Note if you use a JAN or NOS 5751 they are generally better tubes than the current production equivalent (which may in fact be 12AX7 that do not meet the gain character or specification of the intended 12AX7.)

 

[APEMAN]

-

 

[Dreamtheaterrules]

I checked my stash. I have no 12AT7 tubes but do have the Jan/Phillips 5751.

 

[Wayno]

I checked my stash. I have no 12AT7 tubes but do have the Jan/Phillips 5751.

Give it a whirl, I'd be interested as to the result you get,