Mesa MarkV / Saturation 'mod'

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Hi,

That's very interesting. The ice pick highs are the nemesis of all Mark V owners I reckon. Especially in iic+ mode I find. I've tried all sorts of things to eliminate it, different combinations of channel and Master volumes, presence and EQ setting etc. I even tried a bigger coupling cap soldered in place of the small one for iic+ mode after the EQ to try get some more beef out of the mode. Didn't seem to make any noticeable difference unfortunately. However, I was at home with a baby asleep upstairs so didn't get the chance to get it up to any decent level of volume. Had a gig the next day so put the original back incase something could possibly go bang. Maybe I'll try it again and see if it does help the beef of that mode at reasonable volume, it should do I would think. Anyway, I digress, I too have heard many times of substituting the 12AT7 in various other amps for similar reasons. Can't believe I hadn't thought of this before. Definitely gonna scour eBay for one after next payday and check it out.

Thanks for the inspiration.

Great video by the way. Proper chunky tone you got there.
 
Hi Apeman,

Thanks for the tube advice, it sounds interesting. Do you know if it makes a difference if it is the Jan Philips Grey or Black 12AT7WC tube? I see online that both versions are offered.

Thanks!

Mace
 
This makes sense. There is definitely a frequency there that is pretty much gone when its disabled. I've been using with the loop off for a while.
 
Good call there....

I have actually done this before. I also loaded V4 and V5 with the Jan/phillips 12AT7 and that changed everything. Gave the amp a more vintage tone which was nice for a change. I will have to give one of the Jan/Phillips 12AT7 another go but in V6 and leave everything else as is. Also have a JAN/GE 5751 to try there as well. I will have to check my inventory, may even have an RFT 12AT7 available as I bought the 12AT7 for replacements in my RA100's.

I have not given up on the Mark V yet.
 
I will agree with this and will do the acid test this weekend. I had started my tube rolling with all EH tubes, sounded good for a while but once they had a few hours on them I could not get rid of the low frequency hum on the clean channel. If I got past the noise level and just played the amp I did not notice the idle noise. Same applied to the Tung Sol, Loaded the amp with those and it sounded good for a while. Seems that tubes with coiled heater elements tend to add power supply noises (especially the tube positions that use the AC sourced heaters). Old Mesa 12ax7 tubes from the 90's (Chinese tubes with foil square getter) were the best overall in noise reduction. Gain characteristic was more compression on CH3. Also did the mix and match as well but never found ideal tubes to make the amp sound like I wanted it too. Main reason why I bought the JP-2C which ended my tone quest. After that, I lost my interest in the Mark V, and that carpet weight is beginning to collect dust which I find disturbing to the point if I do not use it, it must go mentality. Still if and when it is operating optimally it is a great amp to play though and make use of. The love/hate thing has to stop sometime....right?
 
I use Mesa SPAX7 in V1 as I found this seems too roll of the top end, at least in this amp of mine. Ran though two 12AT7 tubes (RFT and JAN/GE, selected the ones with the least amount of tarnish, not sure if the black is due to silver content or nickel). Was not a fix for me.... These tubes work great in my RA100 since the design uses them on the FXloop send and return. I could have tried the current Mesa 12AT7 as I have a few of those as well but opted out. The Stock 12AX7 tube seems to work great so what I had installed I will stick with at the moment. Mullard long plate RI 12AX7 also do a great job from V4 though V6. Those will roll off the top end. I found that tubes I install into V3 will be the culprit for the hum if they have the coiled heaters (heater wire is actually coiled like a light bulb filament) which are supposed to reduce noise but not introduce it. Typically a non-coiled heater element works better in that position and does not seem to contribute to the hum. Preamp tube positions that use the 6V AC heater circuit: V3, V4, V6, and V7. The tubes that use a 12VDC heater circuit are V1, V2 and V5.

I was looking at the schematic again....
CH3 signal path is: V1A -->CH3 tone stack--> V1B -->CH3 Gain control -->V5A-->V4b-->V3A-->(send return reverb CH3) -->V6A --> EQ Sliders--> FXLoop send/return -->V6B (master/solo). Of course if you opt to bypass the FX loop the signal would just go to the PI circuit (V7).

Since V5 is more critical in the gain chain than V6 I found the 12AT7 to be more effective there but at the time I was experimenting I did not have the schematic. The effect was Darker tone and less gain. V5 may be a better position for a tube with better top end roll off to eliminate the higher harmonics in the distortion (will provide softer clipping on the signal waveform). Would have to borrow the scope and frequency generator for a stable waveform to verify. More rounded corners and perhaps a dip in the center of the square wave would reveal high frequency roll off effects. A signal analyzer would also help to determine the harmonic content based on a single test frequency. This brings back memories some 24 years ago when I had access to such equipment in college. I used my Mark III as a test subject to determine frequency content and gain characteristics during my Senior year project.
 
Holy sh!t balls batman. Apeman is spot on.

Only had half hour and had to be quiet not to disturb baby but still...

Just received a couple JAN GE 12at7 from eBay today, popped one in V6 and wow, everything Apeman said is right. The top end is warmer, even at low volume. Much closer to how the amp sounds with loop bypassed. Can now dial in more gain without getting screech. Chuffed as punch as I find the solo feature extremely useful with the band and now it sounds as good as without as far as I can tell at low volume. Can't wait to get the chance to crank her up and really get her purring.

Also after reading through some of the other threads on tube rolling from bandit and Co I've hopefully got a couple 5751's winding their way over. Gonna have a swap around with them to see what I end up with.

Current V1 - V7:

V1 - Tungsol
V2 - JJ stock mesa
V3 - Sylvania 12AX7 long grey plate
V4 - Sylvania 12AX7 long grey plate
V5 - JJ stock mesa
V6 - JAN GE 12AT7
V7 - Sovtek LPS

V8 - 10 JJ EL34ii

Still have the stock 6L6's so will have to try them again too.

First thing will be to try a 5751in V1 and move the Tungsol to V2 and see how channels 2 and 3 respond. More on that soon hopefully if anyone's interested.

Apeman thank you again, still can't believe I hadn't considered the 12AT7 before. Sorry if I've hijacked your thread.

This amp always had balls, now it has cojones :p
 
Hi apeman,

Yeah worked great thanks.

Had another spare hour over the weekend and tried my second 12at7 in there as well.

Revised;
Current V1 - V7:

V1 - Tungsol
V2 - JJ stock mesa
V3 - Sylvania 12AX7 long grey plate
V4 - Sylvania 12AX7 long grey plate
V5 - JAN GE 12AT7
V6 - JAN GE 12AT7
V7 - Sovtek LPS

V8 - 10 JJ EL34ii

Sounds better still, like bandit stated before, has a more vintage feel to it. Really digging it :) and no noticeable gain drop.

Can't stretch to new 6L6's at the moment as have littluns first birthday coming up but hopefully will get the chance to get the amp out in the garage soon so I can can crank her up a bit and try the stock 6L6's. Preferred the EL34ii's with the original 12AX7'S but got a feeling they might feel better now the highs are tamed a bit.

Got to admit I have been twitching after the JP2C for a while as much as I love the Mark V but this has put that itch well and truly to bed.

I am one happy chappy!
 
Hi,

I also tried the AT7 in V6 to see if it could reduce a bit of ice pick at higher volumes/gain. I was running the Mark V through a Thiele with EVM 1x12 (the older 300W Thiele cabinet). I must say, it seemed my listening position made more of a difference in the tone (on axis or off axis). On axis listening was more harsh on the ears than off axis. This seemed to have a larger effect than the tube V6 tube swap. This was at about 100 dB sound volume.

I'll do a bit more testing with the rectifier 2x12 (stock V30s).

I guess my main point is for those suffering from ice pickiness, listening position and/or cab placement can make a huge difference. Also, just how loud in dB are you experiencing this?

Is it like 90, 100, 110 dB? The human ear can only take so much volume before it also "clips". The perceived frequency response of the human ear is dependent on sound volume. The louder it gets, the more the mids fill in. So, a deep scoped tone at low volume sounds good, but doesn't to me at higher volumes (too much treble and bass). I have some CD's which sound flat and muffled at lower volumes, like 70-80 dB, but when cranked up to 95-100 dB listening level they just come alived, no muffled or soft tones (my tube amp stereo has no tone controls). Guitar tone as similar well. Mesa's are critized for being "muffled" and "under a blanket" or "too thick" and that may be true at home or at low volumes (to some degree). But, when gigging, and turning it up in a big room, the tone balances to the human hearing EQ very, very nicely.

sorry for the ramble...

Mace
 
Hi Apeman,

I'll give it another try for sure. I wanted to a "reset" and go back to my original tube set (from Doug's tubes) so I've been playing with those for a couple weeks now and haven't had time to mess it. I'd rather be playing. haha

But, my question for you would be: how much difference do you hear between standing off axis and on axis when using the Thiele only? I mean, when you're like 4-5 m away from it and directly in line compared with 4-5 m away and at a 45-60 deg. angle to it. To me, this is a dramatic difference in the "ice pick" or "grainy" sound that can occur. Off axis is way less "in your face". I think this is all normal, of course. But, my point is, this "axis vs. off axis" difference to me was much more dramatic than swapping V6 with the JAN AT7. This as at about 100 dB in the room.

That being said, I'll still do some comparison with the tube rolling.

Thanks and keep rocking,

Mace
 
Great thread!

I've been at odds with my MV since purchasing ten years ago but I believe in the versatility of the platform and the Mesa brand itself so I've continued the 'good fight' as it were. Recently, I purchased a retube kit from Doug's Tubes and I have to say, the amp came alive in so many ways. In fact, during one band practice last week, the amp sounded amazing. Like, for the first time ever...it sounded SO GOOD. But alas, as everyone knows how finicky this amp can be, it didn't sound quite as good the next night's practice (same settings of course) but at least I know it's in there...right?

I started following this thread a couple of weeks ago and pulled the trigger on two JanPhillips 12at7s (gray plate) and finally installed them yesterday in v5 and v6. After allowing the tubes to 'burn in' for a few hours, I must say the mod actually removed almost all shrill treble and 'ice pick' highs from the amp. However, the gain curve also suffered quite a lot...to the point where I had the gain on ch2 (Crunch) and ch3 (Extreme) almost dimed and still did not get anything near a luscious tone.

So today I am going to try swapping the JanPhillips 12at7 in v5 back to the Ruby 12ax7 and see what happens. I'll then swap the Ruby in v5 back to the JP12at7 and try replacing the other JP12at7 in v6 and reinstalling a Ruby 12ax7 in its place and will let you know what I find. I'm thinking that if I can remove at least some or most of the shrill highs and retain the majority of the gain structure of the MV, I should have no complaints whatsoever with this amp. That's my hope anyway...

Sorry for the long post...Wish me luck and stay tuned!
 
Instead of using the 12AT7 in V5, try it in V4 which is following the gain stage of V5. The tube positions do not follow the gain stage chain. I have done many tube rolls, actually liked the 5751 in V1 but would probably work well in V5 or V4. unfortunately the cost a bit more than the 12AT7. I will have to play around with my Mark V and see what works. Actually I am satisfied with the 12AX7 tubes that are in it. No shrill or ice pick at the moment. Also, the long plate 12AX7's are typically lower in gain than the short plate designs. JJECC803S is slightly lower in gain than the Mesa 12AX7 tube. I have used them in the V5 and V4 positions and like the results. Tube rolling can become expensive when you fall into that hole.
 
Sorry If i ramble on a bit, but I'm stoked now.

Took Bandits advice, swapped V4 and 5 and wow. Got a couple hours free after work and shopping with the wife today so grabbed the Mark V, shut myself in the garage and cranked her up. Heaven! Not to band levels but loud enough to open up the power section.

Always kind of did what Mace had said and stood to one side a bit before, but don't need to any more. Had the amp sat on top of my PA speakers right at head height, pointed right at me about 2 meters away and no ice at all. Just clean, clear chunk!

iiC+ just rips, seems much more chunky with the top end rolled off the way it is now. Smaller coupling cap, no pull deep, doesn't seem to matter now. Master of Puppets was a dream to play, had the tone dialed in perfectly. Nice and thick sounding right in front, which is heavenly. Can now push up the gain, treble and presence to higher points with out getting screech. Bass too, no flub until nearly 12 o'clock. Just can't get over how full iiC+ sounds now, it's incredible. Crunch on Ch 2 sounds awesome too. Got Donny boiler, I believe it's his, VH brown sound dialed in and it's great. Rage against the machine, foo's GnR etc all sound great. Can't wait to get another chance to turn her up again and experiment with Edge. Just wish I had my gear set up so I could record something. Nothing less than properly micing it up would be a disservice to how great it sounds now.

Apeman, Bandit and the rest of you, thank you muchly

Wayno.
 
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