The Mark V90, Longest running Mark Series to date

[bandit2013]

My first experience with the Mark V90 started back in 2012. This was my third Mesa amp I ever purchased, and I had hoped it to be the pinnacle of excellence as the Mark III and Mark IVb were in some respects. I have owned the Mark III for 23 years before selling it to a friend. It was a great performer in all respects. The difficulty with that amp in general was dialing it in as it was complex to go from lead to clean or crunch and have a good sound for all three channels. Leave it in the lead channel set and forget. I bought it new in 1989 and it had a blue stripe on it. Not green. This was my first regret as I sold it but should have held onto it. My second Mesa was the Mark IVb which was much easier to dial in due to the channel separation of sorts. I enjoyed that amp for 12 years without any issues. Then I decided to get another Mark amp, the Mark V90. Much different than the other two. At the time I bought it, the Mark III had the longest production run of 11 years. Now the Mark V90 has surpassed that production run which is now at 14 years, and they are still in production today. Sure, the Mark VII came out in March of 2023. I finally got mine in July of this year. Also bought the JP2C in 2016. The Mark III and Mark IVb were sold off, not to support any purchases of the next generation. I do regret letting them go and probably would not have done so if they were both head units instead of combo amps. Why am I creating this post? Well to describe my experience with the Mark V90 since I have owned it. My Mark V90 was made in 2012 after the change to the original release of 2009 so it does have the CH3 tone stack changes that occurred in 2010. The actual board change may have occurred at the end of the 2009 year, so it was copywritten in 2009.

For those of you who are familiar with the Mark V90, it may be obvious that there have been changes to mine as a result of component failure. Early on, I had issues with the amp continually red plating the power tubes. Mostly in the Class A sockets. I was lucky to get 2 hours of use before they failed. It was just my luck of the draw I suppose. I should have sent this to Petaluma for repair while it was still under warranty after the screen resistors blew out. Unfortunately, I did not and took it upon myself to void the warranty to replace the screen resistors with something that would but burn up and catch fire like the carbon composition resistors did. It took over 2 years of red plating tubes before the screen resistors burned out. In my trials in tribulations of owning the Mark V90, I did come across two power tubes that would survive the torment of incorrect bias: SED =C= 6L6GC and the Tung Sol 7581. The Stock STR440 would not run for very long before going cherry on me. I eventually gave up on the Mark V90 as I got two other amps to replace it. Royal Atlantic RA100 and the Roadster. I still had the Mark IVb at that time. Since day one, I had some other issues with the Mark V90. It was very brittle sounding in most respects. Ch1 tweed was an ice pick, Ch2 edge was an ice pick and most of Ch3 was an ice pick (MKIV and Extreme). The only work around for CH3 was to dial out the presence and treble and reduce the gain down to about 9am. The other issue which probably some of you have experienced is the terrible tone suck you get with the FX loop. I have searched for a few years to find a solution or something that would actually work in the FX loop of the Mark V. To date, only one brand comes to mind that I am still using, Strymon. Just about all of the Fx pedals that worked with the Mark III and Mark IVb including the rack units I had did not work with the Mark V90. More of a buffer overload and poor performance mostly due to the input buffer tolerance to line level signals but mostly because of the mismatch or high output impedance of the SEND. The FX recovery was just fine. Just for Smiles and Grins, I decided to try slaving the Mark V90 from the SEND jack into the Roaster return. That confirmed my thoughts that the ice pick characteristics were that of the preamp and not the power amp section. Sure, I have discovered that the Mark V90 does respond quite well in tone shaping with different preamp tubes of the same family 12AX7 from short plate to long plate, Mullard to EH, Tung Sol, Chinese, NOS JAN tubes and so on. What may have fixed some of the ice pick sounds resulted in a boxy tone I did not care for. The Mark V90 was placed aside for a rainy day.

Along Came the APEMAN and a novel trick. Now his goal was a means to address some of the FX loop issues if I recall correctly. As a result of this a different characteristic emerged and resulted in the Saturation Mod thread. I was interested in this trick as it may be a fix for my Mark V woes. It had merits. At the time the JAN/Phillips 12AT7 was quite affordable and I had some on hand as I had started tube rolling the Royal Atlantic and it uses a 12AT7 for the FX loop. I gave it a shot and it was interesting. The Mark V schematic can be found online but it is not complete. It is also the first release of the 2009 version. Most of it is accurate for the bulk of the preamp and such but with a few errors. After review of the schematic, and the aid of a few online triode gain calculators I can see the change in gain response across the frequency band. It seemed that the V4B triode circuit used to accentuate the asymmetrical clipping circuit had the tendency to push the upper boundaries of the higher frequency with no limits when using the 12AX7 model in the calculator. When you change it to the 12AT7 you get some good high frequency roll off. I assumed this would cut back on the shot noise effect of odd order harmonics, in other words cut back on the ice pick. It did. Note that the amp will need to have all Mesa 12AX7 (JJ ECC83) tubes installed to take any effect of the JAN/Phillips 12AT7 in V4. To be honest, I am not sure what became of the thread. APEMAN sort of left and most of his posts were deleted. There was some good information to be found from his comments as well as other participants in that thread. I admit, I did go overboard and began making some modifications to the circuits, Removal of C39 and a few others. That may have helped some, but it did not take long before I lost interest in the Mark V90 and basically left the forums for a few years. During that time, I had restored some of the mods but to me it was worth the experiment as I learned from this. C39 was painstakingly difficult to reinstall. I was able to manage though. However, I did not go back to the 120pF cap. Instead, I used a 47pF cap to replace it. After doing that the JAN/Phillips 12AT7 was no longer required in the V4 position. I did leave one mod in the mix of things, it was the 10K resistor to couple the two caps on the GEQ circuit used on the output circuit. These two caps were switched by a relay, one for the IIC+ mode and the other for all other modes. I did not see any reason to remove it. Just for reference, it is not necessary to do any of the hard mods that were discussed in the Saturation Mod thread. If I messed up my Mark V90 in the process, I did not care. I did report what I though worked and excluded some of the other changes I tried. I would recommend only doing the safe mods such as preamp tube rolling as that does not require removal of the amp chassis or digging into a circuit board that could have high voltage stored within its large capacitors. If you ever disconnect any of the ribbon cables, please do ensure that you get them installed correctly. Failure to do so may result in something not working or failure of a JFET or two. That had happened to someone who tried the C39 removal mod, you need to disconnect a few ribbon cables for access, and they forgot to reconnect them when they powered up the amp. Just play it safe and stick with the preamp tube changes. No need to do any mods unless you feel it is absolutely necessary. Get a certified tech to look the amp over first as your issue with the amp could be something else. Hard mods are not worth the effort, and they will void your warranty if you still have one.

Then came along the Mark VII that brought back some interest in the Mark V90. How do they compare? There are some similarities and I have already posted such and no point in repeating here. I have written enough already.

This is just a starting point as I have more to share on my endeavors.

There is more to be said about preamp tube rolling and power tube selection. This will follow this post as I tend to be wordy. Sorry for that.

 

[bandit2013]

Tube rolling: This is one of the best features of the Mark V90 as you can tune the preamp to suit your needs. If you love your Mark V90 as it is, there is no point in doing this. I was not one of the fortunate ones to have a Mark V90 that I thought sounded good. Quite the contrary. As I stated before, it can be very brittle or have an ice pick characteristic that is undesirable. My Mark V90 was originally a head unit. I found it a pain to make changes to preamp tubes due to limited space available. The year mine was made, did not have an access port behind the faceplate like the JP2C and Mark VII have. Instead, I opted to convert mine to a combo. I did not have much luck with the MC90 speaker as I kept blowing them out. Well, it turned out the bias was a bit too rich for the class A sockets which explained why the amp was always red plating the STR440 tubes. I did some trial and error with the bias circuit and modified it to a happy median so I can run the amp with the STR440 tubes without instant failure.

Preamp section: There are many preamp tubes that can be used to tune the preamp. Mullard CV4004, Tung Sol 12AX7, Mullard reissue long plate 12AX7, SovTek LPS. Svetlana 12AX7, Electro Harmonix, Mesa 12AX7 (JJECC83) Mesa SPAX7. Chinese variations, JJECC803s. Any 7025. JAN 5751, JAN 12AX7WC and any other NOS tube you can think of. It will work in the Mark V90. In order to tube roll the preamp, you need to have easy access to the preamp tubes. Best if you can leave the power tubes installed and not have to wait for them to cool down so you can remove them to reach the preamp tubes. I normally just pull the chassis out and place it on the speaker cab inverted. Remove all of the tube shields. Also, most importantly, it is best to use the speaker cabinet you intend to run with your Mark V90.

Since my choice was to use the EVM12L Classic, I had loaded one in the combo shell and also have one in a matching widebody 112 cab.

Some of you have stated your Mark V90 sounded boxy or lacking. You are probably right. Bright or brittle. Well to be honest, most of that characteristic is the preamp tubes. I found the Mesa 12AX7 tubes to be inconsistent. Not complaining about them. They are good tubes but not particularly with the Mark V90 as they do contribute to the boxy tone almost as much as the power tubes. The EVM12L classic speaker is no exception as this will enhance the true nature of the amp's tone. It is boxy it will be more so with the EV. Almost sterile as that speaker has a relatively flat frequency response curve.

For the longest time, the clean channel has had this low frequency hum that I could not get rid of. I have tried many different preamp tubes and it was always there. Mesa 12AX7 to JAN/Phillips 5751. I did have a few Svetlana 12AX7 reissue tubes from New Sensor. I believe I bought them from "thetubestore". Never tried those. Installed into V1 and low and behold the low frequency hum was now gone on the clean channel. That tube is similar to the Tung Sol or Mullard CV4004 but has a bit less gain and does not have the same tone characteristic. This was also the first time I actually enjoyed the tweed mode on the clean channel. More on that later as I believe some of that is related to the power tubes. V2, what I felt made CH2 sound the best was a Tung Sol 12AX7. It cut back on the ice pick sound of the Edge mode and improved the crunch and Mark I modes as well.

I will just to the last tube that will also influence the tone characteristic to some degree. This also effects overall loudness. The phase inverter tube V7. Many may prefer the Sovtek LPS tube. It does a decent job as a phase inverter. Sure, why not use a JAN 12AT7. That will work great too but I found it took away some punch and drive from the power tubes. Since this is a different amplifier compared to the Mark III, Mark IVb, or JP2C, it has some major differences in the negative feedback circuit (presence control). What is especially notable is the Extreme mode on CH3, it adds in a capacitor in the presence circuit and then it switches from the 8 ohm tap to the 4 ohm tap of the OT. The 12AT7 did not seem to behave as good as it could with that particular mode. There is an identical tube to the Sovteck LPS which is labeled as a Mullard reissue 12AX7A. They are the same tube but the Mullard version is the better quality of the two and the Sovtek LPS is the lesser quality version. There is another sold under the Gold Lion brand called the B759. That one is a little different as it has gold plated pins and a high price. I prefer the Mullard reissue 12AX7A for the phase inverter.

Now for the rest. This is where most of the defining features comes into play. V6 will affect tone of the CH1 and CH2 if using the FX loop in active mode. The other triode of V6 is used as the last gain stage of CH3 where some of its defining modes are assigned. IIC+, IV and Extreme. Some tubes like the CV4004 will do good but may tend to make the amp sound boxy. Mesa tube will just make it brighter. My goal was to get the Mark V90 to tighten up a bit, lose the boxy sound and perform well. I had to dig up some old preamp tubes from my Mark III days. Mesa Chinese Military grade Shuguang square foil getter tubes. The one's I have were basically used up. A few were still good though. I did come across a good bargain of these from Doug's Tubes a few years ago. I basically bought most of what he had on hand. I have seen them for sale on Reverb for around $40 each. Not bad for a NOS tube. Yes, they sound terrible in the JP2C, Fizzy is the better term. However, they do work well in the cathode follower circuits of my Rectifier amps. Better yet, they perform exceptionally well in the Mark V90 from V3, V4, V5 and V6. You can just about make them out in the first picture. Here is a close up of the tube in question: The Mesa branded ones on the left and the generic (Ruby) on the right. The Mesa branded ones were tubes I changed in my Mark III when I needed to replace the power tubes which was about every 4-6 months of hard use during the band days back in 1990. There are some that look similar but they are not as good. Those have a halo getter and not the flat square foil getter.

This may be a better picture of the Chinese Military tube that Mesa used back in the 80s to the 90's.

The best feature of these tubes, they are quiet. No hum, no noise at all. Also when used in V3-V6 the characteristics of all three channels are great. The clean channel just rings out with great sound quality. Tweed sounds almost as aggressive as the crunch mode on CH2. CH2 remains tight and not as sloppy as it did with other preamp tubes. CH3 is as aggressive as it should be. Not brittle or ice pick. Low end is tight and punchy almost like the Mark VII.

The Power tube struggle. Since the Mark V90 is a bit different than the Mark IVb, it will not have much if any advantage when running an integrated quad of power tubes. The Mark IV had many advantages as you could run 6V6 if you ran the tweed power (same thing as Variac). You also had the ability to mix and match 6L6GC with EL34 (class A sockets only). The Mark IV also performed really well with different 6L6GC tubes, say for instance SED =C=6L6GC in the class A and TAD 6L6GCSTR in the Class AB sockets. It was a long time so the tubes may have been reversed but that sound was sinister and emulated that of the IIC+ I have heard in recordings or videos. This combination did not do much in the Mark V90 so I gave up on blending any power tubes. That was until recently. Mr TimothyMartin220 did just that with a pair of STR440 in the class A sockets and the STR441 in the class AB sockets. I tried this too after exploring the STR441 and found that was a game changer for the Mark V90. Some of you probably already are using the STR441 as that is what Mesa changed over too after the STR440 when out of production. The blend of the STR441 and the STR440 does sound great. Not as good or as sinister as the SED =C= and TAD tubes like with the Mark IVb. You get the sound of both the STR441 tucked mids and the beefy tone of the STR440. That is what is cool about the Simul-class as you can exploit the effect of different power tubes in the same family but of different construction. If you missed this in the one image, here it is again.

There is more to the Mark V90 than what you may have experienced. Much of this is with preamp tube rolling and some of it is with the power tubes. Enjoy and have fun. No hard mods required.

 

[bandit2013]

I finally got through a series of power tube swaps.
I will use the word outer for the class A/B sockets and inner for the Class A sockets.

I started off with a blend of the STR441 (outer) and STR440 (inner): This sound really good at full power as you will get some of the grind from the STR440 and STR441 as each has a different characteristic to them. With the STR440 in the inner sockets, you only get a blend of the two different tubes in the 90W and 10W settings. At the 45W power mode, it is all STR440. If you like that sound great.

STR448 (red bias color) in outer and inner sockets: Not bad sound. Worked best for the clean and fat and a bit on the bright side for tweed. Crunch and Mark I modes on CH2 were good but the Edge mode brought out the brittle character of the tubes. I tried both tube and diode power settings in the 45W on CH1 and CH2. Tube rectifier made it sound even brighter. Diode rectifier sounded much better. That was unexpected. CH3 was also on the bright side almost as if the tubes had a thinner sound to them. Could be the Red bias color as I found them to be weak with the STR440 tubes. Oh well, these will be reserved for the MWDR when I want to use the 7 string.

STR441 (outer) and STR448 (red inner). Almost the same effect as having all tubes the STR448. Same result. It seems that the inner pair sort of define the overall tone or grind characteristic.

STR441 (outer) and Preferred Series 6L6GC STR [similar to TAD 6L6GCSTR and different than STR448](inner) Almost similar to the combination of the STR441 and STR448. CH1 sounded great except Tweed was on the bright side. Did not care much for CH2 including the crunch mode. CH3 was back to square one on ice pick tones. Not for me.

Finally, just a full complement of the STR441 tubes. This actually had the best overall sound on all three channels. All power modes from 90W down to 10W. CH1 all modes were very nice. CH2 edge was usable as were the other two modes. CH3 had the best grind sound and remained articulate to some extent. I have run all power modes, and even ran with the bright switch on. The base remained tight and the grind on CH3 had that characteristic common to the JP2C or Mark VII.

There is some distortion that occurs in the power amp section and is mostly derived from the class A sockets. I had thought the bias was a bit off when I ran the STR441 tubes for the first time based on the low-end response I was hearing. I had this idea in the back of my mind to experiment with preamp tubes to see if that was related. It was. Before I rolled the preamp, it was quite different with some sagging low end that almost flubbed itself. It was there but not dramatic. The Stock Mesa 12AX7 tubes enhanced the brightness and ensured the boxy tone was in abundance. I tried a few other preamp tubes such as the Mullard CV4004 to see if their character would improve anything. It helped with the ice pick tones but made the Mark V90 more boxy sounding. That is when I remembered I had many of the Chinese Military grade square foil getter tubes, 10 of them were NOS and 8 of them were ANOS Mesa branded versions of the same tube. Some of you who have owned the IIC+ would claim they are fizzy as heck and they had the same effect on the JP2C. Those were my favorite tubes I have used in the Mark IVb that was originally stuffed with the Mesa branded JJECC83s tubes. However, they were stock tubes in the Mark III blue stripe. I had plenty of leftovers when I changed power tubes in that amp, I also replaced the preamp tubes at the same time which was not necessary. At one point I had at least 8 complete sets of them, but I gave them away to the person I sold the Mark III too. I did keep some of them for myself. At that time I did not know what preamp tubes were in the Mark IVb and assumed they were the same.

The combination of the preamp tubes helped to keep the low end in a bold character and not as loose or muddy as it was with the Mesa 12AX7 or other combinations I have tried. Note that I am running two EVM12L speakers for now. I have not tried any of the V30 loaded cabinets yet. That will come next after I get the amp chassis back into the combo shell. It is not that hard to swap power tubes so I can easily go back to the STR440 and STR441 combinations. I have yet to try the STR440 (outer) and STR441 (inner) arrangement.

If you missed out on the preamp tube choice, I wound up with the following:
V1 = current production Svetlana 12AX7
V2= current production Tung Sol 12AX7
V3->V6 = NOS Chinese Military Grade square foil getter 12AX7 (same tubes used by Mesa back in 1980 to 1990 before they changed to other preamp tubes and finally settled on the JJECC83s.)
V7 = current production Mullard 12AX7A (reissue long plate)

To be honest, I could not be happier with the Mark V90 as it is now. Before, I could not stand it much, let alone did I want to sell it to someone and feel guilty for unloading a crappy amp on them. Bargain price perhaps. Or just sell it for less than its real value at GC or Sam Ash. I was tempted to drag it there a few times, or to the curb side along with the trash. Instead, I used the Mark V90 as an experiment. Something to learn from and to explore different things with some of the preamp circuits (mostly minor things that were easy to remove or restore). Why is the Mark V90 different than the other Marks? Other than the GEQ inserted in front of the FX loop which is also used to generate the FX output signal, there are two additional gain stages that are not present with the other mark amps. V3A and V6A do not effectively replace the V2 of the early mark amps as that was used traditionally following the lead drive circuit and as the source for the FX send and FX recovery. The Mark V90 uses V6B as the FX recovery (return). That also means the clean channel also has two extra gain stages not present in the older Mark designs which is the V3A and V3B. If you opt to use the FX loop in active mode and not hard bypass mode, V3 and V6 will influence the tone of all three channels. In hard bypass mode, it will just be V3 as the FX recovery stage is completely bypassed taking out the global controls with it (output and solo). The lead drive circuit topography of the Mark V90 is essentially the same as that used in the Mark IVb (just different tube positions). There may be some differences in the negative feedback circuit (not talking about the presence here). These extra gain stages including V2 for CH2 do provide some room for tunability of the preamp. Not exactly sure why my Mark V90 sound nothing like the more recent version. Perhaps I just was fortunate to get the boxy ice pick option for the hearing impaired and not the general good sounding package deal that most of you have. At least for now, I can actually enjoy the Mark V90 for a change. Not sure I want to compare it to the Mark VII or JP2C at this time as I may get stuck in an endless loop thinking I can make the Mark V sound better than it does now. The key ingredient to some of this success is the STR441 power tubes. That was the best surprise I got when I first tried them in the Mark V90. Had them for several years and never had a good use for they as they sounded terrible in the JP2C. I am done. Nothing to see here, carry on.

 

[rarebitusa]

I've often felt the power section of the V:90 doesn't get the credit it deserves. Running other preamps thru it just creates multiple NADs

 

[bandit2013]

Yes it does. NAD announcement and this is the real deal. My patience has paid off with this experiment. This I did not expect at any time to be possible.

This is what my Mark V90 has in its current state. C39 (120pf) was replaced with a 47pf cap. It was what I had left in my inventory that had the same voltage rating as the original. This probably does not matter much at all so ignore that for now. (some of the mods I did in the Saturation mod thread). I did keep the 10k resistor that couples C49 and C99. It is a simple bridge to connect the two relay contacts that define the IIC+ voice. Probably not important mod to do either. I just thought I would point that out.

Power tube choice: STR441, bias color is green.
Preamp tubes:
V1=Svetlana 12AX7
V2=Tung Sol 12AX7
V3,V4,V5,V6 = NOS Mesa Chinese square foil getter tube from 1989 thru 1990. Aka Ruby Chinese Military Grade square foil getter 12AX7A. These were the means to remove the boxy tone from the Mark V and tighten up the low end.
V7= Mullard reissue 12AX7A long plate.

It was time to run the Mark V90 through a Mesa Vertical 212 cab. I was curious how this will sound. Since I was going to use the cab I had been using with one of the Badlanders for this trial, May as well hook up the Mesa Switch track and compare it to the Mark VII (original tubes).

Now I am impressed with the changes made to the Mark V90. OMG this is now on par with the Mark VII. Actually I think I prefer the Mark V90 a little more.

CH1 clean vs CH1 clean. very much the same tone and characteristic as it was difficult to distinguish the difference. I had to use the bold switch. I have also tried it in normal. The Mark VII sort of sits in between that voicing. They are very similar so they both get merits for excellence in the clean mode.

CH1 Fat vs CH1 fat. Yep, you need to make use of the normal/bold switch in the bold setting on the V to be a match for the Mark VII. Tried the fat modes with the GEQ set as close to each other as possible. That was a dead ringer for equality. There are some slight differences. Felt there was more presence and chime with the Mark V90 compared to the Mark VII. Still no sure which direction to lean towards.

Edge mode/Mark I mode vs ? The Mark VII does not have these voices or modes but I can dial in the Mark IIB voice on CH3 to sound similar. Mark I is much darker sound than the Mark IIB. So there are some differences to give merits too. The edge mode on the V actually sounds much better than it did before I made the tube swaps. I believe the STR441 plays an important role.

For the heavy side of the tone farm:

Mark V-IIC+ vs Mark VII-IIC+: Now we are talking apples to apples finally.
The power tube choice and preamp tubes really paid off with the Mark V from 2012. Not sure the GEQ mod helps but I think it does here. I am glad I kept that 10K ohm Jumper in place as it was a pain to solder in since you had to separate the two orange caps to get access to the leads of the two resistors. I tried to find the pictures I had taken so long ago. Not sure it is still in the saturation mod thread anymore.
Holy Crap, they almost sound the same. I left the tone controls at noon on both amps, set the presence to the same position around 11am. Gain was at noon. Channel master was also around noon and the output volume was at 11 am. Had to adjust the channel master on the Mark VII to be at a similar volume level. The Mark VII in the IIC+ mode is voiced just like the Mark V90 with the bright switch turned on. The added bonus of the Mark V is you can turn it off. Mark VII does not have that feature. Bonus points to the Mark V. You can compensate with the Mark VII by reduction of the presence control or change on the GEQ to remove some of that brightness. The low end has just a subtle difference but I felt they were both on par with each other considering each amp is pushing different power tubes. This was a rude awakening for me, I am very glad I did not sell of the Mark V or give it away to a friend I do not like much. Ha deal with the ice pick hell. Nope, That seems to have been cured once I got away from the Mesa branded JJECC83s tubes in the V. Never expected this.

Mark IV modes. Yep, the same thing here too. Mark V90 delivers the goods just as well as the Mark VII. Again, it is with the Mark V90 using the bright switch to on. More bonus points to the Mark V90 as I can use the switch set to normal to darken the tone.

So what compares to the Extreme mode? When I did the first rundown of the Mark VII I did a brief comparison to the Mark V90 before I made the tube changes. Mark VII mode on the Mark VII is damn close to the Extreme mode on CH3 of the Mark V90. Yep, Now it sounds almost the same but with the bright switch turned on. More bonus points to the Mark V90. I can set it to normal for a darker tone too.

FX loop is the only major difference. The Mark VII did make the proper corrections to the FX loop output impedance. It is much on par with the JP2C so I believe the VII is also a tube buffered send level. It is plate driven so it makes use of a voltage divider network to get to the desired signal level. The Mark V90 makes use of a PNP transistor at the tail end of the GEQ circuit. I do not mind the tone suck issue as my resolve was settled when I moved over to using Strymon gear.

The added bonuses the Mark VII does not have in a tone shaping characteristic.

• Variac Power mode.
• Tube rectifier tracking for CH1 and CH2 for use with 45W power modes.
• Triode/Pentode switch for CH3
• Normal/Bold switch on the CH1
• Normal/Bright switch on CH3
• Mute / tuner out
• Solo/global volume control
• 10W power mode, well the Mark VII does have a 25w power mode. The Mark VII does have a beefy power transformer so the three power modes may not be all that favorable for bedroom level playing. The Mark V90 does a decent job with the 10W power mode for that purpose.

The added bonuses the Mark VII does have that the Mark V90 does not.

• Midi controller and improved switching of channels. Almost noise free. No more relay chatter when using variac power mode or having a loose connection or poor connection of the footswitch cable causing some features not to work.
• Front panel switches to select channels (if not using the footswitch), no more reach around to rotate the knob on the back.
• Front panel switch to turn on/off the FX loop, Mark V has a rotary switch to select fx modes.
• Front panel switch to turn on/off the reverb. Not sure what happens with the Mark V90 as the only means to turn the reverb on/off was with the footswitch.
• Reverb level controls on the front panel.

I am sure I am missing something. Would I consider buying another Mark V90 again. After this experiment has ended I would have to say; yes I would.

Now I want to convert the combo to a head unit. Damn, should have kept the head shell but I sold it. I do not mind the Mark V combo but is much heavier than just the head. Easier to get to the preamp tubes if I need to make any changes. I wonder if Mesa had made any changes to the Mark V90 over the years it has been produced. I am sure some components may be different or if they made any slight design changes to improve on the product without notification. I am finally happy with my Mark V90. Damn this took 11 years to gain some respect for the Mark V90. I held onto it for some reason. Now I know the deal and have no regrets keeping the amp all these years.

 

[rarebitusa]

Holy Turnaround Batman... I am stunned.

 

[bandit2013]

I believe this new found change in the Mark V90 is worthy of a video. I am stoked about this change.
It was not my end goal for the Mark V90 to sound identical to the Mark VII. I just wanted to kill the boxy tone and shrill it had with the stock complement of preamp tubes or even some alternates. The STR441 did introduce more interest in the Mark V90. That was a surprise. It was more rewarding when I decided to see what the V30 cab would sound like. Then the side by side comparison to the Mark VII just nailed the coffin shut on the Mark VII. I like the VII so I have no need to toss it aside in favor of an amp that has more tone variations. That is like saying the JP2C is garbage as it is only a two trick pony. Too bad the Mark VII did not have the voicing switch on each channel like the Mark V90 has as I would have given it a better judgement. I hate overly bright amps. The Mark VII is bright but so far it has not crossed into that ice pick boundary like the Mark V90 has done consistently for the past 11 years of ownership. I do not feel the same way about it now.

I have some vacation time coming up at the end of the month so I will do what I can do make it happen. I will pit the Mark V90 against the Mark VII. I will need to move stuff around first as my studio is full of stuff a wall of guitar and bass amps and a full drum set. I also have a jam session coming up that week so it will be interesting to see if this can be managed.

Yeah, I know I left out the cab clone IR in the features of the Mark VII. I will never make use of it so it was not listed.

I just realized something. Both amps have a 45W power mode. Considering the Mark VII changes the pair of class A tubes from Pentode to triode to get the 25W power mode, the Mark V90 would do the same thing as it has a pentode/triode switch for CH3 right? I do believe you can use it in the 45W power mode as you can in the 90W power. Also the CH1 and CH2 have tube tracking capabilities in the 45W power mode. Wonder if they remain in pentode or triode when using CH1 and CH2? The addition of variac power just adds more flexibility to the Mark V.

OK, the Mark V90 has a total of 9 voicing modes vs the 7 of the Mark VII since two of the voicing modes are duplicated on CH1 and CH2. After the preamp tube and power tube swaps in the Mark V90, I actually found the tweed and edge modes quite useful. Before I tried the STR441 power tubes, I could not tolerate the tweed and edge modes as they were ice pick makers. Some of this is also related to tube choice used in V3 and somewhat related to V6 when using the FX loop in active mode.

I did consider getting another head shell to restore the amp to its original form as it started out as a head unit in the first place. Tempting, but not going to happen. I sort of like the combo with the EV classic as this brings me back to the Mark III combo I used to have. Heavy as hell though. I think if I make any changes, I will need to get the caster plates and castors for the combo since the person who converted their combo to a head sort of opted not to have the castors and plates installed.

Also when stacking the combo on top of the widebody open back 112 cab, the base of the amp is much deeper than the top of the 112 cab. Not a good fit and easy to push the whole thing over.

 

[DW54]

Mr Bandit2013: did I read in one of your posts that you have experienced problems with the footswitch of the Mark5? I've had problems with the EQ function only on 2 different footswitches! First one I ruined trying to change the DPDT eq switch.The second brand new one from Mesa worked fine until it started glitching on EQ only once again. Gently wiggling the cable to footswitch connection sometimes solves the problem temporarily. Obviously the cable connector or the footswitch jack? or could it be more complicated? P.S. Your recent posts have been incredibly informative: keep them coming!

 

[Slash_83]

Mr Bandit2013: did I read in one of your posts that you have experienced problems with the footswitch of the Mark5? I've had problems with the EQ function only on 2 different footswitches! First one I ruined trying to change the DPDT eq switch.The second brand new one from Mesa worked fine until it started glitching on EQ only once again. Gently wiggling the cable to footswitch connection sometimes solves the problem temporarily. Obviously the cable connector or the footswitch jack? or could it be more complicated? P.S. Your recent posts have been incredibly informative: keep them coming!

Ciao Hello, I had problems exactly today with the Mark v footswitch.
I can tell you after several attempts, that the problem was in the central pin of the dpdt of the eq switch . The track (ground) was no longer in contact. I solved it by creating a bridge with a wire to ground.

 

[bandit2013]

I had done something similar with the footswitch, I also did a wire bypass inside to fix the grounding issue. Still, my EQ sometimes works and sometimes it doesn't. My fix was just to leave the GEQ on or off depending on the channel. Considering the design is not much different from the Roadster except for one more channel and no EQ. I have yet to have any issues with that long brick. Also found that some things do not work right all the time if I opt not to use the footswitch. The Mark V is not perfect. I would have to look at what is being offered as a replacement on Mesa's store site. I assume that is now working again. All I can do is add it to wish list but it does appear they made changes. That extruded aluminum used for the original sort of does not really fit with the PCB and it has a bow to it when it is installed. I think they use a hammer or arbor press to get the board inserted into the extruded aluminum channel. In my opinion, the footswitch with the plastic ends and extruded aluminum housing is not really all that good.

 

[mace]

The currently shipping footswitch style is more rounded with flush sides, like the TC-50 footswitch. Sweetwater lost my original footswitch when trouble-shooting a reverb issue. Being the good folks they are they did replace it with a new one, which was the newer rounded style. The only issue I had with the old one was the cable plug went bad, likely someone stepping on the cable when it was plugged into the footswitch. At Mesa's recommendation I replaced the cable with a cheap one from Amazon and it's worked fine since.

 

[bandit2013]

Anyone gone through any tube rolls with your Mark V90? If so, what did you try out and how was the experience?

 

[bandit2013]

I see that the Beijing square foil getter tube may be in the unobtanium category. 6N4-J or whatever they call it. There are tubes that look just like them with the exception of the getter. They are not the same tube. I have a few of those I got in some tube cocktail thing from Doug's tubes. Those just are not good and not the same tube. The square foil getter on dual posts were only made in Beijing.

Just for the sake of sanity. I just ordered some JJ E83CC tubes. They were released sometime in 2019. The "frame grid" type is new to me. They may suck or work. Not sure. Taking a gamble on 7 tubes to find out if they live up to the hype or is it just another blah tube. Then there is the EH 7025 which I probably will not get anytime soon. I found the EH, Tung Sol, and similar tubes tend to get this nasty hum going after a month of use. Yeah, I have tried all full load of Tung Sol, EH, and Mullards without any mix of trade names. Well this was with the STR440 days. The STR441 tubes really do sound much better than the Shuguang 6L6GC tubes that had Mesa's branding.

I also have a few NOS JAN/GE 12AX7WA tubes to mess with. Not sure what to expect with a loaded V90. May have to use a JAN/Phillips 5751 in a few places as I do not have enough of the 'X7WA to fill the amp.

The last tube roll as stated above did sound very close to the Mark VII. However, I have found you need to run the V90 closer to a gig or stage level to get the same effect as the VII. The VII is much louder and has more tone density to it. The JP2C with the STR415 power tubes has that tone density and more gravity to its sound. Heavy, articulate and punch with authority. I do not believe that is achievable with the Mark V90 by any means. You can get somewhere close to the Mark VII but the JP2C is untouchable by either V90 or VII. To me, it does not matter which has more gain, but which has the most usable gain.

 

[Wayno]

Hi Bandit, you may not remember but I was the one who forgot to replace the ribbon cable and blew the JFET. Good to see you back on here. First look on here myself for a few years, been ultra busy with wife, kids, moving house, work etc. Haven't plugged in the Mark V for a few years and only picked up an acoustic once or twice in all this time. Glad you've found some love for the Mark V. I had mine in a very happy place with the tube selection and one or two mods I settled on. Hopefully, I can find the time to "get the band back together" soon and crank that sucker up again.

 

[tbonesullivan]

I had a MESA 7025 STR square getting crack on me. I almost cried. Those square getting Beijing tubes were pretty much what everyone was using in the late 80s and 90s. I got a Rivera R55-12 from 1993, and it was full of them.

 

[bandit2013]

I had a MESA 7025 STR square getting crack on me. I almost cried. Those square getting Beijing tubes were pretty much what everyone was using in the late 80s and 90s. I got a Rivera R55-12 from 1993, and it was full of them.

Yeah, I think I understand what you mean.

 

[bandit2013]

Hi Bandit, you may not remember but I was the one who forgot to replace the ribbon cable and blew the JFET. Good to see you back on here. First look on here myself for a few years, been ultra busy with wife, kids, moving house, work etc. Haven't plugged in the Mark V for a few years and only picked up an acoustic once or twice in all this time. Glad you've found some love for the Mark V. I had mine in a very happy place with the tube selection and one or two mods I settled on. Hopefully, I can find the time to "get the band back together" soon and crank that sucker up again.

I remember. I felt bad about the issue and glad you got it fixed. Still it was a bummer it happened.
Good to hear from you again.

You can always fire up the V any time, I was running mine this morning at 3am. Thanks to my dog waking me up earlier than usual. I jumped onto the Mark VII around 6:30 this morning.

Yeah, Still have the same old ice pick V90. At least I learned a lot from the Saturation mod thread. What works, what does not. That was a cool experiment but have no plans on doing anything like that again.

 

[woodbutcher65]

I have a nice little stash of square foil getter Beijing tubes, now I need to cycle them through an amp and sort out those that are good from those that are bad. Or varying degrees of somewhere in between. It was this thread that alerted me to their potential.

 

[Wayno]

I remember. I felt bad about the issue and glad you got it fixed. Still it was a bummer it happened.
Good to hear from you again.

You can always fire up the V any time, I was running mine this morning at 3am. Thanks to my dog waking me up earlier than usual. I jumped onto the Mark VII around 6:30 this morning.

Yeah, Still have the same old ice pick V90. At least I learned a lot from the Saturation mod thread. What works, what does not. That was a cool experiment but have no plans on doing anything like that again.

Nothing to feel bad about, was my oversight, not yours. I had a lot of fun along the way also. I think I get just as much enjoyment out of tinkering with things as i do using them. Virtually nothing of mine is as standard yeah maybe might be able to squeeze a sneaky hour in playing the V when she thinks I'm renovating!

 

[bandit2013]

Was going to do some recording last night but some heavy storms rolled in. The dog would not leave me alone. Nothing worse than a large freaky dog going nuts due to the loudness of the amp and then the loudness of the thunder outside. Perhaps today if the landscapers can stay out of the neighborhood for a while. That is why I usually wait until dark to do any recording. No fun hearing a leaf blower in the background. I do not have a basement so that is not an option.