NAD: Mesa Boogie Mark VII head. WOW

[mace]

So, are these tubes available anywhere?

“V3,V4,V5,V6 = NOS Mesa Chinese square foil getter tube from 1989 thru 1990. Aka Ruby Chinese Military Grade square foil getter 12AX7A. “

Thanks for the great info. Glad you got your V90 working. I seem to remember in the other ‘V4 Saturation mod’ thread you had some tube cocktail in the V90 which sounded good until it didn’t. Then you went back to current stock Mesa 12AX7s before giving up on it (if I’m remembering correctly).

 

[Neptical]

. EL34 based amps seem to sound better with the V30,

For Boogies, I love my Single Recs, RoVs and Dual Rev. G through my Soldano V30 straight 412 cab. Absolutely PUMMELING tone. Boss SD1 through the front of them all.

But you're right, I love ALL my EL34 Marshalls ( JCMs, Origins and Plexi ) though my V30 cab the most as well.

 

[bandit2013]

So, are these tubes available anywhere?

“V3,V4,V5,V6 = NOS Mesa Chinese square foil getter tube from 1989 thru 1990. Aka Ruby Chinese Military Grade square foil getter 12AX7A. “

Thanks for the great info. Glad you got your V90 working. I seem to remember in the other ‘V4 Saturation mod’ thread you had some tube cocktail in the V90 which sounded good until it didn’t. Then you went back to current stock Mesa 12AX7s before giving up on it (if I’m remembering correctly).

Resource for the old Mesa Chinese square foil getter tube: May be referenced as a Chinese Military grade tube. The keyword is the location of the facility that made them: Beijing.

This is about all I can see that is currently active: Most of the other listings have ended or sold out.

https://reverb.com/item/53575106-12ax7-beijing-foil-getters
The Beijing tubes are not the same thing as the Ruby Silver series with these tubes They may look similar due to the silver clips on the plates but have a round halo getter. Different tube, different factory that made them. Those are not as good.

Yeah, I have chased the tone dragon with the Mark V90 to no end. Before the Saturation mod era I was experimenting with several different preamp tubes but all in the 12AX7 family. This included the Bejing 12AX7 tubes. Some of the Ruby Chinese gen 9 and the silver series from Penta Labs.

My only goal was to see if I could kill the boxy tone of the Mark V. The short, or long term plan was to get the preamp to sound good, stuff the MC90 in the cabinet and sell the amp. Now, it is a keeper. I hope others that pursue this have the same success as I have had. Perhaps having the Mark V90 Lemon was a good thing. The icing on the cake was the lame sounding STR441 tubes. I call them lame as that how they sounded in the JP2C. Blah. They were worse than the STR443 tubes. I could not believe how much different the Mark V90 sounds with the STR441. I have not played through the Mark V90 for hours on end and not get sick from the ***** tone or ice pick voice. 20 minutes was all I could stand. Now it is way better than it ever was. Perhaps I just got lucky this time around.

 

[bandit2013]

I learned something new today about the Mark VII and the JP2C. I decided to slave one amp into the other just to confirm where the GEQ sit. I used a Strymon BigSky and ran it normal with the FX for the VII on the right and the JP2C fx on the left. Odd thing with the Mesa Switch track had sort of a hum, turns out I had the ground coupled. Changed the switch and all was good. Odd thing is I was running this with the two amps before and never noticed the hum. Thought it was the BigSky as it is a new one, needed a second one so it was its trial period. Once the noise issue was fixed. play a bit to get the IIC modes to sound the same. Then swapped the returns on each amp so they slaved into each other.

As it turns out, both the Mark VII and JP2C have the channel masters after the FX loop. Changing the volume on the Mark VII while it was slaving into the JP2C had no effect, The same for the JP slaving into the Mark VII. Yep, the GEQ does follow the FX loop in both amps. I was able to run the clean mode on the Mark VII into the JP2C on CH3 or the Mark VII mode on the Mark VII and hear it from the JP2C. That go noisy as all hell though. The only reason I tried this was something peculiar I was hearing with the Mark VII so slaving to another amp would rule out the power tubes. Either way I did not hear the noise. It occurred with palm muting strings after I hit the cord. It had this raspy overtone that was full of static. I swapped guitar cables and that did not change much. It almost sounded like too much low end was resulting in tube vibrations internal. If I turned the bass down it would go away. I did not hear it when I slaved one amp to the other and vice versa so it was not identified yet. I suspect it is power tube related but could be something else. Reverb was turned off. If I was running the pair of amps at the same time or with the full 4 amp rig, I would never hear it. Hopefully I did not cause any damage to the Mark VII as those STR445 tubes have oversized pins and are hard to remove and install. I can tell the PCB that has the sockets connected to it was flexing by the way the other tubes still installed were moving while removing one of the tubes or getting them installed.

As it seems, the JP2C would fail the IIC+ test since the channel master volume is after the FX loop. It is not a reissue of the IIC+ circuitry, that was obvious by the different stuff loaded into it. It was written as this amp was an accurate reproduction of the IIC+ in signal path which it is not. Not upset about that as it is a good amp as it is.

So, the Mark VII and JP2C share something in common with the Badlander; Channel masters are after the FX loop similar to the global output/solo feature of the Mark V or Dual Rectifier when using the FX loop in active mode. I had thought the same with the Royal Atlantic when I was comparing it to the Triple Crown. Not sure now as that was some time ago.

 

[woodbutcher65]

All I really want to know is, just a summary, I have a Mark V:90 and mine is flawless. Everything always works on it. It's the one amp I'd grab if my house was on fire and I had time to save ONE.

What does a Mark VII bring to the table over and above the Mark V? Would I have a reason to dump one for the other, or does it just add more genuinely good and useful tones to my stable?

I am not a gigging musician, neither do I do any recording.

 

[Darkstar2]

Hi Bandit — would you say the MarkVII passes the C+ fx loop test? If the JP2C doesn’t, it would stand to reason the Mark VII wouldn’t either.

 

[bandit2013]

All I really want to know is, just a summary, I have a Mark V:90 and mine is flawless. Everything always works on it. It's the one amp I'd grab if my house was on fire and I had time to save ONE.

What does a Mark VII bring to the table over and above the Mark V? Would I have a reason to dump one for the other, or does it just add more genuinely good and useful tones to my stable?

I am not a gigging musician, neither do I do any recording.

There are many similarities with the Mark VII and Mark V. I have found the modes in the Mark V to be very similar to the Mark VII. The differences you would notice right away are the voicing switch on each channel (CH1: normal/Bold, CH2: Normal/thick [effects Mark I mode only] and CH3: normal/bright). The Mark VII does not have this feature. The Clean and Fat modes are no different than the clean on CH1 but with the voice switch set to bold. CH3 IIC+ and IV are similar but with the bright switch set to on. There is more flexibility to be found with the Mark V90. Never thought I would come to this conclusion. Then there are the different power options found on the back panel. Diode/Tube tracking for CH1 and CH2 when using 45W power, Pentode/Triode on CH3 that affects the class A tubes. In essence you have more options. I am willing to bet that the triode power mode on CH3 at the 45W power mode is more like a 25W. I have to explore that a bit more. Mark VII runs 45W power in pentode and 25W power in triode. Not sure what year your Mark V90 is. If it came stock with the STR440 tubes and you are still using them, there is much to be gained by using the STR441 power tubes. To me that was a total game changer for me disliking the V to actually loving it. In addition to a few preamp tube changes to curb the boxy tone and having something a bit tighter in response with desired low end I thought was not possible. Actually the simple preamp tube swaps with the Mark V90 placed the amp above the Mark VII in terms of sound quality. It was the first time I was able to get the feel of the Mark V90 I had been missing for the past 11 years since I have owned it.

STR441 power tubes, all sockets. Bias color Green
V1: Svetlana 12AX7
V2: Tung Sol 12AX7
V3,V4,V5,V6 : Chinese Beijing square foil getter tubes. Same as Mesa 12AX7 from 1989 to 1990. These were the stock tubes I had in my Mark III. You can still find them but resources are limited.
V7: Mullard 12AX7 long plate reissue. Same as the Sovtek LPS but better quality as it has more balanced tone for low to top end. I found the current stock Mesa 12AX7 tubes (JJECC83s) sort of adds to the boxy tone of the Mark V. It can also contribute to brittle sounds, tweed, edge and most of CH3. The STR441 power tubes really helped curb the ice pick or brittleness. The Chinese Beijing tubes aided with tightening up the bass response. Tweed sounds great, Edge is very interesting, and the rest of the modes are very pleasing. However, I would say there is no point in changing anything if you are very satisfied with the Mark V90 as it is. I am only suggesting what took me 11 years to figure out to those who are looking to improve their V90 if they are having common issues with boxy sound, ice pick issues or the like. Not all Mark V90 seem to behave this way but mine was a prime example of that.

With that preamp and power amp tube combination, I am getting the same sound from the Mark V as I found with the Mark VII. Actually, I think it sounds much better since you also have voice switches for each channel (not talking about the modes here just the normal/X switch).

If you are one who loves the extreme mode on CH3, the VII mode on CH2 of the Mark VII sounds very similar. Going from the Mark V90 to the Mark VII, you lose two modes. Tweed and Edge.

I do not believe there is much to gain from moving from one amp to another. I only bought the Mark VII as I assumed it would be different. It is to some extent but in many respects it is about the same. Other than the different footswitch control from a change in voltage to select channels it uses Midi which is much better or reliable with long cable runs. I only wish the footswitch cable was shorter than the 25ft cable length they provide.

Yes, there is a difference in the FX loop. The Mark VII has returned to a more traditional form as the send is tube driven and derived from a voltage divider circuit. Mark V uses the output stage from the GEQ to create the FX loop send level. In other words, the output impedance of the Mark V90 has a slight issue of having a high impedance whereas the Mark VII has a lower output impedance. The only fix for this is to use a good fx unit. Strymon products I found to be good with the Mark V90 as I have yet to get the tone loss or overly compressed tone since the input buffers can compensate for the output impedance issue. I stumbled upon Strymon as a last resort. I have gone through many delay pedals and they all had the same common issue, did not work with the Mark V fx loop. Strymon DIG was the first I tried and there were no problems. I did not hear any tone loss or experienced compression due to overdriving the input buffer. BigSky had followed with the same results and now I have several Strymon FX pedals. If you have effects that you like and are successful with the Mark V90, I would like to hear about them. Just note: if you have a stereo in/out pedal, I would not recommend using that FX unit with another amp in combination with the Mark V90. I believe the left input will set the gain factor of the other channel. I can use the BigSky reverb with different amps like the JP2C and Badlander. Those do not compete with each other when sharing the same stereo FX unit. The Triple Crown and the JP2C fared well too. The Mark V90 is different. I would assume that running two Mark V90 in stereo would be possible without any ill effect on tone. Since I have Strymon as a work around for FX, I can make full use of the Mark V90 without any complaints.

 

[bandit2013]

Hi Bandit — would you say the MarkVII passes the C+ fx loop test? If the JP2C doesn’t, it would stand to reason the Mark VII wouldn’t either.

Nope. The Mark VII will not pass the C+test. Both the JP2C and Mark VII place the volume control after the FX loop so change of the volume control while running the amp in IIC+ mode or lead channel would result in change in volume of the signal applied on the return.

If this is accurate, I have found this on may IIC+ sites including Wikipedia.
The way to verify a IIC+ in person is THE LOOP TEST Plug a guitar into the Effects Return on the back of the amp Put the amp in the Lead Channel Turn the Lead Drive and Gain knobs while playing If you hear no effect on volume and sound - that amp is a IIC+

I was under the impression that the JP2C was true to the IIC+ amplifier. I did not expect to note the channel master to be after the FX loop. I did not buy the JP2C under any false pretense of it being an actual IIC+. That is not what sold me on the amp in the first place. It was one German music store that was convincing. They would be the equivalent to Sweetwater in the USA as they do product video reviews or amps, guitar and the like. The introduction of the JP2C by Sessions was what made me want the amp. I do not speak, read or understand German. However, I did not need to understand what was said during the video as the amp and the guitarists fingers did all the talking that was necessary. This guy just digs into the amp in depth quickly. It was just the character of the amp that sold me on getting one. This video is not easy to find. Mesa has dried up in Europe before Covid epidemic, I say probably when Gibson bought Mesa.

 

[bandit2013]

I am starting to hear the differences between the JP2C and the Mark VII. Something seems to be missing with the Mark VII. Not sure what it is but, the JP2C is a far better sounding amp. Makes me wonder if it is the power tube choice in the Mark VII that lends itself to different class. Not saying it is better or worse, just different. Sure, it is Simul-Class vs Class A/B power if we want to point out the differences. The Mark V90 is not that far off the mark as I thought it was.

At least the channel switching issue has not cropped up. I still feel it is a sensitive preamp tube issue.

Also, the pick attack characteristic is much different with the Mark VII than the other two Mark amps I have. Almost as if there is a sensitive preamp tube. The pick attack is sharp and more forward than the rest of the sound I get. This is more or less preamp related. This is the first Mesa amp I did not remove the preamp tubes to test on the tube tester. I think that will be the next thing to do. I have many Mesa 12AX7 tubes on hand, so replacement is not a problem if that is the issue. Also, I am hearing that ping noise when changing channels, may not be anything to worry about but seemed to be a common thing with the Triple Crown or JP2C when I had a near-microphonic tube. The strobe mute should eliminate any noises from channel changes. So far that has been very quiet. This is more of a mechanical noise I hear due to change in plate voltage or configuration changes occur in a given triode circuit that may reveal a microphonic tube may be in the amp. I could probably just tap the tubes and see which one makes noise. I tried tapping on the head across the top of the amp in several places. That trick usually works but this amp is a bit different.

 

[bandit2013]

Well, it was exactly what I thought. Instead of one microphonic preamp tube I got two. V1 and V3. Just tap on them and they ring out into self oscillation when the amp is on the Mark VII mode.

I am glad I had some new Mesa tubes still in boxes. I basically swapped out all of the preamp tubes with some older ones made sometime in 2016 -2018 is when I bought most of them. The amp sounds much better now. Was not expecting much of a change really but no more picky noises on the pick attack. No more ping when channel changes occur. I do hear the typical noise though as that is going to be there no matter what (strobe mute killing the signal path). The original preamp tubes were marked from where they came and also the tubes have an etched number on them. All were the Mesa Branded (JJ ECC83 tubes). Now it just has the same tubes but older production lot. Not etched with any numbers. Just printed with Mesa logo and 12AX7A.

While I was rolling in the Mesa preamp tubes to find one's that had the lowest noise floor, no popping noises, or ping on channel change, I had used the STR440 power tubes (green bias color) to run the amp. That was interestingly different. It reminded me of the JP2C when I first got it.

Since I did not want to mess with getting my hand inside of the small opening, I pulled the chassis out. Since I had to remove the power tubes to do so, it was much easier to use the STR440 since the STR445 are difficult to install due to enlarged pins. So, in the experiment, all tubes had Mesa's blessing marked on the glass. I had even tried a few of the old 1990's Mesa tubes that were in great condition. That did not make much of a difference in tone or gain characteristics. I assume this one is not as tunable as the Mark V90. I could have explored other flavors of 12AX7 but opted not to do so at this time. I took some pictures for you sic ones that need that sort of thing. Here is the gut shot followed by the surprise, two 4 ohm resistors connected in series, I assume this is the load resistor that is used when you remove the speaker cable from the amp. I did not see any internal resistors inside the amp. Lots of relays. PCB is well laid out as I did take a close look but kept my fingers out of there.

It was a tight fit in the head shell. Will be interesting to see how easy it is to get back in. I may remove the faceplate as that adds to some tension on the bottom of the front part of the chassis.

In case you were wondering how the JP2C looks like on the inside, here it is.

Here is the Mark V90 for simplicity at its best. Either way you look at it. Repairs will be complicated on any of these. Much more space to work with inside the Mark V90.

A few comments on the STR440 power tubes in the Mark VII. If you want that power sag characteristic, you will hear it with those tubes. I may try the STR443 power tubes before I get this thing stuffed back into its head shell now that I have found the zinger tubes (microphonic, hypersensitive 12AX7). The STR440 would do great as backup tubes if you have them. I was kind liking the difference they provided compared to the STR445 tubes. Not sure what to expect from the STR443. I did not like them in the JP2C. Probably will have the same opinion about them in the Mark VII.

 

[bandit2013]

Got done with the STR443 much quicker than the time it took to install them. Bass dominant and lacking any character. That would explain why I lost interest in the JP2C when I tried them with that amp. Debating if I want to revisit the STR448 or just move on and get the chassis back into the head shell. I did like the STR440 tubes, those sounded really good.

 

[bandit2013]

Got it all together last night. Took a break to eat dinner. Hint, if you do remove the chassis, it is much easier to get back in if you remove the faceplate. Also it is better to connect the power cable before sliding in the chassis. It can be tricky to get into the socket once you have the chassis installed.

For those who fear the chassis removal trick, the gap in the preamp tube pins all face to the front of the amp. They are not at some weird angle or offset.

If you disconnect the reverb connections, either take a picture of it first which I did not and thought I would remember which is which. I thought, I can just tell which one is for the white wire and which one is for the black by looking at the terminals from the other side. Nope, they are hidden by the preamp board. Multi-meter to the rescue: the terminal for the white wire will not have the ground connected and the one for the black wire will. Measure resistance of the outer ring on the RCA connector to the screw next to it. if it is open that is the white wire connection. It is the one closer to the big power transformer. The manual (online) does not indicate what wire goes where. It would not be hard to ad WH and BK on the simple diagram. As for the plate on the inside, you can't see it since the amp hides most of it.

If you get it connected backwards, it will make a terrible noise, just power down, let the power tubes cool and remove one or both of the center two tubes to get access and swap the wires.

 

[bandit2013]

This amp rips. It can be loud as hell if you want it too be. Once you get the channel master past noon it really opens up. That is when you realize you may need to adjust your settings.

I would say this is on par with the Badlander 100. That amp is a power house too. The only difference with the Badlander is you get what you dialed in at low to high volume. It does not change its character too much. The Mark VII will gain some more power tube distortion at higher volumes. It does sound remarkable at a volume setting of 9am but once you go past noon, it is a different animal. The JP2C was like this when I first got it but that was related to the STR440 power tubes having a bass dominant characteristic at bedroom levels. STR448 or STR415 do not behave that way.

MWDR is also a power house as is the Roadster. Those you practically need to run wide open for best results. Not always, as there is plenty of character to be found at reduced volume. RA100 is another beast in its own right.

As with any amp, there is a learning curve associated with changes in the power section once driven to stage volume. I feel it may be best to find out what that is during rehearsals before you blunder on stage in a live event. If it turns out it does not fit your bill, that can happen. The MKVII may sound damn close to the JP2C loaded with the STR415, there is a major difference between them. JP2C has more authority in the low end punch and delivery of that character sound. The Mark VII seems to be missing that factor. Not sure if that is the difference between Simul-Class and Class A/B. It seems that most of the amps I feel are stage worthy are all Class A/B amps. Simul Class tends to add a layer of power tube distortion that may be greater than what you would get with the Class A/B version. Keep that in mind and cut back on gain to compensate when going to stage volume. I could be totally wrong on this. It has been some time since I ran with the Simul-Class amp with the exception of the Mark V90 that spent more time in storage than in use. The Mark III combo, that was a different era and that amp delivered the goods in a live setting as it was my only rig when I was the lead guitar player in a band back in the 1990s. Now I am a drummer in a group of old farts. Two ME and one EE. If you do not understand the abbreviations, two Mechanical Engineers and one Electrical Engineer.

 

[bandit2013]

It is tough to choose. The JP2C just pushes through with authority but with the STR415 tubes on board. STR440 or STR448 would be the alternative choice.

The Mark V90 does perform much better if you can get it past that bedroom level. At gig level it performs well and that is what I have been using to compare the V to the VII. If you compare them at bedroom level, the Mark VII will win but it is not easy to dial it down to bedroom level.

Yep, confirmed that the V90 using 45W mode in triode has the same or similar character as the Mark VII in 25W power.

The bass player was in town this week I asked him to come over the night before our scheduled jam session to have a chance to hear for himself which he prefers more. Did the demo of the Mark V90 and compared it to the Mark VII. His preference was for the Mark VII. Then I powered up the JP2C and that preference changed to the JP2C. The JP2C had more authority in the delivery of the low end and overall tone. Mark VII was not that far behind it but just a bit different. You can get things very close, but the delivery is different. Same with the Mark V90. As it seems, you can gain more appreciation with the V or the VII at more of a stage level than at bedroom level. It was good to get another opinion for in the room experience. I have him the opportunity to do whatever he wanted with the Mark VII but oddly enough, he did not make any changes to the tone or gain controls. I guess it makes sense as his amp at home is a 1962 Fender Twin Reverb. Not much but just loud. He said he could not make the Mark VII sound like I made it sound. Well, I pushed the volume control on the guitar up. He has this habit to back off on the volume control. He does this with the Bass too. Perhaps out of habit of using the Fender Twin for so many years?

 

[bandit2013]

Last night's jam session was actually a better one. I did play through the Mark VII for a short while but got complaints the amp was too loud by the guitar player behind the drum set. I thought the amp sounded great in the live mix. I did have to say to the guitar player, now you know what I hear when I am playing the drums. Perspective is everything. I can see how this amp could get lost in the mix. The higher the gain the more likely it will loose some composure when you bring the volume up. Just turn the gain down a bit and you should be just fine. It is a learning curve sort of deal. I used to think the JP2C would not work out, it does. Same with the Badlander but that amp just cuts through quite well and it is not ear piercing. As for throwing a boost onto it, I often think many people try the same old tricks that may not be the best approach in all cases. Then again, running the Mark VII along with the JP2C was more of an epic sound and it did not matter if the VII was on the IIC, IV or VII mode. As long as it was in in phase with the JP2C you will get a gain of both amps character. Cab used was the Recto vertical 212 cab. I think when I go on vacation starting next week, I will some time to pull out more cabs and what not to explore with the Mark VII.

Running all 4 amps and hoping for less noise floor, is probably the best sound I have yet to hear. A nice blend of 6L6 and EL34 power is always a good thing. The BADS play well with others of a different type as accent amps. With the Mark VII and JP2C punching through the center and the BADS taking the flank creates a sound that works great. I hear more Mark amp from the blend. If I were to run the 2-BADS with say the Royal Atlantic on point, It is more of a Marshall tone with attitude.

I have spent some time with just the Mark VII. Try to figure it out. Sometimes it is a good thing to keep them separated. The Mark V90 sort of fell behind once again. I guess it depends on how loud you make it, the louder the better for some reason. I still want to make a video comparing the V to the VII. Just have not had the time.

 

[bandit2013]

Here is how the Mark VII compares to the Mark V90. They are close but not quite the same. There is no way to gain that tone density with the Mark V90 as it has a much smaller power transformer. As close as it gets with the change in preamp tubes of the V90. If I ran it with the stock Mesa tubes, there would be a greater difference between the two amps.
Sorry if you were looking for the video. I have decided to re-edit the content based on a friends recommendations.

 

[bandit2013]

Videos have been edited and released. Sorry for those who sat through the original footage. I did not edit those to the point I should have before releasing. I would rather have a video when comparing two amps of similar characteristics without any verbal opinion or other comments that are self degrading on my ability to play the guitar. Here they are again, they will stay up until Youtube kicks me out.

Part 1:


Part 2:

 

[domct203]

They both do their own thing well, I was surprised how many times I preferred the MKV.

That MKVII mode sounds great, very authoritive, how does it feel with expressive single note lines?

Dom

 

[bandit2013]

They both do their own thing well, I was surprised how many times I preferred the MKV.

That MKVII mode sounds great, very authoritive, how does it feel with expressive single note lines?

Dom

The Mark VII in general works well with single note playing. I am sure lead playing will be very similar. The Mark V sort of had a blanket sound. I did not spend much time dialing in the two amps, I basically chose to run the controls at noon as a starring point. Mark V, all controls at noon and I adjusted the output volume to match the loudness of the Mark VII. The difference was with the Mark VII, I could not run the channel volumes at noon as that would be very loud.

The Mark VII feels very much like the JP2C. You feel connected to the amp. You get that urge you want to play more and express that feel you get. The only way to get that feel with the JP2C is with the STR415 power tubes. Expensive but obtainable. The next best thing is the STR448 with a softer control on the bass tightness. They sound great too. I also ran the STR445 power tubes in the JP2C and got similar results as I did with the STR415 power tubes. As for the preamp characteristics, they are very similar, just less modes or options to select for the three channels. JP2C is extremely articulate, the Mark VII is just a bit off but close enough.

The Mark V90 sort of loses its composure as there is that balance you play around with. The dominant tone or tuned upper midrange content cannot be filtered out with the GEQ on the Lead channel as it is a fixed character that is hard wired to the lead drive circuit. I had addressed that in the saturation mod thread, C39 capacitor that couples the grid to the cathode on V4B. I did restore it with a 47pF cap since I basically destroyed the 120pF cap that was there. I may try removing C39 but will be the last time I can do it. I doubt I will try to restore that component again as I do not want to cause any damage to the copper foil traces as the land size around the hole is very small. The Mark IVa does not have this capacitor, the Mark IVb does, but a much larger value, 250pF. Note that C39 is for the Mark V only. The Mark IVb schematic does not have a reference designator.

These are the basic settings I used in the video. I did make some changes while recording but for the most part all the settings were set to noon. Inverting the image helps to reveal the settings on the knobs due to the glare from the overhead lighting and the overall darkness of the image.

Note CH2 on the Mark V was left this way after running the Mark I mode. I started with all settings at noon.

By the time I got through the video in part 2, this was near the end after all of the adjustments.

If I had the stock Mesa 12AX7 tubes in the Mark V90, it would have been brittle and a bit on the muddy side.

I may try removing C39 and see what happens. It will get brighter without that capacitor filtering out most of the frequencies from the V5A gain stage. Not sure what the actual purpose for this change to the lead drive circuit is really meant for. Was it to tune the preamp to work with the MC90 speaker? It is not necessary and does help to cut some of the boxy tones but, like I said, it will become much brighter with it removed. Now I am curious to find out. I really did not want to bring up hard mods on this thread. I personally would not want to recommend that. The V90 I have was one that I never bonded with for the past 11 years. Mostly due to the boxy and ***** tones it delivered and the ice pick issues on tweed, edge and most of CH3. To my surprise, the STR441 power tubes bought out the best of the Mark V90 that I did not expect. Change in the preamp tubes was also an improvement. Unfortunate that the Beijing Square Foil Getter tubes are harder to get in the USA than I previously thought. Those were the tubes Mesa used in the 1980-1990 time frame. Here are the old Mesa tubes next to the Ruby Beijing tubes. Same tube, slight difference in tone as the Mesa tubes are sorted for specific characteristics, Ruby are sorted for performance only and not based on tone or quality. The good thing about the Beijing tubes, no noise floor, they are silent as long as you are not picking up electrical noise with the guitar like I was in the room where I did the video. That room is noisy. The room where all of the gear is setup for jam sessions has no issues with electrical noise. Also, was using the Furman power supply and that did not help with noise pickup from the cable and guitar.

TMI? probably. I did finally get a full set of the JJ E83CC tubes. The first order they messed up and shipped me E88CC tubes, not compatible with a 12AX7 circuit. They looked identical to the Mesa (JJECC83s) tube but once I saw the different part number, looked it up and found that they were not compatible so I did not risk using them. Sent them back and got replacements.

If I find the C39 removal makes that much of a dramatic difference, perhaps I will follow up with another video as I have the character sound from the V90 with it installed in video. That would be a project to splice in before and after effects of a component removal. Not all Mark V90 are created equal, mine is a lemon of sorts and probably should not have been sold.

 

[rarebitusa]

Pretty sure Bandit's tube rolling on the V has played into the improved tones. I can say moving to the split STR-440/STR-441 combination is a pretty noticeable and welcomed V upgrade. My tube sniffing skills are poor and even I could hear the difference. I tried to get some foil-getters but missed out.

There's not many straightforward vids out there yet that do this type of apples to apples comparison so I applaud the effort. Also the inverted pics are very helpful as I was curious about the chan master and output master settings.