Mark V and VII - high gain mode gain stage questions

Hi all,

So, in comparing the V:90 to the VII I'm noticing the VII is a more "gainier" in IIC+ and IV modes than the V:90 is. Then I remember that my V:90 has an AT7 tube in the V4 position, so that may explain the gain difference (although CRUNCH seems a tad more gainy and brighter in the VII than the V:90). (At least, I think the AT7 is still in my V:90.... I don't remember ever removing it ).

So, I got to thinking... is there an equivalent AT7 mod for the VII to bring down the bite a bit? Looking in the Mark V:90 manual tube task chart it shows that CH3 has six gain stages and the Mark VII manual shows only five gain stages for IIC and IV modes.

Anyway, the Mark VII manual tube task chart only lists five gain stages for IIC and IV modes.

Questions:

1) How can the "same" modes in V:90 and VII have a different number of gain stages?

2) In the VII, where should an AT7 be placed to achieve the same (similar) thing as the "AT7 V4 mod in the V:90"? I'm thinking also V4 based on it being 4th gain stage for IIC and IV modes (V4 in the Mark V is also 4th gain stage).

At any rate, I'll have to give it a whirl to see what it sounds like.

If you guys have any thoughts I'd be interested in hearing them!

I would not be too concerned about it. Mark V90 may have a few more gain stages in the path but does not mean more gain overall. That lead drive circuit feeds into V3A, there are a few attenuator voltage dividers before it runs into V6A so the signal level is reduced and will not overdrive the next stage. V6A is more of a voicing stage for the three modes. The IIC+ and IV modes are not as robust as they are with the Mark VII version (this with the 12AX7 in all tube locations in the Mark V90). The same could be said about the JP2C. Both of which only have 5 preamp tubes in total. That design dates back to the IIC+, III and IV. The Mark V was the odd ball in the series. The added gain stages I believe was more of a compromise in the design so that the three modes could be realized on CH3. Overkill perhaps? Mesa did it much better with the Mark VII and got rid of the excess that was not needed to accomplish the end goal.

I tried a JAN/philips 12AT7 in the JP2C, that did not work out very well. If you need to cut some gain from the amp, I would try a JAN 5157 instead of the 12AT7 as that will have more of a similar characteristic to the 12AX7 but with less gain, not as dramatic as the 12AT7. If you needed to drop some of that gain out, I believe the JAN 5751 would have a better fit in the V1 position. Still the crunch and VII modes will place the lead drive circuit in between V1A and V1B. Not sure what would make more sense. IIB uses V4A so a 12AT7 in that position would probably not be all that great for that mode or voicing. I personally would not use the 12AT7 in the Mark VII.

Thanks for the insights and 5751 recommendation. Since I have some JAN AT7's laying around I'm gonna give it a go!

And yeah, I saw that other modes would be affected in the Mark VII V4 position (VII mode and IIB mode). But, I'm curious.

I would try the AT7 in the phase inverter. I have thought about that for some time. Most of the JAN AT7 I have are in the bass amp. Those actually sounded much better than the Tung Sol AT7.

I have two JAN/GE 5751 tubes to play with. Will see what happens with them. I have a hunch that V1 would be the ideal spot for that tube. Now I have to give it a go since I recommended it.

I went ahead and ordered some JJ 5751’s the other day to play with. The JAN one were too rich for my blood.

mace said:

The JAN one were too rich for my blood.

Click to expand...

my thought exactly

Got the 5751’s today. Went down, plugged into the VII and was playing around to calibrate my ears to the ‘as shipped’ tone. Eventually looked at the time and 2 hours had passed. So, I guess the 5751’s will have to wait! LOL. Dang Mark VII…

If you lost 2 hours of time with the Mark VII with the stock tubes, is that a good thing or a bad thing?

Depends how you look at it. Got in some good practice time but spent money on these new tubes and they are still sitting untouched in the box! Someday I'll have to do some tube rolling, but it's been too much fun just playing guitar for now.

I get it. Why change if things sound good?

I have rolled in a few 12AX7 in the one Mark VII out of curiosity. Tried the JJ E83CC tubes (frame grid type), those actually sounded better than the stocker Mesa branded JJ ECC83s. More notably in the noise floor, the E83CC were almost dead silent on the higher gain modes. The other tubes were the old Mesa 1990 Beijing Square Foil Getter tubes, Chinese Miliary 6N4-J which were the stock tubes for the Mark III when I bought it. Just added a hint of more gain, and a bit less noise than the stock tubes.

bandit2013 said:

I get it. Why change if things sound good?

I have rolled in a few 12AX7 in the one Mark VII out of curiosity. Tried the JJ E83CC tubes (frame grid type), those actually sounded better than the stocker Mesa branded JJ ECC83s. More notably in the noise floor, the E83CC were almost dead silent on the higher gain modes. The other tubes were the old Mesa 1990 Beijing Square Foil Getter tubes, Chinese Miliary 6N4-J which were the stock tubes for the Mark III when I bought it. Just added a hint of more gain, and a bit less noise than the stock tubes.

Click to expand...

My issue with my mark V is the high end is making some weird sounds. Its hard to discribe but its like a loose flub of twangeyness it has this issues on all the channels. Its the worse on the clean channels. The tubes you suggested are starting to show up and the x4 pack of vintage chinese square foil getter showed up.

Is some tubes going bad? Do i need to replace the power tubes? As far as I know the tubes have never been replaced in this amp.

Something is for sure off but i cant put my finger on it. Maybe something microphonic?

My apology upfront for the length of my response. If you do not like long responses, put me on ignore so you do not have to read them.

If a tube was going microphonic, you can put your finger on it. I generally do not get in the practice of placing my fingers on hot tubes but have done so from time to time. If they hang down like they do in the V, the power tubes are not as hot at the end as they are on the sides of the glass. Best to wear gloves if you are going to be touching hot glass as you will get burned.

This is just opinion, nothing is absolute, what may work for me may not be the best for you. Things can be subjective, speakers, tubes, guitar, cables, whatever it is. I can only relate to what I found or discovered. Take commends on the Mark V90 with a grain of salt as it were as the Mark V90 I am stuck with is a bit different (ice pick issues) than the normal Mark V90 that sound good.

A side note on Cabinet:
Before jumping into the depths of preamp and power tubes. A few things come to mind. What you stated about the flub and twang sounds. That could be in part due to the cabinet. You did mention you got a Mesa 412 cab before you got the Mark V. Is this correct? The fist question to ask, what wattage does the sticker have on it? (it should be on the jack plate). If it has 240W good, you can skip down to the next post. If it has 280W, well that could be part of the problem. I bought my first Mesa 412 back in 2000, at the same time I bought a Mark IVB combo. Figured I could buy a head later one when I could afford it. Bought the cab new. Rated at 280W. Well, lets just say it was not very compatible with the Mark IVB or the Mark III I had. Flubby tone, honky issues. Some notes would coax the cab into a resonant horn like sound that I could not avoid. Thought the Mark V90 I bought in 2013 would be a better fit. It was not. At the time, I blamed it all on the V30 speaker, which is what it was. The RA100 sounded really good through it but the Roadster was a mud fest. I swapped the speakers out with EVM12L Black Labels which was more work than I wanted it to be. That helped with the Roadster, Mark V90 was pure shrill (I have the ice pick model that only a few people got stuck with). The EVM12L is not the solution for the Mark V, same would go for the Mark IVB. I sold the Mark III combo before I got the V so I cannot relate if that would have been ideal (that amp was stock with the EVM12L black shadow speaker).

Now I was left with one 412 cab that was good for the Roadster but terrible for the RA100. I eventually bought another Mesa (standard slant front) 412 cab. Same size and dimensions to the Oversized cab. the only difference, it has the 60W V30 speakers and not the 70W versions. That made a huge difference in sound. Mark IVB sounded really good with that cabinet. Mark V90 was much better. Then I got my hands on a MWDR, had to have another 412 and settled on another standard slant front. I just want to point out if your 412 cab has the 70W V30 speakers, that could be part of the issue. Some would swear on those over the 60W, I did nothing but swear at them. The 60W version has a tighter low end response, and seems to avoid that resonant horn effect that can get stuck in a feedback issue at that specific frequency or any harmonic of that frequency. It seemed to fail on the G note. Really weird. What may have worked out may not work well for others. I would not recommend the EVM12L speaker for the Mark V90, it has a different voice than the Mark III, JP2C or Mark VII which were epic with the EVM12L speaker. The 60W V30 can be bought direct from Mesa as it will be the UK made version with the proprietary voice coil made specifically for Mesa. Mesa could private label that if they wanted too. The 70W V30 was intended for Marshall and that is what the Silver Jubilee 2551AX cab has in it but with a Marshall sticker on it. They sound exactly like the 70W V30 speakers that were original in the 1999/2000 Mesa cab. Work great with Marshall, Triple Crown or Royal Atlantic but not so good with other amps. The Standard 412 cabs, Vertical 212 cabs, Horizontal 212 cab all have the 60W voice coil. Those cabs sound really good to me.

Once you change the tubes in the amp and still have the same result, it could very much be the cabinet, especially if it has the 70W version of the V30. The only thing I have not tried with that OS Recto cab was to change to the 60W V30 speaker. Since I got those EVM12L speakers in that box, and sealed up, it is difficult to get apart so best to leave it as is with the EV speakers.

Signs of a microphonic preamp tube can vary. Most of the time, they will go into saturation mode or instant feedback if there are any vibrations. Sometimes that needs a signal to excite the tube into feedback. That squeal you cannot control and will not go away until you place the amp into standby. Tap across the top of the amp on the front side of the handle with your knuckles, does not require a hard hit. If you hear any ringing through the speaker, you have a microphonic tube or one that is very sensitive to vibration. Some long plate tubes are more susceptible to vibrations than medium or short plate tubes. I had a few bad Mullard reissue tubes in the batch I had bought. Just changing channels was enough to excite the tube into self-oscillation.

If the power tubes have not been replaced in some time, What tubes are in it? I bought mine when Mesa did not offer any 6L6GC tube except for the STR440, they basically shipped every amp with that tube in it. Mark V, it was more common to find the red color codes than others. Yellows and greens of that tube would work out but the greens had more early distortion characteristics than the reds or yellows. Reds have the highest headroom; grey is the lowest headroom. Codes run red, yellow, green, grey, blue. Depends on the tube in question. I believe the set of STR441 tubes I am running in the V are green coded tubes. They actually sounded really good in the V which surprised me as they sounded lame in the JP2C (this amp needs the early distortion, green or grey and will clean up too much with the reds or yellows. Keep in mind the JP is a Class AB and not Simul-class like the V). I did not care much for the STR448, STR445 or STR443 in the V. Even the famed STR415 tubes were not ideal which is epic in the JP2C amp. Best sounding tube I ever ran in the Mark V90 were the SED =C= 6L6GC tubes as they had a 3D complex harmonic structure and low-end sound that was just amazing. The Ruby 6L6GC version of the STR440 also had a different sound, Those were good too. Similar to the STR440 but deeper tone.

Flubby tones, that could be weak preamp tubes and power tubes. Typically, with power tubes, there will be a tone change when they are needing replacement, losing the low end is the one indicator or losing the top end. Depends on the tube in question. I have only used the STR441 tubes for a few hours, so I do not know what its characteristic is when they reach EOL. They can also cut out on you from time to time, usually an indication they are going to red plate and blow the fuse. If the power tubes are not at the correct bias, they can sound flubby or too bright. Mesa amps are fixed bias that will mean the tubes need to fall within a range of use. Nothing wrong with using tubes that do not have the Mesa branding (if the amp still has a warranty, best to stick with Mesa power tubes, not sure what the rules are on the preamp tubes). I have run many power tubes from different suppliers, Tung Sol, Mullard, SED, Svetlana, EHx, Gold Lion etc. Just be specific what amp it is to be used with when you buy non-Mesa branded tubes. Yes, Mesa will brand those other tubes if they meet their requirements. Depending on volume of the tubes, they may be specific to Mesa as they are a Special tube request or STR that may be different than the stock tubes you find in distribution. Also, it may be different based on how the tube is selected and sorted.

Preamp tubes, they can do some wonky things. When they wear, the preamp tubes will lose some luster in sound, not as crisp or bold and may not provide the gain you used to get. They tent do sound dull. Almost like comparing a fresh set of bronze strings on an acoustic guitar compared to an old set that has lost its brilliance. Flub can be a result of the Mesa 12AX7, it was more evident in the RA100 on the Hi gain channel. It can also be an issue with the Roadster, and Mark V90 but not as dramatic. Dial back on the bass when raising the level on the gain, may need to adjust the 60Hz slider down a bit too. The flub character can be due to the preamp tube, sometimes a different tube used in specific locations will make a huge difference on how much low end you can dial in before the flatulence becomes a tone burden. With the Roadster, the key tube position is V2 which has the cold clipper circuit (V2B triode). That cold clipper is the sub-harmonic generator.

How I loaded up my Mark V90: Use it as a reference.

• V1 + V3 = Svetlana 12AX7. They are much on par with the Mullard CV4004 but with a slight less gain. These tubes removed the 60Hz hum I was getting on CH1, it was rather annoying with any of the other tubes.
• V2 = Tung Sol 12AX7. You can run any tube here, I just wanted something a bit brighter than the Mesa branded JJ tubes. It will only affect CH2. It also only uses one triode.
• V4, V5, V6 = Unobtanium 6N4-J (Chinese Beijing Square Foil getter 12AX7/7025 that Mesa used back in 1990) I have fresh ones from Ruby Tubes purchased from Doug's tubes about 10 years ago. Also have some used ones I ran in the Mark III with the Mesa logo on them.
• V7 = Mullard long plate reissue. It is the better version of the Sovtek LPS tube that most like to run in the phase inverter position. Any tube will work find here. Mesa 12AX7 or you name it. Some tubes may have more low-end gain than others. Some are more balanced or there will be more midrange or less. Depends on the tube structure. The effect will not be very dramatic, but a little change can go a long way as it does not take much to go from tight to flub.
• Power tubes: STR441 green

Some alternate tubes I have tried (just about every current production tube available but these were a help for a while)

• V1, V3 = Mullard CV4004
• V4, V5, V6 = Mullard reissue 12AX7 (long plate)
• V2 = Mesa stock tube (jj ECC83s)
• V7 = Mesa stock tube (jj ECC83s) or the Sovtek LPS.
• Power tubes: SED =C= 6L6GC (Mesa did sell them as STR454, not easy to find)

When the Saturation mode became a thing, I loaded the amp with all Mesa 12AX7 tubes and swapped V4 with a JAN/Phillips 12AT7. That was ok for a while. Cuts out the treble on CH3 and helped to cut out the ice pick. I was using the STR440 green 6L6GC tubes. I did try the Gold Lion KT77 with the 12AT7 in V4, did not favor that. The Mesa 12AX7 in V4 sounded better.

I usually run a bench test with the stock tubes if at all possible. Mesa 12AX7. Then I start replacing one at a time with something different. It can consume a lot of time, but the end result is enjoyment of the amp if you have issue with it from the start. Most of the time I see no need to change anything. MWDR, JP2C, Mark VII, Badlander sort of fell into that category, no need to change anything. With the other amps in my list, it was just a simple change in preamp tubes and or power tubes if needed that made it just ok to really good. RA100 is one of those that became a favorite amp once I found the tubes that work the best.

bandit2013 said:

My apology upfront for the length of my response. If you do not like long responses, put me on ignore so you do not have to read them.

If a tube was going microphonic, you can put your finger on it. I generally do not get in the practice of placing my fingers on hot tubes but have done so from time to time. If they hang down like they do in the V, the power tubes are not as hot at the end as they are on the sides of the glass. Best to wear gloves if you are going to be touching hot glass as you will get burned.

This is just opinion, nothing is absolute, what may work for me may not be the best for you. Things can be subjective, speakers, tubes, guitar, cables, whatever it is. I can only relate to what I found or discovered. Take commends on the Mark V90 with a grain of salt as it were as the Mark V90 I am stuck with is a bit different (ice pick issues) than the normal Mark V90 that sound good.

A side note on Cabinet:
Before jumping into the depths of preamp and power tubes. A few things come to mind. What you stated about the flub and twang sounds. That could be in part due to the cabinet. You did mention you got a Mesa 412 cab before you got the Mark V. Is this correct? The fist question to ask, what wattage does the sticker have on it? (it should be on the jack plate). If it has 240W good, you can skip down to the next post. If it has 280W, well that could be part of the problem. I bought my first Mesa 412 back in 2000, at the same time I bought a Mark IVB combo. Figured I could buy a head later one when I could afford it. Bought the cab new. Rated at 280W. Well, lets just say it was not very compatible with the Mark IVB or the Mark III I had. Flubby tone, honky issues. Some notes would coax the cab into a resonant horn like sound that I could not avoid. Thought the Mark V90 I bought in 2013 would be a better fit. It was not. At the time, I blamed it all on the V30 speaker, which is what it was. The RA100 sounded really good through it but the Roadster was a mud fest. I swapped the speakers out with EVM12L Black Labels which was more work than I wanted it to be. That helped with the Roadster, Mark V90 was pure shrill (I have the ice pick model that only a few people got stuck with). The EVM12L is not the solution for the Mark V, same would go for the Mark IVB. I sold the Mark III combo before I got the V so I cannot relate if that would have been ideal (that amp was stock with the EVM12L black shadow speaker).

Now I was left with one 412 cab that was good for the Roadster but terrible for the RA100. I eventually bought another Mesa (standard slant front) 412 cab. Same size and dimensions to the Oversized cab. the only difference, it has the 60W V30 speakers and not the 70W versions. That made a huge difference in sound. Mark IVB sounded really good with that cabinet. Mark V90 was much better. Then I got my hands on a MWDR, had to have another 412 and settled on another standard slant front. I just want to point out if your 412 cab has the 70W V30 speakers, that could be part of the issue. Some would swear on those over the 60W, I did nothing but swear at them. The 60W version has a tighter low end response, and seems to avoid that resonant horn effect that can get stuck in a feedback issue at that specific frequency or any harmonic of that frequency. It seemed to fail on the G note. Really weird. What may have worked out may not work well for others. I would not recommend the EVM12L speaker for the Mark V90, it has a different voice than the Mark III, JP2C or Mark VII which were epic with the EVM12L speaker. The 60W V30 can be bought direct from Mesa as it will be the UK made version with the proprietary voice coil made specifically for Mesa. Mesa could private label that if they wanted too. The 70W V30 was intended for Marshall and that is what the Silver Jubilee 2551AX cab has in it but with a Marshall sticker on it. They sound exactly like the 70W V30 speakers that were original in the 1999/2000 Mesa cab. Work great with Marshall, Triple Crown or Royal Atlantic but not so good with other amps. The Standard 412 cabs, Vertical 212 cabs, Horizontal 212 cab all have the 60W voice coil. Those cabs sound really good to me.

Once you change the tubes in the amp and still have the same result, it could very much be the cabinet, especially if it has the 70W version of the V30. The only thing I have not tried with that OS Recto cab was to change to the 60W V30 speaker. Since I got those EVM12L speakers in that box, and sealed up, it is difficult to get apart so best to leave it as is with the EV speakers.

Click to expand...

Sadly I have the 280w version. Sucks cant afford to replace for the 240 right now....

Im gonna try the pre amp tube swap the svetlanas will be here this next week got all the other ones even the chinese square foil getters.

Well, that may explain why you are getting some odd characteristics.

I can only relate to the Oversized Recto 412 cab I had. Bought it new in 2000 and never really liked it. 14 years later I decided to replace the 70W V30 speakers with something else. I assumed that all V30s were difficult to work with. I was so wrong. The 60W versions sound amazing. They are voiced differently.

Just hang in there. No need to get rid of the cab, just replace the speakers. One at a time to make ends meet. If you could find a deal on a used Mesa Vertical 212 cab that would be good too. It takes up less space than the 412 cab and sounds almost as big. It will have the 60W V20 if it is rated for 120W, unless someone replaced the spakers. The 412 is not really needed unless you need that extra volume.

I always wanted one which is why I bought it. Now I have 5 of them. However, I have a few amp heads that are too wide to fit on the V212 cab. the RA100 is large as well as the Roadster. Two are the Mesa Standard 412, first one dates back to 2014 and the other 2018. The 4th cab is a cheap traditional sized Egnator cab that I replaced the speakers with Celestion G12H-75 after trying them in the oversized recto cab. Those speakers actually sounded good with the Mark V90. The 5th one is a Marshall 2551 AX 412 to go with the Silver Jubilee 2555x 100W head. Those are the 70W versions of the V30. I still have the original V30 speakers I removed from the Oversized cab if I needed to reuse them but doubt I ever will. I did try the JP2C into the Marshall cab, repeat of the experience I had with the 70W V30 speakers in the Mesa 412 cab. Just not a good fit. JP2C has a 16 ohm output, so does the Roadster. The 70W V30 speakers sound good with Marshalls, just not with Mesa. However, that 2555x head sounded way better through the Standard 412 cab with the 60W V30 speakers. I was using that for a while before getting a matching cab for the Jubilee.

Here is what that amp looks like with its cab. The 412 under the RA100 was made in 2014, the year they discontinued the RA100. Had to special order it with the grill cloth.



I got hooked on the MWDR for a while, had to have another 412 cab. The old OS Recto cab is the one under the Roadster. I could not get the grill to attach from the inside since I had that thing apart too many times. Trying different speakers in it. I went back to the EV speakers and sealed it up. All that foam on the front baffle board keeps the grill from vibrating. I did not get all of the EV speakers at one time, say one every month or longer. When I got 4 of them I replaced the V30. Had to remove the grill though as the screws used for the V30 were too short. Had I started off with the Celestion Cream back, G12H-75 that would have been much easier. The H-75 is much closer to the 60W V30 than the M-65 version which I felt was too bright. H means heavy magnet like the V30. Even though it is 75W rated, it does not sound like the 70W V30 as that is a different voice coil. Different doping in the cone and such. Decent speaker even though it has a flimsy plastic cab glued to the speaker magnet. I have not tried blending speakers, perhaps just two mixed in with the V30 may work out. Take your time, you can still use the 412 as is. It should stay out of its resonance issue if you keep the volume down. May be easier to sell the cab and look for a more recent build. Not sure what year Mesa changed to the 60W version of the V30. They used them early on too, but things changed where Celestion wanted to make them with the 70W voice coil. (assumed). I know for a fact that the 2015 year they were made with the 60W. If not, I would have ripped those speakers out and replaced them with something else.





That EV loaded 412 works best with the JP2C or the Mark VII. Just was not a good fit for the Mark V90. Since the Roadster was so dark it worked well with that amp. When I did the 7 string evaluation, I was running the standard 412 cab as it was out on the floor.

I looked at the Mesa store, for some reason you cannot get the V30 in 8 ohms. If you do decide to change the speakers, the V30, and the cream backs will work in a closed back cabinet. Do not use the MC90 in a sealed closed back cab. You would need to open up the back or port it so the compressed air does not pass through the speaker cone as the cooling port for that speaker passes completely through it. That would be replacing one problem with another. If you do opt to look elsewhere for speakers, review the specifications and confirm it is suitable for a closed back cabinet. You could find a store with the current production 412 cab and play an amp through it. At least that way you would get an idea what it sounds like relative to the 280W version.

You do have a Roadster? How does that amp sound through the 412 cab. If it is the same flub or too much swamp the low end, I would look at the cabinet.

Just a note on the Celestion V30 replacement market, those have a different voice coil than the Mesa 60W version. They are close in sound characteristics but a bit fizzy as some have described. I never tried them but have bought Other Celestion speakers from different resources like Sweetater, American Music Supply (AMS) and other places. Perhaps others can offer an opinion on what you can do with the cab. Hoping I had a fluke with the first 412 cab like I did with the Mark V90.