Considering some alternate 12ax7 tubes...

[bandit2013]

Yep, another one.... I wonder if those that write reviews for tubes, guitars, amps and such get paid for it? I am doing this at my expense and well, why not make comment what I end up discovering. The reasoning for all of this is simple. My coveted Mesa (circa 1990) 12AX7A tubes with the square getter are all nearly past their useful life. These tubes sounded amazing in all three Mesa amps I own. Since I only have 10 of them and not in great condition due to length of use I was wondering what I could find that would be suitable, not sound harsh or brittle and yet kick some ass in the high gain channels. For a while I was wondering where they all went too. It was not until I lost one in the Mark V which took out the reverb that I found a few of them. The rest were in the RA100. That is a pisser. There are a few decent tubes like the Tung Sol, EH, Mesa (JJ) Mullard, Ruby (Preferred Series), without having to go to the expense of shelling out wads of cash for NOS tubes that may or may not sound great in your amp. I decided to buy a few different tubes (already have the Tung Sol, EH, Mesa, Mullard reissue) like the new Mullard CV4004, Preferred Series 7025, Gold Lion B759/12AX7 and the Northern Electric 12AX7 (resource unknown other than Canada). The last two on the list being the most expensive ended up sitting in a box with the other tubes on reserve as standby or maybe I will use them later on in life (no they will not get better with age, maybe with use they may improve).

The last rundown of this lengthy and wordy novel I seem to have started, bla.. bla...bla will come to an end very soon. Once I cut and paste the report (or opinions) from the word document. Not sure if I am just blowing hot air or if anyone is reading this.... sorry if you are getting board at this point. Now for the last of it....

RA100 and Mark IV final tube roll:
My next detailed focus for what pleasure I may obtain from it had to deal with the RA100. The Mark V is set and I am pleased with it. Surprised I rolled out the NE12AX7. It is a good tube if you need more gain than what you have but it can be over the top especially with the Mark V and its inherent brightness. I tend to like darker tones and can tolerate chiming highs but not brittle. By no means did I find the NE12AX7 brittle in the Mark V, it just did not do it for me. Back to the RA100.
I must have been suffering major hearing loss or fatigue in the past few days so today I revisited the RA100 again. This time I did not remove the chassis since it is much easier to access the preamp tubes and waiting for the power tubes to cool down is no big deal. I went back to what I thought sounded really good but this time with my single coil guitar which is what I like to use with this amp. The clean channel can be very dark to some degree. I have tried EH, Tung Sol, Mullard of both types, Preferred Series 7025, Northern Electric and what sounded okay at the time the Gold Lion B759. No need to spend any money on tubes for the clean channel as it is the Mesa 12AX7A sound the best in V4 and V5, period. Rest assured I was going to roll in something else in the V1 and V2. I was fixed on V3 being an NOS RFT 12AT7, seemed to be the quietest tube I have in a 12AT7 as well as add a bit of darkness to the Hi/Lo channel. For those of you who believe V3 is out of the chian when the effects loop is not used, think again. Pull it and see what happens, no sound. V3 will have an impact on tone for both clean and the Hi/Lo channels. What works well for the reverb is the PS 7025. Now for the Hi/Lo channel. There is only one tube I found that rolls off the abundant highs and accentuates the gain structure without making the amp brittle with a single coil guitar. Also the benefit of amazing grunt with a humbucker. Vintage type tones are definitely preserved and not lost. The winner of V1 and V2 goes to the Mullard reissue. I thought the Mesa 12AX7A’s were bright in this amp for the Hi/Lo channel. The other tubes I tried including the NE12AX7 had either too much gain, not enough headroom and enhanced the top end too much. The RA100 is simple but difficult to tune with tubes. Funny from a tube I did not care for much when I first got them, now they are in two of my amps in the front end or latter gain stages and no longer used as a phase inverter.
Mark IV: It did not seem to make a difference what I put into the amp. The clean channel never suffered from any issues. The Mullard CV4004 seemed to work the best in V1, V3 and V4. Preferred series 7025 kept the abundance of gain out of the mud and tightened up the lead channel when used in V2. V5 has been a Sovtek LPS from the start to the end. The NE12AX7 sounded great in V1 for the clean channel. However, did not seem favorable with RH2 or Lead. Things would be different if I channeled the amp through a 412 all of the time but I like the Fane with the Tonker for that punchy attack.
In conclusion: Two tubes I did not thing I would roll out of any of my amps were the most expensive. The Northern Electric (sounds good but there are good sounding tubes at more reasonable cost, and lastly the Gold Lion B759. If it was not for the static issue I may still be using it.

 

[bandit2013]

Primary reason for the alternate tube selection was to find replacement tube for the Mesa (1990's) 12AX7A. I did not expect to be overwhelmed with the end result as I am now with the Mark V.

Original Mesa 12AX7A (JJ select and rebranded tubes): this is a great starting point, or the intended starting point. Considering the cost of the JJ tubes at the retail end compared to other brands, it has a great price point and the tubes are not all that bad. I use them as a bench mark to compare what was to different tubes to what it could be. Perhaps these tubes are the best for you or they are just acceptable. Everything is subjective. I prefer to take advantage of the amp as much as possible.
CH1 Clean is good clarity, shimmer and dryness that one would expect from a good quality amplifier.
CH1 Fat with emphasis on low to mid thickens up the tone.
CH1 Tweed, brittle, nasty, not at all enjoyable.

CH2 Edge is similar to tweed in CH1, thin and brittle
CH2 Crunch is one of my favorites, deep undertones with considerable chop, but week in structure
CH2 Mark I way too much bottom end even with it dialed out, Depending on how you set it up it can sound OK

CH3 Mark IIC Really good gain structure.
CH3 Mark IV not bad, more compression than desired. A bit brittle unless the treble is dialed out, Presence control needs to be cut too.
CH3 Extreme is very precise. Can only use the sliders on the EQ, using preset will pierce ear drums.

With no signal on the input and leaving the channel controls as is, CH1 has a subtle hum, CH2 is quiet, CH3 has a deeper hum. White noise (hiss) can be an issue depending on gain and presence settings.

The old Mesa 12AX7A from the early to mid 1990's sound much better. Brittleness is reduced to some extent.
CH1 Clean is good clarity, shimmer and dryness, a bit of a warmer tone but not much of a change.
CH1 Fat with emphasis on low to mid thickens up the tone, again warmer but not much of a change.
CH1 Tweed, brittle, improved due to top end roll off, tolerable.

CH2 Edge is similar to tweed in CH1, thin and brittle, not much of a change here.
CH2 Crunch is one of my favorites, deep undertones with considerable chop, much more bite. More of a vintage amp gain structure.
CH2 Mark I way too much bottom end even with it dialed out, Depending on how you set it up it can sound OK, no change

CH3 Mark IIC Really good gain structure. More compression than with the JJ type tubes. Not as much fizz.
CH3 Mark IV not bad, more compression than desired. A bit brittle unless the treble is dialed out, Presence control needs to be cut too.
CH3 Extreme is very precise. Can only use the sliders on the EQ, using preset will pierce ear drums. Sounds better but can be brutal if too much treble is used.

With no signal on the input and leaving the channel controls as is, CH1 is almost totally quiet, still some transformer noise but not as prevalent as it was. CH2 is quiet, CH3 has a faint hum I can live with. White noise (hiss) is non-existent.

Last tube roll in the Mark V.
V1, V3, V4= Preferred Series 7025
V2 = Mullard reissue
V5, V6 = CV4004
V7 = Sovtek LPS

CH1 Clean is good clarity, shimmer and dryness, a bit of a warmer tone but not much of a change. Similar to old mesa tubes.
CH1 Fat with emphasis on low to mid thickens up the tone, again warmer but not much of a change. Bridge pickup (humbuker) still strong but not drowning out the bottom end. Perfect for blues.
CH1 Tweed, Sweet chime, still top end sensitive but not brittle. I can now use it with a single coil strat bridge pickup without sounding like breaking glass. Sounds more like a cross between clean and lo gain channels on the RA100.

CH2 Sounds killer. Tone and gain structure is way better. Dark looming undertones but yet stable gain structure. Sounds closer to the crunch voice with the original Mesa 12AX7. I can really enjoy the Edge much better.
CH2 Crunch is one of my favorites, deep undertones with considerable chop, much more bite. This competes with the Mark IV (actual combo I have) and has changed to more of a Marshall killer. Still has the same tones.
CH2 Mark I has no more deep mud. I can actually set some bass and a bit of mid tone to get a great sound. Reminds me of my Mark III. This voice can be sick in a awesome way. Definitely will use it more !

CH3 Mark IIC Really good gain structure. Not much change. Still sounds great
CH3 Mark IV Awesome, more definition, I can dial in more treble and balance out with the presence. Increased headroom with more definition. Chords would always get lost in the fiz or mud. Now I can get some hot tones with setting the gain higher than 10 oclock without drowning in way too much saturation. Brittle no more. Still bright but definitely not brittle
CH3 Extreme is very precise. Just better. Preset and sliders are useable tools now. Gained a slight bit of warmth. This is the liquid gain channel.

 

[bandit2013]

Don't buy into this yet... After cycling though all of my guitars I found what sounded really good a few days ago to sound absolutely terrible. As I am learning more about he Mark V, it seems that tube positions you would assume not influence tone do. It is obvious that V4, V5 and V6 will alter the CH3 character. However, half of the tubes are used by all channels, namely reverb send (V4), reverb return (v5), effects return (V6). Pulled the Mark V chassis again along with the reverb tank. I can get awesome tone without the tank connected, but once it is in the circuit everything changes even if the reverb is turned off. I will begin experimenting with other tubes I have that I have not used, JAN/Phillips 12AT7 (I have 3), I may go back to the Northern Electric which I found a home for in a Carvin V3MC (that little amp needs some help for combo duty, for driving a 412 the 12AT7 made a big difference). Seems once I mount the chassis back into the shell, it sounds terrible. May leave it out for a while until I am satisfied with the amp. I have gone back to original tubes for the moment, they are okay but brittle on a few modes and all of CH3 is hard to enjoy. I may just give up, keep the Mesa tubes in place and trade for a Roadster head. I am beginning to form a love/hate relationship with the Mark V. Not sure what will be next.

 

[dodger916]

 

[dodger916]

Don't buy into this yet...

I am beginning to form a love/hate relationship with the Mark V. Not sure what will be next.

 

[bandit2013]

Crap, reason for using word and copy and paste.
Tried to post my final and poof, prompted me to log in again and reply was gone.
I will try again later....

 

[bandit2013]

:shock: The preamp tube saga continues with the Mark V.
Why I love this amp, it sometimes sounds great. Why I hate it, it sometimes sounds terrible. If you want to dig into the weeds, keep reading, if not, jump down to the next paragraph. I believe the issue revolves around J175M2 which is the JFET that is used as an attenuator it if is operated in its ohmic region, or is it just a simple JFET switch as it is classified. Schematics do not fully show or reveal the network of resistors or whatever connected to the gate of M2. Currently the J175M2 decided to become a short (damaged gate?) and pulls the grid of V4A to signal ground. I removed the JFET and now have abundant reverb (too much actually.) I installed a 220k resistor in place of the JFET (connected from Drain to Source pads on the PCB). That helped to reduce the abundance of reverb. Considering the failed JFET drain to source resistance was 98 ohms, with the reverb active it was barely a whisper. Also there are two back to back Zener diodes D72 and D71 that will serve as voltage limiters so if the signal is over the Zener voltage it will get clipped which may contribute to the issue I am having. With the JFET removed, a 47K resistor would be a better choice than the 220k I put in, however, if the resistance is too low it will pull down the entire filter network that is feeding it (there are two, one from CH3 which is sourced from the signal feeding into V6A (CH3 Master Volume) and the second one is sourced from the output of V1B which runs to V3A. Change in impedance may affect the overall tone of the three channels. Changing V4 (without the reverb in use) did have a tone impact on all channels (obvious that the gain structure of CH3 would also be affected). Heck, why not just get some J175 through digikey since they are not very expensive... Well I dove into the issue a bit further, even when the J175M2 was working, the amp was to sour and brittle. I looked through my boxes of spare parts and found a 1VK ceramic capacitor (560pF) that I used to tone down a bright all maple guitar. Since I was willing to pull the amp out again why not solder that to the 220k resistor I used to replace the JFET. Effectively this will create a low pass filter that will not shunt the majority of the bandwidth of the signal (only the top frequencies and upper harmonics). Much better and the amp is no longer brittle. It is still rather bright but that can be dialed in or out with presence and treble controls. Now it sounds like a tube amp again, no longer suffering the SHOT noise (yes that is an “o” and not supposed to be an “i” but it may as well be.) For those who are not familiar with SHOT noise, common term used to describe solid state amplifiers that are driven into saturation with full clip on both positive and negative rails. In other words your smooth sinusoidal signal is turned into choppy square wave with sharp edges. Sharp square waves when in an audio circuit comprises of all frequencies (fundamental and all upper harmonics) and it sounds like a can full of steel bearings being dropped onto a large steel sheet (proper description was BB’s being dumped into a steel bowl, BB’s being SHOT pellets from a shotgun shell). The low pass filter trick made a world of difference. Not recommended if your amp is in good working order.

:roll: (bypass from the weeds above)
As for the tubes, well I have experimented with a small array of different preamp tubes totaling 76. (18) Mesa (JJ) 12AX7A, (10) Vintage Mesa 12AX7A (Chinese), (5) Mullard reissue 12AX7, (5) Mullard CV4004, (5) Preferred Series 7025, (7) Elecro Harmonix, (7) Tung Sol 12AX7, (1) Tung Sol Gold 12AX7, (3) Sovtek LPS, (1) Ruby HG 7025, (1) Ruby HG JJ 12AX7, (1) Northern Electric 12AX7, (1) Gold Lion B759, (4) JJ 12AX7, (2) Penta Labs 12AX7 (Chinese), (1) JAN/GE 5751, (3) JAN/Phillips 12AT7, (1) RFT 12AT7, and (1) Mesa 12AT7 (Chinese). Prior to repair of the reverb circuit issue I had suffered from, the low gain tubes really sounded great. I had the JAN/Phillips in V4-V6, the RFT in V3, the Mesa in V2 and the JAN/GE in V1. I would have kept this if I never used CH1. This provided the best tone and gain structure for CH3, CH2 was a bit thin but sounded good. I like to use CH1 so this would not work for me. Also what I gained with CH3 I lost in CH2. The only current production tube was the Mesa 12AT7. The rest were NOS. I should have tried this with the V30 412 cabinet. Actually what I was going to settle with was the Preferred Series 7025. This tube packs the full punch, keeps the bass on the tight side, mids are present but not abundant and the highs are crisp and tame (not shrill or ear piercing). Since I only had 5 of them, I opted for the vintage Mesa 12AX7A for V2 (moderate mids makes the CH2 crunch sound more like a Marshall.) The amp was still bright but manageable (yes this was before the fix on the reverb circuit). Packed the chassis back in its shell and was done….(I thought). The next morning, I decided to run the amp through the V30 cabinet (I normally use the EVM12L cab with the Mark V). That was a complete disaster. I would be at my wits end if I only have V30s to use. EVM’s are better suited for the Mark Series amps than the MC90 or V30 (especially if you want to take full advantage of the amp). What made it worse yet, I swapped the SED =C= 6L6GC with Gold Lion KT77’s. I went back to the SED’s since I was tuning for them and not the KT77 (these sounded killer before I had the reverb issue and did not have to change preamp tubes either). This was the deciding point to correct the reverb circuit with a low pass filter. Sounded much better, in fact just what the amp needed. Still bright though. What to use to darken the tone a bit and yet retain the qualities of the PS7025? Not the Mullard CV4004, that tube is the converse for the vintage Mesa 12AX7A. The CV4004 definitely will scoop the mids out of the signal. Tung Sol, maybe, that will darken the tone and roll of the upper end. Then there is the Mullard reissue (long plate that resembles the Sovtek LPS, also looks identical to the Gold Lion B759). Prior to correcting the issue I had with the reverb circuit, the Mullard reissue seemed like too much tube and everything would drown out in muddy bass or undefined gain structure (was having this issue with most except the PS 7025). After the reverb fix I gave the Mullard reissue another chance. However only in strategic positions; V3 and V6. V3 is the Master Volume tube for CH1 and CH2, V6 is the Master Volume for CH3 as well as the effects loop. I have tried the Mullard reissue in other positions and wound up with CH3 very difficult to use without uncontrolled feedback. What worked great for use with EVM12L and V30 cabinets as well as my strat type and other guitars with dual humbuckers is the following:
V1, V4, V5 = Preferred Series 7025
V3, V6 = Mullard reissue 12AX7
V2 = Vintage Mesa 12AX7A (the PS 7025 works well here)
V7 = Sovtek LPS
The Northern Electric 12AX7 and the Gold Lion B759 sounded good but seemed to reduce the signal in the Mark V when used as primary tube. At least I found a use for them in my Carvin V3MC, that small amp had too much gain to start with and needed a bit of reduction. I did try them again in the Mark V but with the same results. The GL B759 still had the static issue in the Mark V, worked without issue in the RA100 and Carvin amp. As for the RA100, the Mullard reissue in V1 and V2 will reduce the brightness in the Hi/Lo channel and actually make it more enjoyable. Still nothing better than the Mesa (JJ) tubes in V4 and V5 (except for the vintage Mesa tubes). The Mark IV gets fed the leftovers. The Mullard CV4004 did not seem to affect the amp as much or was not as noticeable as in the Mark V. I still have to put that back together since I removed all of the tubes to try out in the Mark V. At least I think I am done with tubes for the time being. I am still considering getting yet another Mesa Boogie. This time it will be the Roadster Head, but do I really need another amp to feed?

 

[bandit2013]

I kept the SED =C= 6L6GC in the Mark V if that matters....

I forgot about the Mark IV. Well.... what about it? Since I was able to use two of the Mullard reissue 12ax7 in the Mark V, that freed up two of the Preferred Series 7025s. That is what is in V1 and V2 of the Mark IV, V3 and V4 I used the Mullard CV4004. V5 (PI) as is the case with my other amps, Sovtek LPS. I put the New Sensor Svetlana's back in, they sounded better than the TAD6L6GC-STR (backups for the SED's when they decide to go in the Mark V). So far when it comes to power tubes, the SED =C= including the GT6L6R-2 (gold series NOS Svetlanas, no longer NOS since I put 8 months on them in the V) have held up the best without red plating. I have tried Tung Sol 7581, Svetlana (New Sensor) 6L6GC, EH EL34 and they will cook the seams of the plates. The only exception of the New Sensor tubes are the KT77 (gold lion) As for the TAD, it is hard to notice if the plates are getting too hot since they are coated with a shiny black oxide of sorts. I may eventually try the Mullard 6L6GC (another New Sensor product from Saratov and probably the same as the EH version ). Oddly enough I am beating the Svetlana's in the Mark IV very hard and they are still kicking. Mark IV bias on the tubes is not as hot as the Mark V. I play in the dark sometimes, especially when I tube roll when I install new power tubes. That way I can see if the tubes are going sour (plates begin to glow at seam). The only tubes I have blown out in a short time were the Original Mesa STR 440. I normally use 90W mode to balance the load on the tubes, in 45W mode is when I normally have issues. If I am using the effects loop for the master volume and solo boost it will be V8 that goes first. In hard bypass, V9 becomes the hot tube. S*** happens. Now that Svetlana Electron Devices is not going to build any consumer glass products this year, just wonder about 2015, I may eventually have to find alternates for them at a reasonable cost. I have tried JJ tubes and they only lasted 2 weeks (they did not red plate, one just simply stopped conducting current). Why not try two of the other three in the Mark IV? Did it before but the second time was more of a photo flash or arc welder display than anything. Surprised it did not blow a fuse. Looked like a very hot, high voltage and strong current plasma sphere jumping around the terminals at the bottom of the tube. Perhaps Jacobs Ladder in a compact glass tube. Made for a good Mercury lamp considering how bright and blinding it was. At least the amp survived the ordeal. If I had to rate which amp I currently have is the loudest, take a guess Mark IVb combo, Mark V, or the RA100. And the winner goes to...... Mark IVb. Yes, I practically burned out the voice coil in a WGS Black Hawk HP100, I think the MC90 was toast shortly after I got back into playing again. The Fane AXA Studio 12L Speaker can handle it (has similar ratings as the EVM12L Black Label I am using in the 412 cab).

 

[bandit2013]

I believe I am done with the Mark V. yep. that is becoming an old story now.
As for the Mark IV (b), it is not as tone sensitive to preamp tube changes as it seems. Right now I am running nearly all Mullard CV4004 in the amp with great results. I did like the amp fully loaded with Tung Sol 12ax7 aside from V5. It is hard to decide what sounds better, PS7025 in V1 or V2. The Mullard CV4004 may have a slight scoop in the mids (more noticeable in the Mark V) but does not seem to be a tone killer in the Mark IV. With a Preferred series 7025 in V1, the RH1 is incredible with the remainder CV4004's in V2-V4. It becomes debatable what sounds more acoustic CH1 of the Mark V (lowest gain setting = clean) or RH1 of the Mark IV. With the tube arrangement I believe the winner to be the Mark IV. Keep in mind I am not running the typical speakers in my Mark IV. I am using a Fane Studio 12L which fit okay with the rear mounting but left little or no room for power tube changes. It took more work to modify the grill than it did to open up the baffle to convert to a front mounted speaker. I am also running it as a 4 ohm load in parallel to a Eminence Tonker light in an oversized 1x12 cab. Talk about bottom end that is not loose. Very tight with crisp highs. I can get lost with this amp easily and not want to play though anything else. I did have the TAD6L6GC-STR in the amp for a short while, they sound better if you integrate them with SED =C= (outer with TAD inner). I put the Svetlana tubes back in as I like them better than the other tubes. Considering that they are not true Svetlana's (SED=C=) they are not all that bad (however they did not seem to sound as good in the Mark V). Picture below is before I converted to the front mounting. with the following tube arrangement I get rich clean and dry tones in RH1 that I wish my acoustic would sound like. RH2 is okay if dialed in properly, but the Lead is killer, just with two speakers I have more of a full spectrum than I can get out of the EV12L loaded 412. Forget the V30's unless you like your tone on the thin side. So far the only amp I like with the V30's is the RA100.

A picture of everything else.

 

[swbo101]

I believe I am done with the Mark V. yep. ................. With the tube arrangement I believe the winner to be the Mark IV....................................

What does this mean? Are you getting rid of the V and keeping the IV? Or just done with tube rolling in the V?

 

[bandit2013]

not giving up the Mark V. I am done with tube rolling as it sounds awesome for now.
I try not to focus on rolling more than one amp but this time I over did it. The Mullard CV4004 is an interesting tube. It can be dark or bright, may even provide a mid scoop. All depends where you install it. The Mark V can be tricky due to its complexity. Just one tube can make or break the tone and trying to maintain a good balance with all channels and modes is not easy. The PS7025 is also similar to the M CV4004, generally a bright tube but can really enhance the low end. Done with the Mark V, in terms of tube rolling yes. The winner being the Mark IV in terms of the clean channel only. What classified it as the winner is the dry acoustic tone I can get with it (in part due to the speakers in use). The Mark V has a really great clean channel too. The RA100 is also superb but they are quite different tone and character. I can get similar if not better clean sound out of the Mark V but there is a trade in how the other channels will sound.

My top list amp is the Mark V due to its versatility and array of different tones and gain structure that is achievable. Second on the list is the RA100 and well the Mark IV drops in third place but I enjoy playing through it just as much as the other amps. I had considered replacing the Mark V for a while simply because I could not cut the over the top brightness. The EV's helped and were a big improvement over the V30's in the large cab. I may have a love/hate issue with the Mark V but that was easily fixed with tube changes and repair of the reverb circuit which was the root cause for the high frequency bite that was ripping my ear drums. I am unsure how long the attenuating P-channel JFET was acting up (ever since I brought it home in 2012, new). Since it suffered a gate issue and failed to operate, loosing the reverb was the last straw. I could have replaced the JFET with a new one, considering the amount of work necessary to do it right, removing it and replacing with a pull down resistor was the easy option. After removing J175M2 which was determined to the be failed component, the reverb was too much. Adding a shunt resistor and filter cap resulted in a better tone, controllable reverb level, and best of all, no more breaking glass tone in CH1 tweed, CH2 edge and CH3 (any mode). Now I can make use of the presence controls and add more treble (would normally have them dialed out). Sure, it could be my guitars... a month ago a friend was over with his axe, totally different than my Carvin guitars. Amp still sounded brittle. Compared to the RA100 and Mark IV, never had the issue. I am also considering getting another amp, a DR Roadster (what I originally wanted but could not figure it out when I played through it the first time, Mark V was familiar to me and easy to get good tone, should have taken the one I played through but selected the clean one in the back that was unused and not a demo.) As for the DR Roadster, do I need it? no.. Do I want it? yes. Heck, just get it.... Still have no plans on letting go of the Mark V, I see a long road ahead and hopefully there will be no more JFET issues but they do happen.

 

[bandit2013]

Just when I though I was done with the Mark V... I did a back track on a tube roll. I decided to try a different tube in V1, V4 and V5. However I had to borrow tubes from my other amps to make it happen. First off before removing tubes from my other amps, I retried the low gain tubes again. Jan/GE 5751 in V1 and Jan/Phillips 12AT7 in V4, V5. The effect was a thinning of the high mid, boosting the bass, and thinning out the highs. Too much headroom on CH3 only resulted in total darkness of the channel, still had top end zing but not the direction I wanted to go. I had two Mullard reissue in the RA to darken the Hi/Lo channel. The Mullard reissue is not as bright as say a PS7025 or the Mullard CV4004. So I swapped out V1 of the Mark V and V1 of the RA100. The Preferred series 7025 is a nice tube, but needed a cut in brightness in the Mark V but without sacrificing the tone in the clean channel. That helped to some degree. Actually the RA100 Hi/Lo channel sounds better with PS7025 in V1 followed by the Mullard reissue, Lo channel is not brittle (as is the case with Mesa 12AX7A) and not too dark as is the case with the Mullard reissue. Then I went back to the Mullard CV4004 in V4 and V5. Now the Mark V sounds much closer to what I had with the vintage Mesa 12AX7A tubes but less compressed on CH3 and not too bright either. Finally got a good balance between all channels.

To recap the V,
V1, V3, V6 = Mullard reissue
V2= vintage Mesa 12AX7A (Chinese)
V4, V5 = Mullard CV4004
V7 = Sovtek LPS

I did have the two Mullard CV4004 in the RA100 in the V4 and V5 positions just to see if I could adapt. I actually went back to the Mesa 12AX7A (JJ) again. It seems that other tubes in V4 and V5 will enhance the low end (M CV4004, M reissue, PS7025, TS, EH, Northern Electric, Gold Lion ). The clean channel is a bit dark to start with. I believe what I liked about the Mesa 12ax7a (JJ) is that it seemed to make the clean a bit spongy. The other tubes just tightened it up too much.

RA100
V1 = PS7025
V2= Mullard reissue
V3 =RFT12AT7
V4, V5 = Mesa 12AX7A (JJ)
V6 = PS7025
V7 = Sovtek LPS

Not much changed with the Mark IV. still have the same tubes.

I must be going nuts... yeah, that must be it...

Why such issue with the Mark V? Mostly because it is too bright. I don't want to pillow the speakers. It is not the speakers I am using either as with other amps it is not an issue. I may like it for a while, then sooner or later it just seems too bright. I cannot rule out there is an issue with my amp. If there is, it was there from the start. Sure something happened since November of 2012 and now, lost the JFET that attenuates the reverb send tube. Prior to that, always had the same issue with brightness. Probably the nature of the beast. Could be power tubes, tried many but settled on the SED =C=. Reason why I liked the Vintage Mesa 12AX7A tubes, they were used and did not seem to have abundant top end.

A DR Roadster on the other hand is similar to the Mark V in some respects and similar to the RA100. What I love about the RA100 besides its tone is the Class A/B power amp. It may not saturate as much as the simul-class circuit of the Mark V but that is okay. I believe the overall brightness of the Mark V is contributed by the enhanced class A circuit of the simul-class design. Mark V is also known to drive the primary power tubes a bit hotter than the earlier Marks. In this case it is the Center two tube positions, where as in the Mark IV, the primary are in the outer positions. I think now would be a good time to get a bias probe to see what is going on. I have not bothered since there is nothing to bias.

 

[swbo101]

Why such issue with the Mark V? Mostly because it is too bright.....
I cannot rule out there is an issue with my amp.....
If there is, it was there from the start.......
Prior to that, always had the same issue with brightness. Probably the nature of the beast....

I don't own a V, I have a IV. However I've probably played at least 12 hours on a couple of different V's, combo and 4X12. Neither seemed BRIGHT. Yes not as compressed as the IV, or dark, but I wouldn't call it bright to the point where it was an issue. I would have it get a run through by a tech if you feel the brightness is too much.

just my 2¢

 

[bandit2013]

I really considered it. for now I have been able to compensate with preamp tubes. I know the power tubes will contribute to brightness. SED =C= are known for it but they are not over the top. I have tried many different power tubes and the SED =C= just sound the best. I should pop in the KT77 again and see if the last tube roll made a difference. When I received a Carvin V3MC that I ordered, it too had similar issues. Blah... with an ice pick. I expected I would need to replace the EL84's not knowing what brand they would be so I got Mullard EL84 to install. Turned out the bias was set to overkill (bias for 4 should be in the range of 79 to 82mA, it was factory set to 125mA, that was an easy fix and sound really good now). I wish it was that easy with the Mark V. I am not unhappy with it. Just would be happier if it was not so brittle (and now that is the case, much better and sounds terrific!)

As it goes with the Mark IV, I can put in just about any preamp tube or power tube (as long as they are the same type) and it sounds great. The only complaint I had with it was the MC90 just could not take be beyond bedroom level without breakup. No longer an issue. I did try the MC90 in my other combo, nope, definite issue with voice coil. Oh well, after 14 years it did its job but softly (reason why I had a Recto 412 in the first place). It was not until I sold the Mark III that I wanted more volume. and the story goes on, and on, .........

 

[bandit2013]

I had to make a choice with the Mark V for overall performance. The Mullard reissue did sound great but the down side was with CH3 Mark IV mode. I could not adjust the gain without feedback issues. Reason for changing from the Preferred series 7025 to the Mullard 12AX7 was to cut back on brittleness in tweed (CH1) and edge (CH2) when using a strat with single coils. However, when playing one of my favorite guitars for the heavy stuff, Carvin DC400 Walnut, the tone was on the muddy side. I returned back to the Preferred Series 7025 for V1, V3 and V6 which really opens up the amp for a wide range of versatility for a neck through or set neck guitar with humbuckers (even when tapped to single coil). All channel modes sound incredible, only drawback is a bolt neck with single coils. No big deal.

Back to previous,
V1, V3, V6 = Preferred Series 7025
V2= vintage Mesa 12AX7A (Chinese)
V4, V5 = Mullard CV4004
V7 = Sovtek LPS

I figured I was going to change the tubes again. Since I was using all of the PS7025's (had to remove two from the Mark IV and replace with one CV4004 in V1 and a Mullard reissue in V2 sounds great for what I mainly use the Mark IV for. It is difficult to find preamp tubes for the Mark IV that sound terrible). If I did not mention it before, I took out the TAD in favor of the Svetlana in the IV.

Strat type guitars in most common formats SSS or SSH the RA100 steps in and takes over. So easy to set up and plug and play, matters not what guitar I use, it just sounds great. As for the case with the Mark V, one must dial in the guitar for certain channel modes. Quite a complex amp. I am considering adding another tone monster that is similar to both the RA100 and the Mark V. Sort of a crossroad to both amps but entirely different. So the Dual Rectifier Roadster head is going to be the next object in my studio. Just like most Mesa boogies, you need to learn how to dial it in. Mark III was tricky since all three channels shared common tone controls. Mark IV simplified that by separating the Lead channel from the Rhythm channels. The Mark V is obviously a step in the right direction. In terms of expression and blues or jazz the RA100 clean channel has versatility (the saving grace for that is the attenuator). It does not end there either, The Hi/Lo channel really screams from vintage to heavy. I believe what sets it apart from the Mark Series is the full Class A/B power. Some complain about how sensitive or detailed the RA100 is, in my books it is perfect. The only drawback, if you want monster gain you need to crank it up to saturate the power tubes (or use the power soak). The Roadster on the other hand, is just wide open class A/B. At least it has a 50W mode. I do not have to worry about amplitude of the output since I live alone and can push most amps to their limits without getting a knock on the door by the police at 1AM. At least I do not need a cabinet but may get one just for kicks. If and when I get the Roadster I can experiment with two different 412 Cabinets. I have a traditional sized 412 with the Mesa V30's in it. It is not built as rugged as a Mesa Cab but it sounds great. An there is the larger Recto cab with EVM12L Black Labels I generally use with the Mark amps. I had considered converting the Mark IV to a head and ditch the combo, but not any more since I have a great speaker set up that takes advantage of the Mark IV in all aspects. I did place the Mark V on top of the IV to compare with the same speaker set up ( my speaker wire is long enough to use the Mark IV combo as an extension speaker as long as the amp you are using is sitting directly on top of it.) The Mark V did not sound as good, was not bad but not as sinister. However when I had the WGS Black Hawk HP100 in the IV, the Mark V sounded much better thought the speaker than did the Mark IV amp. The fact that the V and IV sound nothing alike is even better. The Mark V and IV are not the same apple, perhaps one is a peach and the other is a pear. Matters not they are both great amps. Only wish I kept the Mark III. Oh well, at least the person I sold it too is very happy with it.

 

[bandit2013]

Another bummer, no problem to resolve.
RA100 worked great for a little while but decided to pop and make noise in the clean channel. Seems like when I use the Mesa branded JJ tubes this is what I get, hit or miss. I have a few of these to check out and some many other tubes to roll in. The Mullard reissue may sound great in the Hi/Lo channel (V1, V2) but yet I feel something is missing. I will have to pull the amp chassis out for tube rolling (much easier that way without getting tube burns).

Issue with the Hi/Lo channel, it is either too bright or too dull depending on what tubes are in V1 and V2. I may go back to the vintage Mesa Tubes in this amp since they sounded the best overall. It does not matter to me if the preamp tubes are all the same or different. I may even load it up with 12AT7 just to try it. That will definitely darken the tone to some degree but may be worth trying on the Hi/lo channel. I normally use a Strat HSS and soon will be adding an SSS to my guitar collection. My other favorite with this amp is the Carvin version of a Les Paul. This amp may be better served with NOS tubes than current Russian or Chinese tubes. I do like the PS 7025 but in the clean channel it really opens up the bass more than I want. Mullard reissue is much darker and less refined. Mullard CV4004 are a bit different in this amp than the others. It has been a while since I used the Tung Sol and EH tubes. May even try a few JJ branded tubes as well. I know it is not the power tubes since I got the same effect with the KT77 and the Mesa EL34's. I guess it is back to the roots, hopefully I can find enough of the Mesa tubes that are not noisy, I have many that hiss, a few that generate static once they heat up. I am definitely considering the Mesa graphic EQ for this amp to tailor the tone a bit more. The speakers are okay (original V30's out of my Recto Cab), I may not like them much with the Mark amps but they sound great with the RA100. Perhaps I am just too picky or tone deaf.

 

[bandit2013]

Got the RA100 back to perfection. The Vintage Mesa 12AX7A (Chinese) were the answer. However, I did like the tone and gain character I was getting with a Mullard reissue 12AX7 in V2. The rest except for V3 and V7 now have the old Mesa tubes in them. I was hoping to get away from them but with the RA100 I cannot. I will have to try the GT Chinese tubes and hope for the best if they are any good. I would buy them with their native branding but would prefer filtered and selected tubes than hit or miss.