Mark V 90W combo speaker change

The Boogie Board

Help Support The Boogie Board:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Maybe it comes down to terminology. Look at the Plexi, a tremendously percussive amp. The RC time constants of the power rail filter capacitors and resistors come in around half a second. That means you get a huge burst of louder output for the first quarter second at least when you hit the strings. It amounts to a compressor with a slow attack time. The higher impedance power rail gives a lot of sag on that time constant. The Mark V by contrast has short time constants and a very stiff power rail, so it is less dynamic, and what dynamics there are happen on a time scale where they create a distortion texture instead of a percussion.

The RA is the somewhere in the middle with time constants that have been adjusted to shorter values and lower impedance for the clean preamp and longer and saggier for the first two distortion channel stages. Well, I’ve just started looking at it and I’m sure there are things I’m not appreciating yet. I’d like to write a simulation for it.

After more time with it I love the RA even more. I can’t believe how nice it is to play. And it works with all the guitars I’ve tried with it equally well. I’m comparing it to great amps that I love and I think it is my favorite. The texture of the distortion is just so nice, and the clean channel is sweet also. The modern sounding speakers are a big part of it for me.

A fun Mark V trick I’ve been doing is overdriving the gain-reduced channel 3 with good distortion pedals and using the noise gate in the Bass Big Muff. I can get some mechanical sounding textures that I really enjoy. Really I’m hearing completely alien sounds out of that amp now, which suits me.
Some are going to harp on me, why is this content here. It is related to the OP's comments of which they recently got an RA100. I know it has nothing to do with the combo speaker of the Mark V90. The topic sort of changed.

When it comes to the RA100. For the clean channel, I basically back off the bass control. The clean channel has a similar design to the Electra Dyne and the Triple Crown as the three triode gain stages are followed by a pair of op-amps. Unlike the Triple Crown that chokes off the clipping to some degree while in normal mode, you need to use the drive switch to get that into the burn of plexi world, the RA100 trick is simple, just push the gain up.


The Hi/Lo gain does not make use of any op-amp circuits at all. It has 4 cascaded gain stages in hi mode and three cascaded gain stages in lo mode. Hi mode has a dual gain control for the 2nd and 3rd stages which is different. It is sort of Mark/recto like in character once you figure out what power tubes and preamp tubes work best. Surprisingly enough, the common tone and gain controls for the Hi/Lo channels just work without having to change settings to make us of both modes. I typically push the bass and midrange and back off on the treble. With the RFT 12AX7 in V1 and Ei CV492 in V2 it remains tight in the low end. I noticed I forgot what I loaded into the RA100 preamp. Marshall 2555x.

I got a close up of the image above to see what I stuffed in the amp.

preamp tubes ra.JPG

The Hi/Lo gain channels:
  • V1 is the RFT 12AX7 (they were sold as Amperex, bugleboy, RFT, Tesla, Telefunken, Tronal, Globus, Amperex, United Electron, and CV8156). The key is they were made in Germany. There are many other brand names for this tube.
  • V2 is the Ei CV492 often used as counterfeit Mullards, they are really good tubes though.
Alternates I have used before going NOS: Mullard CV4004 in V1 and Mullard 12AX7 in V2.
I found the stock Mesa 12AX7 to be a bit loose, fluby low end on the Hi gain channel. The NOS tubes really tightened up the low end. The current production Mullards just had a bit more gain and did not shore up the bottom end of things, still better than the JJ ECC83s tubes.

The FX Send/Return tube:
V3 is the Mesa 12AT7 Chinese Shuguang tube. It just works in the RA better than the JAN/Phillips 12AT7 but was using that in the RA before I got my hand on the RFT and other NOS tubes. So that is why I had a few of the JAN/Phillips 12AT7 tubes to explore the Mark V saturation mod. When I got the amp, I changed out the V3 with an RFT 12AT7.

The Clean channel:
V4 is just a stock Mesa 12AX7 (JJ ECC83s).
V5, I see the Ei CV492 is in that position. To be honest, it does mot make any difference what preamp tubes you use in the clean channel spots as it will sound much the same.

Reverb tube:
V6 is a JJ ECC803s tube. Long plate version of the ECC83s and has a bit lower gain to it. Sort of softened up the reverb. I was unaware the reverb circuit runs in parallel to the FX loop.

Phase inverter: Typical Sovtek LPS but a Mullard 12AX7 (reissue) is basically the same tube with better characteristics. The Ei CV492 works great as a phase inverter. Considering I have only the boxes left with Mesa tubes in them, I assume I stuffed the Ei in the PI spot in both amps. (RA100 head and the RA100 Combo). It got to that point I did not want to play through anything else but the Pair of RA100s. I eventually added a Boss EQ-200 as it will support a stereo setup. That is when the 7 string came into play.


Yeah, these amps will push some serious air with the 7 string guitars. It does help to have an EQ pedal in the FX loop to get more of a 30Hz boost. I got hooked on the 7 string using the RA100. It just did not work out with the Roadster or the MWDR but there is a fix for the Roadster with some tube swaps. I will not bore you with those details here.


Too bad the Triple Crown 100 was not on par with the RA100. It is a good amp but different in design. Similar sounds but the multi-soak feature only works as an attenuator and does not let you hear that power tube saturation. Also, it does not have a half power mode, instead you have to sacrifice your power tubes with the multi-soak to get that, and it is more like running a 35W amp if that. TC50 is more open and louder than the TC100 at its 50W setting. I generally do not use the multi-soak feature all that much as I can get a similar effect with the RA100 at its 50W power mode. I believe if Mesa wanted to improve the TC series, if they ditch the op-amp circuits following the Hi/Lo gain channels and introduce the dual gain control for the hi gain channel it would be a better amp. Also add a half power mode and address the multi-soak function the same way as the RA. The only thing going for the TC amps, they sound better with the STR447 tubes. Those in the RA100 makes it too forward sounding. Same with the NOS STR450. It is unfortunate that the SED =C= EL34 are out of production. I have yet to find a replacement in the current production market. I have yet to try out any of the JJ power tubes in the RA. Wonder what they have listed in their amp kit.
Have you tried out a Mark VII yet? Mesa went back to the old school sound of the earlier marks. It is built off of the JP2C platform but with a Simul-Class output power section. Like the Mark V, it has several modes per channel. All I can say is that Mesa did a fine job with each of the seven modes. Sure, it has a total of nine but there are two duplicates. Oh yeah, like the JP2C, the Mark VII is a perfect match for the EVM12L speaker (open or closed back format) as it is with the V30 in closed back.

Sure, the RA100 will grow on you. That addiction will cause you more pain, and many seek out more gain, like the BADLander, JP2C and the Mark VII. I blame it all on the Mark V90 for being less than satisfying. Yeah, for those with the problem, they end up with a Roadster or MWDR for a better fix. The RA100 once you figure it out, will keep you in zone much longer than you realize. I personally would rather be hooked on amps and guitars than other things. A bit safer than drag racing as that was something of an addiction in its own way. Too much risk, the need for more speed was for that adrenaline rush. Guitars, amps and music is more of a dopamine craving. 🤪
Thanks for all the info on the RA! I play the thing every day now for a couple of hours. It is so good. I'll definitely work over the tube positions and try to optimize it more, though it may be some time before I can bring myself to change anything.

I will try the Mark VII. But... I already have really great stuff now. I feel like I might be at a kind of endpoint with the RA. I really value the cold and alien noise I can get from the Mark V now that I have the RA. I play the Mark V less, but probably nothing else does what it can do. I listened to many Mark VII recordings on YouTube and it sounds like a great amp. Possibly if I had it first I wouldn't have acquired all these other amps. But the RA seems like a better find.

I have good distortion and fuzz and overdrive pedals that I can use to get hotter, buzzier, noisier sounds out of the amps. The Bogner transformer pedals are my current favorites for warm and heavy sounds. I love noise and clean sounds and rhythmic sounds but never wanted to sound like Van Halen or Metallica, either one.

But I have always wanted and never before had an amp with warmth and richness comparable to my very favorite guitar sounds, which came out of early 1970s rock bands. And no pedal can do that. The actual sounds mostly came out of modded Marshalls and Hiwatts, back at a time when most every amp was unique. The Exile on Main Street sounds and Mott the Hoople sounds are two reference points. Most of the commercially successful bands of the time didn't have the sound, but some did. The RA100 does the whole range of that stuff I want in that regard.

My other target is all the experimental rock music. Especially Fripp and all the King Crimson stuff and the Velvet Underground and the noise bands of the 90s all different times. Well, the Fripp sounds are more accessible with this amp plus pedals than anything else I've had. The noisiest stuff tends to either be easy to get multiple different ways or else practically impossible to replicate. At the end of the day I'm looking for comparable richness and some analogy to my favorite sounds but don't need to replicate anything exactly.

The trouble with the Mark V is that it gave me this whole alien landscape that I am glad to have available but it could not deliver the warm and evocative tones that are the first center of my musical imagination. I guess that I got the thing in the first place out of ignorance but now it is a wonderful tool.

The RA through the EV+Redback cab is also a completely different amp than it was through the other speakers I tried.

After some consideration I decided to load the 2x BN12-300S speakers into the 2x12 Bogner cab. It is a clear, cold, and dark speaker. I haven't heard the speakers as a pair yet but I think they will work well that way. Maybe I will figure out how to add a pair of crossovers with midrange horns to that cab later, and maybe even design ports for it. But to start with I am going to pair that cab with the Bogner Shiva, which is a dark and warm and very percussive amp. And then sometimes it can be an extension cab for the Mark V or the Bassman or a 600W bass extension cab. The BN12-300S is one of my favorite speakers but I haven't liked it in most of the pairings with midrangey guitar speakers so far. The biggest issue is that this speaker is even more sensitive than you would expect from the specification.

I am with you on the value of music to express all the chaos and complexity you may feel and wish to express. I think there is really nothing else like it. And you know... Only with electric and electronic instruments do you get to craft the instrument you crave with this enormous freedom and range.
The RA100 is a Mesa treasure I wish they did not discontinue. The TC series is close, but its character is quite different even if it has a similar tone. They are fun amps though, just lack the dynamic range of the RA. The Badlander 100 sort of snuck in and stole the show but for different reasons. Same with the Mark VII.
The RA100 experience has been really good so far. I will eventually want to polish it but right now it is still too amazing to change. And I’ve been busy recently but I got some 5751 tubes to go back into the MarkV with. When I do that it will take a whole day to get things right and I’ll finally write down what I’ve done. The objective will be to get a little more gain out of channel 3 when the knob is all the way up without losing the broad tonal range I get there now. But there isn’t much more to do and now the Mark V adventure is near the end.

So that all has caused me to allow myself to become interested in another Mesa amp. When I got the Mark V it was really the studio pre that I wanted. I’ve been looking at some photos of the insides of the pre and at some schematics, and I like it. It feels like something I could maintain. I also love how the controls between the two channels bleed over to expand the range. Mainly I like the sound. Maybe it is a little like a Mark IIB. Whatever it is, I hear people getting a great variety of tones from it. And the stereo effects return and outputs seems exciting.

I listened to a bunch of stereo power amps and end up liking the sound of the older Mesa 50/50 and the Marshall 20/20. The Mesa is simple enough and less crowded inside. It has the Mark II style presence circuit which should be fine and anyway easy to modify.

So I think that will be the new amp. I’ll try to use what I’ve learned from the Mark V and get these two units sounding as good as they can.
I get so hooked when I have the RA100's out. I easily lose track of time after firing up the heaters. As of late, I have two BAD100 and Mark VII out in the studio. I still favor the RA100's (head and combo). I find the RA mojo to be most addictive. Still the BAD or the Mark VII seems to fall into that sound category, different tone but just as captivating. This picture was taken before I got a Mesa Bass rig.


The RA100 is also a favorite for the extended range guitars. It helps to add a 11 band GEQ in the loop. The 5 band Mesa Eq is ok but since I run the pair of RA100's in stereo, the Boss EQ200 is in a stereo format.


After the Mesa Bass Rig, I could not run the pair of BADS with the two RA100's as the H212 and Standard 412 cabs took up too much room as they have the same footprint. Going nuts with a 4-amp rig was my itch. Not sure why but I had to do it. There is enough room on the left side to open up the entry door. Also, there is the garage door on the far right. If I were to get the RA100s out, there is only room for both RA100's and one amp on a V212 or just one RA100 and two amps on V212 cabs. Limited space since the drum set in the room takes up more floor space than anticipated.


This is a shot of the wall from a different perspective with the guitar and bass player (I play the drums in the group). Only three guitar amps were out for this picture. Only the one bad behind the guitar player was used along with the full bass rig. The wall was sort of in a state of flux as I was planning on arranging the wall as a BAD, MK7, BAD, MK7 to get a better spread on the stereo separation between the BADS and the Mark VII amps. Still never completed that task. Not sure why. I get lazy sometimes.

It always looks like you’ve built a kind of guitar heaven there.

I haven’t done this yet, but it would be interesting to hear the Mark V through the power amp of the RA100 and vice-versa. One thing I wonder is how much of that RA100 magic I can learn how to make as mods e.g. to the 50/50. But the first step is to isolate the amp and preamp and see what holds up.

The EQ200 looks like a winner too. More later.
Well, the 50/50 came first. It is a hell of an amp. I‘ve been playing it stereo through the 4x12 with a Bogner Wessex console transformer pedal into an Eventide stereo delay and into the power amp. And then with some demented envelope filter fuzz instead of the Wessex also, and also guitar straight into the delay. I think I’d be satisfied with this amp even without a preamp. It feels almost like a pair of 50W Plexis and in low power mode the power stage breaks up at usable volume.

I found a 2x265W Crest solid state power amp for $80 to A/B the 50/50 with and make sure I’m not fooling myself.

Latest posts