The Mark V90, Longest running Mark Series to date

OK, the Mark IVB has been manufactured to 15 years, not sure when in 2009 the Mark V came out, but we have already reached the 15th year of production. 3 more years of production for the Mark V90 to match the 18 year production run of the IV if the versions are ignored. After I realized my mistake, I could not edit the title. Perhaps I could delete this thread.

Too late, I cannot delete or edit the original post to correct for my stupidity.

bandit2013 said:

OK, the Mark IVB has been manufactured to 15 years, not sure when in 2009 the Mark V came out, but we have already reached the 15th year of production. 3 more years of production for the Mark V90 to match the 18 year production run of the IV if the versions are ignored. After I realized my mistake, I could not edit the title. Perhaps I could delete this thread.

Too late, I cannot delete or edit the original post to correct for my stupidity.

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sorry! missed it bud. new here. carry on. great post/info. doing research and tryin to not b SO cornfused by it all and was proud I apparently knowed sumthin!

what IS the known (not guess or stabs) circuit difference between IVA & IVB?

There are two Mark IV models that practically look identical. Mark IVA and the 1993 Mark IVB, before the wide body change. I have seen other videos, they are calling the IVB a IVA and vise versa. the IVB wide body had the to rocker switches next to the GEQ. The top switch was for selecting the GEQ mode and the switch below it was for lead voicing Harmonics/mid gain. The Mark IVA had those on the back side. I would assume the transition model of the Mark IVB also had the same layout as the IVA due to the smaller chassis. I am not a Mesa Boogie Historian so what other differences there are, I have no clue.



Comparing the two schematics, they almost look similar.
Power amp section does have some differences. The IVB has a relay that changes a coupling capacitor on the phase inverter outputs from 180pF to 250pF (CH3), the IVA has only the 250pF cap.

FX loop circuit is different. The IVB had some sort of mono/stereo thing going on so you can bring the stereo effect back to the IVB and then send it out to the satellite amp. For use with the Satellite 60 or the Simul-Satellite. Never got into that aspect of the amp. (I took this from the manual from Mesa's website). I had the Mark IVB but never made use of the stereo FX loop as I did not have a powered satellite amp to go with it.

The tubes used for the lead drive circuit are different positions. Mark IVA it is V3A and V3B where as the Mark IVB separates the lead drive circuit between two tubes. V3A and V4A along with a control grid to cathode capacitor of 250pf. The Mark IVA does not have that cap in its circuit.

Reverb is managed with V3 on the mark IVA but split using V3 and V4 on the Mark IVB.
The pages for the power supply for the Mark IVA are missing. Hard to tell what if any differences are there.
There are probably other differences as well. Not sure what they are as I did not own a Mark IVA.

Since I am sure that the RHY1 and RHY2 channels retained the shared controls, it stands to reason the model was just improved and did not merit a model change. It was more or less a running change but more dramatic make-over than a running change that is transparent to the customer base.

I guess there were different chassis lengths for the various power sections used with the SRG, DRG, HRG, and KRG configurations of the early marks (IIC and III).

That is almost like having the Mark V90 and all of a sudden there is a Mark V that is compact in size and has some changes to its features, may even have less channels and run on EL84 power tubes. Can you really call that a Mark V? Oh, wait they use the same labels on the amp. Then again, some people got confused about the Electra Dyne and Royal Atlantic, it has similar design cues, channels were labeled the same Lo gain, Hi gain and clean. So, they assumed they were designed the same. Well the preamps were completely different in all respects as were the power sections. The only thing they had in common was Mesa Engineering logo and possibly the preamp tubes.

After seeing that video, I would take either Mark IVA or Mark IVAB. Odd, my Mark IVB wide body did not compare to that sound. Not even close.

I had a Mark IVB for exactly one year. Got it at the 2012 Orlando International Guitar Show, traded it for a Mark V 90 and a Mesa horizontal 2x12 (and some cash) at the show in 2013. At the 2014 show I acquired my second Mark V 90 from the same guy.

Yes, my Mark IVB sounded really good, well within the range in that video, but I like the V better and never looked back. I do NOT like the controls setup on the Mark IV, and it had an issue with its output volume control taper. It sounded choked at the bedroom volume level I usually play at. To get it out of the choked range of volume it got unpleasantly loud for a practice session.

I like the Mark V way better in any event. Everything the IV does, the V does better AND I no longer have to play the balancing game, adjusting controls that are shared between channels.

I still have my treasured and trusty Blue Stripe Mark III, and yes that does have some shared controls, but I use it as a one channel amp. It's never NOT in the lead channel. And what a rip-roaring beast it is!

I get that. Mark III lead channel is what made that amp so good. Sure, the clean sound was good as well, but you need to make a compromise how you want to use the amp as it is not something you can change on the fly (easily). Mark IVB sort of resolved that but still had its flaws. Again, it was a compromise on how you wanted to run the amp.

Mark V90 took it to the next step at least in the channel separation aspects. It seemed to be too much of a deviation from the Mark III. The Mark IVB was still closer to its roots, the Mark V90 sort of took a leap away by adding in some novelty features. I think the novelty aspects sort of sterilized the amp too much. The location of the GEQ and its use to create the send level sort of made choosing your effects more complex. I had to abandon most of what worked in the III and IVB without any problems to find something that did.

The JP2C may be a modern version of a throwback design on the IIC+, to me that amp surpasses the Mark V90 on many levels. Has a familiar layout on the front panel. It is a step in the right direction and a return to the roots of the Mark amp. FX loop is much better and not much different than Mark III or IVB. All that stuff I threw out I could have used but they were outdated anyways.

The Mark VII is sort of similar to the JP2C in some ways but different. Yeah, it is loaded with some new features and has some novelty functions like the IIB. Its overall design and sound did not deviate far from the Mark traditional characteristics. It is based on the JP2C platform in some ways. It practically has the same chassis. Mesa did a good job in keeping with tradition as well as the novelty features that did not deviate far from the root characteristics of what a Mark amp should sound like.
No more boxy tone that I first noticed with the Mark IVB, no more ice pick that I got with the Mark V90. It is the simul-class version of the JP2C with added features and one less GEQ. IIC+ and IV modes are great, in other words you get CH2 and CH3 of the JP2C but without the pull switch pots. IIB mode, plus the Badlander on CH1-CH2 using the crunch and VII modes. along with two fat and one clean. I am happy with it.

The FX loop in my Mark V 90W (made in 2012) works perfectly. No tone suck, no volume loss. And I have a LOT of stuff in the loop: rack 10 band para EQ, 14 pedals (incl. parallel blenders, several stereo, analog and digital), buffered stereo splitter, 3 A/B switches, rack BBE Maxcom, and a y-splitter adapter, all returning to 3 amps' FX returns in stereo wet/dry/wet.
With everything in the loop bypassed, it sounds exactly the same as it does with the loop bypassed or with nothing plugged into the loop, and no problems with most of the stuff engaged. The digital pedals have analog dry thru, so it sounds the same (plus FX) as it does without the loop.

DECEMBER said:

The FX loop in my Mark V 90W (made in 2012) works perfectly. No tone suck, no volume loss. And I have a LOT of stuff in the loop: rack 10 band para EQ, 14 pedals (incl. parallel blenders, several stereo, analog and digital), buffered stereo splitter, 3 A/B switches, rack BBE Maxcom, and a y-splitter adapter, all returning to 3 amps' FX returns in stereo wet/dry/wet.
With everything in the loop bypassed, it sounds exactly the same as it does with the loop bypassed or with nothing plugged into the loop, and no problems with most of the stuff engaged. The digital pedals have analog dry thru, so it sounds the same (plus FX) as it does without the loop.

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Indeed, in active mode, the FX loop is pretty transparent. But have you tried hard-bypassing it? Please report back on the overall tone and feel of the amp, after you hard-bypass the FX loop.

danut said:

Indeed, in active mode, the FX loop is pretty transparent. But have you tried hard-bypassing it? Please report back on the overall tone and feel of the amp, after you hard-bypass the FX loop.

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My comment was in response to this statement in the original post: "The other issue which probably some of you have experienced is the terrible tone suck you get with the FX loop. I have searched for a few years to find a solution or something that would actually work in the FX loop of the Mark V. To date, only one brand comes to mind that I am still using, Strymon. Just about all of the Fx pedals that worked with the Mark III and Mark IVb including the rack units I had did not work with the Mark V90."

I flipped on the hard bypass switch once... it bypasses the master volume so it was far too **** loud for the apartment. I've never met an amp I could stand to record without some parametric EQ in the loop, so the loop is just always on on every amp I've ever had.

bandit2013 said:

V3->V6 = NOS Chinese Military Grade square foil getter 12AX7

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Any way to purchase tubes like this today?

Not sure. Most inventory is depleted. Ruby sold them as the 7025, 12AX7, ECC83. However, it is hard to say if it will be the Beijing Square foil getter tube. I have not been able to find any except for old listings on Reverb. Most of what I have are leftovers from the 1990s (used tubes I ran in the Mark III). I did score some NOS versions from Doug's tubes but now out of stock. Bummer that they are very hard to find. They work really good in the Mark V, even better in the Roadster ! I have tried to find more resources for this tube but cannot seem to find any current listings. I have seen the part number listed as 6N4-J and without the -J part. Sometimes just Beijing Foil Getter may be enough for a search. Never thought these would be that hard to find, now they have become unobtainable. Almost as scarce as the RFT ECC83/12AX7. I feel bad even recommending them now. Be weary of scams.

You may find them through aliexpress, not sure I would trust this resource though.

https://www.aliexpress.us/item/3256...=scene:pcDetailTopMoreOtherSeller|query_from: