How to identify a MKIV A or B from frontpanel

[Aart]

For people who want to know:

A:

-Sharp edges of frontpanel
-There's some distance between the logo and power/stanby words.

B:

-Rounded edges of frontpanel
-Logo is just beneath output/standby words.

There are a few exceptions(saw one on ebay. Mostly very early B's with the old frontpanel. Don't think there are many of those.

 

[ytse_jam]

This is very useful, aart. It seems to me that also Eq sliders changed, how about it? Was it just pure cosmetics on the already B version?

 

[Aart]

This is very useful, aart. It seems to me that also Eq sliders changed, how about it? Was it just pure cosmetics on the already B version?

There are versions with other EQ sliders, but i haven't found any consequent changes in them. New B's have the same ones as my A, although I saw A's and B's with other sliders.

 

[6L6C]

Hey I got a question or two.
I bought my Mark IV in 1993 always very happy with it. It was not till I joined the board (less than 6 months ago) that I realized there was an “A” and “B” version.
However maybe I just read wrong but I was under the impression I had the “B” for I have the FX return in Left & Right and also the send for the Satellite.
After looking at AART’s photo’s, my front panel suggest I have a “A”.

Putting all of this aside, what are the differences between the two versions as far as electronic design?
It seems the “B” are more sought after, I know the two versions are supposed the sound different, but different how?
Thanks
John

 

[Aart]

Hey I got a question or two.
I bought my Mark IV in 1993 always very happy with it. It was not till I joined the board (less than 6 months ago) that I realized there was an “A” and “B” version.
However maybe I just read wrong but I was under the impression I had the “B” for I have the FX return in Left & Right and also the send for the Satellite.
After looking at AART’s photo’s, my front panel suggest I have a “A”.

Putting all of this aside, what are the differences between the two versions as far as electronic design?
It seems the “B” are more sought after, I know the two versions are supposed the sound different, but different how?
Thanks
John

Than yours will be probably one of those very early B's.

The tonal differnece is most noticeable in rh2. The B has more gain.
In rhy 1 or Lead the differince is only noticeable if you a/b them.

Some people say that the A is more brutal in the lead channel where the B is more smooth.

 

[Russ]

Interesting comparison. What if someone had a transitional? Or maybe a chassis replacement? I still think the only real way is to look at the pcb but the back panel stands out more for a quick check without having to tear anything open.

 

[Aart]

Well, in most cases it works. So its good to know for people looking for a specific model(platypus for example, bought an A the first time).

 

[Boogiebabies]

Interesting comparison. What if someone had a transitional? Or maybe a chassis replacement? I still think the only real way is to look at the pcb but the back panel stands out more for a quick check without having to tear anything open.

I totally agree. There is about a 600+ count serial number area between late 1993 and 1994 when Mesa went to the flat chassis painting. Like 6L6GC, I have an early IVB with the texured coating and the fixed power cord.

I swear to god I should have never opened my mouth about the A and B variations. It's like the Evelyn Mulwray of amps. A,B,A, No B, no A.

 

[Russ]

I think it was inevitable BB. Someone would have noticed the differences and would have begun discussing it. At least you made informed statements regarding the two and educated us. Who knows, maybe this will become a debate like the JCM800's with the Vertical v. Horizontal inputs (ok, maybe not quite a hard debate on this one) or the early v. later split channels, or even like the plexi v. metal face. Those that have played these amps definitely favor one over the other for whatever reason. Some reasons more obvious than not but there are somethings that are quite subtle about each that set them apart and make them more desireable.

 

[Platypus]

I'm glad you did BB, you made sure I got the right tool for my purposes with your very detailed and educated description. I'm very grateful for what it's worth.

 

[Aart]

Interesting comparison. What if someone had a transitional? Or maybe a chassis replacement? I still think the only real way is to look at the pcb but the back panel stands out more for a quick check without having to tear anything open.

I totally agree. There is about a 600+ count serial number area between late 1993 and 1994 when Mesa went to the flat chassis painting. Like 6L6GC, I have an early IVB with the texured coating and the fixed power cord.

I swear to god I should have never opened my mouth about the A and B variations. It's like the Evelyn Mulwray of amps. A,B,A, No B, no A.

Well, I think its handy in some way, but the difference is so small in many points that almost everybody would be happy with an A or B version.

 

[Boogiebabies]

I am glad that it's useful. I can't knock someone for learning about the A and B, but like me, the IIC+ is an obsession that has taken way too much time. It's guilt more than anything.

After one Mark, they all seem to come at you in the sense that you already know them inside and out. A lot of it is really redundant.

 

[welshboogie]

I am glad that it's useful. I can't knock someone for learning about the A and B, but like me, the IIC+ is an obsession that has taken way too much time. It's guilt more than anything.

After one Mark, they all seem to come at you in the sense that you already know them inside and out. A lot of it is really redundant.

Never a truer word spoken, respect for the BB

 

[siggy14]

OK i cant really tell, but i just won this auction, is this an A or B?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190095339343

For people who want to know:

A:

-Sharp edges of frontpanel
-There's some distance between the logo and power/stanby words.

B:

-Rounded edges of frontpanel
-Logo is just beneath output/standby words.

There are a few exceptions(saw one on ebay. Mostly very early B's with the old frontpanel. Don't think there are many of those.

 

[Random Hero]

^^^

That one in the auction is an A.

I was just browsing eBay, and found this - http://cgi.ebay.com/Mesa-Boogie-Mark-IV-four-rackmount-head_W0QQitemZ120099786340QQcategoryZ10171QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

It has the same as mine, it's a B, with the satellite send, reverb footswitch, Mark IV logo close to the standby, but it has the old style knob on the mode select thing on the back. I've not seen another like that until now.

Mine;

 

[Russ]

Yeah, siggy I would say yours is an A. Random Hero's rackmount find is a B.

 

[siggy14]

thanks, you guys think i should be worried about the rust on the trannies?

 

[Russ]

I don't think a little surface rust is a big deal. You can make anything get light surface rust by touching it because of the alkaline in your skin oils. It would take a while for it to be come a problem. If it is actually really bad to the point where it is causing flaking then I would be more concerned but otherwise I would just play the amp and enjoy it for now. If it bothers you then use a non metal abrasive like a mean green pad and just becareful not to let the dust get into the amp. Maybe lay a magnet close by to attract the rust dust. Then after cleaning with alcohol or something quickly evaporating like that use a good primer and then repaint it. A rust inhibiting paint wouldn't be a bad idea.

 

[JimAnsell]

I just bought a mark IV, is this an A or B?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290098058716&indexURL=2&photoDisplayType=2#ebayphotohosting

 

[siggy14]

Defintly an B and in great shape, good score!

I just bought a mark IV, is this an A or B?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290098058716&indexURL=2&photoDisplayType=2#ebayphotohosting