Yet Another Mark IV A vs B thread!

[Enc3f4L0]

2 weeks ago I bought a Mark IV...

I've always played on a Mark IV A (1990) so I was pretty used to it.
After playing my new one a few times I noticed some differences already. (I played both through the 1x12 EV on the combo)

- IMO the sound of the new one is better. It's darker, has more bite and goes into unwanted harmonics a bit less. I'm not sure how much of this sound difference comes from the different tubes (and the fact that the new one has NEW tubes).

- I liked how it's built. The FU-3 connector on the chassis is more logical (the plug is faced the right way now to fit your finger). The FU-3 itself fits nicely on the back of the head. Easy acces to the preamp tubes from the front.

- I liked the TWEED power mode of the 'A' better... I think this has REALLY changed from one amp to the other. On the A the TWEED was perfect for bedroom playing. It would lower the overall volume and I could still have some similar gain.

I like the 'pull fat' on the lead gain but never did like the 'pull bright' on the lead drive... With the A I didn't need to 'pull bright' on tweed mode to get the gain I like... And the master volume would never go past 1-2.

On the 'B' the tweed mode acts differently... For starters, the difference in volume from tweed to full is way larger than in the 'A'. I could get the volume to 3-4 easily on tweed while on full hardly turn it to 1 (that point where it barely turns on but is already too loud, and you have to fight with the knob to get it right). I have to turn on the 'pull bright' also or else it'll lack gain.

I basically am not using tweed any longer. I prefer using full power now with just the Pull Fat like I used to play.

Anyone else notice these differences?

I can't wait to get my hands on a 2x12 Recto or a 4x12 Rect. Trad.

 

[Russ]

I got a question for you...

Did the old combo cabinet have a threaded footswitch mount? I just got a combo cabinet and the mounts appear to be threaded as opposed to the simple twist in quick release. The mounts on my footswitch are quick release and so I have not mounted the chassis in the combo yet. I tried to get the footswitch to mount but only one side sort of worked. I am assuming it is because it has threads in the hole v. a twisted opening.

 

[Shep]

i hav a IvA in rack mount and it's quick...

 

[SFW]

I have a 1991 and a 2003 model. I prefer the B version, as in MHO, it sounds beefier and meaner in general.

 

[Enc3f4L0]

@Russ: I wouldn't know how to answer your question. I bought my 'A' used and the FU-3 was unable to attach to the back already. On the cab there are just holes on the wood where I suppose the mounts were.

On my new one it has the quick release.

 

[Boogiebabies]

IMO, they hit it with the B. More refined, smooth and it has the ability to get just nasty without the raspiness of the A. A big difference with all Mesa's is the drift or taper of the pots. They are usually 10-15% off. All my old MK II's have different Volumes at varying numbers on the dial. God bless Taiwan.

The A did have a different PT the 561137 and the exact IIC+ lead circuit, but I do not think it put out more power. The PT put out the same 460V as the current 561140.

It's still a great amp.

 

[MesaENGR412]

Sorry for the nooby question,

BUt what are you talking about when you refer to the 'A' and 'B' models? Is the A model the older and the B the newer? Thanx guys!

-AJH

 

[Shep]

it's basicly series 1 (a) series 2 (b)

 

[MesaENGR412]

thanks for the clarification Shep

-AJH

 

[Aart]

I like the A version better.

More "chugga chugga" and "oomph" when playing metal.

Its cuts better through the mix too.

But for rock i would choose the b version.


Owned a B version first, now I own a april 1992 Mark IV A Rackmount export version.

 

[cesjr]

What year did the changes take place, A to B?

 

[Boogiebabies]

Mid to late 1993.

 

[Russ]

Boogiebabies,

Maybe you know this.... Did they ever have a different mounting system for the FU-3 than the little quick twist clips? Were they ever threaded like bolts? My combo cab has threaded mounts. I am wondering if it was not actually a Mark IV cabinet originally. I would think that a tube guard bar would be threaded thus making this particular SUS4 cabinet not a MarkIV cabinet at all. Though it has the recessed areas as if for fingers to turn the mounting (bolt?). I noticed that my new FU-3 has little feet instead of the larger pads that I see on most also. I was just wodering if I need to find an older FU-3 to mount to the combo or if I just need to remove the Quick twist clips for replacement with some kind of knurled finger bolts. I am thinking I am going to order the mounting clips and just replace the threaded pieces that are currently in there to make it an easier ordeal.

 

[igfraso]

Hi,
when you say that the transition was roughly mid to late 1993, does anybody have an idea of what serial number (approx.) we are talking about?

What changes did the IV-B introduced? Different transformers? A jack in the rear panel for a Satellite?

 

[Shep]

more gain rhy2...different vocied lead ...satelite send....differnt O/P tranny

i Thank thats it