Mark IV A vs Mark IV B - Tonal Differences......?????

[Monsta-Tone]

I just pulled the trigger on a Mark IV A.

I know lots of guys here swear by the B, and I seem to remember a lenghty discussion about the differences.


I just spent 30 minutes looking at the drawings for each version.

It looks like much of the differences are in the power supplies.


Here is a list of differences that I noted that might contribute to the differences in tone:

No Harmonics switch in the A version.
More Gain in the B version for the Lead channel.
Various slight changes in resistor values in the power amp.



So, here is my question:

What is the tonal difference between the A & B versions using the same tubes & speakers?

Is it that drastic that the B would be a hands-down better version?

It looks like much of the changes that make it a B, can be done to the A. Has anybody tried this?

Is it even worth it to try?



Ok, so I know it was more than 1 question. Whatcha gonna do.

 

[Johnson]

I recall reading a past thread on this. From what I remember is that there are slight differences in the tone between the two, but that its not a drastic difference, and that both versions sound great in their own right.

 

[Platypus]

I've read that the A is brighter and has a closer to C+ feel to it while the B has more shred on tap and is smoother.

What I've gained from every thread on the topic is that the differences are very subtle and are not gamebreakers as far as which one you get.

 

[Monsta-Tone]

I've been reading a lot of old posts over the last hour and I can't seem to find the one where everybody was bagging on the A's and told the guy to get a B.


I've been using my DC-3 with a Thiele, and it does great, but my drummer is too loud and I seem to be loosing all of my Clean headroom trying to keep up.

So then, I switched to my DC-10 and it keeps up with absolutely no problem, but the Lead channel sounds a bit too Metal for what we are doing.

I used to have a Mark IV, but never really got the chance to experiment with it and find the tones that most Mark IV lovers get.

 

[psychodave]

I have a harmonics switch on my A. I think you are getting some mis-information.

 

[Restless Rocks]

The differences are subtle: The primary difference is as you said concerning the B+ power supply. the IVB runs a slightly lower voltage to the preamp while in Rh I and Rh 2. But when in lead mode the voltage is increased to the preamp. Also the tone shapeing in the lead circuit of the IVA is more akin to the MkIIC+ circuit. The IVB uses a relay to switch between two different "tone shaping" caps between the Phase inverter and the output tubes. These act to filter the extreme highs of the lead channel differently than the R1 and R2. Hence the "more compressed" sound of the IVB. Then there is the obvious FX loop differences. They are both great amps. It could be done but "modding" an A into a B would not be a walk in the park as the circuit boards differ and many would debate wheather the differences are worth that kind of effort. I for one would not alter a vintage Mark IVa.

 

[Aart]

Differences:

FX loop(2 mono fx loops on A, one stereo fx loop on the B).
Satelite send on B

Somewhat more gain on tap in rhy 2 with the B version and a ssomewhat darker lead channel on the B version.

The differences are all minor and you will have a hard time to notice them if you don't AB them.

There isn't a better one of the two. If you like the Mk 4, you will like both, they both get the same tones if you tweak a litle.

 

[trem]

I have a harmonics switch on my A. I think you are getting some mis-information.

+1

 

[ursinus]

I've owned an A and now own a B and the differences are truly minor. +1 on what has already been stated.

 

[Shep]

i reckon some of the best mk IV clip's on here are from the A version amps.. they both sound great.. the b is alittle more refined than the A as far as tone goes but from what i get from my A i don't think thats going to be a big change.. mine sounds amazingly good..

 

[Monsta-Tone]

You guys are getting me all fired up. Can't wait for it to arrive.


I hated R2 on my B version that I used to have.

Do you guys have any advice, short of modding the amp, which may happen anyway.

How do I get killer crunch and Fendery cleans with Dragon II & McCarty pickups.

 

[ursinus]

You guys are getting me all fired up. Can't wait for it to arrive.


I hated R2 on my B version that I used to have.

Do you guys have any advice, short of modding the amp, which may happen anyway.

How do I get killer crunch and Fendery cleans with Dragon II & McCarty pickups.

BB Preamp works wonders on R2.

 

[Johnson]

I've almost heard enough good things about the BB preamp to go out and buy one! :lol:

 

[Blueracer]

Monsta-Tone

PM sent.

Gary