Odd Design Choices: Why is Mark IV Volume Pot so Sensitive?

[SonVolt]

Just out of curiosity, what do you think the design philosophy behind the Mark IV's extremely odd volume taper was? You can't really turn it like a volume knob, you have to kinda nudge it with the side of your finger to make micro-adjustments else it goes from silent to too loud.

Was that intentional? If so.... WHY?

 

[CoG]

I haven't played a Mark IV enough to say, but the Mark III has the same "problem"... when you have the Volume set at like 7.5 or higher. If you have the Volume down around 5, there's a lot more range available on the MV before you hit war loud. As well, on the Mark III, if I've got the Volume up past 7, the Master stops doing much after 3.5. The amp just doesn't get any louder. Treble and Mid also influence this, more if you don't have the Volume up very high.

On the Mark III I think it's part of the series of compromises that makes it a so-so channel switcher but an extremely versatile one-channel amp

 

[J.H.]

I think it's because these amps were designed during a period when louder = gooder.

 

[Chronomariner]

It is how it’s supposed to be.

 

[jsullivan2112]

My old Hiwatt also jumps. Not as immediately, but definitely still a big jump when it does. I just assumed all older tube amps do this?

 

[SonVolt]

I've got lots of old Marshalls and none of them jump in volume quite like the Mark IV.

 

[meesa_jarjar]

Probably a few factors. The main one is the way potentiometers are made, generally they aren't true 'audio' pots, they are an approximation of what would be an ideal taper for a volume control.

Secondly, looking at the IV schem, the 'output level' control is wired in a way that one wouldn't expect it to be wired, so that likely adds additional 'uniqueness' to its response. I'm sure they have their reasons why and that's not a critique, just an observation.

 

[bgh]

Mine has the same "issue", but because I run it through a PS2A, the issue is mitigated. Before I had the PS2 though, it took some fiddling to get it right where I wanted it. Lot's of times I simply used the channel masters to even things out.

 

[woodbutcher65]

I had a IVB and the reason I traded it off for a Mark V is specifically because the output volume just would not work for me at the bedroom volume level I needed it to. At that level, which was very difficult to achieve, it sounded choked. I've had no such issues with the Mark V or Mark III.

I also didn't like the control setup of the IV. It was neither fish nor fowl, not like a Mark III layout that I'm comfortable with, and not like a full three channel layout like a 3 ch Recto or a Mark V.

While I don't disagree that a IV can sound incredible, when it comes to the user interface, I consider it to be Mesa's least well thought out product.

 

[SonVolt]

The IV's lead channel is indeed incredible but the user interface has only the face a mother could love.

 

[user 83127]

The volume pots on this and many mark series are designed to work under differing circumstances.....drive it harder at the output you cannot use as much internal or master volume...drive it lower and you can raise the volume pot in question.....how much gain you have fed also effects how much you can turn that volume up...lower gain and the pot will work to a higher level....so you have everything maxed and the pot maxes out quickly...just think you have only so much signal and if you are pumping it all through the pre amp...then not much opening is required to make it go out the power amp...does this make sense/help?

 

[SonVolt]

The volume pots on this and many mark series are designed to work under differing circumstances.....drive it harder at the output you cannot use as much internal or master volume...drive it lower and you can raise the volume pot in question.....how much gain you have fed also effects how much you can turn that volume up...lower gain and the pot will work to a higher level....so you have everything maxed and the pot maxes out quickly...just think you have only so much signal and if you are pumping it all through the pre amp...then not much opening is required to make it go out the power amp...does this make sense/help?

I usually crank the channel masters, so maybe that's it. I'll have to turn them down and see if the main volume pot is more linear.

 

[user 83127]

I usually crank the channel masters, so maybe that's it. I'll have to turn them down and see if the main volume pot is more linear.

One other thing of note about this amp is the tone pots also have an effect on how much power seems to be in the circuit...like if you took the lead channel and put the tone knobs at 0 (bass, mids, treble), you lose about 3/4 of the power available to the lead circuit and it becomes a very low gain affair even at high gain values on the gain pots. So these also have an effect on the volume pot.