Mark IV - Loudness reduction on Presence Pull-Shift ?!?

Hi everybody,

I'm writing from Munich, Germany (my first post).

I've bought a Mark IV shorthead (US-Version) some weeks ago that I use in combination with a step-down transformer (German grid voltage: 230V 50Hz)

When I pull the presence poti to get a presence shift to higher frequencies, the overall volume decreases. This happens for both the Rhythm II and Lead channel. Is this normal? Or is it a mistake, that may have something to do with my voltage transormation?

The manual says "When the Shifts are pushed in a punchier and more aggresive tone is produced". Well, and it's much louder than with presence-shift enabled

Thanks for answering and giving any comments!

from my 1 gig experience with experimenting with this feature...

this is not normal

Don't worry, this is normal in all MarkIV, in fact with the Presence pushed in, the sound has more bottom end and more volume, it is also less boogie-esque and seems more "rigid" !
With the Presence pulled, the sound lost some volume, but become more focused, with a complex harmonic structure, it also procure a big easy feeling for leads, very fluid and smooth, more in the Boogie style, it's my favorite !!!

Hi Antoine,

well it's good to hear that this seems to be normal, but it's hard to really compare the differences in sound with the presence pulled out or not, if you always have to re-adjust the overall volume.

A guy from the German MesaBoogie distributor told me that this might have to do something with the voltage conversion (US-model amp used in Germany). What the amp would like to see is 115V 60Hz, but my voltage converter only delivers 115V at 50Hz.

Does anybody know if I would also have to convert the grid frequency to ensure best sound quality and longest life-time for my amp and tubes?

Bye,
MArtin

Furman Sound makes a voltage regulator for international use that delivers 117V/60Hz no matter what you plug it into. The upside of this: your amp gets what it wants no matter where you are. Downside..this thing probably costs more than your amp (about $1500 US)! And if it doesnt solve your problem, that was a pricey experiment.

As for tube life, the amp's rectifier converts the incoming AC current to DC for the tubes to run on, so I dont see a problem there.

Antoine said:

Don't worry, this is normal in all MarkIV, in fact with the Presence pushed in, the sound has more bottom end and more volume, it is also less boogie-esque and seems more "rigid" !
With the Presence pulled, the sound lost some volume, but become more focused, with a complex harmonic structure, it also procure a big easy feeling for leads, very fluid and smooth, more in the Boogie style, it's my favorite !!!

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I'll have to keep trying all these options on the mark... There's so many, and I'm learning something new everytime I use it...

I have '93 Mark IV and when I pull the presence shift the volume does drop a bit also. This is probably normal due to less low end being produced.

Thanks a lot for your answers, I'm glad that it's nothing to worry about. Although it would be more satisfactory if one could switch to presence-shift without this reduction in volume...

@NoGlassNoClass: The rectifier is able to produce DC voltage no matter what AC-frequency you feed into it? (sorry I'm not good in tube amp technique...)

Bye,
MArtin

fivestar45 said:

The rectifier is able to produce DC voltage no matter what AC-frequency you feed into it?

Click to expand...

Yes. The rectifier converts the incoming AC to DC, then the tubes convert the current back to AC at whatever frequency the note you play is. For example an A note=440Hz. A loud A note is 440Hz at a higher voltage. Hope this helps. At any rate, I dont see how a 50Hz line voltage could damage your amp, especially if it works ok now.

my volumes drop as well when I pull the R2 or Lead prescence control. I think this is normal.......its a lot more noticible at lower volumes I believe.

my volumes drop as well when I pull the R2 or Lead prescence control. I think this is normal.......its a lot more noticible at lower volumes I believe.