Mark IV mode squeal. Need help from other owners!

[jressell]

When I set up my Mark V in the Mark IV mode I get a very high pitched squeal. Here are the settings:

Mark V head
Mark IV mode
Gain 3 o'clock
Output volume >1 o'clock
Presence 10 o'clock
Treble 3 o'clock
Mid 9 o'clock
Bass 10 o'clock

EQ sliders on from left to right:
3/4 up
3/4 up
Almost completely down
3/4 up
5/6 up

Master volume: 9 o'clock

When I increase the Output volume of CH3 the squeal gets loud. It can also be removed by turning down the channel. It can also be removed by bring down the 80 and 240 sliders.

Anyone else having these problems?

 

[mejoshee]

When I set up my Mark V in the Mark IV mode I get a very high pitched squeal. Here are the settings:

Mark V head
Mark IV mode
Gain 3 o'clock
Output volume >1 o'clock
Presence 10 o'clock
Treble 3 o'clock
Mid 9 o'clock
Bass 10 o'clock

EQ sliders on from left to right:
3/4 up
3/4 up
Almost completely down
3/4 up
5/6 up

Master volume: 9 o'clock

When I increase the Output volume of CH3 the squeal gets loud. It can also be removed by turning down the channel. It can also be removed by bring down the 80 and 240 sliders.

Anyone else having these problems?

you're running the treble pretty high. which is fine. but squealing is going to be pretty much your life from now on

seriously though, do you think you can cut it down a little? try easing back the 7500 slider. also, do you have the bright switch on?

i find it interesting you can control squeal by bringing down the low-end sliders. what's probably happening is the bass is rattling the tubes a little. you might even have a microphonic tube. drop the gain a little bit and tap on the individual preamp tubes with like a chopstick or wooden dowel. if one starts to make it feedback worse, then you might need to replace that one. hopefully that's not the case... :?

squealing is warned of in the manual. have you read it? there are certain settings around or above which you'll probably have uncontrollable squealing just cause of how high the gain is on that channel. i keep my volume about 11 o'clock and make the output a little lower, like 9-10. so, idk how many watts that roughly puts out at that point, but i don't think i'm running mine nearly as loud as yours.

 

[pathos45]

get a noise supressor, its a high gain amp and your usein the highest gain channel and your gains at 3 its going to happen even if you were in chrunch mode with gain dimed. turn your gain down you may think more gain will mean more crushing distortion but with this amp put the gain around noon or 1 and the baby will tighten right up and make the sqweeling go away. but def look into a ns2 or isp dic.

 

[4406cuda]

I experienced the same thing when I had the channel master above 1 o'clock. I know keep my channel volume and master around 11 o'oclock and there is no squealing.

 

[jressell]

I've read the manual; however, I can reproduce the squealing in every channel and mode with enough tweaking to the output and master volumes. The other settings have very little to do with it. I called Mesa and he said it sounded abnormal and we ruled out a microphonic tube. I can reproduce this squeal in Ch1, Clean, with everything to 12 o'clock with only adjustments to the output and master volume. I know what the "quick" answers are; however, I want to know if other users can reproduce on their Mark Vs what I hear. That way I can go to bed knowing it's the design of the amp and something I had to work around and not a back X, Y, or Z in the actual amp.

Thanks for your input guys but have any of your actually turned the knobs on your amps to reproduce the sound?

 

[jressell]

but i don't think i'm running mine nearly as loud as yours.

I'm running it pretty quietly. Saying it's bedroom volume is pushing it.

 

[4406cuda]

I only experienced the squealing in the Mark IV mode when I had the channel master too high. If you are experiencing it on all the channels, I would have Mesa take a look at it.

 

[mejoshee]

jressell, still having issues?