Preamp troubles

[radicalcut]

Hi people, I'm the happy new owner of a Mark V head, it's awesome!
I've had, however, the following issues:
1. Channel two sounds lifeless. I have to crank the gain to max to get a decent tone in it. Mark I mode sounds like only bass frequencies come through. Channels 1 and 3 sound wonderful, though.
2. Using my Decimator GString on channel 3 leads to a high-pitched squeal. When I've had only my Memory Boy on the FX loop everything was fine.
So, searching older threads, it seems I might have two busted preamp tubes - V2 and V6, right? I don't have any spares to test with, but I have another amp with working Sovtek 12AX7s. Could I take these and put them on the Mark to test?
Thanks!

 

[SteveO]

V2 is channel 2 only, that much I remember. Yes, the Sovtek 12ax7s will work fine for testing purposes.

 

[golfnguitarz]

Just checking: the manual does state that in Mark I mode, you may want to turn the Bass and maybe the Mids all the way down and crank the Treble (not the exact words).

 

[radicalcut]

Just checking: the manual does state that in Mark I mode, you may want to turn the Bass and maybe the Mids all the way down and crank the Treble (not the exact words).

Yes, but the problem is Mark I mode is still too boomy even with bass all the way down... I haven't had time to swap the tubes yet, but I'll try do it soon.
Thanks guys!

 

[eudaimonia02912]

Mark I mode doesn't play nicely with the other modes. You can get some awesome settings out of it, but you'll often have to use settings that make it hard to use it with the other channels.

Try this:
Crank the master on channel 2 up to 3:00. Put the presence at 2-3:00. Dime the treble. Bass off. Mid nearly off. Gain at 1:00. Put the graphic eq in an upward sloping curve, i.e., cut the bass frequencies and boost the treble frequencies to taste. Enjoy.

 

[golfnguitarz]

Mark I mode doesn't play nicely with the other modes. You can get some awesome settings out of it, but you'll often have to use settings that make it hard to use it with the other channels.

Try this:
Crank the master on channel 2 up to 3:00. Put the presence at 2-3:00. Dime the treble. Bass off. Mid nearly off. Gain at 1:00. Put the graphic eq in an upward sloping curve, i.e., cut the bass frequencies and boost the treble frequencies to taste. Enjoy.

+1

I forgot to mention the graphic EQ that eudaimonia pointed out. Give Mark I some time and some volume. After initially hating it, I find I can get a really nice Marshally grind out of it. I use 10 watt mode at home to get it to break up a little quicker at lower volumes.

 

[radicalcut]

Last night I took the time to check every tube in the amp and there were a couple that were loose. I pushed them back into the sockets and everything is good now. I suppose they got dislodged during transport.
Thanks for the tips guys!