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Discussion Forum for Mesa Boogie Products
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PostPosted: Mon Jun 26, 2017 10:22 pm 
Mark IV

Joined: Thu Aug 15, 2013 12:20 am
Posts: 656
Location: Tucson, AZ
As far as bleed goes:

On Channel 2, the bleed goes away by turning the presence all the way up. It works the same on Channel 3, except mine gets quieter, but doesn't completely mute.

The presence is connected mechanically to the PI, with relays making or breaking the connection. Whether it's proximity or just the sheer amount of voltage, it leaks a bit from there. Well, it's the only path from before all the volume controls to the power amp that makes sense to me and accounts for an interaction with the presence in both modes on both of those channels.

2007 3 Channel Dual Recto w/loop mod

My Humble Music Tech Blog:
Dual Rectifier Index

PostPosted: Tue Jul 18, 2017 11:55 pm 
Mark I

Joined: Fri Oct 19, 2007 5:12 pm
Posts: 27
As far as I've learned, screamingdaisy is correct. It is not a "fault" with your amp itself, but a problem with using one tube for the FX loop and another function.

I called Mesa once and complained about it. Told them it must still be a parallel loop. Whoever I talked to insisted it was a serial design, but didn't comment further or inform me about the tube bleed. I found out about that later on my own.

Most all amps I've seen use the same design, but don't exhibit quite the same bleed due to differences in gain structure and how the circuit itself works. I remember reading something about an amp that was made with a dedicated 12ax7 for the FX loop circuit (a Soldano perhaps?) and in theory I'm guessing that would solve the problem. Or at least prevent the issue in the first place.

Anyway, I use a G Major 2 with a Dual Rec Multiwatt myself. By running the head at normal to hotter levels, I can get the overall sound pretty far louder than the bleed and thus don't notice it as much. I also use a Rivera Rockcrusher (which is the bees knees, BTW) and it allows me to keep the volume reasonable while cranking the head.

Sorry I couldn't be much more help than that. Other than to tell you I don't think there is anything "wrong" with your amp.

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