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Re: Modification for Mesa Boogie .50 Caliber

1/5/2000 8:51 PM
Re: Modification for Mesa Boogie .50 Caliber
I've tried plugging into the poweramp and out of the preamp  
the problem seems to be in the preamp-section.  
By the way, what's R.G. Tube amp debug?  
1/5/2000 9:18 PM
1/5/2000 9:25 PM

1/4/2000 10:01 AM

Replace the "boost" tube with a 12AT7. If your amp doesn't have a graphic EQ put one on the loop.
1/5/2000 1:10 AM

GFR, What effect will this have to the tone? I would try it, but my amp isn't with me right now. Thanks, Mark.
1/5/2000 10:24 AM

With a 12AT7 you'll have slightly less gain at the boost stage, so you'll have less distortion afterwards (but still lots available) with less buzzing harmonics. There are rumours that Allan Holdsworth Calliber's were moded this way.  
Another mod worth trying is to remove the bypass capacitor at the cathode of the boost stage. This will give you much less gain - the amp will sound more "vintage" and less "shred" :)  
If there's still too much gain you can try both mods at the same time (12AT7 with the cathode resistor unbypassed).  
The graphic EQ on the fx loop (if the amp has not a built-in graphic EQ) can help you to trim off the offending buzz without sacrificing gain and sustain too much.
1/5/2000 8:47 PM

I'm curious about the mod at the cathode of the boost stage.  
There is a 680 Ohm resistor and a 3.3uF cap placed parallel over the resistor there  
Do you refere to the capacitor or the resistor?  
Do you mean i should take it out and leave it at that  
or "jumper" the place where the component came from.

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