Mesa Boogie 50 Caliber +

[trackerdan]

Hello, I have just purchased a 1989 Mesa Boogie 50 Caliber +. A nice clean amp. I've noticed there is a very minimal effect when actuating the Presence knob? I called Mesa and they stated that was about par for this particular amp model. Also it has GT 6L6 power tubes in it and a ceramic biasing potentiometer inside the amp chassis. This does not bother me so much although all my previous Mesa's have been factory stock. What I do like is the sparkling clean tone of this amp. Even with the wimpy Reverb springs that are inside the amplifier chassis section, this amp has about the best Fender type tone I have ever heard from a Mesa. It really sparkles. The overdrive is as Boogie as it should be. Someone even was kind enough to install a cooling fan in the bottom of the cabinet.

I am tempted to return it to original Mesa fixed bias spec's; but hesitate. I've also considered putting a real Reverb tank in the bottom?

Any thoughts or input would be greatly appreciated.

Thanks,

TD

 

[les_paul]

I talked to a guy who used to be an authorized Mesa authorized tech. He informed me that a bias on the amps goes a long way. For this reason I wouldn't return it to factory specs.

If you intend on hanging on to this amp, I'd say replace the reverb tank. If you think you may sell it don't bother with it. Sell it to some metal player who doesn't care about the 'verb.

 

[Monsta-Tone]

Congrats on the amp!

The problem with the Presence is that it's not a normal circuit. Instead of bleeding off some of the excess highs from the negative feedback, they installed it on the Output Volume, much the same way as the DC series has a resistor across the Output Volume.

Have your amp tech rip out the stock Presence circuit and install a standard circuit for it. This will make the Output Volume pot much more user friendly at lower volumes and will make the Presence pot work properly!


As for the Bias, I would just check it and leave it.

You could easily have your tech install a better reverb tank too if you plan on keeping the amp.