gibson ga-45 maestro

[metallicafan]

i just found the schematic on this a few days ago so i'm hopefully going to get around to replacing the caps and resistors soon i was just wondering what i can do to tighten the bass response on it and possibly lower the treble just a little. it seems a little too bright to me and the tone pot just isn't getting it quite where i want it to be. also i was wondering if anyone has any advice on a new rectifier tube it has the 5y3 in it now and i know there a couple others that will swap without major modification but i can't seem to find too much about how the different rectifiers change the tone and feel of the amp. any help is appreciated and if you need any info on the amp to help me out just ask.

[capnjuan]

It's your amp but before I got to wondering about messing with its frequency response, I'd get the caps done including the cathode resistor bypass caps in the preamp, PI if present, and on the power tubes ... will make a substantial difference in the bass. Same with the 5Y3; you can put different 5Y3s in there and get subtle shifts in tone ... big shift if your old one is weak. Good luck with your amp. CJ

[RWood]

I agree with CJ's response - get it working as it was originally intended before modding it.

I will add that I serviced one of these a few months ago that benefited from two new coupling caps, the pair of .047uF caps that lead to the grids (pin 5) of the power tubes. A pretty easy repair that did not require removal of the circuit board. Since you mention replacing the caps, make sure you don't skip those two.


RWood

[Enzo]

That's a rule in our shop - always fix it before you change it.

[metallicafan]

I agree with CJ's response - get it working as it was originally intended before modding it.

I will add that I serviced one of these a few months ago that benefited from two new coupling caps, the pair of .047uF caps that lead to the grids (pin 5) of the power tubes. A pretty easy repair that did not require removal of the circuit board. Since you mention replacing the caps, make sure you don't skip those two.


RWood

thanks for pointing that out. i'm gonna do a full recap job and new tubes i just was wondering what i might wanna order with all that so once i get the recap job done if i still wanna change it i'll have it there already. would anyone recommend replacing the pots while i'm at it i need to replace the one for volume 1 but would changing the rest really change the tone any and also whats a good replacement/upgrade for the pots?