Emperor-TK
Well-known member
I need help understanding the basics of how a phase inverter and presence control works for an A/B tube amp. I'm in the process of converting a Laney A100H into a Marshall (model 2204). The two are similar enough where I just went with the power section of the Laney, but the tone is very bright, to the point that I can't turn the treble up past 1 or 2. I'm wondering if the presence section might be to blame.
For reference:
EDIT: Image deleted due to hosting issues
I used the 5K presence pot from the Marshall schematic, but for some reason I put a 680nF cap in instead of the 100nF used by both Marshall and Laney (I can't remember why).
So my questions are:
1. How does the pot resistance and the capacitor value effect tone/performance?
2. From what I've read, I see that the inverted signal is taken from the transformer to drive the bottom of the phase inverter section. But I can't figure out what function the 4 resistors in the T-configuration serves.
A brief walkthrough of how this section works would be greatly appreciated.
Thanks,
Chris
For reference:
EDIT: Image deleted due to hosting issues
I used the 5K presence pot from the Marshall schematic, but for some reason I put a 680nF cap in instead of the 100nF used by both Marshall and Laney (I can't remember why).
So my questions are:
1. How does the pot resistance and the capacitor value effect tone/performance?
2. From what I've read, I see that the inverted signal is taken from the transformer to drive the bottom of the phase inverter section. But I can't figure out what function the 4 resistors in the T-configuration serves.
A brief walkthrough of how this section works would be greatly appreciated.
Thanks,
Chris