Help with Ampeg B-25

[C Moore]

http://www.prowessamplifiers.com/schema ... g/B25.html

Channel 1, the Ultra Low switch at the top of the print. I am not sure what the switch is switching. To my eye, with the switch open, the 10M resistor is in parallel with the .001 cap.
So what happens when the switch is closed? Does the 10M get bypassed?
Thank You

[Bob-I]

What you're missing is that the operative component is the .001uF cap. The 10M resistor is only there to prevent a click when you flip the switch.

Open the .1uF and .001uF are in series making total capacitance under .001uF making the tone brighter. With the switch closed the .001uF is bypassed making the total capacitance .1uF and the tone far deeper.

[C Moore]

Hey, thank you so much. That makes it clear as day.
I am the classic example of a guy "with just enough knowledge to be dangerous". I do the best I can to retain all of this stuff.
Thanks again, I really appreciate it.