Chuck D. Bones
Circuit Wizard
The MID switch affects the gain mainly at the mid frequencies, however the left position produces boost over a very broad freq range.
I intentionally reduced the bandwidth of the 3rd stage because there is very little going on above 10KHz. Output transformers and speakers all roll-off in the 5-10KHz range. The feedback cap (C9 in the schematic above) can serve two purposes.
1. It reduces the bandwidth so we don't amplify frequencies we can't hear.
2. It helps maintain stability by ensuring that the opamp has sufficient phase margin.
In the Dark Esbat, R19 is low enough that C15 is not required for stability.
I intentionally reduced the bandwidth of the 3rd stage because there is very little going on above 10KHz. Output transformers and speakers all roll-off in the 5-10KHz range. The feedback cap (C9 in the schematic above) can serve two purposes.
1. It reduces the bandwidth so we don't amplify frequencies we can't hear.
2. It helps maintain stability by ensuring that the opamp has sufficient phase margin.
In the Dark Esbat, R19 is low enough that C15 is not required for stability.