beginner here, please be nice :)
I'm interested in the following DI-style box for my guitar, which I'm going to build, and I'm working on analyzing it. http://www.generalguitargadgets.com/pdf/ggg_ssim_m_sc.pdf
So far I've done reasonably well with figuring out the 4-stage op-amp filters. I'm considering filtering out the DC at the end (I think it's at ~4.5v?), and reducing the gain by modifying R2... but there are some basics that I am not sure on.
The top part of the schematic uses a voltage divider to power the op-amps, it seems so that it can amplify the AC signals from 0..9v, centred on ~4.5v.
- C10/C11 seem to be part of low-pass filters to strip AC from the power lines
- why would we bother doing this if we assume the power supply is clean, or use a battery?
- how can C10 filter the +9v rail without a resistor? wouldn't the 9v just snap to the power source and bypass the capacitor?
- My calculations put the C11/R13 low-pass filter very low, at 1/3 hz. I guess that's basically strict DC?
- assuming the op-amps take their power from the power rails, wouldn't this modify the voltage divider, making the DC offset change dynamically based on power consumption?
I assume these are basic / beginner questions for AC circuits, so I hope they're easy to answer. I appreciate all the help in advance.