I want to use a 'subtractive filter' in a SC filter. From what I understand this only works for first-order filters, cos with higher orders it will always only yield a 6dB slope (messing with the overall filter phase), unless phase compensation is used -- which makes it more complicated. Anyway, it's for a GSSL SC filter board designed by Steffen. It's several RC filter settings plus four active filters in this case.
The idea is to add an AUX channel and then 'sum' the high-pass filter signal with the uncompromised polarity-flipped signal to swap the filter: that is, convert high pass into low pass. Overall polarity at the output of the SC filter should not matter cos it will be full-wave rectified anyway. Would the atttached schematic work ?
Is it OK to derive the AUX channel from after the input buffer as drawn (question mark, red line) ?
Is it OK to insert a switch to simply cut the AUX line before the output buffer without grounding ?
Any comment is highly appreciated. I am not good at filter design.
The idea is to add an AUX channel and then 'sum' the high-pass filter signal with the uncompromised polarity-flipped signal to swap the filter: that is, convert high pass into low pass. Overall polarity at the output of the SC filter should not matter cos it will be full-wave rectified anyway. Would the atttached schematic work ?
Is it OK to derive the AUX channel from after the input buffer as drawn (question mark, red line) ?
Is it OK to insert a switch to simply cut the AUX line before the output buffer without grounding ?
Any comment is highly appreciated. I am not good at filter design.