In the EF section, a diode pump charges a capacitor, but a good portion of the control signal leaks through. So I sent the EF's voltage through a low-pass filter consisting of a 4.7k resistor and 1uF capacitor (knee frequency of 34 Hz). This was dumb for a couple reasons. For the lowest channel (center around 45 Hz), it doesn't filter out enough of the control signal, so the control can bleed into the output. For the higher channels (say, 200 Hz and up), it filters out everything, but prevents the voltage from dropping as rapidly as it otherwise could (poor response time to step inputs).
So, I'm incorporating a slight re-design in which the EF's low-pass filter now uses a 180k resistor and a capacitor of value C (the defining capacitor value for that channel, also used in the main band-pass filters for the channel). This leads to new decay time constants and better performance all around. Here is a list of the defining capacitor value, central frequency, and the amount of time for the channel output to decay to 1/10 of its former value (using the new EF filter section) for each channel:
- 220 nF, 45 Hz, 107 ms
150 nF, 66 Hz, 78 ms
100 nF, 99 Hz, 59 ms
68 nF, 145 Hz, 42 ms
47 nF, 210 Hz, 39 ms
33 nF, 299 Hz, 35 ms
22 nF, 448 Hz, 31 ms
15 nF, 657 Hz, 26 ms
10 nF, 986 Hz, 25 ms
6.8 nF, 1450 Hz, 25 ms
4.7 nF, 2098 Hz, 25 ms
3.3 nF, 2988 Hz, 24 ms
2.2 nF, 4482 Hz, 24 ms
1.5 nF, 6573 Hz, 23 ms
Finally, here is the new simulation in Falstad's applet:
http://www.falstad.com/circuit/#%24+1+4 ... 05+2+-1%0A