I'VE BEEN VERY STUPID.
My second attempt at the ADSR failed, and then I realized that I can't put the actual 2164 currents through the digital switch -- I don't fully understand why, but I just can't. If the 2164s are all on, and all connected to the LPF stage, then stray currents through the switch will always cause the 2164 VCAs to interact and be weird.
However, I figured out how to do it (bear in mind that I haven't built it yet, or even simulated it, but I know it will work). I will have all three 2164 VCA inputs connected to their source voltages through 30k resistors, connected to the LPF output through 30k resistors, and all 2164 VCA outputs connected to the inverting input of the LPF opamp. I will control their control voltages with the analog switch. In order to use just a 4066 switch (cuz it's cheap), I will use pull-up resistors to default the control pins to +5V (which shuts 2164 VCAs off completely), and then override these pull-up resistors with buffered control voltages through the 4066 switches.
This will guarantee no "funny stuff" at the LPF, and should work like a hot damn. I actually did something similar in the original (analog) Quadra circuit, so there is history for this idea.
I'm gonna simulate this new concept right now, and do a new layout tonight, and build the new (third) attempt tomorrow. Wish me luck.
My second attempt at the ADSR failed, and then I realized that I can't put the actual 2164 currents through the digital switch -- I don't fully understand why, but I just can't. If the 2164s are all on, and all connected to the LPF stage, then stray currents through the switch will always cause the 2164 VCAs to interact and be weird.
However, I figured out how to do it (bear in mind that I haven't built it yet, or even simulated it, but I know it will work). I will have all three 2164 VCA inputs connected to their source voltages through 30k resistors, connected to the LPF output through 30k resistors, and all 2164 VCA outputs connected to the inverting input of the LPF opamp. I will control their control voltages with the analog switch. In order to use just a 4066 switch (cuz it's cheap), I will use pull-up resistors to default the control pins to +5V (which shuts 2164 VCAs off completely), and then override these pull-up resistors with buffered control voltages through the 4066 switches.
This will guarantee no "funny stuff" at the LPF, and should work like a hot damn. I actually did something similar in the original (analog) Quadra circuit, so there is history for this idea.
I'm gonna simulate this new concept right now, and do a new layout tonight, and build the new (third) attempt tomorrow. Wish me luck.
Statistics: Posted by Dr. Sketch-n-Etch — Tue Jun 18, 2024 1:35 am