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Post by mkjackn on Jan 9, 2022 21:07:46 GMT
Hello all, After some a fair amount of reading, watching and experimenting I've managed to get something akin to an envelope follower running in falstad. My issue is that due to AE's single supply set up the output of the follower is between 2.5v and 5v. Ideally the output would be between 0v and 5v, has anyone tackled something similar or have an ideas about scaling the output? I've attached the schematic for reference  Attachments:
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Post by keurslagerkurt on Jan 9, 2022 23:19:52 GMT
Oh, interesting! Would you mind sharing the falstad txt of link, i'm curious to see how it works 😃 There are a few options that come to mind for the rescaling. You could use a differential amplifier like explained in the solution to this question: electronics.stackexchange.com/questions/93423/how-to-amplify-and-offset-the-voltage-in-an-opampFor your case, Vr would be ground, RF/R1 would be 2,V2 would be your circuit output and V1 would be 2.5V reference (can be made with just a voltage divider probably). It's probably also doable with a Cap and resistor biasing to 2.5V together with a transistor (basicly a crude VCA / boost circuit) but i think the opamp is easier to get right. This will Mean you'll have a spare opamp (as they always come in two). Maybe you could also add a last inversion for a second inverted output (can be cool for ducking?) Or it might be possible to try and eliminate one of the earlier op-amps or put the rescaling together with one of the earlier op-amps? |
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Post by pt3r on Jan 10, 2022 6:43:06 GMT
Oh, interesting! Would you mind sharing the falstad txt of link, i'm curious to see how it works 😃 There are a few options that come to mind for the rescaling. You could use a differential amplifier like explained in the solution to this question: electronics.stackexchange.com/questions/93423/how-to-amplify-and-offset-the-voltage-in-an-opampFor your case, Vr would be ground, RF/R1 would be 2,V2 would be your circuit output and V1 would be 2.5V reference (can be made with just a voltage divider probably). It's probably also doable with a Cap and resistor biasing to 2.5V together with a transistor (basicly a crude VCA / boost circuit) but i think the opamp is easier to get right. This will Mean you'll have a spare opamp (as they always come in two). Maybe you could also add a last inversion for a second inverted output (can be cool for ducking?) Or it might be possible to try and eliminate one of the earlier op-amps or put the rescaling together with one of the earlier op-amps? These are the kind of questions that I ask myself on a regular basis. Wouldn't it be interesting to compile these electronic diy FAQs in some kind of sticky thread? Just wondering. I surely can't be the only one asking these "simple" questions from time to time. |
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Post by mkjackn on Jan 10, 2022 9:40:16 GMT
Oh, interesting! Would you mind sharing the falstad txt of link, i'm curious to see how it works 😃 There are a few options that come to mind for the rescaling. You could use a differential amplifier like explained in the solution to this question: electronics.stackexchange.com/questions/93423/how-to-amplify-and-offset-the-voltage-in-an-opampFor your case, Vr would be ground, RF/R1 would be 2,V2 would be your circuit output and V1 would be 2.5V reference (can be made with just a voltage divider probably). It's probably also doable with a Cap and resistor biasing to 2.5V together with a transistor (basicly a crude VCA / boost circuit) but i think the opamp is easier to get right. This will Mean you'll have a spare opamp (as they always come in two). Maybe you could also add a last inversion for a second inverted output (can be cool for ducking?) Or it might be possible to try and eliminate one of the earlier op-amps or put the rescaling together with one of the earlier op-amps? Thanks for the pointers, ill give the differential amplifier a go ASAP looks like exactly what I've been looking for! Yeah definitely planning an inverted output, ducking was the motivation to start figuring it all out! here is the .txt aswell, its a bit temperamental at them moment |
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Post by keurslagerkurt on Jan 11, 2022 10:53:11 GMT
Been watching a bit at the code & falstad (havent tested with an mp3 yet, quickly tried but it didnt seem to play, probably i did something wrong), and a few thoughts: - I would use a smaller input cap, i usually use 220nF for the input stage. I think that might give you a quicker attack. - I don't really get what the output, most right pot needs to do, is it to filter out higher frequency noise? Does that give a smoother curve or smth? Not an expert in enveloppe followers, so would def like to learn a bit about the workings of the circuit  |
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