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Vintage threads from the first ten years
Diodes and impedance?
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 7/31/2000 4:21 PM |
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| JOHN | Diodes and impedance? If I use diodes for clipping(series or to ground)Will they change the impedance? |
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| 7/31/2000 4:31 PM |
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Don Symes |
Impedance of what? Diodes have a non-linear impedance, that's what a graph of their I/V curve is showing you. Don't use them to try to clip speaker-level signals if that's what you're asking. What are you up to? Details help us help you. |
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| 7/31/2000 8:55 PM |
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| JOHN | Don, I,ve got a opamp output thru a 15uf cap,then a series 100 ohm resistor then 2 diodes(one reversed)to ground then the output jack. |
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| 7/31/2000 10:37 PM |
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| Don Symes |
You're on the right track. I thinky ou'll benefit most by studying the schematics at http://ampage.org/stompbox/ or http://www.geofex.com Start with the MXR Distortion + and move on from there. In general, you'll want to move the diodes and the series resistor) between the op-amp and the cap. Consider adding an output buffer (voltage follower or unity gain) to isolate the clipping stage from the next effect. Good luck, and keep asking questions. |
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| 7/31/2000 10:43 PM |
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| John Greene |
The diodes change to load impedance the opamp sees. Before the diodes are driven over their threshold the load impedance is 100 ohms in series with whatever is the input impedance of the following stage. When the diodes break over, the load impedance is basically 100ohms. --johng |
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