discrete_vca
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discrete_vca [2012/04/04 14:44] – created wadmin | discrete_vca [2018/08/26 09:36] (current) – external edit 127.0.0.1 | ||
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In my quest to design effective audio applications, | In my quest to design effective audio applications, | ||
- | ==== Concept | + | === Concept === |
The VCA schematic is given herebelow: | The VCA schematic is given herebelow: | ||
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{{ : | {{ : | ||
- | The concept is to feed the input into a 10k + 100R network, operating as a voltage divider, and to propagate the middle point of this dividing bridge to an inverter amplifier through a transistor operated in its variable resistor part. | + | The concept |
+ | |||
+ | === how it works === | ||
+ | |||
+ | The idea is to feed the input into a 10k + 100R network, operating as a voltage divider, and to propagate the middle point of this dividing bridge to an inverter amplifier through a transistor operated in its variable resistor part. | ||
* VG1 is the audio signal source | * VG1 is the audio signal source | ||
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R1 may also be changed if the enveloppe voltage is lower or higher than 5V. | R1 may also be changed if the enveloppe voltage is lower or higher than 5V. | ||
- | ==== Operation | + | === Operation === |
The behaviour of the VCA is shown herebelow: | The behaviour of the VCA is shown herebelow: | ||
{{ : | {{ : | ||
+ | |||
+ | The signal is slightly distorted, however the global response is transient friendly. | ||
* 5V triangle signal is fed into the VCA | * 5V triangle signal is fed into the VCA | ||
* Enveloppe voltage range is 5V. | * Enveloppe voltage range is 5V. | ||
- | ==== Pros & Cons ==== | + | === Pros & Cons === |
Pros : | Pros : | ||
- | - Very low component count | + | * Very low component count |
- | - Large dynamic range | + | |
- | - Linear response | + | |
+ | * Input signal can have any DC component | ||
Cons : | Cons : | ||
- | - Sensitive to noise | + | * Sensitive to noise |
- | - Very sensitive to ground feedback noise | + | |
- | - Linear response :) | + | * Slight distorsion on signal |
+ | * Attenuator operation, not suitable for low voltage sources | ||
+ | * Linear response :) | ||
+ | |||
+ | ==== Conclusion ==== | ||
+ | |||
+ | When building an analog synth, and looking for a simple way to control amplitude, this schematic provides a handy way to generate signal enveloppe on a 5Vpeak audio signal. | ||
+ | |||
+ | Great care has to be taken on analog design, especially when mixing with digital components. using a dedicated analog ground for this schematic is recommended. |
discrete_vca.1333550657.txt.gz · Last modified: 2018/08/26 09:36 (external edit)