First audio electronics project - looking for some reference

[lefthandRED]

Hi, I am currently studying a Music Technology degree in Scotland. I am building a VCA controlled compressor for my 4th year project and am currently in the research stage.

I have some electronics experience but am learning a lot of the more technical stuff as I go.

What I am looking for just now is a way to make my detector circuit for the control signal to be analysed with. I have looked into true RMS detection and am going for something a little more basic.

Am I right in thinking that if I precision rectify the AC audio signal into a variable DC and then filter out the high frequencies I will be left with a representation of my audio RMS?

Any advice would be appreciated, especially to existing detection circuits.

p.s. I am not interested in letting an IC do this for me, I'm happy to use op amps but i want the circuit as discrete as possible after this.


Nick.

 

[mehtadhaval]

you are correct in ur approach.
Try this : First make an transistor amp ckt to increase i/p level. Then rectify the o/p of the ckt and put a big capacitor filter. And then again put a transistor ckt to make it compatible with microcontroller voltage levels. (I am assuming that u are detecting the presence of the signal using a microcontroller).

one simple transistor amp ckt is shown below :

Simple Microphone Preamplifier

 

[franciscorc]

HI

No your approach is not the RMS value.Your idea to make a precision rectifier and flter the signal is a very good start point.

But do not use a large filtering, because of if you do that you are going to decrease frequency response.The output signal of this circuit(precision rectifier and filter) is envelop of the audio signal. I have simulated this circuit in Proteus and it works. If you think you can control your VCA amplifier using the envelop it is a great idea.

Best