I have an 31 band graphic equaliser that uses a LED to indicate if the equaliser section is 'in' or 'out' of the audio path.
To do this, it looks to me, that an audio signal is sent to the non-inverting input of C4558 dual opamp, the output signal is then rectified and sent to the non-inverting input of the other half of the op amp. It is then 'compared' to a reference voltage on the inverting input, which depending if higher or lower will turn the LED on or off.
My problem is that the LED doesn't turn on and I can't for the life of me work out how such an arrangement is supposed to work. The LED should indicate the circuit is 'in' whether or not an audio signal is present. I'm hoping someone has come across this kind of circuit arrangement before and will be able to help me understand what the problem might be. I've mapped out a circuit diagram as best I can. The equaliser functions as it should and switches in and out as it is supposed to, it's just that the LED won't light to say so!
It seems complicated for such a simple task. Any ideas would be appreciated.
To do this, it looks to me, that an audio signal is sent to the non-inverting input of C4558 dual opamp, the output signal is then rectified and sent to the non-inverting input of the other half of the op amp. It is then 'compared' to a reference voltage on the inverting input, which depending if higher or lower will turn the LED on or off.
My problem is that the LED doesn't turn on and I can't for the life of me work out how such an arrangement is supposed to work. The LED should indicate the circuit is 'in' whether or not an audio signal is present. I'm hoping someone has come across this kind of circuit arrangement before and will be able to help me understand what the problem might be. I've mapped out a circuit diagram as best I can. The equaliser functions as it should and switches in and out as it is supposed to, it's just that the LED won't light to say so!
It seems complicated for such a simple task. Any ideas would be appreciated.
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