DC biasing audio signal

Posted on Feb 6, 2014

My audio source will be a Line Level Audio -2V to +2V AC passed through a 220uF coupling cap and then a low pass filter(RC, 2 pole). The signal will be read by an ADC another one that i have seen is I don`t quite understand this FET-BJT preamp circuit And the schematic is for a pre-amp, and there are 2 versions and both add a bias. using the second one looks like it will work best for my

DC biasing audio signal
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application, using something like this- is there any other improvements I can make other then Stable Vref/power rails. The signal is going to be read by an ADC, for a BPM counter(beats per min) And Kellenjb you are correct coupling cap and not decoupling - fixed jsolarski May 18 `11 at 12:31 As a note: I use the first solution with no problems but my circuit is definitely not a high fidelity one as it is on a model aircraft with lots of other noise (motors, servo, wind etc. ) Thomas O May 18 `11 at 16:11 Don`t use the first circuit. Any noise or spikes on the power supply will be mixed with your signal. Because the bias point is connected directly to the signal, you can`t filter out power supply noise without also filtering out the signal. Do use the second circuit. It produces a mid-point voltage that is tightly coupled to ground, so the DC component is half the supply, but the AC component (noise and spikes) is filtered out by the capacitor. That`s not a complete circuit, though, you still need to connect it to your signal. The output is the same as the input, just shifted upward by 2. 5 V. The resistor on the input ensures that the input side of the capacitor is at 0 VDC, to prevent pops during connection. The resistor on the output side of the AC coupling cap biases that side to the DC bias voltage. If your circuit already has a clean, low impedance DC bias voltage source, connect to that. Otherwise, you can use circuit...

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