Contents
How are digital potentiometers used for audio control?
Abstract: Digital potentiometers (pots) offer advantages for audio volume (gain) control applications and can replace bulky mechanical pots, especially in handheld portable devices such as MP3 players, PDAs, cell phones, mobile Internet devices, or stereo AM/FM radios.
What are the ideal op amp transfer equations?
Similar equations have been developed in other books, but the presentation here empha- sizes material required for speedy op amp design. The ideal op amp equations are devel- oped in Chapter 3, and this chapter enables the reader to rapidly compute op amp transfer equations including ac response.
How are op amps used in single power supply systems?
The emphasis on single power supply systems forces the designer to bias circuits when the inputs are referenced to ground, and Chapter 4 gives a detailed procedure that quickly yields a working solution every time. Op amps can’t exist without feedback, and feedback has inherent stability problems, so feedback and stability are covered in Chapter 5.
Where to put a volume control in a preamp?
[in the diagram below I used op-amp symbols for both the pre-amp and the class D amp, and class D amp has differential output.] The best place to put a volume control is probably on the output of the preamp stage before the coupling capacitor.
How does a DC biasing audio signal work?
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.
How does a DC biasing capacitor prevent pop sound?
The resistor on the input ensures that the input side of the capacitor is already at 0 VDC bias when an external circuit is connected, to prevent “pop” sounds (if the voltage suddenly jumped from 2.5 V to 0 V). The resistor on the output side of the AC coupling cap biases that side to the DC bias voltage.
Which is the best circuit for biasing audio?
The first circuit, the simple resistor divider, is by far the easiest, quickest, and cheapest solution. It is also the solution that most audio circuits use. Unless you are wanting pro-audio levels of performance, this is the method that I would recommend. The “correct” solution would be to have a separate power rail that is at the bias voltage.