Archive for the ‘Audio’ Category
Digitally Controlled Phase Shifter
As shown in a schematic diagram below, this circuit implementation of phase shifter circuit is well suited to using digital potentiometer to control the resistive control element of the phase shifter. The phase at a given frequency is now under control of a digital signal using this circuit which is optimized …
Bandpass Filter’s Gyrator Frequency Calculator
Gyrators are synthetic inductors, which are often used to form bandpass filters. As shown in the two examples here, the active buffering device can be a transistor or op-amp. This type of bandpass filter is commonly used in graphic equalizers and other frequency control circuits such as tone controls. In the gyrator frequency calculator here, …[Read More]
Typical LED indicator consist of resistor (R2) and LED, connected in series with a switch. When the switch is closing or opening, a glitch noise may occur at the supply line. To avoid this noise, R2 and C1 are added to the indicator circuit and value of R1 is adjusted. Very slightly delay is provided …[Read More]
Passive Treble Control for Guitar Pedal
The R1/C1 network makes a low pass filter when the wiper is at the grounded end of the tone pot, and there is a treble cut. The C1 cap bypasses R2 when the wiper is adjusted so that it is at the top end of the pot and it creates a treble boost. The 100k …[Read More]
Passive Baxandall Tone Control (2 Band Equalizer)
Variation of the famous Baxandall circuit is shown in the passive circuit in figure 1. Smoothly increasing +- 6 dB/octave slope of boost or cut is the feature of this circuit. Although the “shelves” are outside the audible range with these component values, the bass and treble filters have a shelving response. The threshold and …[Read More]
Single Cell 1.5V Hearing Aid
This is a hearing aid circuit with 1.5v supply. This circuit is used to detect very faint sounds, then deliver the sounds to an 8 ohm earpiece. This circuit requires 1.5v input voltage, need only a single cell battery. Here is the schematic diagram of the circuit: This circuit can be assembled in a small …[Read More]
Simple LDR Light Alarm
This is a light alarm circuit. This circuit uses Light dependent resistor (LDR). When there is no light fall on the LDR, the transistor driving the speaker is not turned on, because its resistance is high. When the LDR receives light, its resistance decreases and the collector of the second transistor falls. The first transistor …[Read More]
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