Archive for category: Audio and Amplifier

Easy Audio Mixer by LM837

Audio and Amplifier | By: Diagram mania

The mixer itself is a fixed-gain summing amplifier based on an LM837. It sums up all the six microphone preamp signals into a single output. This is called the MIX OUT, and is a rear-panel socket. The single output is split into two outputs, to allow easy connection to external stereo equipment. The idea behind […]

Audio Mixer by 2N3819 Junction FET

Audio and Amplifier | By: Diagram mania

This simple circuit mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consumes very little power. The mixer is shown with two inputs, but you can add as many as you want by just duplicating the “sections” which […]

Microphone Mixer by 741

Audio and Amplifier | By: Diagram mania

This relatively simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs. Part R1, R2, R3 3 1K 1/4W Resistor R4, R5, R6 3 10K Logarithmic Pot R7 1 1Meg 1/4W Resistor R8, R10 2 10K […]

Sound Effects Generator by UM3561

Audio and Amplifier | By: Diagram mania

This circuit uses a UM3561 IC to produce four different sound effects. Nothing too complicated here. The IC produces all the sound effects, the output at Pin 3 being amplified by the transistor. A 64 ohm loudspeaker can be substituted in place of the 56 ohm resistor and 8 ohm loudspeaker. The 2 pole 4 […]

Self-Resonance Piezo Buzzer with 1-18V

Audio and Amplifier | By: Diagram mania

As power is first applied, the piezo is drawing a lot of current through R1 & 2 and shunts it away from the base of the transistor. At some point, as the piezo begins to saturate, the shunting effect diminishes to the point where the transistor starts turning on. This starts discharging the piezo, which […]

Enhanced 4 Digit Alarm Keypad by 4081

Audio and Amplifier | By: Diagram mania

Audio Level Meter by BC108

Audio and Amplifier | By: Diagram mania

Audio levels can be monitored using a small panel meter with this circuit built from discrete components The circuit has a flat frequency response from about 20Hz to well over 50Khz. Input sensitivity is 100mV for a full scale deflection on a 100uA meter. Built on two common emitter amplifiers, the first stage has a […]

Water Level Alarm by 4011

Audio and Amplifier | By: Diagram mania

A circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath or cold storage tank. This circuit will trigger with any fluid with a resistance under 900K between the maximum separation distance of the probes. Let […]

Fuzz box by all FET

Audio and Amplifier | By: Diagram mania

All-FET design Valve-like distortion behavior This circuit was designed to obtain a valve-like distorted sound from an electric guitar or other musical instrument. For this purpose a very high gain, three-FET amplifier 2N3819 circuit, was used. The output square wave shows marked rounded corners, typical of valve-circuits when driven into saturation. Therefore, the distorted sound […]

Audio VU Meter by LM324

Audio and Amplifier | By: Diagram mania

This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores. The 1K resistors in the circuit are essential so that the LED’s turn on at different audio levels. […]