Circuit Amp with Tone Controls Soft Switching Schematic Diagrams

Circuit Amp with Tone controls Soft switching schematics Circuit Electronics,

Notes:
The soft switching is enabled by a BD131 transistor wired as a switch in emitter follower configuration. The collector is wired to a permanent supply voltage, the 2H series inductor serves only to filter out power supply hum. This inductor is not too important and may be omitted if the DC supply is adequately smoothed. The control voltage is applied to the BD131 base terminal, the 10u capacitor and 10k resistor having a dual purpose:-
i) a gradual charge of the 10u capacitor ensures that the transistor will switch linearly from 0 volts to full supply, and
ii) serves as a hum filter ensuring a very smooth dc supply to the amplifier and tone controls.
LED1 will light when the amplifier is on. The control voltage should ideally be 0 volts when the amplifier is off and full supply voltage when on. The LM380 is shown driving two 8 ohm loudspeakers, the load is therefore 4 ohms. The 4u7 capacitor acts as a crude crossover, lower frequencies are impeded and so this loudspeaker may be a "tweeter" type.
Schematics for Amp with Tone controls Soft switching Circuit Electronics
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Circuit Audio VU Meter Schematic Diagrams

Circuit audio VU Meter schematics Circuit Electronics,
Notes
The 1K resistors in the circuit are essential so that the LED's turn on at different audio levels. There is no reason why you can't change these resistors, although anything above 5K may cause some of the LED's to never switch on. This circuit is easily expandable with more op-amps, and is not limited to use with the LM324. Pretty much any op-amp will work as long as you look up the pinouts and make sure everything is properly connected.

The 33K resistor on the schematic is to keep the signal input to the circuit at a low level. It is unlikely you will find a 33K resistor, so the closest you can get should do. The value of this resistor may need to be changed, so it is best you breadboard this circuit before actually constructing it on pcb. The circuit in it's current form will accept line level inputs from sources such as the aux out on a Hi-Fi, all though could be easily modified to accept speaker inputs.

The audio + is connected to the main positive rail, while the audio - is used for signal input. The 50k pot can be used to vary the sensitivity of the circuit.

Schematics for audio VU Meter Circuit Electronics
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Circuit Low Voltage Preamplifier Schematic Diagrams

Circuit Low Voltage Preamplifier schematics Circuit Electronics,

Description:
This is a special low voltage version of my audio preamp. T1's emitter voltage is biased close to half supply voltage (1.5V) to allow for maximum output voltage swing. Both transistors are direct coupled and have closed loop feedback to aid temperature stability.

T2 realizes the amplifiers full voltage gain, and for low noise operation, T2 collector current is about 70uA. T1 merely buffers T2 and operates in emitter follower mode providing a good low output impedance.
Schematics for Low Voltage Preamplifier Circuit Electronics
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Circuit Op-Amp Mic Preamp Schematic Diagrams

Circuit Op-Amp Mic Preamp schematics Circuit Electronics,
Description:
A high quality microphone preamplifier using a single power supply, suitable for dynamic or electret microphones. The op-amp used can be any low noise, high performance type, e.g. NE5534,TL071, OPA 371 etc
Schematics for Op-Amp Mic Preamp Circuit Electronics
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Circuit 150W Car Amplifier Schematic Diagrams

Circuit 150W Car amplifier schematics Circuit Electronics,

LA47536 Four-Channel 45 W BTL Car audio Power amplifier
The LA47536 is a 4-channel BTL power amplifier IC developed for use in car audio systems. The output stage features

- A pure complimentary structure that uses V-PNP transistors on the high side and NPN transistors on the low side to provide high power and superb audio quality.

- The LA47536 includes almost all the functions required for car audio use, including a standby switch, a muting function, and each protection circuit. It also provides a self-diagnosis function (output offset detection). (Sanyo)
Schematics for 150W Car amplifier Circuit Electronics
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