Showing posts with label Audio. Show all posts
Showing posts with label Audio. Show all posts
Bicycle Horn Using Tone Generator KA2411
An interesting circuit of a bicycle horn based on a popular, low cost telecom ringer chip is described here. This circuit can be powered using the bicycle dynamo supply and does not require batteries, which need to be replaced frequently. The section comprising diodes (D1 and D2) and capacitors (C1 and C2) forms a half-wave voltage-doubler circuit. The output of the voltage doubler is fed to capacitor C3 via resistor R1. The maximum DC supply that can be applied to the input terminals of IC1 is 28V. Therefore zener diode ZD1 is added to the circuit for protection and voltage regulation. The remainder of the circuit is the tone generator based on IC1 (KA2411).
Audio Source Touch Selector
Often you need to connect output from more than one source (preamplifier) such as tape recorder/player and CD (compact disc) player to audio power amplifier. This needs disconnecting/connecting wires when you want to change the source, which is quite cumbersome and irritating. Here is a circuit that helps you choose between two stereo sources by simple touch of your hand. This circuit is so compact that it can be fixed within the audio power amplifier cabinet and can use the same power supply source. The circuit uses just two CMOS ICs and a few other componenets. The ICs used are MC14551/CD4551 (quad 2-channel analogue multiplexer) and CD4011 (quad 2-input NAND gate).
Schematic:
click for large image
Musical Touch Bell UM66
This musical call bell circuit can be operated by just bridging the gap between the touchplates with one’s fingertips. Thus there is no need for a mechanical ‘on’/‘off’ switch because the touch-plates act as a switch. Other features include low cost and low power consumption. The bell can work on 1.5V or 3V, using one or two pencil cells, and can be used in homes and offices. Two transistors are used for sensing the finger touch and switching on a melody IC. Transistor BC148 is npn type while transistor BC558 is pnp type. The emitter of transistor BC148 is shorted to the ground, while that of transistor BC558 is connected to the positive terminal.
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| Musical Touch Bell UM66 |
Stereo LED Power (VU) Meter
DRM Direct Mixer EF95/6AK5
This hybrid DRM receiver with a single valve and a single transistor features good large-signal stability. The EP95 (US equivalent: 6AK5) acts as a mixer, with the oscillator signal being injected via the screen grid. The crystal oscillator is built around a single transistor.
50W Audio Amplifier Using IC TDA1562
The integrated output amplifier described in this article consists of little more than one integrated circuit. It is intended especially for use in motor vehicles and other battery-operated applications. Although it appears simple and hardly worth looking at, the amplifier can produce an appreciable audio power output. The circuit diagram in Figure 2 emphasizes how few external components are needed to construct a complete output amplifier.
100W Quad Car Amplifier
This quad final amplifier is actually intended to be used in a car, but it can naturally also be used for a variety of other medium-power applications. The TDA7375A can be successfully used in all situations in which a reasonable amount of audio power is desired and only a relatively low supply voltage is available. This IC is the successor to the TDA7374B, which forms the heart of the active loudspeaker system described earlier this year. Such a quad IC amplifier is naturally an excellent choice for this application, especially since the individual amplifiers can be connected in pairs in the bridge configuration, which allows them to provide approximately four times as much power.
SDR Soundcard Tester
The key to using a soundcard successfully in digital signal processing or digital radio applications lies principally in the characteristics of the soundcard itself. This applies in particular to SDR (software defined radio) programs that turn your PC into a top-class AM/SSB/CW receiver, assuming your soundcard cooperates. If you want to experiment with SDR and avoid a lot of frustration, it is worth checking fi rst whether the PC soundcard you plan to use is suitable. There are three essential elements to success:
Circuit diagram:
SDR Soundcard Tester Circuit Diagram
- the soundcard must have a stereo line-level input;
- the card must be equipped with an input anti-aliasing filter; and
- the sample rate must be at least 48 kHz and the card must be able to cope with signals up to 24 kHz.
Circuit diagram:
SDR Soundcard Tester Circuit Diagram
Test Beeper For Audio Amplifiers
The test beeper generates a sinusoidal signal with a frequency of 1,000 Hz, a common test frequency for audio amplifiers. It consists of a classical Wien-Bridge oscillator (also known as a Wien-Robinson oscillator). The network that determines the frequency consists here of a series connection of a resistor and capacitor (R1/C1) and a parallel connection (R2/C2), where the values of the resistors and capacitors are equal to each other. This network behaves, at the oscillator frequency (1 kHz in this case), as two pure resistors. The opamp (IC1) ensures that the attenuation of the network (3 times) is compensated for.
In principle a gain of 3 times should have been sufficient to sustain the oscillation, but that is in theory. Because of tolerances in the values, the amplification needs to be (automatically) adjusted. Instead of an intelligent amplitude controller we chose for a somewhat simpler solution. With P1, R3 and R4 you can adjust the gain to the point that oscillation takes place. The range of P1 (±10%) is large enough the cover the tolerance range. To sustain the oscillation, a gain of slightly more than 3 times is required, which would, however, cause the amplifier to clip (the ‘round-trip’ signal becomes increasingly larger, after all).
Circuit diagram:
In principle a gain of 3 times should have been sufficient to sustain the oscillation, but that is in theory. Because of tolerances in the values, the amplification needs to be (automatically) adjusted. Instead of an intelligent amplitude controller we chose for a somewhat simpler solution. With P1, R3 and R4 you can adjust the gain to the point that oscillation takes place. The range of P1 (±10%) is large enough the cover the tolerance range. To sustain the oscillation, a gain of slightly more than 3 times is required, which would, however, cause the amplifier to clip (the ‘round-trip’ signal becomes increasingly larger, after all).
Circuit diagram:
Test Beeper Circuit Diagram
Stepped Volume Control
Louder music, sirens or speech in response to higher ambient noise levels? This simple circuit has the answer, and it may enable your robot to be at least as noisy or loud-mouthed as the others in an arena.
The circuit consists basically of a microphone, a level detector, a 4-state counter and four analogue switches connected to a resistive ladder network. Looking at the circuit diagram, the signal from electret microphone M1 is amplified by T1 whose collector voltage appears across a potentiometer. M1 gets its bias voltage through R4. Depending on the setting of P1, the 4040 counter will get a clock pulse when a certain noise level (threshold) is exceeded.
Circuit diagram:
The circuit consists basically of a microphone, a level detector, a 4-state counter and four analogue switches connected to a resistive ladder network. Looking at the circuit diagram, the signal from electret microphone M1 is amplified by T1 whose collector voltage appears across a potentiometer. M1 gets its bias voltage through R4. Depending on the setting of P1, the 4040 counter will get a clock pulse when a certain noise level (threshold) is exceeded.
Circuit diagram:
Stepped Volume Control Circuit Diagram
Stereo to Mono Converter Using FET
High quality portable unit, Suitable for Subwoofer amplifiers
This simple circuit mixes two or more channels into one channel (e.g. stereo into mono). The circuit can mix as many or as few channels as you like and consume very little power. The mixer is shown with two inputs, but you can add as many as you want by just duplicating the "input sections" which are clearly visible on the schematic.
Circuit Diagram:
This simple circuit mixes two or more channels into one channel (e.g. stereo into mono). The circuit can mix as many or as few channels as you like and consume very little power. The mixer is shown with two inputs, but you can add as many as you want by just duplicating the "input sections" which are clearly visible on the schematic.
Circuit Diagram:
Mini High-Performance 12V 20W Stereo Amplifier
Amplifiers which run from 12V DC generally don’t put out much power and they are usually not hifi as well. But this little stereo amplifier ticks the power and low distortion boxes. With a 14.4V supply, it will deliver 20 watts per channel into 4-ohm loads at clipping while harmonic distortion at lower power levels is typically less than 0.03%.
This is an ideal project for anyone wanting a compact stereo amplifier that can run from a 12V battery. It could be just the ticket for buskers who want a small but gutsy amplifier which will run from an SLA battery or it could used anywhere that 12V DC is available – in cars, recreational vehicles, remote houses with 12V DC power or where ever.
Because it runs from DC, it will be an ideal beginner’s or schoolie’s project, with no 240VAC power supply to worry about. You can run it from a 12V battery or a DC plugpack. But while it may be compact and simple to build, there is no need to apologise for “just average” performance. In listening tests from a range of compact discs, we were very impressed with the sound quality.
This is an ideal project for anyone wanting a compact stereo amplifier that can run from a 12V battery. It could be just the ticket for buskers who want a small but gutsy amplifier which will run from an SLA battery or it could used anywhere that 12V DC is available – in cars, recreational vehicles, remote houses with 12V DC power or where ever.
20W Stereo Audio Amplifier
Because it runs from DC, it will be an ideal beginner’s or schoolie’s project, with no 240VAC power supply to worry about. You can run it from a 12V battery or a DC plugpack. But while it may be compact and simple to build, there is no need to apologise for “just average” performance. In listening tests from a range of compact discs, we were very impressed with the sound quality.
Audio Level Adapter
The problem that this circuit is designed to solve appeared when the author was installing a new radio in his Audi A3. The new radio had four outputs for loudspeakers and a line-level output for a subwoofer. However, the A3 as delivered from the factory already has an amplifier for the rear loudspeakers, as well as the pre-installed subwoofer, in the boot space. The original Audi radio therefore has only line-level outputs for the rear loudspeakers. So, to replace the original radio without making other changes to the installed amplification system, he needed to convert the outputs of the new radio corresponding to the rear loudspeakers into line level outputs.
Most of the commercially-available adapters to do this job contain small transformers for galvanic isolation. These introduce phase shifts and create a certain amount of distortion, which the author was keen to minimize. The result is this simple adapter circuit that does not employ a transformer. The outputs of most radios available today have a differential (bridge-type) push-pull output stage. There is thus no ground output, just two outputs per channel with a 180 ° phase difference between them. If the outputs are each connected to a common point via a 100 Ω resistor, that point becomes a virtual ground.
Circuit diagram:
Most of the commercially-available adapters to do this job contain small transformers for galvanic isolation. These introduce phase shifts and create a certain amount of distortion, which the author was keen to minimize. The result is this simple adapter circuit that does not employ a transformer. The outputs of most radios available today have a differential (bridge-type) push-pull output stage. There is thus no ground output, just two outputs per channel with a 180 ° phase difference between them. If the outputs are each connected to a common point via a 100 Ω resistor, that point becomes a virtual ground.
Circuit diagram:
Audio Level Adapter Circuit Diagram
Super 3 Watt Audio Power Amplifier
The TDA1015 is a monolithic integrated audio amplifier circuit in a 9-lead single in-line (SIL) plastic package. The device is especially designed for portable radio and recorder applications and delivers up to 4 watt in a 4 ohm load impedance. The very low applicable supply voltage of 3,6 V permits 6 V applications.
45 Watt Class-B Audio Power Amplifier
45W into 8 Ohm - 69W into 4 Ohm, Easy to build - No setup required
These goals were achieved by using a discrete-components op-amp driving a BJT complementary common-emitter output stage into Class B operation. In this way, for small output currents, the output transistors are turned off, and the op-amp provides all of the output current. At higher output currents, the power transistors conduct, and the contribution of the op-amp is limited to approximately 0.7/R11. The quiescent current of the op-amp biases the external transistors, and hence greatly reduces the range of crossover.
The idea sprang up from a letter published on Wireless World, December 1982, page 65 written by N. M. Allinson, then at the University of Keele, Staffordshire. In this letter, op-amp ICs were intended as drivers but, as supply voltages up to +/- 35V are required for an amplifier of about 50W, the use of an op-amp made of discrete-components was then considered and the choice proved rewarding.
The discrete-components op-amp is based on a Douglas Self design. Nevertheless, his circuit featured quite obviously a Class A output stage. As for proper operation of this amplifier a Class B output stage op-amp is required, the original circuit was modified accordingly. Using a mains transformer with a secondary winding rated at the common value of 25 + 25V (or 24 + 24V) and 100/120VA power, two amplifiers can be driven at 45W and 69W output power into 8 and 4 Ohms respectively, with very low distortion (less than 0.01% @ 1kHz and 20W into 8 Ohms).
This simple, straightforward but rugged circuit, though intended for any high quality audio application and, above all, to complete the recently started series of articles forming the Modular Preamplifier Control Center, is also well suited to make a very good Guitar or Bass amplifier. Enjoy!
Circuit diagram:
These goals were achieved by using a discrete-components op-amp driving a BJT complementary common-emitter output stage into Class B operation. In this way, for small output currents, the output transistors are turned off, and the op-amp provides all of the output current. At higher output currents, the power transistors conduct, and the contribution of the op-amp is limited to approximately 0.7/R11. The quiescent current of the op-amp biases the external transistors, and hence greatly reduces the range of crossover.
The idea sprang up from a letter published on Wireless World, December 1982, page 65 written by N. M. Allinson, then at the University of Keele, Staffordshire. In this letter, op-amp ICs were intended as drivers but, as supply voltages up to +/- 35V are required for an amplifier of about 50W, the use of an op-amp made of discrete-components was then considered and the choice proved rewarding.
The discrete-components op-amp is based on a Douglas Self design. Nevertheless, his circuit featured quite obviously a Class A output stage. As for proper operation of this amplifier a Class B output stage op-amp is required, the original circuit was modified accordingly. Using a mains transformer with a secondary winding rated at the common value of 25 + 25V (or 24 + 24V) and 100/120VA power, two amplifiers can be driven at 45W and 69W output power into 8 and 4 Ohms respectively, with very low distortion (less than 0.01% @ 1kHz and 20W into 8 Ohms).
This simple, straightforward but rugged circuit, though intended for any high quality audio application and, above all, to complete the recently started series of articles forming the Modular Preamplifier Control Center, is also well suited to make a very good Guitar or Bass amplifier. Enjoy!
Circuit diagram:
45W Class-B Amplifier Circuit Diagram
Automatic Loudness Control
Simple add-on module, Switchable "Control-flat" option
In order to obtain a good audio reproduction at different listening levels, a different tone-controls setting should be necessary to suit the well known behavior of the human ear. In fact, the human ear sensitivity varies in a non-linear manner through the entire audible frequency band, as shown by Fletcher-Munson curves.
A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels.
Fortunately, the human ear is not too critical, so a rather simple circuit can provide a satisfactory performance through a 40dB range. The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7.
Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below. C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.
Circuit diagram:
In order to obtain a good audio reproduction at different listening levels, a different tone-controls setting should be necessary to suit the well known behavior of the human ear. In fact, the human ear sensitivity varies in a non-linear manner through the entire audible frequency band, as shown by Fletcher-Munson curves.
A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels.
Fortunately, the human ear is not too critical, so a rather simple circuit can provide a satisfactory performance through a 40dB range. The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7.
Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below. C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.
Circuit diagram:
Automatic Loudness Controller Circuit Diagram
60 Watt Audio Power Amplifier
This project shows you how to build high quality 60 - 90W (into 4 Ohm load) powerful Amplifier. It suits for guitar or bass amplifier
To celebrate the hundredth design posted to this website, and to fulfil the requests of many correspondents wanting an amplifier more powerful than the 25W MosFet, a 60 - 90W High Quality power amplifier design is presented here. Circuit topology is about the same of the above mentioned amplifier, but the extremely rugged IRFP240 and IRFP9240 MosFet devices are used as the output pair, and well renowned high voltage Motorola's transistors are employed in the preceding stages.
The supply rails voltage was kept prudentially at the rather low value of + and - 40V. For those wishing to experiment, the supply rails voltage could be raised to + and - 50V maximum, allowing the amplifier to approach the 100W into 8 Ohm target: enjoy! A matching, discrete components, Modular Preamplifier design is available here: Modular Audio Preamplifier.
30 Watt Audio Power Amplifier Schematic
Including Preamp, Tone Controls, Reg dc Power Supply, 18 Watt into 8 Ohm - 30W into 4 Ohm loads
This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. The Power Amplifier section employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with 0.08% THD @ 1KHz at the onset of clipping (0.04% @ 1W - 1KHz and 0.02% @ 1W - 10KHz) and up to 30W into a 4 Ohm load.
To obtain such a performance and to ensure overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedance. Finally, as the amplifier requires only a single rail supply, a very good dc voltage regulator capable of supplying more than 2 Amps @ 40V can be implemented with a few parts also.
Circuit diagram:
This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. The Power Amplifier section employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with 0.08% THD @ 1KHz at the onset of clipping (0.04% @ 1W - 1KHz and 0.02% @ 1W - 10KHz) and up to 30W into a 4 Ohm load.
To obtain such a performance and to ensure overall stability of this very simple circuitry, a suitable regulated dc power supply is mandatory. This is not a snag because it also helps in keeping noise and hum of the preamp to very low levels and guarantees a predictable output power into different load impedance. Finally, as the amplifier requires only a single rail supply, a very good dc voltage regulator capable of supplying more than 2 Amps @ 40V can be implemented with a few parts also.
Circuit diagram:
Peak Indicator
A simple circuit to detect a peak of musical or audio signal. Each time where the level of signal exceeds the level + 4dB, turns on led D1. It is useful in each channel of console of sound, in final amplifiers or in that other application, to we needed. With the prices of circuit, the indicate begins with levels above + 4 dB (1.25V rms). For adaptation in different levels of signal, we can use a trimmer, before capacitor C1.
Circuit Diagram:
Circuit Diagram:
Peak Indicator Circuit Diagram
Mini Alarm
This mini alarm circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means of a tiny cord. If the bag is snatched abruptly, the magnet looses its contact with the reed switch, SW1 opens, the circuit starts oscillating and the loudspeaker emits a loud alarm sound. A complementary transistor-pair is wired as a high efficiency oscillator, directly driving a small loudspeaker. Low part-count and 3V battery supply allow a very compact construction. This circuit is suit for doors & windows alarm.
Circuit Diagram:
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