Audio schematics

Commercially available hearing aids are quite costly. Here is an inexpensive hearing aid circuit that uses just four transistors and a few passive components.... [read more]

This circuit, connected to 32 Ohm impedance mini-earphones, can detect very remote sounds. Useful for theatre, cinema and lecture goers: every word will be clearly heard. You can also listen to your television set at a very low volume, avoiding to bother relatives and neighbors. Even if you have a faultless hearing, you may discover unexpected sounds using this device: a remote bird twittering will seem very close to you.... [read more]

This low-cost, general-purpose electronic hearing aid works off 3V DC (2x1.5V battery). The circuit can be easily assembled on a veroboard. For easy assembling and maintenance, use an 8-pin DIP IC socket for TDA2822M.... [read more]

Here's a top-class headphone amplifier that can drive high or low impedance 'phones to full power levels, with very low noise and distortion. For best performance, it can be teamed with the Stereo Preamplifier described last month. Alternatively, it can be used as a standalone unit, requiring only a power supply and a volume control pot for use with any line-level signal source (CD/MP3 player etc). It even includes dual outputs, so you can listen with a friend!... [read more]

Apart from the obvious usage as a headphone amplifier, the circuit can be used for a range of applications where a wide bandwidth low power amplifier is needed. The circuit is based on an opamp, with its output current boosted by a pair of transistors.... [read more]

The mentioned shunt-feedback configuration also allows the easy addition of frequency dependent networks in order to obtain an useful, unobtrusive, switchable Tilt control (optional). When SW1 is set in the first position a gentle, shelving bass lift and treble cut is obtained. The central position of SW1 allows a flat frequency response, whereas the third position of this switch enables a shelving treble lift and bass cut.... [read more]

This amplifier can be directly connected to CD players, tuners and tape recorders. It is tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohm. Schematic shows left channel only. B1, SW1, J1 & C3 are common to both channels. R3 value was calculated for headphone impedance up to 300 Ohm. Using 600 Ohm loads or higher, change R3 value to 100K.... [read more]

Some lovers of High Fidelity headphone listening prefer the use of battery powered headphone amplifiers, not only for portable units but also for home "table" applications. This design is intended to fulfill their needs. An improved output driving capability is gained by making this a push-pull Class-B arrangement. Output power can reach 100mW RMS into a 16 Ohm load at 6V supply with low standing and mean current consumption, allowing long battery duration.... [read more]

The LME49830 EF125WT1 amplifier PCB module showcases National Semiconductor’s LME ultra-high fidelity power amplifier input stage ICs (drivers). The LME49830 is a fully complementary bipolar 200V input stage IC with 56mA (typical) of output current that has been optimized for audio applications. With 56mA of current drive, the IC can drive numerous power transistors to achieve high levels of output power. The LME49830’s ultra-low distortion and low-noise, combined with a user adjustable compensation scheme results in a tightly controlled, but highly dynamic listening experience.... [read more]

This circuit is intended to be placed in the same box containing the loudspeaker, forming a compact microphone amplifier primarily intended for speech reinforcement. A device of this kind is particularly suited to teachers, lecturers, tourists' guides, hostesses and anyone speaking in crowded, noisy environment. The circuit's heart is formed by the TDA7052 Audio power amplifier IC, delivering a maximum output of 1.2W @ 6V supply.... [read more]

Designs for audio amplifiers with DC coupling to the load are not often encountered these days, even though they offer definite advantages.... [read more]

Using this low-cost project one can reproduce audio from TV without disturbing others. It does not use any wire connection between TV and Loud Speaker. In place of a pair of wires, it uses invisible infra-red light to transmit audio signals from TV to Loud speakers, Without using any lens a range of up to 6 meters is possible. Range can be extended by using lenses and reflectors with IR sensors comprising transmitters and receivers.... [read more]

Here is the schematic for an 8 watt audio power amplifier. This amp can be used as a simple booster, the heart of a more complicated amplifier or used as a guitar amp. It is very small and portable unit and can be powered through 12V battery.... [read more]

This small amplifier is constructed around the TDA2003 IC, capable of delivering 4Wrms at 4ohms. The TDA 2003 has improved performance with the same pin configuration as the TDA 2002. The additional features of TDA 2002, very low number of external components, ease of assembly, space and cost saving, are maintained.... [read more]

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.... [read more]

This solid-state push-pull single-ended Class A circuit is capable of providing a sound comparable to those valve amplifiers, delivering more output power (6.9W measured across a 8 Ohm loudspeaker cabinet load), less THD, higher input sensitivity and better linearity.... [read more]

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.... [read more]

It's based on a Philips class-H audio amplifier IC and can deliver 36W RMS OR 70W music power, all from a 13.8V supply. Our new Mighty Midget Amplifier can really pack a punch - around 36W RMS continuous into a 4-ohm load when using a 13.8V supply. However, it's the 70W of output power that it can deliver during dynamic (music) signal conditions that really make you sit up and take notice.... [read more]

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.... [read more]

This amplifier was designed to be self-contained in a small loudspeaker box. It can be feed by Walkman, Mini-Disc, iPod and CD players, computers and similar devices fitted with line or headphone output. Of course, in most cases you will have to make two boxes to obtain stereo.... [read more]

This is a 25 Watt basic power amp that was designed to be (relatively) easy to build at a reasonable cost. It has better performance than the standard STK module amps that are used in practically every mass market stereo receiver manufactured today.... [read more]

High Quality very simple unit, No need for a preamplifier... [read more]

2 x 18W Hi-Fi Stereo Power Amplifier based around two TDA2030 ICs. It has good input sensitivity, low distortion, good operating stability and full protection against overloads and output short-circuits. It can be used as a booster amplifier for existing small systems or to drive a second pair of speakers besides the ones already connected to the system. The board needs a symmetrical power supply of ±18Vdc/3A and can be connected to loads of 8 or 4 Ohm.... [read more]

Improved 3 Transistor Audio Amp (80 milliwatt)... [read more]

Here is a little audio amplifier similar to what you might find in a small transistor radio. The input stage is biased so that the supply voltage is divided equally across the two complimentary output transistors which are slightly biased in conduction by the diodes between the bases. A 3.3 ohm resistor is used in series with the emitters of the output transistors to stabilize the bias current so it doesn't change much with temperature or with different transistors and diodes.... [read more]

The example below illustrates using an op-amp as an audio amplifier for a simple intercom. A small 8 ohm speaker is used as a microphone which is coupled to the op-amp input through a 0.1uF capacitor. The speaker is sensitive to low frequencies and the small value capacitor serves to attenuate the lower tones and produce a better overall response.... [read more]

Tube power amplifier 5W with EL84... [read more]

Tube power amplifier 3W with 6BX7... [read more]

Tube Power amp. Dynaco ST-70... [read more]

It's a classic designing of final amplifier 35 W, with two EL34 in push-pull, from the Siemens and Halske, with year of designing 24/3/1953 and code SV410/1. The amplifier it worked from 1954 until 1989, whenever it came also out except operation, with mean of operation 15 hours per day.... [read more]