Description

This project is based on ISD2560P IC which allows you to record 60 seconds voice and then playback the recorded voice with very high quality. As shown in the schematic, the input source is an electret microphone. If a dynamic microphone is used,  R2,R3,R4 resistors and C3,C5,C7 capacitors will be omitted and microphone will be connected to the 17 and 18 numbered pins directly. Since it has better frequency response, we choose electret microphone in this project.

Controlling the circuit is very simple. Sw1 switches between record and playback modes. Push button B1 is used for start and pause functions. B2 stops the during process.

To record voice, first move Sw1 to the record position and then push B1 once. IC will start recording and during this process red LED will bright. One push to B1 pauses and second push continues recording. You can record 60 seconds by this way. To stop recording push B2.

To listen the voice recorded before, move Sw1 to playback position then push B1. During the playback process red LED will bright again. One push to B1 pauses and second push continues playing. To stop playback push B2...

Description

When I set out to design this amplifier, my aim was to create a product most suitable for the reproduction of complex music and speech signals. Although I placed high emphasis on electrical characteristics, the single most important requirement is achieving an audibly superior sound, vivid spatial imaging and superb tonal clarity.

Although the average listening level is normally less than 10 watts, my design approach was to create an amplifier with ample reserve power, but biasing it for class A at average listening levels reducing cross-over distortion to extremely low levels.

There is not one capacitor in the signal path, improved the accuracy of the tonal characteristics of instruments and voices significantly.
The RAS 300 has almost zero phase distortion far beyond the audio range resulting in perfect resolution and totally un-coloured sound.

Amplifier Specification:
Maximum Output: 240 watts rms into 8 Ohms, 380 watts rms into 4 Ohms
Audio Frequency Linearity: 20 Hz - 20 kHz (+0, -0.2 dB)
Closed Loop Gain: 32 dB
Hum and Noise: -90 dB (input short circuit)
Output Offset Voltage: Less than 13 mV (input short circuit)
Phase Linearity: Less than 13 0 (10 Hz - 20 kHz)
Harmonic Distortion: Less than 0.007% at rated power
IM Distortion: Less than .009% at maximum power

Description

In this application, we are building a gaincard like amplifier. This application type is named gainclone in the audio world. To take a satisfactory audio response,  we are adding a Linkwitz equaliser to the feedback line and adding bass compensation also.

We are using LM3886 which is the revised version of its brother LM3875.Briefly features of LM3886 are.

Maximum Output Power: 68W RMS - 108W Peak
THD: %0.03 at 60W
SNR: 110dB at 60 W - 92.5dB at 1W
PSRR: 120dB
Protection Circuitries: DC/AC Short circuit protection and thermal protection
Output Class: Conjugate AB-A

Description

VU (Volume Unit) meters are often included in analog audio equipments to display a signal level in Visual Units. We are building a mono input VU meter in this project. You can build one pair to use them in stereo mode.

Input sensitivity is about 1 Volt rms, up to +6dB.  You can adjust the input amplitude by using the multiturn 50k linear potentiometer (POT1).  Circuit needs symmetric ±12V power supply because of the LM324 opamp. We used metal film resistors (1% tolerance) so accuracy is sufficiently high. Visual duration can be adjusted by using linear 10k potentiometer (POT2).  LEDs  should be 5mm x 5mm in size for best fit. But we used standard LEDs and this caused a little shift as you can see from the image. Dot/Bar switch determines the operation mode of LM3915. 

PCB is 1:1 scaled. You can print and transfer it without making any change.

Click here to download schematic, layout and PCB files.

Click here to watch the project video.

Description

This circuit is a small stereo amplifier for all suitable applications like amplifying small speakers, boxing, etc. It is also suitable for car use but before, the power supply must be choked with at least 150mH and it must give up to approximately 6 to 7 amps during the upstream performance.

Technical data:
Performance  of TDA2005M: (for this circuit); At 14.4 V supply voltage: 2 x 20 watts (stereo) into 4 Ohms.
Distortion: Approx. 0.2% at 4 Watts into 4 ohm load.
Frequency Range: Approx. 20 Hz to 22 KHz.
Input Sensitivity: Approx. maximum 150 mV rms. .
Power supply: + 8 to 18 volts, approx. maximum 3.5 Amps per channel.

Appropriate heatsink for the amplifier is SK08 with a height of 50 mm  (approx. 2.5 K per watt). You should drill the cooler after soldering the board to center it properly. The TDA2005 also needs not be isolated from the heat sink, since the metal mounting part of the IC is grounded. You should use thermal paste to improve the heat dissipation. After the assembly , case construction is left to the builder. 100K potentiometers are used for adjusting the input volume. The potentiometers are absent in the layout. The 100K resistors need only be installed if the 100 K potentiometers are not used as shown in the layout.

You should use a well designed quality transformer to get less noise. It will be another good way to use a sufficient battery to power the circuit. Keep the supply wires as short as possible. Input source should be isolated from the external noises too. It is recommended to use coaxial cable to connect the input audio.

Click here to download schematic, PCB and layout files.