Free electronic circuit design and schematic diagram
If we want to record very low frequency or DC signal on an audio recording system, we have to convert the DC/low frequency signal into the spectrum of audible sound. The figure of DC response data recording system is shown below. We can record low-frequency analog data (DC to 10kHz) anywhere, store, and then reproduced. The frequency spectrum of the […]
Read more
Microphone can’t be directly connected to a power amplifier because the signal is too weak. Standard audio power amplifier accept about 1 Vrms to give a full volume (maximum power), and off course there’s such microphone has such high level output. To provide signal with high enough amplitude, we can use a pre-amplifier circuit shown in the schematic diagram below: […]
Read more
This is a compressor circuit that can be used for dynamic mic, condenser mic, or electric guitar pickup. This circuit doesn’t produce very good sound output, but it has very stable amplitude/volume. This compressor circuit design is unique since it uses base current control for manipulating the gain. Here is the schematic diagram of the circuit: The first and second […]
Read more
Door intercom is very useful for home security. If you receive a door knock or door bell/alarm, you can push this intercom knob and ask the guest to identify his/her self, before deciding to open the door to welcome. Here is the schematic diagram of the circuit: To install this door intercom, except for right side speaker, you should place […]
Read more
This is a 3 Band Equalizer circuit. This circuit is made to control the treble, middle and bass range. This circuit uses a single op-amp. With single op-amp we can build equalizer which has three ranges, high frequency, mid frequency, and low frequency. Here is the schematic diagram of the circuit: This circuit has a cut off frequencies of 10kHz, […]
Read more
Microphone pre-amp is a very simple circuit, most all low noise op-amp will be sufficient for this circuit (TL071, TL082, OPA371, NE5534, etc). This circuit will be suitable for dynamic microphone, electret microphone (or a condenser microphone with active circuit inside). A condenser microphone (without voltage bias source) won’t work for this circuit. If you want to use it, you […]
Read more
This is a Stereo VU Booster circuit. In this circuit, shown in the schematic diagram, transistor FCS9014 is used. Actually you can use almost any type of small signal NPN transistor. This transistor usually used for regulator and pre-amp circuit. Here is the schematic diagram of the circuit: The schematic diagram show only one channel, so you have to build […]
Read more