Circuit-Zone.com - Electronic Projects
Posted on Wednesday, July 28, 2010 • Category: Headphone Amplifiers
This is an article about my new PCB design for HiFI headphone amplifier using audiophile OPA2132 OP-AMP chip. Main feature is that the new PCB fits exactly to the classic Altoids tin-can. This new headphone amplifier incorporates moreover bass-boost circuit and constant current charger for 9V battery.
Posted on Wednesday, July 28, 2010 • Category: Audio DAC
This device is fully functional sound card for PC. The main advantage of using PCM2704 against PCM2702 is much easier construction. As you can see on the block diagram it has built-in 5V and 3.3 voltage regulator, HID interface (MUTE, VOL+, VOL-), S/PDIF output. The circuit can be powered directly from USB port. Next advantage is that the output DAC is able to drive directly 32ohms headphones, but the output power is only 12mW. For all details please refer to the PCM2704 datasheet.
Posted on Thursday, July 15, 2010 • Category: FM Transmitters
This Phone FM transmitter connects in series to your telephone line and transmits the telephone conversation over the FM band when you pick up the telephone handset. Transmitted signal can be tuned by any FM receiver. The circuit includes an "On Air" LED indicator and also provides a switch which can be used to turn off the transmitter. A unique feature of the circuit is that no battery is needed to operate the circuit since power is taken from the telephone line. The transmitter uses only a short piece of wire aerial about 4" / 10 cm long to transmit the signal and some of the RF signal is also radiated through the telephone line itself. The circuit might be used to share or record conversations, but is not intended for illegal use.
Posted on Thursday, July 8, 2010 • Category: FM Transmitters
This is a high performance low noise 500mW amplifier / booster for all low power FM transmitters such as BA1404, BH1417, BH1415, 433MHz transmitter modules, etc. The amplifier chip is an integrated circuit containing multiple transistor stages and all other parts conveniently within a single small package. Boosting your FM transmitter has never been easier and the output signal can also directly drive 2n4427 or 2n3886 transistors for 1W or 5W of RF output power.
Posted on Saturday, June 12, 2010 • Category: FM Transmitters
This small FM transmitter includes a limiter, a microphone amplifier and a PLL digital tuning. All the parts are placed on one circuit board. The RF power is switchable between 1W and 0,2W.
The schematic diagram is divided into three parts: RF part (numbered from 1), PLL (numbered from 30) and audio part (numbered from 50).
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