Audio Kits
Infrared headphones receiver
Use this infrared headphones receiver with the ir headphones transmitter.
Use 600Ω headphones. BPW41N and BP104 have a filter for visible light and are centered on 950nm at 250C. At normal light illumination and 3 to 4 meters distance the audio distorsion were 1 - 2%, wich is not bad for such a simple ir headphones [...]
Infrared headphones transmitter
The transmitter offers a optical link (infrared) for headphones. Three infrared leds (ir) are polirised by T1 current, P1 is used to adjust the current level . Current consumption of this headphones infrared transmitter is about 60mA at 9V. Maintain separated adapter ground and audio signal ground to prevent current reactions thru LED.
The optical link [...]
Microphone amplifier with low noise
This low noise microphone amplifier is build with MAT02 produced by PMI. This mic amplifier is very performant and has a very low noise level. The amplification can be 20dB or 23.5dB (10x or 15x ) selected by S1.
The output impedance is 70 Ω at 23.5 dB gain and with R3 = 220KΩ the input [...]
