U1a operates as a low-noise microphone preamp. Its gain is only about 3.9 because the high output impedance of the drain of the FET inside the electret microphone causes U1a’s effective input resistor to be about 12.2K. C2 has a fairly high value in order to pass very low frequency (about 20 to 30Hz) heartbeat sounds.... Read more »
Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types... The output power is around 60W.... Read more »
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.... Read more »
The circuit is based around Monolithic Linear SANYO integrated circuit LA3600 to create a low noise and completely high quality 5-band graphic equalizer which can be used for any portable tape recorders, component stereos, radio cassette recorders, car stereos, etc.... Read more »
The project is based around the hybrid integrated circuit STK4050 manufactured by Sanyo to build a low noise mono audio amplifier with complete high quality.... Read more »
Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components, which you find at home. The and transistors can be any NPN type power transistor, but do not use Darlington types... The output power is around 60W.
The circuit is based around Monolithic Linear 
