Circuit Lake

This is a simple and low cost desktop headphone amplifier for the office. The amplifier concept is simple and follows a typical single-ended class A circuit utilizing an active constant current source (CCS) in place of a passive resistor. A CCS doubles the efficiency of the circuit over that where a passive load resistor is used, bringing it to a maximum of 25%. (more…)

This circuit is for detecting any audio signal with justable noise offset. It could be used to generate a radio mute signal eg. from a PDA.

The circuit is consisting of: (more…)

I want to build high quality preamplifier with built-in DAC from SPDIF or USB for my power amplifier Leachamp. I tried to design DAC from USB with this circuit on one-sided PCB and I was successful.

Schematics is from datasheet of PCM2902. Circuit includes DAC and ADC, SPDIF output and input and HID part with 3 buttons for MUTE, VOL+ and VOL-. I used only DAC part. Other parts are not used. For high quality playback is needed to use external low-drop voltage stabiliser for DAC part. I used LP2951CM which was available at local store. Output voltage is set to about 3.7V with two resistors. Circuit board is designed regarding to good ground placement and separating of analog and digital ground. These ground are connected in one point at USB connector.
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