Swahiliteknolojia

Introduction I want to build high quality preamplifier with built-in DAC from SPDIF or USB for my power amplifier  Leachamp . I had available circuit PCM2902. I tried to design DAC from USB with this circuit on one-sided PCB and I was succesful. Circuit description 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. Schematics diagram   schematics in Eagle Placement procedure After drilling holes for crystal, output pads and USB connector I placed integrated circuit PCM2

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Page 1 All the circuits and projects we describe in these articles consist of very important "building blocks" that you can add to other designs. This time we describe the concept of touching a plate (or two plates separated by a small gap) and turning a circuit ON or OFF. A TOUCH PLATE is classified as a high impedance device (or high impedance circuit) as the effect of a finger will be detected by the circuit connected to the plate. To learn more about the concept of high impedance circuits, see Page 77 of our Basic Electronics course. If only a single plate is present, the circuit will actually be picking up "mains hum" from the finger. To prove this, take the project into an open space such as a large park and try the circuit. It will not work. If the plate has a signal on it (from an oscillator), the effect of your finger will be to remove the signal (or reduce its amplitude considerably) and a detecting circuit will be activated. If the circuit has

Page 1 All the circuits and projects we describe in these articles consist of very important "building blocks" that you can add to other designs. This time we describe the concept of touching a plate (or two plates separated by a small gap) and turning a circuit ON or OFF. A TOUCH PLATE is classified as a high impedance device (or high impedance circuit) as the effect of a finger will be detected by the circuit connected to the plate. To learn more about the concept of high impedance circuits, see Page 77 of our Basic Electronics course. If only a single plate is present, the circuit will actually be picking up "mains hum" from the finger. To prove this, take the project into an open space such as a large park and try the circuit. It will not work. If the plate has a signal on it (from an oscillator), the effect of your finger will be to remove the signal (or reduce its amplitude considerably) and a detecting circuit will be activated. If the circuit has