PCM2704 USB sound card

An very nice audio application circuit is the USB sound card that can be used with speakers or headphones . This USB mini sound card circuit is based on the PCM2704 circuit , manufactured by Texas Instruments . Also for this project you can use some other circuit similar with PCM2704 : PCC2705, PCM2706, PCM2707. Using this circuit you can build an very simple , high efficiency USB sound card that require few external components and has many features like : up to eight human interface device (HID) interfaces ,S/PDIF out with SCMS .

Maximum output power for 32 ohms headphones is around 12 mW, but if you want to connect a speaker that will provide much power you can connect an additional audio amplifier .
The PCM2704 integrated circuit has an internal 5 and 3.3 volts voltage regulator so , you don’t need to use any external voltage regulator .

Because this circuit is powered from the USB port , you don’t need an external power source .
As you can see in the circuit diagram , at the output of the circuit is connected an additional amplifier , to drive two speakers, but you can eliminate this audio amplifier and connect an jack connector for headphones .

For this PCM2704 project you need : 12-MHz crystal resonator, C1 and C2 must be : 10-pF to 33-pF capacitor , C3-C7: 1-mF ceramic capacitor , C8 10-mF electrolytic capacito; C9 and C10: 100-mF electrolytic capacitor ; C11 and C12: 0.022-mF ceramic capacitor; C13 and C14 must be 1-mF electrolytic capacitor ;R1- 1 MΩ resistor. R2 and R9 are 1.5 kΩ resistors; R3 and R4 are 22 Ω resistors; R5 and R6 are 6 Ω resistors ;R7and R8 are 330 Ω resistors .
As you can see in the schematic circuit , this sound card circuit will provide volume control and muting function.