Ton Giesberts
About the article

S/PDIF output

For OSCAR and other digital audio-equipment

S/PDIF output
The standard MP3 CD player is not provided with an S/PDIF-output that would have enabled the transmission of digital audio signals to other equipment. With the aid of this circuit, designed around an IC from Crystal, an optical and coaxial S/PDIF signal is generated from a kind of I2S signal in the OSCAR MP3-player.Althoiugh the OSCAR MP3 player is fitted with analogue audio outputs that may be connected to other hi-fi equipment or the line input of a sound card, it would be easier and less lossy to transfer the signal in digital form to another piece of equipment with digital input, especially when recording tracks using, for instance, a DAT- or MD-recorder.As standard, OSCAR does not possess an output that provides a digital audio signal in usable form. However, on the main circuit board is a connection that provides digital audio data in a ‘raw’ format. This signal must first be correctly encoded with additional information bits and then transmitted with the correct bi-phase modulation and amplitude.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1 = 8 x 10k? resistor array
R2 = 10k?
R3,R5 = 270?
R4,R6 = 75?
R7 = 8k?2
R8 = 4?7
R9 = 4 x 10k? resistor array
C1 = 22µF 40V radial
C2,C3 = 47nF
C4,C6,C7,C8 = 100nF ceramic
C5 = 47µF 25V radial
L1 = 47 µH choke
IC1 = CS8402A-CP (Crystal)
IC2,IC3 = 74HCT74
IC4 = TOTX173 (Toshiba)
JP1 = 3-way pinheader + jumper
JP2 = 2 x 3-way pinheader + jumper
K1 = 10-way boxheader
K2,K3 = cinch socket, PCB mount (e.g., T-709G from Monacor/Monarch)
S1 = 8-way DIP switch
S2 = 4-way DIP switch
TR1 = ferrite ring core, Philips type TN13/7,5/5-3E25, primary 20 turns, secondary 2 x 2 turns, lacquered wire 0.5 mm dia.
PCB, order code 000131-1
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