Article
Coaxial S/PDIF Output
This circuit is an alternative to the optical S/PDIF output described elsewhere in this issue. The quality of the connection provided by this link is usually better than that of an optical link (less jitter). In order to avoid earth loops, a small output transformer is normally used for digital audio signals. The construction of such a transformer has been described several times in Elektor Electronics. It is based on a Philips toroidal core, with 20 turns on the primary and 2 turns on the secondary, both using 0.5-mm varnished copper wire.
Materials
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 the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
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PCB
Component list
Resistors:
R1 = 1M?
R2 = 220?
R3 = 75?
Capacitors:
C1,C3 = 100nF ceramic
C2 = 47nF ceramic
C4 = 47µF 25V radial
Inductor:
L1 = 47µH
Semiconductor:
IC1 = 74HC86
Miscellaneous:
K1 = 2-pin SIL header
K2 = cinch socket, PCB mount (e.g., Monacor/Monarch T-709G)
K3 = 4-pin SIL header
Tr1 = ferrite ring core Philips type TN13/7,5/5-3E25. Primary 20 turns, secondary 2 turns
R1 = 1M?
R2 = 220?
R3 = 75?
Capacitors:
C1,C3 = 100nF ceramic
C2 = 47nF ceramic
C4 = 47µF 25V radial
Inductor:
L1 = 47µH
Semiconductor:
IC1 = 74HC86
Miscellaneous:
K1 = 2-pin SIL header
K2 = cinch socket, PCB mount (e.g., Monacor/Monarch T-709G)
K3 = 4-pin SIL header
Tr1 = ferrite ring core Philips type TN13/7,5/5-3E25. Primary 20 turns, secondary 2 turns
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