Description

This is a circuit that will add an SPDIF (Sony / Philips Digital InterFace) digital output to a DBS IRD. A Crystal CS8402A chip is used to convert the audio decoder digital data to the SPDIF format. The output is 48 kHz, two channels - suitable for use with a DAC or digital Dobly ProLogic decoder. This circuit will not provide Dolby Digital (AC-3) output.

Why?

I built this to connect my 2nd generation Uniden UDS-100 DSS IRD to my new Denon AVD-2000 digital surround processor. (The AVD-2000 has no analog inputs) This allowed me to retire the NEC PLD-910 Doby ProLogic decoder I have been using for the past 10 years.

Warning!

Do not attempt to build this if you have no experiance building electronic prototypes. Do not build this if you do not understand how it works and how to connect it to the IRD PCB.

IRD Connections

Seven connections to the IRD PCB are used. Keep all leads as short as possible.

Recommended Reading

Design Compromises

The SPDIF output does not use a transformer, so there is no ground loop isolation. The output resistor divider network provides voltage level and impedance that is very close to the SPDIF spec.

Schematic

Schematic in Abobe Acrobat (PDF) format

Top of circuit board Bottom of circuit board Jacks
Top of circuit board Bottom of circuit board SPDIF output RCA jack Installation in a Hughes E-11

© 2000 Kevin Timmerman