Audio Engineering

574 Chapter 18

over an electrical interface that has much in common with the interconnection standards
employed in analogue video. Limitations of AES data traveling on twisted pairs and
terminated in XLRs include poor RF radiation performance and a limitation of maximum
transmission distance to 100 m. The proposed unbalanced interface is suitable for
transmission distances of up to 1000 m. Furthermore, by a prudent choice of impedance
and voltage operating level, coupled with a sensible specifi cation of minimum rise time,
the signal is suitable for routing through existing analogue video cables, switchers, and
distribution amplifi ers.

The salient parts of the signal and interface specifi cation are given in Table 18.1.

TOT     172

Optical

SPDIFlink

CoaxialSPDIF

link

BNC

R 3

Vcc

Vcc Vcc

TTL

levelSPDIF

signal

75 R

R 1

R 2

100 R

330 R

TTL level signal

SPDIF data format

TOR     172

ELECTRIC PERCEPTION LTDEMAIL: 100601,[email protected]

Title OPTICAL/COAXIAL SPDIF LINKS

Size

A

Document Number

C:\ORCAD\DRWNGS\OPTO.SCH

Date: March 20, 1999 Sheet of

REV

Figure 18.5 : Optical digital audio interface and adaptation to coaxial SPDIF.