Handbook for Sound Engineers

1472 Chapter 39

An AES3 receiver must correctly interpret data when
a random data signal that is not less than Vmin= 200 mV
and Tmin=0.5Tnom, as shown in Fig. 39-10, is applied to
the receiver.

If cable lengths of over 100 m are to be used,
optional receiver equalization may be applied. The
amount of equalization needed depends on the cable
characteristics, length, and the frame rate of the AES3
signal. The AES3 Standard suggests that at a 48 kHz
frame rate an equalizer with a boost that rises to a
maximum of 12 dB at 10 MHz would be appropriate.
The receiver must introduce no errors due to the
presence of common mode signals as large as 7 Vp at
any frequency from dc to 20 kHz. This is not enough

range to protect an AES3 receiver from the application

of 10 Vdc digital phantom power as specified in the

AES42 (AES3-MIC) Digital Interface for Microphones

Standard.

The receiver must introduce no data errors from jitter

that does not exceed 10 unit intervals (UI) at frequen-

cies below 200 Hz decreasing to not exceeding 0.25 UI

at frequencies over 8 kHz. Of course the recovered

clock from such a high jitter signal may cause other

problems, but at least the data must be decoded

correctly.

39.3.7 AES3 Connectors

The connector for AES3 signals is what is commonly

called the XLR, and is standardized in IEC 60268-12 as

the circular latching 3 pin connector. Outputs are on

male connectors and inputs are on female connectors

just as in common analog usage of this same connector.

The shield or ground connection is on pin 1, and the

signal connections are on pins 2 and 3. With AES3

digital signals, the relative polarity of pins 2 and 3 is

unimportant.

To avoid confusion with analog audio signal connec-

tors, AES3 suggests that manufacturers label AES3

outputs “digital audio output,” or “DO;” and AES3

inputs “digital audio input,” or “DI.”

An alternative modified XLR connector has been

proposed to help make clear that the signal on the

connector is digital and not analog, and via a keying

scheme reducing the chances of accidental interfacing

of inputs and outputs that are incompatible. There has

been much discussion in the AES about changing to this

Figure 39-9. Benchmark Media Systems DAC-104 is a four channel 24 bit 96 kHz sampling rate D/A converter. An example
of a high performance D/A, it provides jitter reduction of 100 dB at 1 kHz and 160 dB at 10 kHz. Total harmonic distortion
plus noise (THD+N) is less than 0.00079% at –3 dB FS at any sampling rate and test frequency.

Figure 39-10. AES3 eye diagram. Tnom = 0.5 unit interval
(UI) (see Fig. 39-5); Tmin = 0.5 Tnom; Vmin = 200 mV. The eye
diagram is one of the most powerful tools used to examine
the quality of received data. The larger the open area of the
eye the better. The limits shown are the most closed an eye
should ever be for correct reception of the AES3 data.

Tmin

Tnom

Vmin