Specifications

Mitsubishi (Melco) PD Interface
The Mitsubishi 2-track and multitrack interconnect formats are similar to the Sony SDIF format – but not enough
for direct compatibility. Like the Sony format, the Mitsubishi 2 track “DUB” connections are unbalanced,
although different in their ability to directly drive high speed optical isolators on the receiving end (for improved
ground isolation). The digital audio travels on separate lines along with a word clock line (at the sample rate)
and a bit clock line running at 48 times the sample rate. The bit clock runs in bursts, with silence in between,
resulting in the 32-bit time slots of a sample being compressed into a shorter duration than the full word clock
cycle. The Mitsubishi interconnect uses four lines for a stereo signal instead of Sony’s three. Its important that
all four run together as any timing skew with the bit clock, caused by different length runs, can result in errors
in the audio when it is decoded.
The multitrack version of the Mitsubishi interconnect is a little different. There are still four lines for a stereo
connection, except the lines are balanced and the bit clock operates continuously at a 32 times multiple of the
word clock. One full cycle of a sample transfer occupies 32 time slots spread evenly over one word clock cycle.
No emphasis identification is transmitted in the Mitsubishi Interface standard although Otari made modifica-
tions to handle emphasis in some of their PD format multi-track recorders. The interconnect can handle up to
20 bit sample, transmitted MS first. The word clock is a short pulse instead of the evenly spaced rise and fall of
the Sony clock.
Yamaha Interconnect
The Yamaha 2-track interconnect and its variations are like the missing link between the above formats and the
AES/EBU format. The Yamaha format uses balanced connections and two lines to transmit stereo audio. One
line carries the left and right samples transmitted with the least significant bit (LSB) first. The other line carries
a symmetrical word clock whose transitions coincide with the LSBs of the left and right samples. The stereo data
is transmitted over a single pair by taking the first half of the word clock cycle to send up to 24 bits of a left
sample, sitting in 32 times slots, followed by the companion right sample over the next 32 time slots. A total
64 time slots are transmitted for every word clock cycle. This two-line interconnect is also used to combine a
number of digital audio products together by cascading from one device to the next in an input to output
sequence. Each subsequent device then adds its output to the previous devices output.
ADAT, TDIF Other Interconnects
Several other multi-line digital interconnects exist. Some are proprietary, used to connect products from the
same manufacturer, while others are internal interconnects, sometimes adapted for connection to the outside
world by another specialty manufacturer. Two of the most common interconnects that are growing in impor-
tance are the Alesis ADAT optical and Tascam TDIF 8-track interconnects. These formats were developed specif-
ically for their respective modular digital multitrack (MDM) systems. The ADAT uses an optical format in which
the physical transmitters and receivers are the same as for TosLink S/PDIF (which is why the AD-1000 can han-
dle both with the same connector); however the format carries all eight channels rather than just two. As a
result, the AD-1000 repeats its two channels across the eight channels in the ADAT (the first AD-1000 channel
appears on the od-numbered tracks, while the second appears on the even tracks). Tascam’s TDIF interface is a
bi-directional multi-line interface using a DB25 connector. It also carries eight-track information.
AES/EBU Interface
AES/EBU, AES3-1985, ANSI S4.40-1985, AES3-1992, EBU Tech.3250- E.CCIR Rec.647 (1986), CCIR Rec.647
(1990) Confused? Well, don’t be. These are different standards are lumped together and called AES/EBU, the
connection designed to standardize plugging one digital box to another. AES is the Audio Engineering Society
and EBU is the European Broadcasting Union. These organizations and others have worked very hard to bring
us a standard method of sending professional digital audio across a single interconnect with maximum com-
patibility. Generally the approach work well as long as the potential weaknesses are kept in mind when string-
ing things together. A better understanding of how two channels of digital audio flow across a single connec-
tion helps highlight the pitfalls.
Electrically, the AES/EBU signal is tailored to use microphone-type cable, although in fact the bandwidth is a
good deal wider than regular mic cable can handle successfully. Microphone cable normally carries analog audio
AD-1000 Operating Manual
Page 53