RME Audio ADI-642 Spécifications télécharger pdf (Page 22)

Single Speed Sample rate range originally used in Digital Audio. Typical applications are 32 kHz (digital radio broadcast),

44.1 kHz (CD), and 48 kHz (DAT).

Double Speed Doubles the original sample rate range, in order to achieve higher audio quality and improved audio

processing. 64 kHz is practically never used, 88.2 kHz is quite rare in spite of certain advantages. 96 kHz is

a common format. Sometimes called Double Fast.

Quad Speed Controversially discussed way of ensuring hi-end audio quality and processing by quadrupling the sample

frequency. 128 kHz is non-existent, 176.4 kHz is rare, if at all then 192 kHz is used, e.g. for DVD Audio.

Single Wire Standard audio data transfer, where the audio signal’s sample rate is equal to the rate of the digital signal.

Used from 32 to 192 kHz. Sometimes called Single Wide.

Double Wire Before 1998 there were no receiver/transmitter circuits available that could receive or transmit more than

48 kHz. Higher sample rates were transferred by splitting odd and even bits across the L/R channels of a

single AES connection. This provides for twice the data rate, and hence twice the sample rate. A stereo

signal subsequently requires two AES/EBU ports.

The Double Wire method is an industry standard today, however it has a number of diﬀerent names, like

Dual AES, Double Wide, Dual Line and Wide Wire. The AES3 speciﬁcation uses the uncommon term Single

channel double sampling frequency mode. When used with the ADAT format, the term S/MUX is commonly

used. Double Wire not only works with Single Speed signals, but also with Double Speed. As an example,

Pro Tools HD, whose AES receiver/transmitter only work up to 96 kHz, uses Double Wire to transmit 192

kHz. Four channels of 96 kHz turn into two channels of 192 kHz.

Quad Wire Similar to Double Wire, with samples of one channel spread across four channels. This way single speed

devices can transmit up to 192 kHz, but need two AES/EBU ports to transmit one channel. Also called Quad

AES.

S/MUX Since the ADAT hardware interface is limited to Single Speed, the Double Wire method is used for sample

rates up to 96 kHz, but usually referred to as S/MUX (Sample Multiplexing). An ADAT port supports four

channels this way.

S/MUX4 The Quad Wire method allows to transmit two channels at up to 192 kHz via ADAT. The method is referred

to as S/MUX4. Note: All conversions of the described methods are lossless. The existing samples are just

spread or re-united between the channels.

48K Frame Most often used MADI format. Supports up to 64 channels at up to 48 kHz.

96K Frame Frame format for up to 32 channels at up to 96 kHz. The advantage of this format against 48K Frame using

S/MUX: the receiver can detect the real (double) sample rate on its own and immediately. With 48K Frame

and S/MUX, the user has to set up the correct sample rate in all involved devices manually.

MADI 56/64-Channel Mode MADI, the serial Multichannel Audio Digital Interface, has been deﬁned already in 1989 as an extension of

the existing AES3 standard. MADI contains 28 AES/EBU signals (56 audio channels) in serial, and the sample

rate can vary by +/-12.5%. A data rate of 100Mbit/s cannot be exceeded. Because an exact sampling

frequency is used in most cases, the 64 channel mode was introduced oﬃcially in 2001. It allows for a

maximum sample rate of 48 kHz + ca. 1%, corresponding to 32 channels at 96 kHz, without exceeding the

maximum data rate of 100 Mbit/s. Older devices understand and generate only the 56 channel format.

Newer devices often work in the 64 channel format, but oﬀer still no more than 56 audio channels.

Terminology

42 Optical Fibres 43Technical Glossary

Optical bres have become a new standard.

Why glass fibre optics?

The need for huge data transmissions is constantly growing. In the

near future traditional twisted-pair copper cables will not meet

the requirements of ethernet networks. With Gigabit or 10 Gigabit,

traditional cables reach the physical limits. Only optical glass ﬁbres

will meet future transmission demands.

Advantages of Optical Fibre compared to Copper Cable:

- Insensitive to electromagnetic disturbance

- Optical cables can be run in parallel to power cables etc.

- No crosstalk, hum or potential diﬀerences

- No inﬂuence on audio quality also in long distance applications

- Signiﬁcantly less weight

Many manufacturers oﬀer optical cables and connectors, and even

complete road-ready systems with cable drums, with up to 2000

m in total length. Please ask your Premium Line dealer for the

supporting product line of RME-approved digital audio cables from

ALVA Cableware (www.alva-audio.com).

Multimode and Singlemode fibres

All RME MADI products provide optical I/Os for the use with

multimode ﬁbres. They consist of a core, a cladding and a primary

coating. The light-transmitting cable core is made of ﬁbres of glass,

and carries the actual signal. The coating totally reﬂects the light

and thus conducts it within the core.

The coating is a protective layer against mechanical damage and

is usually between 150 and 500 µm in thickness. Between the

cladding and the coating, there is a ﬁne layer of lacquer (2 to 5 µm)

to keep out moisture. The coating is usually made of soft plastic, but

special versions with extremely stable coatings are also available.

By now, optical cables can be manufactured cheaper than copper

based cables.

Singlemode transceivers are available on request for all units

and allow for an operation within existing singlemode networks,

without additional expensive converters.

Multimode ﬁbre example

- Diameter core: 50 µm or 62.5 µm

- Diameter wrap glass: 125 µm

- Max. transmission width: 2000 m

- Outside diameter: 4 - 9 mm

- Label: 50/125 (orange) or 62.5/125 (blue)

Connectors

Like most other MADI devices, the RME MADI products use the

common SC-Plug (IEC 874-19) for optical connection. The SC

connector is compact and ensures a reproducible and constant

connection quality.

The SC duplex version combines two ﬁbres. An automatic interlock

prevents accidental interruption of the connection.

The ﬁbre type, explicitly required for optical MADI connections,

must be a 50/125 µm or 62.5/125 µm multi-mode ﬁbre (MM ﬁbre).

MADI . Optical Fibres Requirements

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