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User’s Guide DMC-842

 © RME

49

 

19.7 MADI Basics 

 
MADI, the serial 

M

ultichannel 

A

udio 

D

igital 

I

nterface, has been defined already in 1989 as an 

extension of the existing AES3 standard following several manufacturers' wish. The format also 
known as AES/EBU, a balanced bi-phase signal, is limited to two channels. Simply put, MADI 
contains 28 of those AES/EBU signals in serial, i. e. after one another, and the sample rate can 
still even vary by +/-12.5%. The limit which cannot be exceeded is a data rate of 100Mbit/s. 
 
Because an exact sampling frequency is used in most cases, the 64 channel mode was intro-
duced 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. The effective 
data rate of the port is 125 Mbit/s due to additional coding. 
 
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. The rest is being eaten 
up by control commands for mixer settings etc.. The ADI-6432 shows that this can be done in a 
much better way, with an invisible transmission of 16 MIDI channels plus serial RS232 data 
stream, and the 64-channel MADI signal still being 100% compatible. 
 
For the transmission of the MADI signal, proved methods known from network technology were 
applied. Most people know unbalanced (coaxial) cables with 75 Ohms BNC plugs, they are not 
expensive and easy to get. The optical interface is much more interesting due to its complete 
galvanic separation, but for many users it is a mystery, because very few have ever dealt with 
huge cabinets full of professional network technology. Therefore here are some explanations 
regarding 'MADI optical'. 
 

  The cables used are standard in computer network technology. They are thus not at all 

expensive, but unfortunately not available in every computer store. 

 

 

The cables have an internal fibre of only 50 or 62.5 µm diameter and a coating of 125 µm. 

They are called network cables 62.5/125 or 50/125, the former mostly being blue and the lat-
ter mostly being orange. Although in many cases not clearly labeled, these are always (!) 
glass fibre cables. Plastic fibre cables (POF, plastic optical fibre) can not be manufactured in 
such small diameters. 

 

 

The plugs used are also an industry standard and called SC. Please don't mix them up with 

ST connectors, which look similar to BNC connectors and are being screwed. Plugs used in 
the past (MIC/R) were unnecessarily big and are not being used any longer. 

 

 

The cables are available as a duplex variant (2 cables being glued together) or as a simplex 

variant (1 cable). The ADI-6432's optical module supports both variants. 

 

 

The transmission uses the multimode technique which supports cable lengths of up to al-

most 2 km. Single mode allows for much longer distances, but it uses a completely different 
fibre (8 µm). By the way, due to the wave-length of the light being used (1300 nm), the opti-
cal signal is invisible to the human eye. 

 

Summary of Contents for DMC-842

Page 1: ...terface with Line Outputs 8 Channel AES to Analog ADAT Interface AES EBU Format and Sample Rate Conversion Optional 64 Channel MADI Interface 24 Bit 192 kHz Digital Audio MIDI Remote Control 24 Bit In...

Page 2: ...el in Detail 9 1 General 16 9 2 Gain 16 9 3 Digital Phantom Power 16 9 4 Mode 2 17 9 5 Stereo Inactive 17 9 6 M S Processing 17 9 7 SRC 18 9 8 PAR 18 9 9 Sync 18 10 The Setup Men 10 1 General 19 10 2...

Page 3: ...on and Background 37 16 3 Cables and Termination 38 17 MIDI 38 Technical Reference 18 Technical Specifications 18 1 Analog 40 18 2 Digital Inputs 40 18 3 Digital Outputs 41 18 4 Digital 41 18 5 MIDI 4...

Page 4: ...re and water from entering the device Never leave a pot with liquid on top of the device Do not use this product near water i e swimming pool bathtub or wet basement Danger of condensation inside don...

Page 5: ...User s Guide DMC 842 RME 5 User s Guide DMC 842 General...

Page 6: ...and Characteristics The DMC 842 is an 8 channel interface for AES42 digital microphones with full remote control lability and optional MADI I O In a standard 19 box with 2 unit height the device offe...

Page 7: ...ands for the Parameter settings mode see below Pushing the knob SET several times lets you access all functions consecutively The rotary encoder is a highly intuitive multifunctional device It is used...

Page 8: ...see chapter 18 9 The AES I Os are transformer coupled ADAT OUT TOSLINK Optical ADAT outputs These provide the same signals as the AES EBU outputs but in ADAT format WORD IN BNC A push switch allows to...

Page 9: ...responding LEDs are flash ing Pressing once all GAIN displays start flashing gain setting pressing twice selects all DPP then STEREO and so on To activate or deactivate a specific function per channel...

Page 10: ...nformation can be found on our website http www rme audio com Distributor Audio AG Am Pfanderling 60 D 85778 Haimhausen Tel 49 08133 91810 Manufacturer IMM Elektronik GmbH Leipziger Strasse 32 D 09648...

Page 11: ...t in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own ex pense RoHS This product has been soldered lead free an...

Page 12: ...12 User s Guide DMC 842 RME...

Page 13: ...User s Guide DMC 842 RME 13 User s Guide DMC 842 Usage and Operation...

Page 14: ...stands for the Parameter settings mode see chapter 11 Setting the GAIN can be done in two ways Individually Hit the SELECT button of one or several channels The corresponding GAIN displays start flas...

Page 15: ...clock at 44 1 kHz or 48 kHz DS QS With the DS LED additionally lit the sample rate will be 88 2 or 96 kHz with QS lit it will be 176 4 or 192 kHz A selection of DS and QS is also possible when using...

Page 16: ...B in steps of 1 dB The device has its own gain control operational even in the asynchronous Mode 1 and as shown in the block diagram is placed in front of the SRCs When the microphone signals support...

Page 17: ...TIVE LED lights up automatically The gain can not be set directly for inactive channels Therefore in Stereo mode the gain display of the right channel is turned off 9 6 M S Processing The DMC 842 incl...

Page 18: ...vices CD players DAT machines etc can be used in a setup of digital devices just as if they were externally synchronized The SRC decouples input and out put clock sets the output clock to the common r...

Page 19: ...sed to insert the device s audio data ID 01 channels 1 8 ID 02 channels 9 16 ID 03 channels 17 24 ID 04 channels 25 32 ID 05 channels 33 40 ID 06 channels 41 48 ID 07 channels 49 56 ID 08 channels 57...

Page 20: ...on has to be manually activated in each unit The following table lists the delay in samples from two up to eight units connected serially When using four units the data of the first unit are delayed b...

Page 21: ...ADAT and MADI at sample rates in the Double Speed and Quad Speed range is only possible when all units are synced by Single Speed word clock Because of the S MUX method the device else can not know wh...

Page 22: ...received from the microphone When this feature is supported the DMC 842 switches off its gain control The choice can also be done manually Selecting the setting 42 AES42 the gain stage of the micropho...

Page 23: ...computer The Parameter menu includes a direct display only for the most important functions The others are configured by a combination of command byte and parameter byte based on the table found in t...

Page 24: ...control Such a function can be useful to prevent gain changes where audio should stop but the gain should stay unchanged or to dim the level meters of unused channels 11 5 Peak Limiter LImItEr Defaul...

Page 25: ...Command Processor and the MIDI outputs This MIDI Through function pro vides the base for a simplified serial MIDI cabling when using multiple DMC 842s The same is true for remote control via MADI wher...

Page 26: ...e combination with a HDSP e MADI PCI card offering a direct control of the DMC 842 via MADI The remote control software then uses a virtual MIDI port of the card port 3 which directly sends and receiv...

Page 27: ...de 2 display Activation of DPP SRC Stereo odd channels only and M S The channel name can be edited Gain setting Setting the Directivity Pattern Choice of Mute and Phase Inversion Selection of the Pre...

Page 28: ...l interface port Please note that this port is with out functionality at this time and reserved for future upgrades The functionality of a RS232 extender pass through of the serial data via MADI as kn...

Page 29: ...User s Guide DMC 842 RME 29 User s Guide DMC 842 Inputs and Outputs...

Page 30: ...s the clock on the AES wire In case a conversion from to Single Double and Quad Wire is required the ADI 192 DD an 8 channel universal sample rate and format converter is highly recommended Emphasis A...

Page 31: ...yright Copy permitted Format Professional Category General Generation not indicated 2 Channel No Emphasis Aux bits audio use 24 bit Origin DMC8 Connecting devices with coaxial SPDIF ports to the DMC 8...

Page 32: ...AES outputs As interesting as this is you don t need to think about it 96 kHz capable ADAT hardware like all current RME digital interfaces re combine the data automatically The user and the DAW soft...

Page 33: ...etermining the block of eight channels used by an individual device is determined automatically Auto ID or manually in the setup menu ID ID 01 channels 1 8 ID 02 channels 9 16 ID 03 channels 17 24 ID...

Page 34: ...activated in each unit ADI 642 Activate ADC Auto Delay Compensation in the first unit ID of the master is always 1 All following units become Slave and compensate the respective delay automatically T...

Page 35: ...13 13 dBu 14 dB The DMC 842 delivers an undistorted maximum level of 27 dBu The referencing is based on full scale of the DA converters 0 dBFS will be reached at 13 19 or 24 dBu output level respectiv...

Page 36: ...position and the yellow LED lights up Another push will release it again and de activate the termination Output The DMC 842 s word clock output is constantly active providing the current sample freque...

Page 37: ...er it also has some disadvantages The word clock is based on a fraction of the really needed clock For example SPDIF 44 1 kHz word clock a simple square wave signal has to be multiplied by 256 inside...

Page 38: ...rd clock delivering devices are designed as low impedance types but all word clock inputs as high impedance types in order to not weaken the signal on the chain But there are also negative examples wh...

Page 39: ...User s Guide DMC 842 RME 39 User s Guide DMC 842 Technical Reference...

Page 40: ...Level range 1 0 Vpp 5 6 Vpp Lock Range 27 kHz 200 kHz Jitter when synced to input signal 1 ns Jitter suppression 30 dB 2 4 kHz I64 MADI Card Coaxial via BNC 75 Ohm according to AES10 1991 High sensit...

Page 41: ...Cable length coaxial up to 100 m Optical via FDDI duplex SC connector 62 5 125 and 50 125 compatible Cable length optical more than 500 m Generates 56 channel and 64 channel mode and 96k frame Single...

Page 42: ...firmware I64 MADI Cards with the latest firmware have a sticker with the firmware version date code on them 20070217 The firmware of the I64 MADI Card can be updated in the factory Please contact the...

Page 43: ...honix Signal In 1 2 In 1 2 In 3 4 In 3 4 In 5 6 In 5 6 In 7 8 In 7 8 D Sub 15 2 4 16 18 5 7 19 Signal Out 1 2 Out 1 2 Out 3 4 Out 3 4 Out 5 6 Out 5 6 Out 7 8 Out 7 8 D Sub 21 8 10 22 24 11 13 25 GND i...

Page 44: ...a 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...

Page 45: ...e rate is generated internally and thus slightly higher or lower than the DMC 842 s internal sample rate Result When reading out the data there will frequently be read er rors that cause clicks and dr...

Page 46: ...g While the delays of digital interfaces can be disregarded altogether the analog inputs and out puts do cause a significant delay Modern converter chips operate with 64 or 128 times over sampling plu...

Page 47: ...also work with double sample rate It was then possible to transmit two channels of 96 kHz data via one AES EBU port But Double Wire is still far from being dead On one hand there are still many devic...

Page 48: ...rinciple because the audio information is stored in the same place in the data stream However there are blocks of additional information which are different for both standards In the table the meaning...

Page 49: ...coaxial cables with 75 Ohms BNC plugs they are not expensive and easy to get The optical interface is much more interesting due to its complete galvanic separation but for many users it is a mystery b...

Page 50: ...eadyClock has originally been de veloped to gain a stable and clean clock from the heavily jittery MADI data signal The embedded MADI clock suffers from about 80 ns jitter caused by the time resolutio...

Page 51: ...User s Guide DMC 842 RME 51 20 Block Diagram...

Page 52: ...h channel 40h Request microphone data input 1 41h Request microphone data input 2 42h Request microphone data input 3 43h Request microphone data input 4 44h Request microphone data input 5 45h Reques...

Page 53: ...parameters AES42 commands are transmitted in groups of 4 Bytes nn1 nn2 oo1 oo2 Request Levelmeter Data Format F0 00 20 0D 42 Bank no dev ID 11 F7 This string triggers a shorter dump of only the level...

Page 54: ...7 Gain x x 0 63 0 63dB 1dB steps 0Dh 13 Ch 7 settings x x see channel settings table 0Eh 14 Ch 8 Gain x x 0 63 0 63dB 1dB steps 0Fh 15 Ch 8 settings x x see channel settings table 10h 16 Setup 1 x x...

Page 55: ...Hold 0 off 1 on LSB 0 Lock Keys 0 unlock 1 lock 12h Channel Lock Sync 1 MSB 7 0 6 reserved Request only 5 Input 2 RX AES42 0 Mode 1 1 Mode 2 Request only 4 Input 1 RX AES42 0 Mode 1 1 Mode 2 Request...

Page 56: ...nc 0 no sync 1 sync Request only LSB 0 Input 7 Lock 0 unlock 1 lock 16h Host Lock Sync MSB 7 0 6 reserved Request only 5 WCK Sync 0 no sync 1 sync Request only 4 WCK Lock 0 unlock 1 lock Request only...

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