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User’s Guide OctaMic XTC   

© RME

 

 

9. The Input Channel in Detail 

 

9.1 Gain 

 
The OctaMic XTC 

GAIN

 can be set in steps of 1 dB per channel. Setting the amount of amplifi-

cation is done digitally, therefore being very accurate and 100% reproducable. The gain change 
itself is performed within the analog domain. 
 
The range of the adjustable gain is 
65 dB. Additionally an attenuator 
(PAD) of -20 dB is available. The 
total gain range is therefore 85 dB. 
The TRS Line input gain range is 
shifted by about 9 dB. The AD-
converter in the OctaMic XTC 
reaches full scale already at an 
input level of –53 dBu (Gain 65 dB, 
XLR input), but also at +32 dBu 
(Gain 0 dB, PAD active). Therefore 
the inputs are both sophisticated 
microphone and line types. 
 
The picture to the right shows 
levels and gains in an overview and 
in relation to the different inputs. 
The instrument input has no PAD, 
and a gain range of 55 dB. 
 
XLR and TRS Line have a gain 
range of 55 dB in steps of 1 dB, 
and another step of 10 dB. 
Additionally a PAD of -20 dB with 
XLR and -18 dB with TRS Line is 
available. 
 
 

9.2 Phantom Power 

 
The LED 

+48V

 indicates activated phantom power for the XLR input. Phantom power should 

only be activated when using condenser microphones which require such a power supply. 
 

Connecting and disconnecting microphones while phantom power is active causes a high 
voltage surge, which can destroy the microphone input stage! Switch phantom power off 
before connecting/disconnecting any external device. 

 
The OctaMic XTC turns on the phantom power smoothly during one second, from 0 to 48 Volts. 
This technique is advantageous for the connected microphone as well as the OctaMic XTC. 
 
The phantom power of the OctaMic XTC is short-circuit proof. With a maximum load on all eight 
channels the internal voltage from the power supply does not drop below 47 Volts. 

 

Summary of Contents for OctaMic XTC

Page 1: ...hannel Microphone Line AD Converter 4 Channel Line Phones DA Converter 8 Channel Analog to AES ADAT Interface 64 Channel MADI Interface ADAT AES MADI Format Converter 24 Bit 192 kHz Digital Audio MIDI Remote Control USB 2 0 Class Compliant Operation 24 Bit Interface AutoSet SteadyClock QuickGain AES 3 AES 10 ...

Page 2: ...18 8 5 2 Setups Menu 20 8 6 Clock 21 9 The Input Channel in Detail 9 1 Gain 22 9 2 Phantom Power 22 9 3 AutoSet 23 9 4 Instrument Line 23 10 Using Multiple Units with MADI 10 1 Delay Compensation 24 10 2 Compensation ID 26 11 Remote Control 11 1 MIDI 26 11 2 MIDI over MADI 26 Inputs and Outputs 12 Analog Inputs Outputs 12 1 Mic Line In XLR 28 12 2 Line In TRS 28 12 3 Instrument In 28 12 4 Phones L...

Page 3: ... 21 3 Digital Outputs 46 21 4 Digital 46 21 5 MIDI 46 21 6 General 47 21 7 Firmware 47 21 8 MADI User Bit Chart 47 21 9 Connector Pinouts 48 22 Technical Background 22 1 Terminology 50 22 2 Lock and SyncCheck 51 22 3 Latency and Monitoring 52 22 4 DS Double Speed 53 22 5 QS Quad Speed 53 22 6 AES EBU SPDIF 54 22 7 Signal to Noise ratio in DS QS Operation 55 22 8 MADI Basics 56 22 9 SteadyClock 57 ...

Page 4: ...isture 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 t turn on before the device has reached room temperature Installation Surface may become hot during operation ensure sufficient ventilation Avoid direct sun light and do not place it near other so...

Page 5: ...User s Guide OctaMic XTC RME 5 User s Guide OctaMic XTC General ...

Page 6: ...f the following OctaMic XTC Power cord Manual 1 optical cable TOSLINK 2 m 3 Brief Description and Characteristics The OctaMic XTC is a full range hi end preamp and AD DA converter in reference quality fully remote controllable In a standard 19 box with 1 unit height the device offers numerous ex traordinary features like Intelligent Clock Control ICC SyncCheck SteadyClock QuickGain AutoSet MIDI ov...

Page 7: ...and a se lection of the signal source by encoder 2 The volume of Phones 1 2 is directly controlled by encoder 1 and 2 when the display shows the level meter overview The key GROUPS brings up the group screen Encoder 1 changes between Group All and Group 1 to 4 Encoder 2 changes all gains of the corresponding group simultaneously The key CHANNEL gives access to Pre Amp Gain Amount of amplification ...

Page 8: ...ur AES EBU outputs AD sig nals and four AES EBU inputs clock synchronization monitoring format conversion The 25 pin D sub connector is wired according to the widely spread Tascam standard pinout see chapter 13 1 The AES I Os are transformer coupled The high sensitivity type input accepts all common digital sources even SPDIF USB 2 0 Windows Firmware update Mac OS X Class Compliant audio interface...

Page 9: ...ching off and sets them automatically when switching on the next time The storing process is triggered 5 seconds after the last change 5 Accessories RME offers several optional components for the OctaMic XTC Part Number Description OK0050 Optical cable Toslink 0 5 m 1 7 ft OK0100 Optical cable Toslink 1 m 3 3 ft OK0200 Optical cable Toslink 2 m 6 6 ft OK0300 Optical cable Toslink 3 m 9 9 ft OK0500...

Page 10: ...f business drawn up by Audio AG apply at all times 7 Appendix RME news and further information can be found on our website http www rme audio com Distributor Audio AG Am Pfanderling 60 D 85778 Haimhausen Tel 49 08133 918170 Manufacturer IMM Elektronik GmbH Leipziger Strasse 32 D 09648 Mittweida Trademarks All trademarks and registered trademarks belong to their respective owners RME Hammerfall and...

Page 11: ...ser is encouraged to try to correct the interference by one or more of the following measures Reorient or relocate the receiving antenna Increase the separation between the equipment and receiver Connect the equipment into an outlet on a circuit different from that to which the receiver is connected Consult the dealer or an experienced radio TV technician for help RoHS This product has been solder...

Page 12: ...12 User s Guide OctaMic XTC RME ...

Page 13: ...User s Guide OctaMic XTC RME 13 User s Guide OctaMic XTC Usage and Operation ...

Page 14: ...ncoders The encoders can be turned endlessly but also pressed adding a key function Their current functionality is clearly shown in the display In general turning them either changes the current parameter or moves the selection cursor horizontally to the next page Pressing the encoders moves the selection cursor vertically up with 1 and down with 2 as indicated by the arrows in the display On the ...

Page 15: ...hannels are retained Group All Current group settings are ignored all 8 channels are affected by gain changes Group 1 to 4 The channels not assigned to any group are shown in light gray to the left channel number and right current gain The level meter is always active for all channels The OctaMic XTC has 8 channels therefore no more than 4 groups with 2 channels each can be defined The group assig...

Page 16: ... out activating AutoSet is then done in the Groups page To avoid shifts in panorama AutoSet should work ganged with stereo channels so that gain changes of one channel are also applied to the other one This function is part of the groups and thus available for up to 8 channels simultaneously This also means that for using ganged AutoSet a stereo pair like Mic1 2 has to be defined and activated exp...

Page 17: ...nd phase errors Mute Muting a channel Allows to remove a signal without the need to change the current gain Phones 1 and 2 has the following entries Volume Sets the output level from 64 dB up to 6 dB in steps of 1 dB Mute is also available Balance Adjustable from 1 left through 0 middle to 1 right Source Selection of the signal source Play 1 2 and 3 4 relate to software playback in Class Compliant...

Page 18: ...48 64 88 2 96 128 176 4 and 192 kHz Setting the correct sample rate is even necessary in slave mode with external clocking via word or one of the digital inputs Only with AES the real current sample rate can be detected With the other S MUX formats the user has to inform the unit whether the input signal is in the single double or quad speed range WCK Alw Singl Word Clock Always Single Speed Choic...

Page 19: ...l source of the ADAT output Choices are Mic 1 8 ADAT In AES In MADI In in groups of eight Playback 1 8 5 12 9 16 13 20 17 24 ADAT 2 Out See ADAT Out AES Out See ADAT Out MADI 1 8 etc See ADAT Out All eight 8 channel groups of the MADI output can be freely assigned to the above signal sources Recording Inputs 1 to 8 are fixed to the USB Class Compliant mode recoding channels 1 to 8 The Class Compli...

Page 20: ...e USB MIDI ports 1 or 2 Choices are USB1 USB2 MADI In DIN In Control Off The source Control means feedback response status data sent by the XTC MIDI DIN out Defines the source of the data sent to the MIDI DIN output Choices are USB1 USB2 MADI In DIN In Control Off The source Control means feedback response status data sent by the XTC MIDI ov MADI Defines the source of the data sent via MIDI over M...

Page 21: ...connected to it must be slave In order to avoid clicks and drop outs due to faulty or missing synchronicity a special process called SyncCheck compares the incoming data and the OctaMic XTC internal clock The sync state is indicated by a flashing error or constantly lit OK STATE LED A selection of Double and Quad Speed is also possible when using external clock Slave If the OctaMic XTC should oper...

Page 22: ...e different inputs The instrument input has no PAD and a gain range of 55 dB XLR and TRS Line have a gain range of 55 dB in steps of 1 dB and another step of 10 dB Additionally a PAD of 20 dB with XLR and 18 dB with TRS Line is available 9 2 Phantom Power The LED 48V indicates activated phantom power for the XLR input Phantom power should only be activated when using condenser microphones which re...

Page 23: ...both of these alternatives Thanks to the flexible threshold setting and easy manual correction of set values the OctaMic XTC is fit for all applications AutoSet can be activated in CHANNEL as well as on the gain pages brought up by the chan nel s SELECT key a push on encoder 1 and 2 activates AutoSet The label AS in the display changes from light gray to black With grouped channels the field AutoS...

Page 24: ...nits 2 and 3 are delayed by 6 and 3 samples respectively At Double Speed and Quad Speed the values rise Please note that in Double Speed no more than four in Quad Speed no more than two OctaMic XTC can be used serially with MADI Units Delay Delay DS Delay QS DC DC DS DC QS 2 3 6 12 21 18 12 3 6 12 21 18 4 9 18 21 18 5 12 21 6 15 21 7 18 21 8 21 21 Inputs and outputs are delayed in different ways W...

Page 25: ... to use several devices serially Simply set Delay Comp in all units to Auto CA quickly check the IDs in the display and you re ready to enjoy all channels within just one MADI cable and sample aligned 10 2 Compensation ID Default 1 Available settings 1 2 3 4 5 6 7 8 In Auto CA mode the ID defines the 8 channel group within the MADI signal that is used to insert the device s audio data ID 1 channel...

Page 26: ...I signal from the Control input to the Control output port This option is especially useful with serial MADI cabling as remote commands would otherwise get stuck already at the first unit within the MADI chain 11 2 MIDI over MADI MADI allows for a transmission of 64 audio channels over long distances with a single line perfect But what about MIDI Be it remote control commands or sequencer data in ...

Page 27: ...User s Guide OctaMic XTC RME 27 User s Guide OctaMic XTC Inputs and Outputs ...

Page 28: ...of con denser microphones The usage of a hi end integrated circuit PGA 2500 plus a fully symmetri cal signal path guarantees outstanding sound quality stunning low THD and maximum Signal to Noise ratio in any gain setting Due to the XTC s flexibility its signal to noise ratio is not easy to determine The EIN value is constant across a very wide amplification range typically 127 dBu at 150 Ohm inpu...

Page 29: ...d Low High equals an output level of 17 dBu at 0 dBFS Low a level of 4 dBV 4 2 dBu They can thus also be used as high quality yet unbalanced line outputs Setting the output level i e the monitoring volume is done directly by turning the encoder knob 1 Phones cannel 1 2 and 2 Phones channel 3 4 Changing the monitoring volume is there fore very easy and quickly done In case the outputs should operat...

Page 30: ...at Professional Category General Generation not indicated 2 Channel No Emphasis Aux bits audio use 24 bit Origin HDSP Connecting devices with coaxial SPDIF ports to the OctaMic XTC outputs is ac complished by simple cable adapters XLR RCA To achieve this pins 2 and 3 of an XLR plug are being connected to the two contacts of a Phono RCA plug The ground shield of the cable is only connected to pin 1...

Page 31: ...aMic XTC auto matically activates Sample Split mode S MUX at 88 2 and 96 kHz distributing the data of one channel to two output channels The internal frequency stays at 44 1 48 kHz Therefore the sample clock at the ADAT outputs is only half the frequency of the AES outputs As interesting as this is you don t need to think about it 96 and 192 kHz capable ADAT hardware like all current RME digital i...

Page 32: ...f the MADI output signal is also done in the MADI Settings menu MADI Format sets the format to 56 or 64 channels MADI Frame sets the format to 48k Frame or 96k Frame when operating at 88 2 and 96 kHz Sample rates higher than 48 kHz can be transmitted with the standard 48k Frame as well but then there is no automatic detection of the real sample rate This is the main advantage of the 96k Frame but ...

Page 33: ...User s Guide OctaMic XTC RME 33 ...

Page 34: ...XTC s word clock output is constantly active providing the current sample fre quency as word clock signal In master mode the word clock will be fixed to 44 1 kHz or 48 kHz DS x 2 QS x 4 In any other case the sample rate is identical to the one present at the cur rently chosen clock input When the current word clock source fails the last valid sample rate will be held automatically Selecting the op...

Page 35: ...ock is not only the great problem solver 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 the device using a spe cial PLL to about 11 2 MHz This signal then replaces the one from the quartz crystal Big disadvantage because of the high multiplication fa...

Page 36: ...y all outputs of word 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 when the 75 Ohms are built into the device and cannot be switched off In this case the network load is often 2 x 75 Ohms and the user is forced to buy a special word clock distributor...

Page 37: ...User s Guide OctaMic XTC RME 37 User s Guide OctaMic XTC Class Compliant Mode ...

Page 38: ...ument inputs 2 hi power headphone outputs and all common digital interface ports ADAT AES and MADI All this can be used with up to 24 channels in and out simultaneously Everything is available fully digital via USB in uncompromised quality with up to 192 kHz and 24 bit And of course a Sysex capable double MIDI I O Note that since iOS 5 multichannel recording is supported and since iOS 6 multichann...

Page 39: ...e tested adapters would not work at all others only with short cables and only one adapter came close to the quality of the original But as soon as 8 channel recording or 96 kHz playback was initiated the Apple Kit always performed much better We also recommend the purchase of a dock to dock extension cable to avoid having the CCK attached to the iPad directly with the heavy USB cable hanging down...

Page 40: ...ted as normal audio device but is not available for WDM or ASIO operation Mac OSX supports USB Audio 2 0 even with more than 2 channels The XTC offers 24 input and 24 output channels at up to 96 kHz but can also be used in a resource saving 8 channel mode with up to 192 kHz Alsa Linux does not work with USB 2 Class Compliant interfaces at this time but it seems it can be fixed recompiled to do so ...

Page 41: ...o outputs Phones 1 Phones 2 ADAT AES and MADI menu Digital Routing In slave mode with external clock the XTC and with it the iPad will be synchronized to an external digital sample rate if there is a valid digital input signal With a wrong sample rate heavy audio noise will occur Without any digital input signal the XTC stays in master mode The current sample rate is the one set by Mac OS X or iOS...

Page 42: ...42 User s Guide OctaMic XTC RME ...

Page 43: ...User s Guide OctaMic XTC RME 43 User s Guide OctaMic XTC Technical Reference ...

Page 44: ...dB up to 65 dB in steps of 1 dB PAD 18 dB Maximum input level Gain 0 dB 21 dBu Maximum input level Gain 0 dB with PAD 39 dBu Maximum input level Gain 65 dB 44 dBu Signal to Noise ratio SNR Gain 10 dB 113 dB RMS unweighted 117 dBA Inst TRS In 5 8 Input 6 3 mm TS jack unbalanced Input impedance 800 kOhm Hi Z Gain range 10 dB up to 65 dB in steps of 1 dB Maximum input level Gain 10 dB 21 dBu Maximum ...

Page 45: ... Jitter when synced to input signal 1 ns Jitter suppression 30 dB 2 4 kHz Word Clock BNC not terminated 10 kOhm Optional internal termination 75 Ohm Automatic Double Quad Speed detection and internal conversion to Single Speed SteadyClock guarantees super low jitter synchronization even in varispeed operation Not affected by DC offsets within the network Signal Adaptation Circuit signal refresh th...

Page 46: ...duplex SC connector 62 5 125 and 50 125 compatible Cable length optical up to 2000 m Generates 56 channel and 64 channel mode and 96k frame Single Wire up to 64 channels 24 bit 48 kHz Double Wire 96k frame up to 32 channels 24 bit 96 kHz Quad Wire up to 16 channels 24 bit 192 kHz 21 4 Digital Clocks Internal AES In ADAT In word clock In MADI In Low Jitter Design 1 ns in PLL mode all inputs Interna...

Page 47: ...ternally based on programmable logic By re programming of a little component called Flash PROM both function and behaviour of the unit can be changed at any time At the time of writing this manual the unit is shipped with firmware 21 35 The firmware version is displayed after power on for about one second on the display and listed in the menu SETUP Options General Settings SW Version Firmware Upda...

Page 48: ...sure that the connectors are clearly labelled with Tascam and Ya maha The cable can only be used when the Tascam side is connected to a Tascam connector and the Yamaha side is connected to a Yamaha connector Yamaha 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 1 14 2 15 3 16 4 17 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 5 18 6 19 7 20 8 21...

Page 49: ...e GND TS jacks analog input 5 8 Inputs 5 to 8 are unbalanced Tip hot Ring n c not connected Sleeve GND TRS Phones jack The analog monitor outputs on the front are accessible through stereo 1 4 TRS jacks This allows a direct connection of headphones In case the output should operate as Line output an adapter TRS plug to RCA phono plugs or TRS plug to TS plugs is required The pin assignment follows ...

Page 50: ...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 D...

Page 51: ...e rate is generated internally and thus slightly higher or lower than the XTC s internal sample rate Result When reading out the data there will frequently be read errors that cause clicks and drop outs Also when using multiple inputs a simple LOCK is not sufficient The above described problem can be solved elegantly by setting the OctaMic XTC from internal clock to MADI In its internal clock will...

Page 52: ...µs Oversampling 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 plus digital filtering in order to move the error prone analog filters away from the au dible frequency range as far as possible This typically generates a delay of about 40 samples equalli...

Page 53: ...ld 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 devices which can t handle more than 48 kHz e g digital tape recorders But also other common interfaces like ADAT or TDIF are still using this technique Because the ADAT interface does not allow for samp...

Page 54: ...n principle 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 of the first byte 0 is shown for both formats The first bit already determines whether the following bits should be read as Professional or Consumer information Byte Mode Bit 0 1 2 3 4 5 6 7 0 Pro...

Page 55: ... This can be verified with RME s DIGICheck The function Bit Statistic Noise measures the noise floor by Limited Bandwidth ignoring DC and ultrasound The reason for this behaviour is the noise shaping technology of the analog to digital convert ers They move all noise and distortion to the in audible higher frequency range above 30 kHz That s how they achieve their outstanding performance and sonic...

Page 56: ...d 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 networ...

Page 57: ...dyClock 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 resolution of 125 MHz within the format Common jitter values for other devices are 5 ns while a very good clock will have less than 2 ns The picture to the right shows the MADI input signal with 80 ns of jitter ...

Page 58: ...58 User s Guide OctaMic XTC RME 23 Block Diagram ...

Page 59: ...l parameter data bytes Message type is set to 30h Set Parameter Sets any number of parameters mm nn can be repeated freely Request Level Meter Data Format F0 00 20 0D 69 dev ID 11 F7 This string triggers a dump of the level meter data 0xf0 0x00 0x20 0x0d 0x69 MIDI device ID command ID parameter index parameter LSB parameter MSB set flags 0xf7 multiple parameters per message allowed each consisting...

Page 60: ...Settings x x s d 11 Phones 2 Volume x x n a 12 Phones 2 Balance x x n a 13 Phones 2 Settings x x s d 14 Digital Routing ADAT Out ADAT2 Out see Details below x x s d 15 Digital Routing AES Out x x s d 16 Digital Routing MADI 1 8 MADI 9 16 x x s d 17 Digital Routing MADI 17 24 MADI 25 32 x x s d 18 Digital Routing MADI 33 40 MADI 41 48 x x s d 19 Digital Routing MADI 49 56 MADI 57 64 x x s d 20 Digi...

Page 61: ...c 5 6 x n a 29 Level Meter Mic 7 8 x n a 30 Level Meter Phones 1 x n a 31 Level Meter Phones 2 x n a Details Channel Settings Mic Flag LSB Bit 0 5 Gain 0 0dB 1 10dB 56 65dB 0x01 Bit 6 Phase Invert 0x02 MSB Bit 0 Mute 0x04 Bit 1 AutoSet 0x08 Bit 2 48V 0x10 Bit 3 Pad Channel 1 4 Instrument Channel 5 8 0x20 Bit 4 6 Group 0 off 1 4 group 0x40 Phones Volume LSB Bit 0 3 1 10 dB of Volume dB 65 0 n a MSB...

Page 62: ...14 MADI 15 MADI 16 MADI 9 10 MA 11 12 MA 13 14 MA 15 16 64 MADI 17 MADI 18 MADI 19 MADI 20 MADI 21 MADI 22 MADI 23 MADI 24 72 MA 17 18 MA 19 20 MA 21 22 MA 23 24 MADI 25 MADI 26 MADI 27 MADI 28 80 MADI 29 MADI 30 MADI 31 MADI 32 MA 25 26 MA 27 28 MA 29 30 MA 31 32 88 MADI 33 MADI 34 MADI 35 MADI 36 MADI 37 MADI 38 MADI 39 MADI 40 96 MA 33 34 MA 35 36 MA 37 38 MA 39 40 MADI 41 MADI 42 MADI 43 MADI ...

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