Users Guide

OctaMic II

SteadyClock

Professional Mic / Line Preamp and AD-Converter 8-Channel Microphone / Line Preamp with Line Outputs 8-Channel Analog to AES / ADAT Interface 24 Bit / 192 kHz Digital Audio

AES-Bit Interface

Important Safety Instructions..3

General

Introduction...6 Package Contents...6 Brief Description and Characteristics.6 Accessories...7 Warranty...8 Appendix...8

Usage and Operation

Front Panel Displays...12 Controls...Rear Panel 8.1 Connectors...13 8.2 DIP Switches...External Synchronization 9.1 Word Clock - BNC..14 9.2 ADAT Optical..14 7.1 7.2 7

Inputs and Outputs

Analog Inputs / Outputs 10.1 Mic / Line In...16 10.2 Line Out...Digital Outputs 11.1 AES / EBU..18 11.2 ADAT Optical..Word Clock 12.1 Technical Description and Background..20 12.2 Cables and Termination..21 10

Technical Reference

13 Technical Specifications 13.1 Analog...24 13.2 Digital Inputs...24 13.3 Digital Outputs..25 13.4 Digital..25 13.5 General...25 13.6 Connector Pinouts..Technical Background 14.1 Terminology..28 14.2 DS Double Speed..29 14.3 QS Quad Speed..29 14.4 AES/EBU SPDIF..30 14.5 SteadyClock..Block Diagram..32
Users Guide OctaMic II RME
Important Safety Instructions
ATTENTION! Do not open chassis risk of electric shock The unit has non-isolated live parts inside. No user serviceable parts inside. Refer service to qualified service personnel.
Mains The device must be earthed never use it without proper grounding Do not use defective power cords Operation of the device is limited to the manual Use same type of fuse only
To reduce the risk of fire or electric shock do not expose this device to rain or moisture. Prevent moisture 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 sources of heat, like radiators or stoves. When mounting in a rack, leave some space between this device and others for ventilation.
Unauthorized servicing/repair voids warranty. Only use accessories specified by the manufacturer.
Read the manual completely. It includes all information necessary to use and operate this device.

1. Introduction

The OctaMic II's innovative concept allows for amplification and digitization of ALL analog signal sources. Be it high-level stage signals, typical studio signals, lower level and high-impedance instruments, or dynamic, condenser or ribbon microphones: OctaMic II understands them all in a way that is simply thrilling. When developing the OctaMic II we used all our experience, and also the experience of our customers, to create a unique, excellent and high-quality unit. As successor of the OctaMic D the device offers the approved quality of its predecessor, adding lots of improvements in detail.

2. Package Contents

Please check that your OctaMic II package contains each of the following: OctaMic II Power cord Manual 1 optical cable (TOSLINK), 2 m
3. Brief Description and Characteristics
8 balanced XLR/TRS mic/line inputs 54 dB gain range Analog input level from 40 dBu up to +21 dBu Large frequency range (200 kHz) with special EMI input filtering Input impedance: XLR 2 kOhm, TRS 5 kOhm Signal to noise ratio (SNR): 129 dB EIN @150 Ohm THD: < 0.0005 % @ 30 dB Gain Channel separation: > 110 dB Frequency response 0.5 dB: 5 Hz - 200 kHz Line Out: 1/4" TRS (6.3 mm stereo jack), servo-balanced Maximum output level: +21 dBu Output impedance: 75 Ohm Output level switchable Hi Gain / +4 dBu / -10 dBV Word clock input 4 x AES/EBU Out per D-sub, 8 channels @ 192 kHz 2 x ADAT Out, 8 channels @ 96 kHz SNR ADC: > 110 dBA Sample rate range ADC: 28 kHz 200 kHz THD AD: < 0.00032 %, < -110 dB

4. Accessories

RME offers several optional components for the OctaMic II: Part Number OK0050 OK0100 OK0200 OK0300 OK0500 OK1000 Description Optical cable, Toslink, 0.5 m Optical cable, Toslink, 1 m Optical cable, Toslink, 2 m Optical cable, Toslink, 3 m Optical cable, Toslink, 5 m Optical cable, Toslink, 10 m

BO25MXLR4M4F1PRO Digital Breakout Cable Pro, AES/EBU 25-pin D-sub to 4 x XLR male + 4 x XLR female, 1m BO25MXLR4M4F3PRO Digital Breakout Cable Pro, AES/EBU 25-pin D-sub to 4 x XLR male + 4 x XLR female, 3 m BO25MXLR4M4F6PRO Digital Breakout Cable Pro, AES/EBU 25-pin D-sub to 4 x XLR male + 4 x XLR female, 6 m BO25M25M1PRO Digital D-sub Cable Pro, AES/EBU 25-pin D-sub to 25-pin D-sub, 1m Digital D-sub Cable Pro, AES/EBU 25-pin D-sub to 25-pin D-sub, 3m Digital D-sub Cable Pro, AES/EBU 25-pin D-sub to 25-pin D-sub, 6m

BO25M25M3PRO

BO25M25M6PRO

5. Warranty

Each individual OctaMic II undergoes comprehensive quality control and a complete test at IMM before shipping. The usage of high grade components should guarantee a long and trouble-free operation of the unit. If you suspect that your product is faulty, please contact your local retailer. Audio AG grants a limited manufacturer warranty of 6 months from the day of invoice showing the date of sale. The length of the warranty period is different per country. Please contact your local distributor for extended warranty information and service. Note that each country may have regional specific warranty implications. In any case warranty does not cover damage caused by improper installation or maltreatment replacement or repair in such cases can only be carried out at the owner's expense. No warranty service is provided when the product is not returned to the local distributor in the region where the product had been originally shipped. Audio AG does not accept claims for damages of any kind, especially consequential damage. Liability is limited to the value of the OctaMic II. The general terms of business drawn up by Audio AG apply at all times.

6. 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 / 91810 Manufacturer: IMM Elektronik GmbH, Leipziger Strasse 32, D-09648 Mittweida
Trademarks All trademarks, registered or otherwise, are the property of their respective owners. RME, DIGICheck and Hammerfall are registered trademarks of RME Intelligent Audio Solutions. DIGI96, SyncAlign, ZLM, SyncCheck, TMS, TotalMix and OctaMic II are trademarks of RME Intelligent Audio Solutions. Alesis and ADAT are registered trademarks of Alesis Corp. ADAT optical is a trademark of Alesis Corp. Microsoft, Windows, Windows XP, Windows Vista and Windows 7 are registered trademarks or trademarks of Microsoft Corp. S/MUX is copyright Sonorus. Copyright Matthias Carstens, 02/2011. Version 1.2 All entries in this Users Guide have been thoroughly checked, however no guarantee for correctness can be given. RME cannot be held responsible for any misleading or incorrect information provided throughout this manual. Lending or copying any part or the complete manual or its contents as well as the software belonging to it is only possible with the written permission from RME. RME reserves the right to change specifications at any time without notice.

CE / FCC Compliance

This device has been tested and found to comply with the limits of the European Council Directive on the approximation of the laws of the member states relating to electromagnetic compatibility according to RL2004/108/EG, and European Low Voltage Directive RL2006/95/EG.
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user 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.
This product has been soldered lead-free and fulfils the requirements of the RoHS directive.

ISO 9001

This product has been manufactured under ISO 9001 quality management. The manufacturer, IMM Elektronik GmbH, is also certified for ISO 14001 (Environment) and ISO 13485 (medical devices).

Note on Disposal

According to the guide line RL2002/96/EG (WEEE Directive on Waste Electrical and Electronic Equipment), valid for all european countries, this product has to be recycled at the end of its lifetime. In case a disposal of electronic waste is not possible, the recycling can also be done by IMM Elektronik GmbH, the manufacturer of the OctaMic II. For this the device has to be sent free to the door to: IMM Elektronik GmbH Leipziger Strae 32 D-09648 Mittweida Germany Shipments not prepaid will be rejected and returned on the original sender's costs.

7. Front Panel Controls

7.1 Displays
+48V (LED) lights up when phantom power is active. The CLIP LED has been designed to act like the OVR LEDs of the ADI-8 series. It lights up 2 dB before the chosen reference level plus a headroom of 9 dB. At Hi Gain the LED lights up at +17 dBu output level, selecting +4 dBu it lights up at +11 dBu. SIG (Signal) indicates the presence of an input signal. The LED has a detection range of more than 50 dB using multiple brightness states. With this, SIG acts as useful level control, helping to set GAIN correctly.

DIP Switch 5 6

Function External synchronization source AES (D-sub) or word clock (BNC) Clock internal (Master) or external (Slave) Internal Clock 44.1 kHz or 48 kHz Activates Double Speed Mode* Activates Quad Speed Mode* AES output state Professional or Consumer
*Note on DIP switch 4/5: At internal clock, the switches DS and QS multiply the value set with switch 3 by a factor of 2 or 4. So if switch 3 is set to 48 kHz, switch 4 will turn it into 96 kHz, switch 5 turns it into 192 kHz. At external clock switch 3 is of no meaning, because the unit is synchronized to the incoming clock. However, switch 4 and 5 pre-define the frequency range to Single Speed, Double Speed or Quad Speed. For example if the OctaMic shall operate at 176.4 or 192 kHz, switch 5 has to be set to the lower position. The OctaMic will now generate an output signal in the Quad speed range (176.4 or 192 kHz), even with a word clock input signal of only 44.1 kHz, or an AES input signal of 96 kHz. With external synchronization active (switch 2 down) and both switches 4 and 5 in lower position, the function Follow Clock (FC) is active. In this case the OctaMic II follows the input clock 1:1. A further configuration of the current sample rate range (Single, Double or Quad Speed) is not required.
9. External Synchronization
The digital inputs of the OctaMic II are used for external synchronization only. In case the clock shall not be generated internally (operation mode Master), an external synchronization (operation mode Slave) is available via word clock or AES (SPDIF). The SteadyClock technology of the OctaMic II guarantees exceptional performance in all clock modes. Thanks to a highly efficient jitter suppression, the AD-conversion always operates on highest sonic level, being completely independent from the quality of the incoming clock signal. When the current word clock source fails, the last valid sample rate will be held automatically.

9.1 Word Clock - BNC

The word clock input is activated by DIP switches 1 and 2. Both switches must be set to their lower position. Thanks to RME's Signal Adaptation Circuit, the word clock input still works correctly even with heavily mis-shaped, dc-prone, too small or overshoot-prone signals. Thanks to automatic signal centering, 300 mV (0.3V) input level is sufficient in principle. An additional hysteresis reduces sensitivity to 1.0 V, so that over- and undershoots and high frequency disturbances don't cause a wrong trigger. The word clock input is shipped as high impedance type (not terminated). A push switch allows to activate internal termination (75 Ohms). The switch is found beside the BNC socket. Use a small pencil or similar and carefully push the blue switch so that it snaps into its lock position. Another push will release it again and de-activate the termination. Due to the outstanding clock control a synchronization of the output signal to the input signal is not only possible at identical sample rates, but also at half, quarter, double and quad sample rates. Example 1: DIP switch 3/4/5 in upper position results in a sample rate of 44.1 kHz. The external synchronization source (word clock or AES) can now be 44.1 kHz, 88.2 kHz or 176.4 kHz. Example 2: DIP switch 3/5 in lower position results in a sample rate of 192 kHz. The external synchronization (word clock or AES) source can now be 48 kHz, 96 kHz or 192 kHz.

9.2 AES D-Sub

Using the D-sub connector, an AES, AES/EBU or SPDIF signal can be used for synchronization. Set DIP switch 1 to the upper position and DIP switch 2 to the lower position. The OctaMic II's synchronization input uses AES 1 (see chapter 11.1). The input is transformerbalanced and ground-free. Thanks to a highly sensitive input stage, a SPDIF signal can also be fed by using a simple cable adapter phono/XLR. 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 of the XLR plug. With AES synchronization is possible not only at identical sample rates, but also at half, quarter, double and quad sample rates.
10. Analog Inputs / Outputs

10.1 Mic / Line In

The OctaMic has 8 balanced Mic and Line inputs via 1/4" TRS (stereo) and XLR combo jacks on the rear panel. The electronic input stage is built in a servo balanced design which handles unbalanced and balanced signals correctly, automatically adjusting the level reference. XLR The pin assignment follows international standards. With XLR, pin 2 is + or hot, pin 3 is or cold, pin 1 is ground. Pin 1 is connected to the chassis directly at the socket (AES48). When using unbalanced cables be sure to connect pin 3 (-) to 1 (ground). Otherwise noise may occur, caused by the unconnected negative input of the balanced input. The OctaMic II offers an adjustable amplification from +6 dB up to +60 dB. This equals a sensitivity of +14 dBu down to 40 dBu, referenced to full scale of the AD-converter. The soft switching, hi-current phantom power (48 Volt) provides a professional handling of condenser microphones. The usage of a hi-end integrated circuit (That 1510) guarantees outstanding sound quality, lowest THD, and maximum Signal to Noise ratio in any gain setting. The OctaMic II's 'overall' amplification from analog input to analog output depends on the analog output reference setting. The EIN is not affected by this setting, since the S/N ratio scales 1:1 with the output amplification. The input impedance is 2 kOhm.
TRS The pin assignment follows international standards. With TRS, tip is + or hot, ring is or cold. When using unbalanced cables with stereo TRS jacks, the 'ring' contact of the cable's jack should be connected to pin 1 (ground). Otherwise noise may occur, caused by the unconnected negative input of the balanced input. The TRS jacks have a fixed level attenuation of 7 dB. Based on the adjustable amplification from +6 dB up to +60 dB, the sensitivity is +21 dBu down to 33 dBu, referenced to full scale of the AD-converter. Therefore the TRS inputs are true full level Line inputs, and the unit can also be used as Line amplifier. The TRS jacks are free of phantom power. The unbalanced input impedance is 5 kOhm.

10.2 Line Out

The 8 short circuit protected, low impedance and servo balanced line outputs are available as (stereo) 1/4" TRS jacks. The electronic output stage is built in a servo balanced design which handles monaural and stereo jacks correctly. The pinout follows international standards. Tip + or hot, ring or cold. To maintain an optimum level for devices connected to the analog outputs, the OctaMic includes a switch which allows to change the reference level of all 8 outputs simultaneously. The OctaMic II can generate a maximum level of +21 dBu without distortion. However, the CLIP LED has been designed to act like the OVR LEDs of the ADI-8 series. It lights up 2 dB before the reference level selected on the back of the unit, plus a headroom of 9 dB, is reached. At Hi Gain the LED lights up at +17 dBu output level, selecting +4 dBu it lights up at +11 dBu, selecting 10 dBV it lights up at 0 dBV. Setting Hi Gain +4 dBu -10 dBV Reference +19 dBu +13 dBu +2 dBV Clip LED +17 dBu +11 dBu 0 dBV True Clip +21 dBu +15 dBu +4 dBV ADC Level -2 dBFS -2 dBFS -2 dBFS
This also means that the CLIP LED lights up 4 dB before the OctaMic II actually reaches the maximum level. Such an additional headroom is considered to be useful in real world operation. The chosen reference level has no meaning for the digital outputs. The AD-conversion is designed for a level of 2 dBFS as soon as the Clip LED lights up. Selecting +4 dBu the output signal is attenuated by 6 dB, so for the same output level the amplification has to be increased via GAIN. With this trick the OctaMic reaches the maximum signal to noise ratio on +4 dBu based inputs (like our ADI-8 series), because microphone preamps have better EIN values at higher amplification. In case of an extreme recording situation, where the gain of the OctaMic is no longer sufficient, selecting Hi Gain will again provide the highest amplification possible. The same is true and even more efficient at 10 dBV. In this case the output level is reduced by around 14 dB the same happens to the basic noise of the unit!

11. Digital Outputs

11.1 AES/EBU
The four AES/EBU outputs are provided on the rear of the OctaMic II via a 25 pin D-sub connector with Tascam pinout (also used by Digidesign). A digital breakout cable will provide 4 male (and 4 female) XLR connectors. Every output is transformer-balanced, ground-free and compatible to all devices with AES/EBU ports. Besides the audio data, digital signals in SPDIF or AES/EBU format contain a channel status coding, which is being used for transmitting further information. The output signal coding of the OctaMic II has been implemented according to AES3-1992 Amendment 4: 32* / 44.1 / 48 / 64* / 88.2 / 96 / 176.4 / 192 kHz according to the current sample rate Audio use No Copyright, Copy permitted Format Professional Category General, Generation not indicated 2-Channel, No Emphasis Aux bits audio use, 24 bit Origin: 8MIC

12. Word Clock

12.1 Operation and Technical Background
In the analog domain one can connect any device to another device, synchronisation is not necessary. Digital audio is different. It uses a clock, the sample frequency. The signal can only be processed and transmitted when all participating devices share the same clock. If not, the signal will suffer from wrong samples, distortion, crackle sounds and drop outs. AES/EBU, SPDIF, ADAT and MADI are self-clocking, an additional word clock connection in principle isn't necessary. But when using more than one device simultaneously problems are likely to happen. For example any self-clocking will not work in a loop cabling, when there is no 'master' (main clock) inside the loop. Additionally the clock of all participating devices has to be synchronous. This is often impossible with devices limited to playback, for example CD players, as these have no SPDIF input, thus can't use the self clocking technique as clock reference. In a digital studio synchronisation is maintained by connecting all devices to a central sync source. For example the mixing desk works as master and sends a reference signal, the word clock, to all other devices. Of course this will only work as long as all other devices are equipped with a word clock or sync input, thus being able to work as slave (some professional CD players indeed have a word clock input). Then all devices get the same clock and will work in every possible combination with each other. Remember that a digital system can only have one master! If the OctaMic II uses its internal clock, all other devices must be set to Slave mode. But word clock 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 special PLL (to about 11.2 MHz). This signal then replaces the one from the quartz crystal. Big disadvantage: because of the high multiplication factor the reconstructed clock will have great deviations called jitter. The jitter of a word clock is much higher as when using a quartz based clock. The end of these problems should have been the so called Superclock, which uses 256 times the word clock frequency. This equals the internal quartz frequency, so no PLL for multiplying is needed and the clock can be used directly. But reality was different, the Superclock proved to be much more critical than word clock. A square wave signal of 11 MHz distributed to several devices - this simply means to fight with high frequency technology. Reflections, cable quality, capacitive loads - at 44.1 kHz these factors may be ignored, at 11 MHz they are the end of the clock network. Additionally it was found that a PLL not only generates jitter, but also rejects disturbances. The slow PLL works like a filter for induced and modulated frequencies above several kHz. As the Superclock is used without any filtering such a kind of jitter and noise suppression is missing. The actual end of these problems is offered by the SteadyClock technology of the OctaMic II. Combining the advantages of modern and fastest digital technology with analog filter techniques, re-gaining a low jitter clock signal of 22 MHz from a slow word clock of 44.1 kHz is no problem anymore. Additionally, jitter on the input signal is highly rejected, so that even in real world usage the re-gained clock signal is of highest quality.

12.2 Cabling and Termination
Word clock signals are usually distributed in the form of a network, split with BNC T-adapters and terminated with resistors. We recommend using off-the-shelf BNC cables to connect all devices, as this type of cable is used for most computer networks. Actually you will find all the necessary components (T-adapters, terminators, cables) in most electronics and computer stores. The latter usually carries 50 Ohm components. The 75 Ohm components used for word clock are part of video technology (RG59). Ideally, the word clock signal is a 5 Volt square wave with the frequency of the sample rate, of which the harmonics go up to far above 500 kHz. To avoid voltage loss and reflections, both the cable itself and the terminating resistor at the end of the chain should have an impedance of 75 Ohm. If the voltage is too low, synchronization will fail. High frequency reflection effects can cause both jitter and sync failure. Unfortunately there are still many devices on the market, even newer digital mixing consoles, which are supplied with a word clock output that can only be called unsatisfactory. If the output breaks down to 3 Volts when terminating with 75 Ohms, you have to take into account that a device, of which the input only works from 2.8 Volts and above, does not function correctly already after 3 meter cable length. So it is not astonishing that because of the higher voltage, word clock networks are in some cases more stable and reliable if cables are not terminated at all. Ideally 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. Note that such a device is generally recommended for larger studios. The OctaMic II's word clock input can be high-impedance or terminated internally, ensuring maximum flexibility. If termination is necessary (e.g. because the OctaMic II is the last device in the chain), push the switch at the back (see chapter 9.1). In case the OctaMic II resides within a chain of devices receiving word clock, plug a T-adapter into its BNC input jack, and the cable supplying the word clock signal to one end of the adapter. Connect the free end to the next device in the chain via a further BNC cable. The last device in the chain should be terminated using another T-adapter and a 75 Ohm resistor (available as short BNC plug). Of course devices with internal termination do not need T-adaptor and terminator plug.

13. Technical Specifications

13.1 Analog

Microphone/Line 1-8 Input: Neutrik XLR/TRS Combo jack, electronically balanced Input impedance: XLR 2 kOhm, TRS 10 kOhm balanced Frequency response 0.1 dB: 20 Hz 100 kHz Frequency response 0.3 dB: 10 Hz 150 kHz THD @ 30 dB Gain: < -106 dB, < 0.0005 % THD+N @ 30 dB Gain: < -100 dB, < 0.001 % Channel separation: > 110 dB CMRR 20 Hz 20 kHz: > 55 dB EIN @ 30 dB Gain @ 150 Ohm: 122 dBu EIN @ 40 dB Gain @ 150 Ohm: 126 dBu EIN @ 50/60 dB Gain @ 150 Ohm: 128 dBu EIN @ 30 dB Gain @ 0 Ohm: 122.5 dBu EIN @ 40 dB Gain @ 0 Ohm: 128.8 dBu EIN @ 50/60 dB Gain @ 0 Ohm: 130.3 dBu Gain range: +6 dB up to +60 dB Maximum input level XLR, Gain +6 dB: +14 dBu Maximum input level XLR, Gain +60 dB: -40 dBu Maximum input level TRS, Gain +6 dB: +21 dBu Maximum input level TRS, Gain +60 dB: -33 dBu
Line Out 1-8 Maximum output level: +21 dBu Output: 6.3 mm TRS stereo jack, servo-balanced Output impedance: 75 Ohm Output level switchable Hi Gain / +4 dBu / -10 dBV
AD-Conversion Resolution: 24 bit Signal to noise ratio (SNR): 110 dB RMS unweighted, 114 dBA Frequency response @ 44.1 kHz, -0.5 dB: 5 Hz 20.6 kHz Frequency response @ 96 kHz, -0.5 dB: 5 Hz 45.3 kHz Frequency response @ 192 kHz, -1 dB: 5 Hz - 90 kHz THD+N: < -110 dB, < 0.0003 % Channel separation: > 110 dB

13.2 Digital Inputs

AES/EBU 1 x 25-pin D-sub, transformer-balanced, galvanically isolated, according to AES3-1992 High-sensitivity input stage (< 0.3 Vpp) SPDIF compatible (IEC 60958) Accepts Consumer and Professional format Lock Range: 27 kHz 200 kHz Jitter when synced to input signal: < 1 ns Jitter suppression: > 30 dB (2.4 kHz)
Word Clock BNC, not terminated (10 kOhm) Switch for 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 Transformer coupled, galvanically isolated input Not affected by DC-offsets within the network Signal Adaptation Circuit: signal refresh through auto-center and hysteresis Overvoltage protection 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)

13.3 Digital Outputs

AES/EBU 4 x, transformer-balanced, galvanically isolated, according to AES3-1992 Output voltage Professional 4.5 Vpp Format Professional according to AES3-1992 Amendment 4 Single Wire: 4 x 2 channels 24 bit, up to 192 kHz ADAT 2 x TOSLINK Standard: 8 channels 24 bit, up to 48 kHz S/MUX: 16 channels 24 bit / 48 kHz, equalling 8 channels 24 bit 96 kHz

13.4 Digital

Clocks: Internal, AES In, word clock In Low Jitter Design: < 1 ns in PLL mode, all inputs Internal clock: 800 ps Jitter, Random Spread Spectrum Jitter suppression of external clocks: > 30 dB (2.4 kHz) Effective clock jitter influence on AD-conversion: near zero PLL ensures zero dropout, even at more than 100 ns jitter Supported sample rates: 28 kHz up to 200 kHz

14. Technical Background

14.1 Terminology
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.

14.2 DS - Double Speed

When activating the Double Speed mode the OctaMic II operates at double sample rate. The internal clock 44.1 kHz turns to 88.2 kHz, 48 kHz to 96 kHz. The internal resolution is still 24 bit. Sample rates above 48 kHz were not always taken for granted, and are still not widely used because of the CD format (44.1 kHz) dominating everything. Before 1998 there were no receiver/transmitter circuits available that could receive or transmit more than 48 kHz. Therefore a work-around was used: instead of two channels, one AES line only carries one channel, whose odd and even samples are being distributed to the former left and right channels. By this, you get the double amount of data, i. e. also double sample rate. Of course in order to transmit a stereo signal two AES/EBU ports are necessary then. This transmission mode is called Double Wire in the professional studio world, and is also known as S/MUX (Sample Multiplexing) in connection with the ADAT format. Not before February 1998, Crystal shipped the first 'single wire' receiver/transmitters that could 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 sampling frequencies above 48 kHz (a limitation of the interface hardware), the OctaMic II automatically uses Sample Multiplexing in DS mode. One channel's data is distributed to two channels according to the following table: Analog In DS Signal Port 1 1/2 ADAT3/4 ADAT5/6 ADAT7/8 ADAT1/2 ADAT3/4 ADAT5/6 ADAT7/8 ADAT2
As the transmission of double rate signals is done at standard sample rate (Single Speed), the ADAT outputs still deliver 44.1 kHz or 48 kHz.

14.3 QS Quad Speed

Due to the small number of available devices that use sample rates up to 192 kHz, but even more due to a missing real world application (CD.), Quad Speed has had no broad success so far. An implementation of the ADAT format as double S/MUX (S/MUX4) results in only two channels per optical output. Therefore the OctaMic II does not support this mode at the ADAT outputs. The AES outputs provide 192 kHz as Single Wire only.

14.4 AES/EBU - SPDIF

The most important electrical properties of 'AES' and 'SPDIF' can be seen in the table below. AES/EBU is the professional balanced connection using XLR plugs. The standard is being set by the Audio Engineering Society based on the AES3-1992. For the 'home user', SONY and Philips have omitted the balanced connection and use either Phono plugs or optical cables (TOSLINK). The format called S/P-DIF (SONY/Philips Digital Interface) is described by IEC 60958. Type Connection Mode Impedance Level Clock accuracy AES3-1992 XLR Balanced 110 Ohm 0.2 V up to 5 Vpp not specified IEC 60958 RCA / Optical Unbalanced 75 Ohm 0.2 V up to 0.5 Vpp I: 50 ppm II: 0.1% III: Variable Pitch not specified

Jitter

< 0.025 UI (4.4 ns @ 44.1 kHz)
Besides the electrical differences, both formats also have a slightly different setup. The two formats are compatible in 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 Pro Con Bit 0 P/C P/C 1 Audio? Audio? 5 Emphasis Locked Copy Emphasis 7 Sample Freq. Mode
It becomes obvious that the meaning of the following bits differs quite substantially between the two formats. If a device like a common DAT recorder only has an SPDIF input, it usually understands only this format. In most cases, it will switch off when being fed Professional-coded data. The table shows that a Professional-coded signal would lead to malfunctions for copy prohibition and emphasis, if being read as Consumer-coded data. Nowadays many devices with SPDIF input can handle Professional subcode. Devices with AES3 input almost always accept Consumer SPDIF (passive cable adapter required).

14.5 SteadyClock

The SteadyClock technology of the OctaMic II guarantees an excellent performance in all clock modes. Its highly efficient jitter suppression refreshes and cleans up any clock signal, and provides it as reference clock at the word clock output. Usually a clock section consists of an analog PLL for external synchronization and several quartz oscillators for internal synchronisation. SteadyClock requires only one quartz, using a frequency not equalling digital audio. Latest circuit designs like hi-speed digital synthesizer, digital PLL, 100 MHz sample rate and analog filtering allow RME to realize a completely newly developed clock technology, right within the FPGA at lowest costs. The clock's performance exceeds even professional expectations. Despite its remarkable features, SteadyClock reacts quite fast compared to other techniques. It locks in fractions of a second to the input signal, follows even extreme varipitch changes with phase accuracy, and locks directly within a range of 28 kHz up to 200 kHz. SteadyClock has originally been developed 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 (top graph, yellow). Thanks to SteadyClock this signal turns into a clock with less than 2 ns jitter (lower graph, blue). Using the input sources of the OctaMic II, word clock and AES/EBU, you'll most probably never experience such high jitter values. But SteadyClock is not only ready for them, it would handle them just on the fly. The screenshot to the right shows an extremely jittery word clock signal of about 50 ns jitter (top graph, yellow). Again SteadyClock provides an extreme clean-up. The filtered clock shows less than 2 ns jitter (lower graph, blue). The cleaned and jitter-freed signal can be used as reference clock for any application, without any problem. The signal processed by SteadyClock is of course not only used internally, but is also used to clock the digital outputs ADAT and AES/EBU.

User's Guide

OctaMic / OctaMic D

Portable Professional Mic Preamp 8-channel Microphone / Line Preamp with Line Outputs Universal Power Supply Input Optional 8-Channel 192 kHz 24 Bit ADC

AES-Bit Interface

Contents
Introduction.. 3 Package Contents.. 3 Brief Description and Characteristics. 3 Technical Specifications.. 3 4.1 Analog.. 3 4.2 ADC Modul.. Power Supply.. Operation and Usage 6.1 Controls... 5 6.2 Mic/Line Inputs.. 6 6.3 Line Outputs... The ADC Module 7.1 DIP Switches.. 7 7.2 External Synchronization.. Digital Outputs 8.1 AES Sub-D.. 9 8.2 ADAT Optical..Word Clock 9.1 Operation and Technical Background.11 9.2 Cabling and Termination..Technical Background 10.1 DS - Double Speed..13 10.2 QS Quad Speed...13 10.3 AES/EBU SPDIF..Accessories...Warranty...Appendix...Block Diagram OctaMic..CE / FCC Compliance..4

User's Guide OctaMic RME

1. Introduction
Thank you for choosing the OctaMic. This unique Mic Preamp allows to connect any kind of microphone to any line level inputs. Thanks to the option of battery-powered operation and removable rack ears, the OctaMic makes an ideal companion to the Hammerfall DSP System in mobile recording situations. But excellent signal/noise ratio, sophisticated discrete Class-A technology, and lots of professional features make the OctaMic your first choice also in studio use!

2. Package Contents

Please check that your OctaMic's package contains each of the following: OctaMic User's guide Power supply 12 V / 1.25 A and power cord
3. Brief Description and Characteristics
8 separate microphone inputs with discrete Class-A frontend Phantom power 48V, low cut and phase switchable per channel 48V, Clip and Level LED per channel Gain +10 dB up to +60 dB adjustable per channel Reference level switchable Hi Gain / +4 dBu / -10 dBV Fully compatible to RME's ADI-8 series and HDSP series Servo balanced inputs and outputs Wide frequency response with special RF input filters Wide operating voltage range 100% hum-free via internal switching regulators
4. Technical Specifications
Current drawn at 12 Volt operating voltage: 850 mA (10 Watts) Accepted power supply voltage DC 8 V 28 V, AC 8 V 20 V. Dimensions: 483 x 44 x 205 mm Weight: 2 kg

4.1 Analog

Inputs: XLR or 1/4" TRS (stereo) jack, servo balanced Impedance: 2 kOhm Signal to Noise ratio (SNR): 129 dB EIN @150 Ohm THD: 0.006% @ 30 dB Gain Crosstalk: > 110 dB Frequency response 0.5 dB: 5 Hz - 200 kHz Line Out: 1/4" TRS (stereo) jack, servo balanced Maximum output level: +21 dBu Output impedance: 47 Ohm Output level switchable Hi Gain / +4 dBu / -10 dBV
SNR ADC Module: > 110 dBA Sample rate range ADC Module: 28 kHz 200 kHz THD ADC Module: < 0.00032 %, < -110 dB

4.2 ADC Modul

AES Input 1 x XLR via 25 pin D-sub, transformer balanced, ground-free, according to AES3-1992 High-sensitivity input stage (< 0.3 Vss) SPDIF compatible (IEC 60958) Lock range: 27 kHz 200 kHz Jitter when synced to input signal: < 2 ns
Wordclock Input BNC, not terminated (10 kOhm), switch for internal termination 75 Ohm Automatic Double/Quad Speed detection and internal conversion AC-coupling, not effected by DC-offsets within the network Signal Adaptation Circuit: signal refresh through auto-center and hysteresis Overvoltage protection Level range: 1.0 Vss 5.6 Vss Lock range: 27 kHz 200 kHz Jitter when synced to input signal: < 2 ns

AES/EBU Outputs 4 x via 25 pin D-Sub, transformer balanced, ground-free, according to AES3-1992 Output voltage Professional 4.5 Vss, Consumer 2.1 Vss Format Professional according to AES3-1992 Amendment 4 Format Consumer (SPDIF) according to IEC 60958 Single Wire: 4 x 2 channels 24 bit, up to 96 kHz
ADAT Optical 2 x TOSLINK Standard: 8 channels 24 bit, up to 48 kHz Sample Split (S/MUX): 2 x 8 channels 24 bit / 48 kHz, equalling 8 channels 24 bit 96 kHz

5. Power Supply

In order to make operating the OctaMic as flexible as possible, the unit contains a switching regulator of the latest technology, which not only has a high efficiency (> 90%), but also prevents internal hum noise by operating at 150 kHz. Another advantage: the OctaMic accepts any power supply with voltages between 8 and 28 V DC, no matter which polarity, and even between 8 and 20 V AC. Given the power supply can deliver the current needed. The supplied high-quality switching power supply, 12 V / 1.25 A, not only accepts any mains voltage between 100 V and 240 V (usable world-wide), but is also fully regulated against voltage fluctuations. Additionally it only weighs 150 g in spite of its high power of 15 Watts. The large voltage range of the OctaMic also allows for the use of a rechargeable lead-battery instead of a power supply, for completely independent mobile operation. A matching connection cable (power jack to terminals 6.3 mm) is available from RME. A Panasonic LCR122R2PG battery, 12 V 2.2 Ah, can operate the OctaMic for 2 hours.

6. Operation and Usage

6.1 Controls
The front of the OctaMic has the gain knobs, switches for low cut, phantom power and phase, Clip Hold, Reference Level and several status LEDs: +48V (LED) lights up when phantom power is active. Phantom power should only be activated when using condensor microphones which require such a power supply. The CLIP LED has been designed to act like the OVR LEDs of the ADI-8 series. It lights up 2 dB before the chosen reference level plus a headroom of 9 dB. At Hi Gain the LED lights up at +17 dBu output level, selecting +4 dBu it lights up at +11 dBu. SIG (Signal) indicates the presence of an input signal. The LED has a detection range of more than 50 dB using multiple brightness states. With this, SIG acts as useful level control, helping to set GAIN correctly. GAIN allows for a stepless and very precise adjustment of the amplification between +10 dB and +60 dB. +48V (switch) activates phantom power. Phantom power should only be activated when using condensor microphones which require such a power supply, and only on the specific channel. LO CUT activates a hi-pass at 80 Hz, 18 dB per octave. This filter can remove rumble and other low frequency noise. PHASE changes the polarity. Phase cancellations and sound changes can be caused by using multiple microphones at different places, or wrongly soldered cables. In such cases PHASE can eliminate the error by adding an additional phase inversion. Clip Hold is activated by pressing the key for two seconds. As soon as an overload is detected, the corresponding Clip LED begins to flash once per second. With this, a momentary overload stays visible for a longer time. Pressing the key once resets the Clip display. Pressing the key again for two seconds deactivates the Clip Hold mode. Hi Gain / +4 dBu / -10 dBV: Defines the reference level of the Line Level Outputs. See chapter 6.3, Line Outputs.

The back of the OctaMic has the 8 analog inputs and outputs, the power supply connector AUX, the analog D-sub output, or the optional ADC module (see chapter 7) with all the digital inputs and outputs. MICROPHONE / LINE INPUTS: 8 Neutrik XLR / TRS combo jacks. Thanks to the servo balanced designs and a high maximum input level (+10 dBu), the inputs can be used balanced or unbalanced, with XLR or TRS jack, with microphone or line levels nearly everything is possible. LINE LEVEL OUTPUTS: 8 TRS (stereo) jacks. The electronic output stage is built in a servo balanced design, handling monaural (unbalanced) and stereo jacks (balanced) correctly. AUX: Connect power supply, lead-battery or battery. See chapter 5, Power Supply.

6.2 Mic/Line Inputs

The OctaMic offers 8 balanced Mic and Line inputs via 1/4" TRS (stereo) and XLR combo jacks. The electronic input stage is built in a servo balanced design which handles monaural and stereo jacks correctly. When used unbalanced it automatically corrects the gain by 6 dB. When using unbalanced cables with stereo TRS jacks, the 'ring' contact of the cable's jack should be connected to pin 1 (ground). Otherwise noise may occur, caused by the unconnected negative input of the balanced input. The pinout follows international standards. XLR pin 2 + or hot, pin 3 or cold, pin 1 ground. TRS tip + or hot, ring or cold.

6.3 Line Outputs

The 8 short circuit protected, low impedance and servo balanced line outputs are available as (stereo) 1/4" TRS jacks. The electronic output stage is built in a servo balanced design which handles monaural and stereo jacks correctly. When used unbalanced it automatically corrects the gain by 6 dB. The pinout follows international standards. TRS tip + or hot, ring or cold. To maintain an optimum level for devices connected to the analog outputs, the OctaMic includes a switch which allows to change the reference level of all 8 outputs simultaneously. The OctaMic can generate a maximum level of +21 dBu without distortion. However, the CLIP LED has been designed to act like the OVR LEDs of the ADI-8 series. It lights up 2 dB before the reference level selected on the back of the unit, plus a headroom of 9 dB, is reached. At Hi Gain the LED lights up at +17 dBu output level, selecting +4 dBu it lights up at +11 dBu, selecting 10 dBV it lights up at 0 dBV. Setting Hi Gain +4 dBu -10 dBV Reference +19 dBu +13 dBu +2 dBV Clip LED +17 dBu +11 dBu 0 dBV True Clip +21 dBu +15 dBu +4 dBV ADC Level -2 dBFS -2 dBFS -2 dBFS

This also means that the CLIP LED lights up 4 dB before the OctaMic actually reaches the maximum level. Such an additional headroom is considered to be useful in real world operation. The chosen reference level has no meaning for the ADC module. The ADC modul is designed for a level of 2 dBFS as soon as the Clip LED lights up. Selecting +4 dBu the output signal is attenuated by 6 dB, so for the same output level the amplification has to be increased via GAIN. With this trick the OctaMic reaches the maximum signal to noise ratio on +4 dBu based inputs (like our ADI-8 series), because microphone preamps have better EIN values at higher amplification. In case of an extreme recording situation, where the gain of the OctaMic is no longer sufficient, selecting Hi Gain will again provide the highest amplification possible. The same is true and even more efficient at 10 dBV. In this case the output level is reduced by around 14 dB the same happens to the basic noise of the unit!

7. The ADC Module

The ADC Module replaces the analog D-sub output by a high quality digital converter card. The card includes clock generation, clock recovery (SteadyClock) and AD-conversion.

7.1 DIP Switches

The DIP switches are used to configure the ADC Module. The following diagram, also printed on the back of the unit, shows the function controlled by each switch.

DIP Switch 5 6

Function External synchronization source AES (D-sub) or word clock (BNC) Clock internal (Master) or external (Slave) Internal Clock 44.1 kHz or 48 kHz Activates Double Speed Mode* Activates Quad Speed Mode* AES output signal Professional or Consumer
*Note on DIP switch 4/5: At internal clock, the switches DS and QS multiply the value set with switch 3 by a factor of 2 or 4. So if switch 3 is set to 48 kHz, switch 4 will turn it into 96 kHz, switch 5 turns it into 192 kHz. At external clock switch 3 is of no meaning, because the unit is synchronized to the incoming clock. However, switch 4 and 5 define the frequency range between Single Speed, Double Speed and Quad Speed. For example if the OctaMic shall operate at 176.4 or 192 kHz, switch 5 has to be set to the lower position. The OctaMic will now generate an output signal in the Quad speed range (176.4 or 192 kHz), even with a word clock input signal of only 44.1 kHz, or an AES input signal signal of 96 kHz.
7.2 External Synchronization
The inputs of the ADC Module are used for external synchronization only. In case the clock shall not be generated internally (operation mode Master), an external synchronization (operation mode Slave) is available via word clock or AES (SPDIF). SteadyClock, integrated into the ADC Module, guarantess exceptional performance in all clock modes. Thanks to a highly efficient jitter suppression, the AD-conversion always operates on highest sonic level, being completely independent from the quality of the incoming clock signal. And even in an error state SteadyClock will help: when the current word clock source fails, the last valid sample rate will be held automatically.

Wordclock - BNC The transformer balanced, ground-free word clock input is activated by DIP switches 1 and 2. Both switches must be set to their lower position. The word clock input is shipped as high impedance type (not terminated). A push switch allows to activate internal termination (75 Ohms). The switch is found beside the BNC socket. Use a small pencil or similar and carefully push the blue switch so that it snaps into its lock position. Another push will release it again and de-activate the termination. Thanks to RME's Signal Adaptation Circuit, the word clock input still works correctly even with heavily mis-shaped, dc-prone, too small or overshoot-prone signals. Thanks to automatic signal centering, 300 mV (0.3V) input level are sufficient in principle. An additional hysteresis reduces sensitivity to 1.0 V, so that over- and undershoots and high frequency disturbances don't cause a wrong trigger. Due to the ADC Module's outstanding clock control a synchronization of the output signal to the input signal is not only possible at identical sample rates, but also at half, quarter, double and quad sample rates! Example 1: DIP switch 3/4/5 in upper position results in a sample rate of 44.1 kHz. The external synchronization source (word clock or AES) can now be 44.1 kHz, 88.2 kHz or 176.4 kHz. Example 2: DIP switch 3/5 in lower position results in a sample rate of 192 kHz. The external synchronization (word clock or AES) source can now be 48 kHz, 96 kHz or 192 kHz.
AES D-sub Using the D-sub connector, an AES, AES/EBU or SPDIF signal can be used for synchronization. For this to work, DIP switch 1 has to be set to the upper position, DIP switch 2 to lower position. The D-sub connector uses the widely known and often found pinout of the Tascam recorders (TEAC). Therefore multicores D-sub to XLR can be ordered easily. These cable have 4 XLR outputs male and 4 XLR inputs female. The ADC Module's synchronization input uses AES 1 (see chapter 8.1, AES D-sub). The input is transformer balanced and ground-free. Thanks to a highly sensitive input stage, also SPDIF signals can be processed by using a simple cable adapter (RCA/XLR).
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 of the XLR plug.

Using the AES input, a synchronization is again possible at half, quarter, double and quad sample rates, see above.

8. Digital Outputs

8.1 AES D-sub
The ADC Module provides the four AES/EBU outputs via a 25 pin D-sub connector. The D-sub connector uses the widely known and often found pinout of the Tascam recorders (TEAC). Therefore multicores D-sub to XLR can be ordered easily. These cable have 4 XLR outputs male and 4 XLR inputs female. The inputs 2 to 4 are not used by the ADC Module. Every output is transformer-balanced and compatible to all devices with AES/EBU port. The format is set by DIP switch 6 to Professional or Consumer. If AES PRO is chosen, the output level is almost 5V. If CON (Consumer) is chosen, the output signal will have a channel status compatible to SPDIF, and the output level will be reduced to 2V. Connecting devices with coaxial SPDIF ports to the ADC Module's outputs (the XLR Multicore) is accomplished 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 of the XLR plug.
The Channel Status of the ADC Module has been implemented according to AES3-1992 Amendment 4. 32* / 44.1 / 48 / 64* / 88.2 / 96 / 176.4 / 192 kHz according to sample rate Audio use No Copyright, Copy permitted Format Consumer oder Professional Category General, Generation not indicated 2-Channel, No Emphasis Aux bits Audio use, 24 Bit Origin: 8MIC
* This value is set automatically in external synchronization mode as soon as the sample rate is recognized.
Note that most consumer-orientated equipment (with optical or phono SPDIF inputs) will only accept signals in Consumer format! The status 'Professional' should always be active when sending data to a device with AES/EBU input (when XLR connectors are used).
Pinout D-sub Signal D-sub In 1/2+ 24 In 1/212 In 3/4+ 10 In 3/423 In 5/6+ 21 In 5/69 In 7/8+ 7 In 7/820

Signal D-sub

Out 1/2+ 18

Out 1/26

Out 3/4+ 4

Out 3/417

Out 5/6+ 15

Out 5/63

Out 7/8+ 1

Out 7/814

GND is connected to pins 2, 5, 8, 11, 16, 19, 22, 25. Pin 13 is not connected.

8.2 ADAT Optical

The ADC Module provides two digital outputs in ADAT optical format. As the ADAT optical signal is physically specified up to 48 kHz only, the ADC Module automatically activates Sample Split mode (S/MUX) at 88.2 and 96 kHz, distributing the data of one input 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 kHz capable ADAT hardware, like all current RME digital interfaces, re-combine the data automatically. The user (and the DAW software) does not see any split data, but just single channels at the expected double sample rate. At frequencies not higher than 48 kHz (Single Speed), the outputs MAIN and AUX operate simultaneously and carry the same audio data. With this it is possible to distribute the output signal to two devices (2 x ADAT splitter). Up to 96 kHz (Double Speed), the ADAT outputs can be used in parallel to the AES outputs. In Quad Speed mode (128 kHz up to 192 kHz), the ADAT outputs are operated synchronously at Single Speed sample clock, but do not provide any audio data. The ADAT optical outputs of the ADC Module are fully compatible to all ADAT optical inputs. A usual TOSLINK cable is sufficient for connection. ADAT Main Interface for the first or only device receiving an ADAT signal from the OctaMic. Carries the channels 1 to 8. When sending a Double Speed signal, this port carries the channels 1 to 4. In Quad Speed mode ADAT MAIN carries an empty but synchronous ADAT signal. ADAT AUX Copy of the data at the MAIN output. When sending a Double Speed signal, this port carries the channels 5 to 8. In Quad Speed mode ADAT AUX carries an empty but synchronous ADAT signal.

9. Word Clock

9.1 Operation and Technical Background
Correct interpretation of digital audio data is dependent upon a definite sample frequency. Digital signals can only be processed or transferred between devices if these share the same clock. Otherwise the signals are misinterpreted, causing distortion, clicks/crackle or dropouts. AES/EBU, SPDIF and ADAT are self-clocking, so an additional line for word clock could be considered redundant. In practice however, using several devices at the same time can cause problems. For example, if devices are connected in a loop without there being a defined master device, self-clocking may break down. Besides, the clocks of all devices must be synchronized from a single source. Devices without SPDIF inputs (typically playback devices such as CD players) cannot be synchronized via self-clocking. In digital studios, synchronization requirements can be met by connecting all devices to a central sync source. For instance, the master device could be a mixing desk, sending a reference signal - word clock - to all other devices. However, this will only work if all the other devices have word clock inputs (e.g. some professional CD players) allowing them to run as slaves. This being the case, all devices will receive the same clock signal, so there is no fundamental reason for sync problems when they are connected together. But word clock also has some disadvantages. The word clock is based on a fraction of the actually 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 special PLL (to about 11.2 MHz). This signal then replaces the one from the quartz crystal. Big disadvantage: because of the high multiplication factor the reconstructed clock will have great deviations called jitter. The jitter of a word clock is typically 15 times higher as when using a quartz based clock. The end of these problems should have been the so called Superclock, which uses 256 times the word clock frequency. This equals the internal quartz frequency, so no PLL for multiplying is needed and the clock can be used directly. But reality was different, the Superclock proved to be much more critical than word clock. A square wave signal of 11 MHz distributed to several devices - this simply means to fight with high frequency technology. Reflections, cable quality, capacitive loads - at 44.1 kHz these factors may be ignored, at 11 MHz they are the end of the clock network. Additionally it was found that a PLL not only generates jitter, but also also rejects disturbances. The slow PLL works like a filter for induced and modulated frequencies above several kHz. As the Superclock is used without any filtering such a kind of jitter and noise suppression is missing. No wonder Superclock did not become a commonly accepted standard. The actual end of these problems is offered by RME's SteadyClock technology. Combining the advantages of modern and fastest digital technology with analog filter techniques, re-gaining a low jitter clock signal of 11 MHz from a slow word clock of 44.1 kHz is no problem anymore. Additionally, jitter on the input signal is highly rejected, so that even in real world usage the regained clock signal is of highest quality.

9.2 Cabling and Termination
Word clock signals are usually distributed in the form of a network, split with BNC T-adapters and terminated with resistors. We recommend using off-the-shelf BNC cables to connect all devices, as this type of cable is used for most computer networks. You will find all the necessary components (T-adapters, terminators, cables) in most electronics and/or computer stores. Ideally, the word clock signal is a 5 Volt square wave with the frequency of the sample rate, of which the harmonics go up to far above 500 kHz. To avoid voltage loss and reflections, both the cable itself and the terminating resistor at the end of the chain should have an impedance of 75 Ohm. If the voltage is too low, synchronization will fail. High frequency reflection effects can cause both jitter and sync failure. Unfortunately there are still many devices on the market, even newer digital mixing consoles, which are supplied with a word clock output that can only be called unsatisfactory. If the output breaks down to 3 Volts when terminating with 75 Ohms, you have to take into account that a device, of which the input only works from 2.8 Volts and above, does not function correctly already after 3 meter cable length. So it is not astonishing that because of the higher voltage, word clock networks are in some cases more stable and reliable if cables are not terminated at all. Ideally all outputs of word clock delivering devices are designed with very low impedance, but all word clock inputs with high impedance, 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. Note that such a device is generally recommended for larger studios. Also, 75 Ohm cable is almost impossible to find these days. 50 Ohm cable is standard - this will also work as long as the termination resistors are 75 Ohm. The ADC-Module's word clock input can be high-impedance or terminated internally, ensuring maximum flexibility. If termination is necessary (e.g. because the OctaMic is the last device in the chain), push the switch at the back beside the BNC socket. In case the OctaMic resides within a chain of devices receiving word clock, plug a T-adapter into its BNC input jack, and the cable supplying the word clock signal to one end of the adapter. Connect the free end to the next device in the chain via a further BNC cable. The last device in the chain should be terminated using another T-adapter and a 75 Ohm resistor (available as short BNC plug). Of course devices with internal termination do not need T-adaptor and terminator plug.

10. Technical Background

10.1 DS - Double Speed
When activating the Double Speed mode the ADC Module operates at double sample rate. The internal clock 44.1 kHz turns to 88.2 kHz, 48 kHz to 96 kHz. The internal resolution is still 24 bit. Sample rates above 48 kHz were not always taken for granted, and are still not widely used because of the CD format (44.1 kHz) dominating everything. Before 1998 there were no receiver/transmitter circuits available that could receive or transmit more than 48 kHz. Therefore a work-around was used: instead of two channels, one AES line only carries one channel, of which the odd and even samples are being distributed to the former left and right channels. By this, you get the double amount of data, i. e. also double sample rate. Of course in order to transmit a stereo signal two AES/EBU ports are necessary then. This transmission mode is being called Double Wire in the professional studio world, and is also known as S/MUX in connection with the ADAT format. The DTRS recorder DA-98HR by Tascam also uses this technique, which is called Dual Line here. Not before February 1998, Crystal shipped the first 'single wire' receiver/transmitters that could 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 sampling frequencies above 48 kHz (a limitation of the interface hardware), the ADI-8 DD automatically uses the described Sample Split method in DS mode. One channel's data is distributed to two channels according to the following table: Analog In DS Signal Port 1 1/2 MAIN 2 3/4 MAIN 3 5/6 MAIN 4 7/8 MAIN 5 1/2 AUX 6 3/4 AUX 7 5/6 AUX 8 7/8 AUX
As the transmission of double rate signals is done at standard sample rate (Single Speed), the ADAT outputs still deliver 44.1 kHz or 48 kHz.

10.2 QS Quad Speed

Due to the seldomly found devices using sample rates up to 192 kHz, but even more due to a missing real world application (CD.), Quad Speed has had no broad success so far. An implementation of the ADAT format as double S/MUX would result in two channels per optical output. Devices using this method are not known to us, so we decided to do without this format. The AES outputs provide 192 kHz as Single Wire only. This is forced by the space not available for further D-sub connectors, necessary for Double Wire (Quad Wire.) implementation.

10.2 AES/EBU - SPDIF

The most important electrical properties of 'AES' and 'SPDIF' can be seen in the below table. AES/EBU is the professional balanced connection using XLR plugs. The standard is being set by the Audio Engineering Society based on the AES3-1992. For the 'home user', SONY and Philips have omitted the balanced connection and use either Phono plugs or optical cables (TOSLINK). The format called S/P-DIF (SONY/Philips Digital Interface) is described by IEC 60958.
Type Connection Mode Impedance Level Clock accuracy
AES3-1992 XLR Balanced 110 Ohm 0.2 V up to 5 Vss not specified

Jitter

< 0.025 UI (4.4 ns @ 44.1 kHz)
IEC 60958 RCA / Optical Un-balanced 75 Ohm 0.2 V up to 0.5 Vss I: 50ppm II: 0,1% III: Variable Pitch not specified
Besides the electrical differences, both formats also have a slightly different setup. The two formats are principally compatible, 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. Already in the first bit there is the decision, whether the following bits should be read as Professional or Consumer information. Byte Mode Pro Con Bit 0 P/C P/C 1 Audio? Audio? 5 Emphasis Locked Copy Emphasis 7 Sample Freq. Mode
As can be seen, the meaning of the following bits differs quite substantially in both formats. If a device like a common DAT recorder only has an SPDIF input, it usually understands only this format. In most cases, it will switch off when being fed Professional-coded data. The table shows that a Professional-coded signal would lead to malfunctions for copy prohibition and emphasis, if being read as Consumer-coded data. This actually happened in former times, but if found today then it was implemented to force the costumer to buy a more expensive device. Nowadays many devices with SPDIF input can handle Professional subcode. Devices with AES3 input almost always accept Consumer SPDIF (passive cable adapter necessary).

11. Accessories

Part number 37011 Description Power supply for HDSP CardBus card
Robust and light weigth switching power supply, 100V-240V AC, 12V 1.25 A DC.

12. Warranty

Each individual OctaMic undergoes comprehensive quality control and a complete test at RME before shipping. The usage of high grade components allow us to offer a full two year warranty. We accept a copy of the sales receipt as valid warranty legitimation. If you suspect that your product is faulty, please contact your local retailer. The warranty does not cover damage caused by improper installation or maltreatment - replacement or repair in such cases can only be carried out at the owners expense. RME does not accept claims for damages of any kind, especially consequential damage. Liability is limited to the value of the OctaMic. The general terms of business drawn up by Synthax Audio AG apply at all times.

13. Appendix

RME news, driver updates and further product information are available on our website: http://www.rme-audio.com
Trademarks All trademarks, registered or otherwise, are the property of their respective owners. RME is a registered trademark of RME Intelligent Audio Solutions. OctaMic is a trademark of RME Intelligent Audio Solutions.
Copyright Matthias Carstens, 3/2004. Version 1.0 Although the contents of this Users Guide have been thoroughly checked for errors, RME can not guarantee that it is correct throughout. RME does not accept responsibility for any misleading or incorrect information within this guide. Lending or copying any part of the guide or the RME Driver CD, or any commercial exploitation of these media without express written permission from RME Intelligent Audio Solutions is prohibited. RME reserves the right to change specifications at any time without notice.
14. Block Diagram OctaMic
15. CE / FCC Compliance Statements
This device has been tested and found to comply with the EN55022 class B and EN50082-1 norms for digital devices, according to the European Council directive on counterpart laws in the member states relating to electromagnetic compatibility (EMVG).
This device has been tested and found to comply with the requirements listed in FCC Regulations, part 15 for Class B digital devices. Compliance with these requirements provides a reasonable level of assurance that your use of this product in a residential environment will not result in harmful interference with other electronic devices. This equipment generates radio frequencies and, if not installed and used according to the instructions in the Users Guide may cause interference harmful to the operation of other electronic devices. Compliance with FCC regulations does not guarantee that interference will not occur in all installations. If this product is found to be the source of interference, which can be determined by turning the unit off and on again, please try to eliminate the problem by using one of the following measures: Relocate either this product or the device that is being affected by the interference Use power outlets on different branch circuits, or install AC line filters Contact your local retailer or any qualified radio and television engineer FCC compliance statement: Tested to comply with FCC standards for home or office use.