User’s Guide ADI-2 Pro FS Conversion done right 32 Bit / 768 kHz Hi-Res Audio SteadyClock FS SyncCheck 2 Channels Analog / Digital Converter 4 Channels Digital / Analog Converter AES / ADAT / SPDIF Interface 32 Bit / 768 kHz Digital Audio USB 2.
General 1 2 3 4 5 Introduction ...............................................................5 Package Contents .....................................................5 System Requirements ..............................................5 Brief Description and Characteristics.....................6 First Usage - Quick Start 5.1 Connectors and Controls ........................................7 5.2 Quick Start ..............................................................8 5.3 Operation at the unit..............
17 Modes 17.1 Auto...................................................................... 34 17.2 Preamp ................................................................ 35 17.3 AD/DA Converter ................................................. 36 17.4 USB...................................................................... 37 17.5 Digital Through..................................................... 39 17.6 DAC ..................................................................... 40 18 Balanced Phones Mode.
Installation and Operation – iOS 29 30 31 32 General .....................................................................62 System Requirements ............................................62 Setup ........................................................................62 Supported Inputs and Outputs ..............................62 Technical Reference 33 Technical Specifications 33.1 Analog Inputs .......................................................64 33.2 Analog Outputs .............................
1. Introduction RME’s ADI-2 Pro is a true milestone in many ways. Looking at the multitude of AD/DA converters, USB DACs and dedicated headphone amps available, RME developers felt they all lacked obvious features that are unavoidable to enjoy operation as well as when listening to music.
4. Brief Description and Characteristics The ADI-2 Pro is a 2-channel analog input to digital and 4-channel digital to analog output converter in a half-rack (9.5") enclosure of 1 U height. Latest 32 bit / 768 kHz converters offer up to 124 dBA signal to noise ratio. This value is not only printed in the brochure – it is what the unit achieves in real-world operation. Reference class tech specs throughout are combined with an unprecedented feature set.
5. First Usage – Quick Start 5.1 Connectors and Controls The front of the ADI-2 Pro has 3 hi-precision rotary encoders with push function, 4 buttons, a standby power button, a high resolution IPS display, and two TRS headphone outputs. The output channels 1/2 and 3/4 feed two phones outputs via two independent Extreme Power driver circuits, optimized for both high and low impedance headphones. Their unbalanced output signal is of highest quality.
5.2 Quick Start Connect the unit to the included power supply and push the Standby button to start. The ADI-2 Pro ships with Basic Mode Auto activated (SETUP – Options – Device Mode / DSD – Basic Mode). The input selection for SPDIF (coaxial or optical), and the source selection for Phones Out 3/4 are also set to Auto, the SRC is activated for the SPDIF input.
The unit has several informative screens on the top level. These are Global Level Meters, Analyzer Input, Analyzer Output 1/2, Analyzer Output 3/4, State Overview and Dark Volume. Change between them by pushing encoder 1 or 2 whenever any of them is displayed. To quickly call them up simply press any of the 4 buttons several times. In all these screens turning encoder 1 and 2 brings up the quick access to Bass and Treble, with ± 6 dB maximum boost/cut. 5.
5.5 Playback In the audio application being used, the ADI-2 Pro must be selected as output device. It can often be found in the Options, Preferences or Settings menus, as Playback Device, Audio Devices, Audio etc. After selecting a device, audio data is sent to an analog or digital port, depending on which has been selected as playback device. Increasing the number and/or size of audio buffers may prevent the audio signal from breaking up, but also increases latency i.e. output is delayed. 5.
6. Power Supply In order to make operating the ADI-2 Pro as flexible as possible, the unit has a universal DC input socket, accepting voltages from 9.5 Volts up to 15 Volts. An internal switching regulator of the latest technology with high efficiency (> 90%) prevents internal hum noise by operating above audible frequencies. Internally the switching regulator is followed by standard linear regulators, followed by super low-noise linear regulators.
8. Features Explained 8.1 Extreme Power Headphone Outputs During the development of the ADI-2 Pro an extensive research on today’s headphone amp technology as well as headphones has been carried out. Many (many!) headphones later a maximum output level of +22 dBu (10 Volt) was set as development goal, as it will drive even insensitive headphones sufficiently, while a maximum output current of around 260 mA per channel will result in lots of power for lower impedance phones (1.5 Watts @ 32 Ohm).
8.2 Dual Phones Outputs Many features and design decisions on the ADI-2 Pro come from personal usage and experience. For example when comparing headphones: it turns out to be very difficult when having just one headphone output. Changing the phones on the head is already a disrupting process which hinders easy comparison, but without proper level adjustment first, and the need to unplug one and to plug the other, comparisons are only possible for coarse differences.
This is one of the many major features that can’t be found on any similar device: a high-quality 5-band parametric EQ, usable at up to 768 kHz sample rate, easy to set up and adjust, with a graphical display showing the resulting curve, and multiple storage places including individual naming. So whatever EQ setting you need, it is loaded and modified quickly. And there is not only one, but three such EQs, separately for the analog inputs, and both stereo analog outputs.
Here is an example on how it works: the user’s typical lowest level listening volume is at -35 dB at the unit. This value is now set by the user as Low Vol Ref in the Loudness menu. Then Bass and Treble Gain can be set between 0 and +10 dB. Default is +7 dB for both. Increasing the volume by turning the Volume knob causes the gain in Bass and Treble to be lowered smoothly over a range of 20 dB.
8.8 DSP Limitations There is never enough DSP power – no matter how much you add (frustrated developer). That is true even for the ADI-2 Pro. Although being equipped with a quite capable 2.17 Giga FLOPS DSP chip, plus using the FPGA to perform further calculations (RME’s virtual DSP for mixing/routing, level meters, filtering, Crossfeed), 768 kHz sample rate takes its toll. The calculation power available at 48 kHz is divided by 16 (!) then. Even at 384 kHz it is just 1/8 of that at 48 kHz.
User’s Guide ADI-2 Pro FS Basic and Stand-Alone Operation Details User’s Guide ADI-2 Pro FS – v 2.
9. Operation and Usage General operation and usage of the ADI-2 Pro are explained in chapter 5.2, Quick Start, and chapter 5.3, Operation at the unit. The ADI-2 Pro ships with Basic Mode Auto activated.
11. VOL The VOL key brings up an extended volume screen with balance control. Pushing the big Volume knob changes the volume setting between outputs 1/2 and 3/4, which can then be adjusted by both Volume knob and encoder 1. Encoder 2 sets the Balance parameter. The volume and balance setting is also found in the menu I/O, Settings, at the end of the list. The status bar at the bottom of the display shows the current dB value of both volume settings.
Trim Gain Left, Trim Gain Right Digital amplification of the input signal between 0 and +6 dB, in steps of 0.5 dB. Main use is to fine-tune the input sensitivity so that it matches the reference output level of external gear. Phase Invert Available settings are Off, Both, Left and Right. Inverts the phase (180°) on the corresponding channel. M/S-Proc Activates M/S processing. Monaural content is sent to the left, stereo to the right channel. AD Filter Short Delay Sharp, Short Delay Slow, Sharp, Slow.
Subpage Parametric EQ R is only shown with Dual EQ set to On. It has the exact same entries as listed above. 12.2 Main Output 1/2 12.2.
De-Emphasis Auto, OFF, ON. Default: Auto. For manually de-/activating the DAC's de-emphasis filter. See chapter 34.4. Volume Mirrors the direct volume control via Volume knob or encoder 1. The output level can be set between -96 dB and +6 dB, mostly in steps of 0.5 dB. The encoders use a special accelerator algorithm. Turning the knob fast increases the step size. At moderate turning speed the changes in dB follow the intended volume change. Only at slower turning the finest steps will be used.
12.2.3 Loudness Subpage Loudness has the following entries: Enable ON, OFF. Default: OFF. Bass Gain Maximum Bass amplification. Adjustable between +1 dB and +10 dB in steps of 0.5 dB. Default: +7 dB Treble Gain Maximum Treble amplification. Adjustable between +1 dB and +10 dB in steps of 0.5 dB. Default: +7 dB Low Vol Ref Reference level for highest Bass/Treble amplification, referenced to the Volume set in dB. Available range is -90 dB to -20 dB. Default: -30 dB.
13. EQ The key EQ brings up a graphical EQ screen (Bode plot) to set the EQ quickly and with full overview. It is available on all analog I/Os. The I/O - Settings submenu Parametric EQ mirrors the settings done in this screen. On the top level, turn encoder 1 to change between Analog Input, Main Output 1/2 and Phones Out 3/4. Turning encoder 2 will scroll through all 5 bands, as can be seen in the parameter line.
If the frequency graph is shown as grey line the EQ is disabled. There are two ways to change this state: ¾ Push key EQ again to change to the page EQ Enable / Presets, see below. ¾ Push key I/O, select current channels, Subpage Parametric EQ, EQ Enable ON or OFF Pushing the EQ key a second time brings up the EQ Enable / Presets screen. In this screen the EQ can be switched on and off, and EQ presets can be stored and loaded comfortably.
14. SETUP The key Setup gives access to two top level screens: Options and Load/Store all Settings. Options has the subpages SPDIF / Remap Keys, Device Mode / DSD, Clock, Phones and Display. 14.1 Options 14.1.1 SPDIF / Remap Keys Subpage SPDIF / Remap Keys has the following entries: SPDIF In Available settings are: Auto, Coax, Optical. Default: Auto. SRC (Sample Rate Converter) Available settings are: Off, AES In, SPDIF In. Note: In case a DoP signal (DSD) is detected, SRC is automatically switched off.
14.1.2 Clock Clock Source Choices are Auto, INT (Internal, Master), AES, SPDIF. Sample Rate Choices are 44.1, 48, 88.2, 96, 176.4, 192, 352.8, 384, 705.6 and 768 kHz. When clocked externally the ADI-2 Pro supports the same sample rates. When using 352.8 or 384 kHz sample rate the level meter display shows a single channel of audio sent out from SPDIF, or received in case a signal of 192 kHz sample rate is attached. The reason is that the ADI-2 Pro includes a special SMUX mode.
14.1.4 Phones Dual Phones OFF, ON. Default: OFF. With Dual Phones ON the phones output PH 1/2 will be active. Default state is Off, as PH 3/4 is the main phones output and should be used exclusively unless two phones are to be connected. If Dual Phones is on and two phones are plugged in, a push on VOLUME toggles between 1/2, 3/4 and linked volume control (with the marker over both). When VOLUME is turned the Dual Volume screen is shown then. Bal Phones Mode OFF, ON, Auto. Default: OFF.
Show Vol. Screen ON, OFF. Default: ON. When turning the VOLUME knob the Volume screen is shown. LCD Brightness Adjustable from 20% to 100%. Default is 80%. LCD Tint Control Adjustable from -8 (yellow) to 8 (blue). Enables compensation of the display's colour deviation as well as suiting the user's taste. 14.2 Load/Store all Settings This option allows to save the whole state of the unit as Setup in 9 memory slots. The EQ Presets are not included, they are stored separately and are available for any setup.
15. Top Screens The ADI-2 Pro has four different meter screens: a global level meter that shows all signal levels of all I/Os simultaneously, an Analyzer showing the audio signal content on the analog inputs and both analog outputs 1/2 and 3/4, a state overview showing the digital states of AES, SPDIF and USB, and a dark Volume screen with comprehensive information. Pushing the small encoder 1 or 2 while any meter screen is active cycles through all meter screens.
15.3 State Overview The State Overview screen is a typical RME feature. Since 20 years we prefer to give our customers more information at hand than just ‘something there’. The Settings dialogs of our audio interfaces include detailed Input Status analysis to simplify setup and ease trouble-shooting. Additionally RME provides a free tool with any audio interface, DIGICheck, which analyzes levels, Channel Status and bit stream content, the true hardware sample rate and much more.
The inclusion of the SRC status helps to find simple errors that can happen due to the many options of the ADI-2 Pro, which naturally reside in different parts of the menu structure. For example the SRC might be active, but SPDIF signal is dead audio-wise. A quick glance at the State Overview will reveal that the SRC was set to work on the wrong input (AES)… 15.
Dual Phones Mode required Phones output PH 1/2 is considered an additional output for two specific cases: usage of two headphones and balanced phones operation. Therefore plugging in phones into output PH 1/2 brings up a warning that this output is coupled to the rear outputs, and should only be used if required. PH 1/2 stays deactivated until Dual Phones mode has been activated via SETUP. Overload / Short detected An internal overload can be caused by too high output levels and too low load impedance.
The ADI-2 Pro also shows certain Info Messages during normal operation, to explain the current state and to point out possible problems. In AD/DA and DAC mode, a Non-Audio Channel Status causes the DA section to be muted. An info message Non-Audio signal at SPDIF input gives a hint why there is currently no analog audio at the outputs present. In USB mode, an Emphasis Channel Status brings up the info message Emphasis detected at SPDIF input.
17.2 Preamp Preamp: Analog in to Analog out (internal digital routing). This mode can be activated manually by selecting Basic Mode – Preamp. The device enters Preamp mode automatically when Basic Mode is set to Auto and no digital input signal and no USB is detected. Analog input signals are automatically routed to the analog outputs.
17.3 AD/DA Converter AD/DA: Converter Mode, analog in to all digital outs, digital in to all analog outs. This mode can be activated manually by selecting Basic Mode – AD/DA. The device enters AD/DA mode automatically when Basic Mode is set to Auto and a digital input signal is detected. The detected digital input signal will also become the signal source. In case more than one digital signal is found the user has to manually select the source to be monitored (I/O – Output Channel - Settings – Source).
17.4 USB USB: interface mode. This mode can be activated manually by selecting Basic Mode – USB. The device enters USB mode automatically when Basic Mode is set to Auto and a USB connection is detected. USB has priority over AD/DA mode. In USB mode all inputs are routed to USB, all outputs are fed from USB. In SETUP – Options – Device Mode / DSD – CC-Mode the unit can be configured as 2-channel (Stereo) or 6/8channel (Multi-channel) device.
Class Compliant Multi-channel mode With USB connected all digital and analog inputs (6 channels) are routed to USB recording. In the same way USB playback will feed all outputs separately (8 channels). In 6/8 channel mode all I/Os can be used separately. Phones output 3/4 provides USB playback of channels 1/2 when its Source is set to Auto (default).
17.5 Digital Through Mode This additional mode is a manual option only, it is not available via Basic Mode Auto. It has to be activated manually by selecting Basic Mode – Dig Thru. The purpose of the Digital Through Monitor is exactly what its name describes. A single digital input signal is passed through the unit and can be monitored on the analog outputs at the same time.
17.6 DAC This additional mode is a manual option and not available via Basic Mode Auto. It must be activated manually by choosing Basic Mode – DAC. This mode simplifies operation and source selection. Using the ADI-2 Pro as a typical HiFi DAC becomes a breeze: ¾ Simple 2 channel stereo operation ¾ Easiest switching between the sources to be monitored, like USB and SPDIF In this mode the source selection of Main Out 1/2 also defines the clock source of the unit.
18. Balanced Phones Mode In balanced operation, two identical power amplifiers are used to drive one side of the phones each. Compared to normal, grounded operation, the voltage seen by the phone driver/speaker is doubled. The power sent to it is even quadrupled. With the comparatively low power required by headphones, and its already powerful Extreme Power outputs, the balanced phones mode of the ADI-2 Pro has not been optimized for more power, but more fidelity. See chapter 34.
19. DSD 19.1 General DSD (Direct Stream Digital) is a stream with single bit resolution, but multiple times the sample rate of the CD. DSD64 equals 64 times 44.1 kHz = 2.8 MHz, DSD128 5.6 MHz, DSD256 11.2 MHz. Versions with multiples of 48 kHz also exist, up to 12.2 MHz. To transfer DSD data over SPDIF, AES or even USB, DSD over PCM (DoP) is the de-facto standard.
19.3 DSD Playback During a DSD playback all DSP functions of all channels are temporarily disabled, even when transmitting PCM. This is signalled in several menus by brackets around the (ON). Analyzer and level meter show DSD signals in blue color, the current mode is therefore easy to recognize. The change between PCM and DSD causes a low volume click noise. For optimized sound and fidelity, the ADI-2 Pro does not use any lossy analog volume control, hence can't suppress the DAC's click noise.
Software to record DSD audio: Name VinylStudio OS Win/Mac URL www.alpinesoft.co.uk Sound-It! Win/Mac http://www.ssw.co.jp Pyramix Win www.merging.com AudioGate4 Win/Mac www.korg.com 19.5 DSD Level Meter While most DACs, even ones seen as 'Hi-End', leave the user clueless during DSD operation, the ADI-2 Pro continues to show level as well as spectral content. To be able to show the analog I/Os audio signals on level meters and Analyzer the DSP performs an additional DSD to PCM conversion.
User's Guide ADI-2 Pro FS Inputs and Outputs User’s Guide ADI-2 Pro FS – v 2.
20. Analog Inputs The ADI-2 Pro has two analog line inputs that can operate with levels up to +24 dBu. The electronic input stage uses a servo balanced design which handles unbalanced (TS jacks) and balanced signals (TRS / XLR) correctly, automatically adjusting the level reference. ! When using unbalanced cables with the XLR inputs, pin 3 of the XLR jack should be connected to ground. Otherwise noise may occur, caused by the unconnected negative input of the balanced input.
21.2 Line Out TS 1/2 The ADI-2 Pro has two unbalanced analog outputs that can operate with levels up to +19 dBu. The short circuit protected, low impedance line outputs 1/2 are available as 1/4" TS jacks on the back of the unit. When inserting a stereo TRS connector the ring contact is connected to ground. Due to the unbalanced operation the TS outputs follow all Ref Lev settings, but stay at +19 dBu when +24 dBu is selected. For Auto Ref Level see next chapter. 21.
If operation of the phones output 1/2 is desired, the Dual Phones mode has to be switched on. The menu has the additional option to turn off the rear outputs as soon as PH 1/2 is plugged in. Default is Mute On when plugged. While these outputs are praised as ideal headphone outputs, eventually as well as technically they also are ideal line outputs. 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.
Output As can be seen in the block diagrams of chapter 17, in most modes all digital outputs carry the same signal. The ADI-2 Pro then operates like a splitter/distributor. The input signal is converted to several digital formats at the same time, and can be used up to three times (AES, SPDIF coaxial, SPDIF optical or ADAT). In USB multi-channel mode the AES output becomes playback channels 5/6, see chapter 17.4.
Output With SPDIF identical signals are available at both the optical and the coaxial output. An obvious use for this would be to connect two devices, i.e. using the ADI-2 Pro as a splitter (distribution 1 on 2). Under Setup – Options – SPDIF / Remap Keys – Optical Out the output format can be manually changed from SPDIF to ADAT. Only two channels are sent via ADAT, the same that are still available at the coaxial output.
User's Guide ADI-2 Pro FS Installation and Operation – Windows User’s Guide ADI-2 Pro FS – v 2.
23. Driver Installation Note: Since FPGA firmware 177 the ADI-2 Pro is fully compatible to Windows 10 (1709 or newer) when operated in CC mode Stereo. An installation of RME drivers is still recommended. They add ASIO (PCM, DSD DoP and DSD Native) and 768 kHz WDM. They are also required for firmware updates and DIGICheck. Additionally the Multi-channel mode is not fully working in Windows 10 (tested with 1803). RME is constantly improving their drivers.
24. Configuring the ADI-2 Pro 24.1 Settings Dialog Configuration of the ADI-2 Pro is usually done directly at the unit. For ASIO operation sample rate and buffer size (latency) can be set via a dedicated settings dialog. The panel 'Settings' can be opened by clicking on the fire symbol in the Task Bar's notification area Any changes made in the Settings dialog are applied immediately confirmation (e.g. by clicking on OK or exiting the dialog) is not required.
24.2 Clock Modes - Synchronization In the digital world, all devices must be either Master (clock source) or Slave (clock receiver). Whenever several devices are linked within a system, there must always be a single master clock. ! A digital system can only have one master! If the ADI-2 Pro’s clock mode is set to 'Internal', all other devices must be set to ‘Slave’. To cope with some situations which may arise in studio practice, defining a sync reference is essential.
25.2 DVD-Playback (AC-3/DTS) AC-3 / DTS When using popular DVD software players, their audio data stream can be sent to any AC3/DTS capable receiver via the ADI-2 Pro. ! The sample rate must be set to 48 kHz in the ADI-2 Pro Settings dialog, or the software will only playback the down-mixed analog signal via SPDIF. In some cases an ADI-2 Pro output device has to be selected in >Control Panel / Sound / Playback< and be set as Default, or the software will not recognize it.
25.5 ASIO Start the ASIO software and select ASIO MADIface USB as the audio I/O device or the audio driver. The sample rate is set by the ASIO application. The buffer size (latency) is set in the RME Settings dialog. The number of available channels depends on the current Class Compliant mode: 2 channels I/O when set to Stereo, 6 in / 8 out when set to Multi-channel. See chapter 14.1.3. Note: changing the CC-Mode requires to temporarily disconnect the ADI-2 Pro from the computer. The ASIO 2.
User's Guide ADI-2 Pro FS Installation and Operation – Mac OS X User’s Guide ADI-2 Pro FS – v 2.
27. General The ADI-2 Pro is a UAC 2.0 Class Compliant device. Mac OS X has full UAC support built-in, there is no driver installation required. Connect computer and ADI-2 Pro with a USB cable. Mac OS X detects the new hardware as ADI-2 Pro (serial number). The number of available channels depends on the current Class Compliant mode: 2 channels I/O when set to Stereo, 6 in / 8 out when set to Multi-channel. See chapter 14.1.3.
27.2 Clock Modes - Synchronization In the digital world, all devices must be either Master (clock source) or Slave (clock receiver). Whenever several devices are linked within a system, there must always be a single master clock. ! A digital system can only have one master! If the ADI-2 Pro’s clock mode is set to 'Internal', all other devices must be set to ‘Slave’. To cope with some situations which may arise in studio practice, defining a sync reference is essential.
User’s Guide ADI-2 Pro FS - v 2.
User's Guide ADI-2 Pro FS Installation and Operation – iOS User’s Guide ADI-2 Pro FS – v 2.
29. General The ADI-2 Pro operates in Class Compliant mode (UAC 2.0), a standard that is natively supported by operating systems like iOS, Mac OS X, Linux and Windows 10 (since 1709). No proprietary drivers are required, the device will be directly recognized. The ADI-2 Pro provides iOS devices with the professional analog I/O connections they lack.
User's Guide ADI-2 Pro FS Technical Reference User’s Guide ADI-2 Pro FS – v 2.
33. Technical Specifications 33.1 Analog Inputs XLR • Input: XLR, servo-balanced • Input impedance balanced: 18 kOhm, unbalanced: 9 kOhm • Input sensitivity switchable +24 dBu, +19 dBu, +13 dBu, +4 dBu @ 0 dBFS • Digital Trim Gain range: 0 dB up to +6 dB • Signal to Noise ratio (SNR) @ +13/19/24 dBu: 120.x dB RMS unweighted, 124.x dBA • Signal to Noise ratio (SNR) @ +4 dBu: 119 dB RMS unweighted, 123 dBA • Frequency response @ 44.1 kHz, -0.1 dB: 5 Hz – 20.5 kHz • Frequency response @ 96 kHz, -0.
Phones 1/2 As Output 1/2 TS, but: • Output: 6.3 mm TRS jack, unbalanced, stereo • Output impedance: 0.1 Ohm • Signal to Noise ratio (SNR) @ +22 dBu: 117 dB RMS unweighted, 120 dBA • Signal to Noise ratio (SNR) @ +7 dBu: 114 dB RMS unweighted, 118 dBA • Output level at 0 dBFS, Ref Level +19 dBu, load 100 Ohm or up: +22 dBu (10 V) • Output level at 0 dBFS, Ref Level +4 dBu, load 8 Ohm or up: +7 dBu (1.73 V) • THD @ +18 dBu, 32 Ohm load, 1.2 Watt: -110 dB, 0.0003 % • THD+N @ + 18 dBu, 32 Ohm load: -107 dB, 0.
33.4 Digital Outputs AES/EBU • 1 x XLR, transformer-balanced, galvanically isolated, according to AES3-1992 • Output level 2.7 Vpp • Format Professional according to AES3-1992 Amendment 4 • Single Wire mode, sample rate 44 kHz up to 200 kHz SPDIF coaxial • 1 x RCA, according to IEC 60958 • Output level 0.
33.7 Connector Pinouts Pin assignment of the 9-pin D-sub connector, breakout cable SPDIF / AES Note: The digital breakout cable is identical to the one used in HDSPe series cards. Pin 1 2 3 Name GND SPDIF Out + SPDIF In + Pin 4 5 6 Name AES Out + AES In + SPDIF Out - Pin 7 8 9 Name SPDIF In AES Out AES In - TS jack analog output The 1/4" TS jacks on the rear are wired according to international standards: Tip = + (hot), Ring = GND, Sleeve = GND.
34. Technical Background 34.1 Lock and SyncCheck In the analog domain one can connect any device to another device, a synchronization is not necessary. Digital audio is different. It uses a clock base. 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.
34.2 Latency and Monitoring Preamp Mode In Preamp mode the analog input signal is converted to digital, processed by the DSP, then converted back to analog. An ADC and DAC have a specific delay caused by their internal oversampling and anti-alias filtering. This delay has been reduced significantly in the last years, and is now so small that usually it is impossible to hear. The values of the AD and DA conversion are shown in the table below.
34.3 Balanced Phones Mode Headphones usually share one wire between left and right channel: the common ground, hence operation is unbalanced. A different way to build a powerful output stage uses a balanced design. Both wires to the speaker are ‘phase’, there is no ground connection. This technique is mostly used in car audio, as the operating voltage is limited to 12 Volt, and balanced operation, here called bridging, delivers double the output voltage and four times the output power to the speaker.
This design, as common as it is, has several disadvantages: • an analog inverter stage has to be added to the signal path • the common mode situation of the signal at the phones is compromised by the difference between + and – phase, caused by the analog inverter • multiple relays and laborious cabling with wires running back and forth from/to the PCB are typical for such a design The ADI-2 Pro deserves a different, better way to go balanced.
The Advanced Balanced mode of the ADI-2 Pro is as unique as brilliant. Balanced mode never made as much sense as when implemented like done here! In Advanced Balanced mode the ADI-2 Pro’s maximum output level rises to +13 dBu for HiPower Off and +28 dBu for Hi-Power On. The signal to noise ratio rises from 117 dB / 120 dBA to 120 dB / 123 dBA. Or in other words: while the output level rises by 6 dB, the noise rises only by 3. And therefore stays inaudible as in normal operation.
34.5 Noise Levels in Hi-Speed Modes The outstanding signal to noise ratio of the ADI-2 Pro AD-converters can be verified even without expensive test equipment, by using record level meters of various software. But when activating higher sample rates, the displayed noise level will rise from -120 dBFS to -114 dBFS at 96 kHz, and –92 dBFS at 192 kHz. This is not a failure.
It needs to be mentioned that the ADC used in the ADI-2 Pro has improved noise shaping filters, adapted to the higher sample rate range that it offers. Indeed the rise in noise over frequency is much lower than in former converter chips, where for example at 192 kHz sample rate the wideband noise measurement would not reach -92 dBFS, but only -79 dBFS.
Common interface jitter values in real world applications are below 10 ns, a very good value is less than 2 ns. The screenshot shows an extremely jittery SPDIF signal of about 50 ns jitter (top graph, yellow). SteadyClock turns this signal into a clock with less than 2 ns jitter (lower graph, blue). The signal processed by SteadyClock is of course not only used internally, but also used to clock the digital output.
34.7 AD Filter Curves 34.8 DA Filter Curves 44.1 kHz 76 User’s Guide ADI-2 Pro FS - v 2.
34.9 DA Impulse Responses Short delay Sharp Sharp Short Delay Slow Slow The screenshots above show the analog output signal of the DAC filters, stimulated by a digital single sample impulse at 44.1 kHz sample rate. While Slow has the most perfect response, it looses around 1.2 dB already at 15 kHz, see chapter 34.8. Both Short Delay are IIR filters, the other two are FIR type. FIR is phase linear over the whole frequency range.
34.10 AD Impulse Responses On the AD side the ADI-2 Pro offers four filters: Short Delay Sharp, Short Delay Slow, Sharp and Slow. Basically these behave and operate exactly the same way as the filters already described for the DAC. SD Sharp and Sharp offer the most linear frequency response and highest suppression of mirroring (aliasing) at high frequency input signals.
34.11 Frequency Response Measurements 34.12 Loudness User’s Guide ADI-2 Pro FS – v 2.
34.13 Total Harmonic Distortion Measurements 80 User’s Guide ADI-2 Pro FS - v 2.
34.14 Extreme Power Charts User’s Guide ADI-2 Pro FS – v 2.
34.15 Phones Distortion Comparison 34.16 Impedance based Level Meters PH 1-4 The horizontal level meters in various screens of outputs 1 to 4 show the digital level fed to the DAC. Above 32 Ohms the level meter's display matches the real analog output level (0 dBFS = +22 dBu). But at 32 Ohms the ADI-2 Pro delivers only +19 dBu, at 16 Ohms +15 dBu to the phones outputs, because a reasonable current limiting circuit prevents a too high output power at lower load impedances.
34.17 USB Audio An ADI-2 Pro can achieve a performance similar to a PCI or PCI Express based soundcard when used with an optimal PC. Low CPU load and click-free operation even at 64 samples buffer size are indeed possible on current computers. However, using older computers a simple stereo playback will begin to cause a CPU load of more than 30%. A computer blocked for a short time – no matter if ASIO or WDM – will lose one or more data packets.
One should not underestimate the effect on higher sample rates with PCM and DSD, though. Those require to transfer data of multiples of the amount typical for a channel at 48 kHz: Base Channels 48 kHz 2 96 kHz 4 192 kHz/DSD64 8 384 kHz/DSD128 768 kHz/DSD256 16 32 Now it should be clear why the above advice can be quite important even for an ADI-2 Pro.
An effective fix can be provided by a digital compensation filter, put into the DA path of the ADI2 Pro, always and only active at 384 kHz sample rate. This filter is fine-tuned to achieve a near perfect frequency response when self-measuring from DA to AD (loop) at 384 kHz. The picture below shows the ADI-2 Pro in loopback mode, XLR Out to In, at 384 kHz sample rate.
For the technician: • • • In many measurement applications the generator level is intentionally set below 0 dBFS, when measuring the frequency response and also when measuring THD (-1 or -3 dBFS). Test signals with a frequency close to the DAC's filter slope often cause aliasing effects and other unwanted intermodulation products. For clean measurements at such high frequencies levels are often reduced to -10 dBFS. If such high frequencies are used for measurements at all.
Will this cause a deterioration in sound? No, for two reasons. The input of the ADI-2 Pro has an impedance of 9 kOhm, which is high enough to not overstrain even older Hi-Fi units with higher impedance outputs (up to 1 kOhm). That is even more true with newer units having outputs significantly below 1 kOhm. Additionally the input of the ADI-2 Pro has been designed to have the exact same technical specifications, no matter if a balanced (XLR) or unbalanced (mono 6.35 mm) signal is applied.
How can I quickly change between USB playback and the digital input to monitor these? The ADI-2 Pro actually addresses this case with its auto mode – which fails when the USB cable remains in the ADI-2 Pro, and the computer is still powered on. The switching of the source of the Main Output 1/2 is blocked in USB mode, as it is used for playback. The solution is to manually change the Basic Mode from Auto to AD / DA. More is not necessary.
34.20 Digital Volume Control The ADI-2 Pro deliberately avoids an analog level adjustment by means of a potentiometer. Its digital version surpasses an analog one in practically every conceivable point. Typical disadvantages of setting with potentiometers: • Synchronicity errors lead to panoramic shifts and significant volume deviations left / right, in particular near the end points of the adjustment range.
The following measurement shows a digital full-scale sine of 1 kHz, 16 bits without dither, which is reduced in level by 40 dB. Also shown are a full-scale sine of 1 kHz with 24 bit, at 60 dB and 96.3 dB level attenuation, which is the lowest volume setting the ADI-2 Pro offers. A high-resolution FFT like HpW Works makes it possible to disassemble the signal into individual frequencies, and to identify unwanted components down to a level of -190 dBFS.
34.21 Bit Test A bit test is used to check the playback path for unwanted changes in the playback data. Playback software can cut bits, add dither, or change the level - without these changes becoming noticed easily. A poorly programmed driver can manipulate bits, and a playback hardware could be both badly designed and defective (hanging bits, swapped bits). Even such features as proper channel assignment, left/right synchronicity and polarity can be tested by a well-made bit test.
34.22 M/S Processing The mid/side principle is a special positioning technique for microphones, which results in a mid signal on one channel and a side signal on the other channel. This information can be transformed back into a stereo signal quite easily. The process sends the monaural mid channel to left and right, the side channel too, but phase inverted (180°) to the right channel. For a better understanding: the mid channel represents the function L+R, while the side channel represents L-R.
User's Guide ADI-2 Pro FS Miscellaneous User’s Guide ADI-2 Pro FS – v 2.
35. Accessories There are several items available for the ADI-2 Pro: Part Number Description NT-RME-2 Power supply for ADI-2 Pro. Robust and light-weight switching power supply, 100 V-240 V AC, 12 V 2 A DC. Lockable DC connector. BO968 Digital breakout cable (9-pin D-sub to 2 x XLR and 2 x RCA) USB2M RME USB 2 cable, length 78” (2m) RM-19-X 19" Rack Adapter, mounted on the sides of the ADI-2 Pro Unirack Universal rackmount adapter (tub for two 9.
37. Appendix RME news, driver updates and further product information are available on RME’s website: http://www.rme-audio.com Worldwide distribution: Audio AG, Am Pfanderling 60, D-85778 Haimhausen, Tel.: (49) 08133 / 918170 Acknowledgements The Bauer Binaural Crossfeed effect in the ADI-2 Pro was inspired by Boris Mikhaylov’s bs2b implementation. Trademarks All trademarks, registered or otherwise, are the property of their respective owners.
38. Declaration of Conformity CE 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 RL2014/30/EU, and European Low Voltage Directive RL2014/35/EU. FCC This device complies with Part 15 of the FCC Rules.
