INT203 Owner’s Manual Weiss Engineering ltd. Florastrasse 42 8610 Uster Switzerland Phone: Fax: Email: Web: +41 44 940 20 06 +41 44 940 22 14 weiss@weiss.ch www.weiss-highend.com www.weiss.ch www.asiaweiss.
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iii Introduction Dear customer, Congratulations on your purchase of the INT203 Firewire I/O Interface and welcome to the family of Weiss equipment owners! On the following pages I will introduce you to our views on high quality audio processing. These include fundamental digital and analog audio concepts and the INT203 Firewire I/O Interface. I wish you a long-lasting relationship with your INT203. Yours sincerely, Daniel Weiss President, Weiss Engineering ltd.
iv Copyright and Liability Authors: Daniel Weiss & Rolf Anderegg, Weiss Engineering ltd. TEXLayout: Samuel Groner & Rolf Anderegg, Weiss Engineering ltd. Date: October 15, 2013 Weiss Engineering ltd. reserves the right to make changes to product specification or documentation without prior notice. Updated manuals and datasheets are available at our website for downloading. Weiss Engineering ltd.
v A Short History of Weiss Engineering Ltd. Having studied electrical engineering, Daniel Weiss joined the Willi Studer (Studer-Revox ) company in Switzerland. His work included the design of a sampling frequency converter and of digital signal processing electronics for digital audio recorders. In 1985, Mr. Weiss founded the company Weiss Engineering ltd. From the outset the company concentrated on the design and manufacture of digital audio equipment for mastering studios.
vi 1985 Introduction of the 102 Series, a 24 bit modular digital audio processor for mastering studios 1986 Introduction of one of the first sample rate converters for digital audio 1987 Introduction of one of the first digital equalizers 1989 Introduction of one of the first digital dynamics processors 1991 Introduction of the Ibis digital mixing console, built for the mix-down of classical music 1993 Introduction of the Gambit Series of digital audio processors, which employ 40 bit floating point processi
1 Contents Introduction iii A Short History of Weiss Engineering Ltd. 1 Advanced Digital & Analog Audio Concepts Explained 1.1 Jitter Suppression & Clocking . . . . . . . . . . . . . . . . . 1.2 Jitter handling in the INT203 Firewire I/O Interface . . . . 1.3 Up-/Oversampling & Sampling Rate Conversion in General 1.4 Dithering . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Digital Level Control . . . . . . . . . . . . . . . . . . . . . . 1.6 Firewire vs. USB . . . . . . . . . . . . . . . . .
2 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Digital Inputs . . Digital Outputs . Synchronization . Power . . . . . . Level Control . . Bit Transparency Polarity Control A Contact . . . . . . . . . . . . . . . . . . . . Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Chapter 1 Advanced Digital and Analog Audio Concepts Explained 1.1 Jitter Suppression and Clocking What is jitter and how does it affect audio quality? In the audio field the term jitter designates a timing uncertainty of digital clock signals. In an analog to digital converter (A/D) the analog signal is sampled (measured) at regular time intervals; in the case of a CD, 44 100 times a second or every 22.675737 µs (microseconds).
4 however in a well-designed system these converters employ a synchronous design, where jitter does not play any role. Of course a conversion between 96 kHz and 44.1 kHz as in the example above can be done in a synchronous manner as well. An ASRC in fact is only required either where one or both of the sampling frequencies involved are changing over time ( varispeed“ mode of digital audio ” recorders) or where it is unpractical to synchronize the two sampling frequencies.
5 transfer point of view, they provide increasing jitter attenuation above some chosen corner frequency. Jitter attenuation is just one aspect of PLL design. Other considerations include frequency range and intrinsic jitter. It can be shown that conventional designs are bound by a fundamental tradeoff between these three aspects. For example, specifying a frequency range of one octave means using a low-Q oscillator. But that makes for high intrinsic jitter when the loop corner frequency is held down.
6 happens in the so-called analog to digital converter (A/D). The inverse in the digital to analog converter (D/A). A physical law states that in order to represent any given analog signal in the digital domain, one has to sample that signal with at least twice the frequency of the highest frequency contained in the analog signal. If this law is violated so called aliasing components are generated which are perceived as a very nasty kind of distortion.
7 So engineers looked for ways to enhance those filters. They can’t be eliminated because we are talking laws of physics here. But what if we run the whole thing at higher sampling rates? Like 96 kHz or so? With 96 kHz we can allow frequencies up to 48 kHz, so the reconstruction filter can have a transition band between 20 kHz and 48 kHz, a very much relaxed frequency response indeed. So let’s run the whole at 96 kHz or even higher! Well — the CD stays at 44.1 kHz.
8 are correlated with the audio signal, hence the resulting error is also correlated and thus there are distortions and not just noise (noise would be uncorrelated). The dithering technique now is used to de-correlate the error from the signal. This can be achieved by adding a very low level noise to the original 24 bit signal before truncation. After truncation the signal does not show any distortion components but a slightly increased noise floor.
9 let’s assume we have a 8 bit gain factor for a level control. If we apply that to a signal coming off a CD we multiply a 8 bit gain factor with a 16 bit sample value. The result is up to 24 bits long (the sum of the wordlengths of the two factors).
10 distorted at all, despite the 8 bit resolution. Remember, a 16 bit system has 65 536 quantization steps while a 8 bit system has only 256 quantization steps — a huge difference. And still, the properly dithered 8 bit system sounds great. www.weiss-highend.ch/computerplayback/shapeddither.mp3 This is what a properly dithered level control is capable to do.
11 No collisions, no glitches. From a practical perspective, this also makes it safer to send a lot more audio via Firewire. That’s why most of the multichannel interfaces (18 channels, 24 channels, etc.) are Firewire devices, and USB devices usually just send a two channel stereo signal. For hooking up your mouse, keyboard or thumb drive, USB is plenty fast and plenty cheap. For hard drives, either one will do (although Firewire is somewhat more reliable).
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13 Chapter 2 The INT203 Firewire I/O Interface 2.1 Features The INT203 Firewire I/O Interface extends your computer with digital audio inputs and outputs. It allows you to: • playback audio from your computer to digital audio equipment (D/A converter, digital audio processing, etc.) • connect your computer to digital audio sources (A/D converter, digital audio transports, etc.
14 computer. Thus two separate digital stereo sources will be available (for recording, routing, etc.) within the computer’s audio system (4 channels). Since certain recording applications simply call for stereo sources, the primary input switch (fig. 2.3) allows you to select which of the input connectors is chosen as the primary of the two stereo inputs. 2.1.
15 If the INT203 powers up with the computer connected and with no external power supply connected, then obviously bus power is available. If preferred, the external power supply may still be connected in that case. The INT203 then automatically switches over to the external power supply. Figure 2.1: 4 pin Firewire socket 2.1.
16 INT203’s output. Bit transparency means that the bits fed from the harddisk to the INT203 are not changed in any manner. 2.1.8 Frontpanel • Power switch • Power /Bit Transparency Check LED • Bit Transparency Check switch • Infrared receiver (for optional remove control) • 2 6-pin Firewire 400 sockets, which one is used does not matter • Power socket for an external power supply 2.1.
17 Figure 2.2: INT203 frontpanel Figure 2.
18 Windows: 1. Do not connect the device. 2. Double click WeissFirewireInstaller.exe 3. Click Next 4. Select the directory where you’d like to install the tools. Usually you can use the default values and click Next 5. Select if you’d like to create a desktop icon. Next 6. Click Install 7. You will be asked if you’d like to continue the installation because the driver/software didn’t pass the Windows-Logo-Test. Select Continue. 8. Select Yes, restart the computer now and click Finish Mac: 1.
19 appropriate external power supply (available from Weiss) has to be connected to the INT203 and the power switch at the INT203 has to be switched to on. The INT203 should now be recognized automatically. In Windows tell the installation window that you do not want to check the Microsoft website for drivers and then let the drivers be installed automatically. Ignore warnings concerning Windows Logo Test and continue the installation until completed.
20 2.3.3 Input via AES/EBU and/or S/PDIF Connection Connect the output of any digital audio source to the INT203. Use either the XLR or RCA connectors as applicable. Make sure that the INT203 is synchronized to the connected source, resp. sources. Choose the correct master sync source as applicable in your digital audio setup (refer to section 2.1.4). Automatic sync lock is attempted when an external sync source is selected.
21 Make sure all those processing elements are bypassed. Particularly the sampling rate conversion can creep in unnoticed. I.e. the sampling rate in the Weiss Firewire IO window has to match the sampling rate of the file played, else a conversion is going on in the operating system. For iTunes there is another issue to consider: Whenever the sampling rate is changed in the AudioMidi setup or the Weiss Firewire IO window, the iTunes program has to be restarted to regain bit transparency.
22 The maximum gain is 0 dB (a gain factor of 1.0), i.e. the INT203 can not amplify the signal and thus makes sure that there are no overs occurring within the INT203. The mute switch allows to toggle between fully off (muted) and the volume set with the volume control. Absolute Polarity control: Pressing the mute switch for a few seconds toggles the operation mode to polarity control. In that mode the 4 key switches the polarity to 0◦ and the 5 key switches to 180◦ (i.e. inverted polarity).
23 the indicated sampling rate does not necessarily reflect the one fed from the external device. In this case set the sampling rate as indicated by the Measured Sampling Rate within Device Settings/General. Sync Source selects the clock to which the INT203 should sync to. For playback this is usually the INT203’s Internal clock generator. Buffer Size larger buffer sizes increase robustness against dropouts; lower buffer sizes provide low latency. Operation Mode determines the stability of the system.
24 the external device. In this case set the sampling rate as indicated by the Measured Sampling Rate within Device Settings/General. Sync Source selects the clock to which the INT203 should sync to. For playback this is usually the INT203’s Internal clock generator. Operation Mode determines the stability of the system. Try other modes if clicks are encountered during playback. Global Settings/Info Information about the driver version. Device Settings/General tory.
25 Chapter 3 INT203 Technical Data 3.1 Digital Inputs • (1) XLR connector • (1) RCA connector • all inputs accept professional or consumer standard, i.e. accept AES/EBU or S/PDIF signals. • Maximum input wordlength: 24 bits • The unit has to be power cycled in order for any primary input selection change to take effect (IN1 /IN2 ) • (2) Firewire connectors 3.
26 • the computer is slaved to the INT203 • Extremely efficient Jitter attenuation down to subsonic frequencies 3.4 Power Bus power from the Firewire connector or power from an external power supply, 8 . . . 12 V/0.2 A 3.5 Level Control With the (optional) Remote Control unit the digital output gain can be controlled between 0 dB and -60 dB: From 0 dB to -20 dB in 0.5 dB steps and from -20 dB to -60 dB in 1 dB steps. In the 0 dB gain position the INT203 is fully bit transparent, i.e.
27 Appendix A Contact For any questions, suggestions etc. feel free to contact us at: Weiss Engineering ltd. Florastrasse 42 8610 Uster Switzerland Phone: Fax: Email: Web: +41 44 940 20 06 +41 44 940 22 14 weiss@weiss.ch www.weiss-highend.com www.weiss.ch www.asiaweiss.
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