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About this blog

Over my time reading and writing on the forum there appears to be a need for an aggregated list of component descriptions for "things" in the computer audio chain.   I intend this blog to meet that need.  I am very open to suggestions for entries that I can write about as well as have enough knowledge to describe in a concise manner.  PM me with suggestions please.

Entries in this blog

Music Server / Streamer

Servers, Servers everywhere but not a bit to drink!   As I outlined when talking about the DAC, music data is sent serially to the DAC.   I like the record player analogy.  The stylus on the turntable is transferring what is in the grove at this very second.   So what does the server or streamer do?  In the most basic form, it provides the user interface to operate the software.  That software then reads the data from the local hard drive, or it connects to an online service and reads the music file data from there.  Finally, it sends that data to the DAC for decoding and playback.   Streamer or server software can be designed to run on all kinds of hardware: your PC or Mac, or NAS, an iPhone or iPad.  In more advanced systems the server/streamer is run on dedicated equipment purchased for the purpose.  One example is the Chord Poly.  It is a dedicated streamer that only works hooked up to a Chord Mojo DAC/AMP.  There is streaming software built into some network bridges like the Sonore Rendu series.  Another example is the Roon Labs nucleus products that are purpose-built for this work.   The Roon Labs How Roon Works webpage is a cleanly done pictorial overview of their software.  They break their system into multiple parts and explain them succinctly.   https://roonlabs.com/howroonworks.html   I have a lot more to say about servers and software.  There will be more posts on this subject. Bob

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S/PDIF AES3 or AES/EBU and TOSLINK

I love acronyms, but these are a mouthful.   S/PDIF  (Sony/Phillips Digital Interface) TOSLINK  Toshiba Link  AES3 or AES/EBU  Audio Engineering Society/European Broadcasting Union   The standards were co-developed for the consumer / professional markets.  They define both the data transmission formats as well as the connectors and cabling used to connect devices to transfer digital audio.  These standards include stereo and multi-channel audio formats.   There is some complexity in cable designs.     In AES3 the first is a balanced connection using the XLR connector. The second is an unbalanced connection using 75-ohn BNC  connectors and cable.   The third is TOSLINK. S/PIDF uses an unbalanced connection with RCA connectors and TOSLINK.   The TOSLINK standard defines fiber-optic connectors and cabling for both the professional and consumer designs.  There is a second connector standard called Mini-TOSLINK fits into a 1/8in audio jack where the emitter and sensor are at the tip of the connector.   NOTE: TOSLINK is not the same standard as computer networking optical cabling.  It just happens to use a similar fiber-optic cable.    These connections are subject to some of the same issues that USB has.  There are both clocking and jitter issues and like USB cabling matters.     Here are some Wikipedia articles to take you further.   https://en.wikipedia.org/wiki/S/PDIF https://en.wikipedia.org/wiki/AES3 https://en.wikipedia.org/wiki/TOSLINK   Bob  

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D to D Converter

Digital to Digital conversion is a "process"  that translates one type of digital into another.  D to D conversions have multiple use cases such as converting USB to SPIDF or I2S.     One example of this kind of device is the Sonore UltraDigial. Another is the Aurender UC-100.  You can visit their product pages for more information.  

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SFP Transceiver

In modern networking, there are multiple media types including various types of Ethernet, Fiber Optic and Coax cabling.  The Small Form Factor (SFP) transceiver is a standards-based device that is used to allow different physical network media connections to network devices such as switches.  SFP has a standard mechanical and electrical interface for interchangeably.   Many applications of the SFP are for fiber-optic network connections that provide electrical separation or long distance transmission needs. In most home networking situations, we do not see any use of SFP devices.   There is a growing use case for fiber-optic networking cabling to provide electrical noise isolation.  I will expand on this in a later blog post.   For reference here is the Wikipedia entry for SFP:   https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver      

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Analog Wednesday: The Pre-amplifier and Amplifier

Welcome to my first Analog Wednesday!  "Stuck in the Middle With You" With apologies to "Stealers Wheel."   DAC's to the left of me,
Speakers to the right, here I am,
Stuck in the middle with you       I do not want to leave out the parts of the system that make the sound!  In a file-based or digital music system something has to make the air move, and that is the speakers.  (OR Headphones). Working upstream from the speakers we need amplification to power the speakers.  In a system of separate components, there are usually two devices.   The Pre-amplifier takes signals from a DAC or a CD player or in a particular case a Turntable.  Many times the preamplifier has an input selection switch system to pick the source input.  Most preamplifiers have the volume control for the system.   The inputs and outputs of the preamplifier are at what we call line level.  Line level cannot drive speakers!   So the pre-amp is an input switcher and volume control!   The next device in line is the power amplifier.  This is where line-level or low voltage signals are transformed to drive speakers.   Where this gets interesting is in devices like the Mytek Brooklyn DAC that is a DAC, Phono-stage, digital or analog volume control, input switch, and pre-amp.  WHEW, a stereo swiss army knife!   Another device that is "all-in-one" is the Naim Unity Atom that does even more by including a power amplifier.  And do not forget the Chord Mojo and others that are a DAC with integrated headphone amplifier built-in.   There are also systems like the KII Three or the KEF LS50W that have it all neatly tucked into the speakers!  These are not your 1970 JBL's!   I will discuss the analog portions of the system over time and will try for Wednesdays!     Bob    

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USB -- Universal Serial Bus

USB stands for Universal Serial Bus which is used to connect peripherals to computers. USB is used for data transfer, audio, power delivery and more.  The USB standards group has released three major versions of the standard.   In our daily lives, we use  USB to charge all kinds of devices. The mouse and keyboard on your computer probably use USB interfaces in one way or another.  We synchronize or transfer data between devices such as printing or file transfer to disk drives.  The USB "stick" is another regular use case.   The universal aspect of USB does mean complexity.  One example in the head picture of this post is the Chord Mojo DAC/Headphone amp.  There are two Micro-USB connections on the Mojo.  One is for power/charging, and the other is for data transfer to the DAC.   What I am here to talk about is USB audio.  I am going to "gloss over" this subject as it is just too extensive.  There are links below for further study.  The USB standards group has released three variants of USB Audio. Almost all of our USB DACs use USB Audio Version 2.0.  On macOS and Linux you usually do not need drivers; on Windows, drivers are almost always required.   The technology used to transfer audio between the computer and the DAC is NOT the same as transferring data files to a disk drive.  Errors in this process that can and do influence/corrupt the audio data.  It is an imperfect transfer mode.   Some of the factors that can cause issues in USB audio are listed here: Electrical noise from the computer Interference in the cable Grounding issues Imperfect clocking or jitter   Even with these issues, USB audio is one of the most used methods of getting digital or file-based audio to the DAC for audio playback.  You can spend a lot of money in a system to up the odds of delivering better data to the DAC.   As I said above, there is a LOT more to talk about USB, and this is not exactly the right place for extended discussion it is an introduction!      References:   Wikipedia:  https://en.wikipedia.org/wiki/USB
USB-IF https://www.usb.org/search/node?keys=USB Audio
EDN https://www.edn.com/design/consumer/4376143/1/Fundamentals-of-USB-Audio https://www.edn.com/design/consumer/4403381/USB-audio-simplified    

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DAC -- Digital to Analog Convertor

The DAC is the heart of a file-based or streaming digital audio system.       Storing music or video for that matter in a digital format has some significant advantages.   The physical space needed is trivial to non-existent as a problem.  There are a lot fewer issues with long term storage such as moisture problems, print-through on magnetic tape and many more.  Digital also makes the effort of copying and transferring content almost zero.  File-based storage of music brings up issues of copyrights and much more.   I will not dwell on that here.   Computers can store music in files using many different methods.  For the sake of brevity, I am going to ignore format here.  Getting the digital data from the computer to the DAC is done using several methods.  In the end, the DAC receives the digital music file serially from start to end. The music file is not transferred to the DAC as it would be to a disk drive.  
 
***Now all you DAC designers out there give me this one. I am overly simplifying on purpose.  ***    A DAC can use one or multiple methods of conversion.  The process is rather simple.  In PCM (Pulse Coded Modulation) audio formats, a group of digital bits is formed up into a numeric value depending on the specified encoding size such as 16 or 24 bits which sets an instantaneous analog audio output level.  The process happens at that prescribed bit rate of the audio file such as 44..1 Kbps.  (44 thousand times per second in this example).       While PCM is pervasive, there is another format called DSD (Direct Stream Digital).  This format is encoded and decoded differently than PCM.  While the process is different, the intended results are the same.     Finally, there is another encoding format called MQA that is used to envelop the PCM data to provide information to the DAC subsystem.  The stated purpose of MQA is to inform the decoding process about the original recording and encoding of the data to improve playback.  MQA has a HOTLY contested premise, and I am only re-stating the purpose here not endorsing or otherwise commenting.   In this extremely brief overview of the DAC, I am not discussing filtering, clocking or other processing methods used in production equipment. I want to discuss one other about the DAC. The influence of other things around the DAC.  One example is the power supply for the DAC.  We have many instances where a "good" power supply improves the sound quality of the DAC.  The influence of upstream components on the DAC is wild.  Welcome to the center of your digital universe.     Here are three articles on Wikipedia for reference.  Please note that Wikipedia has these marked for some edits.   https://en.wikipedia.org/wiki/Digital-to-analog_converter https://en.wikipedia.org/wiki/Direct_Stream_Digital https://en.wikipedia.org/wiki/Master_Quality_Authenticated  
 

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The NAS (Network Attached Storage)

The NAS (Network Attached Storage) is a type of computer that, in general, has a single function.  It contains some form of data storage devices such as disk drives or SSD devices.  The primary purpose of a NAS is to make the information stored on the drives available to other computers on the network through file sharing.  Ordinarily, the user interface is via a web browser.     Over time the operating system and applications on NAS computers have gotten more powerful. Companies such as Synology and Qnap have developed many tools in their NAS devices to allow them to function on many more roles that the file server. In audio applications, the NAS is principally used to store large quantities of music files.  Also, the NAS can have software applications installed to act as a music server and more.   There is more information on Wikipedia:    https://en.wikipedia.org/wiki/Network-attached_storage  

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