The Analog to Digital conversion process.

Introduction
The analog to digital conversion process is actually the conversion of the pressure variations in the air to binary information that the computer can process. This is done via the process known as sampling

Fig 1. Analog to Digital to Analog Process (Source : Wikipedia)

Sound
Sound is actually pressure variations in the air. It is vibration that propagates as audible mechanical wave of pressure and displacement. Sound needs a medium to travel and it is usually air most of the time. 

Binary Information
However, a computer cannot process such information. For a computer or DAW (Digital Audio Workstation) to process this information, it would require the information to be presented in bits. A bit is simple a "1" or a "0". 

1 bit is simply 2 wordlength, 2 bit is 2^2, which is 4 wordlength. A simple permutation of the bit will be as below 

1 Bit = 2^1 = 2

2 Bit = 2^2 = 4

3 Bit = 2^3 = 8

4 Bit = 2^4 = 16

5 Bit = 2^5 = 32

6 Bit = 2^6 = 64

7 Bit = 2^7 = 128

8 Bit = 2^8 = 256

9 Bit = 2^9 = 512

10 Bit = 2^10 = 1024

11 Bit = 2^11 = 2048

12 Bit = 2^12 = 4096

13 Bit = 2^13 = 8192

14 Bit = 2^14 = 16384

15 Bit = 2^15 = 32768

16 Bit = 2^16 = 65536

Sound In Digital CD

CD audio has a sampling rate of 44100Hz and 16 bit resolution for each stereo channel. Analog signals that have not been already been bandlimited must passed through anti-aliasing filter before conversion. This will prevent distortion caused by audio signals with frequencies higher than the Nyquist frequency. The Nyquist frequency is half of the system's sampling rate. For CD, the Nyquist frequency is 22050Hz which is actually the upper range of the human ear hearing limits. Hence, a CD is able to record exactly what a normal human can hear. 

Sampling

The conversion from analog to digital, otherwise know as the sampling process depends mainly on 2 things. The sampling rate and the dynamic range, otherwise known as the resolution.

It is common in recording to use sampling rate of 48,000Hz. This is higher than the CD sampling rate.

A complete list of audio sampling rate is as below : 

  

Sampling rate	Use
8,000 Hz	Telephone and encrypted walkie-talkie, wireless intercom[10][11] and wireless microphone[12] transmission; adequate for human speech but without sibilance; esssounds like eff (/s/, /f/).
11,025 Hz	One quarter the sampling rate of audio CDs; used for lower-quality PCM, MPEG audio and for audio analysis of subwoofer bandpasses.[citation needed]
16,000 Hz	Wideband frequency extension over standard telephone narrowband 8,000 Hz. Used in most modern VoIP and VVoIP communication products.[13]
22,050 Hz	One half the sampling rate of audio CDs; used for lower-quality PCM and MPEG audio and for audio analysis of low frequency energy. Suitable for digitizing early 20th century audio formats such as 78s.[14]
32,000 Hz	miniDV digital video camcorder, video tapes with extra channels of audio (e.g. DVCAM with 4 Channels of audio), DAT (LP mode), Germany's Digitales Satellitenradio, NICAM digital audio, used alongside analogue television sound in some countries. High-quality digital wireless microphones.[15] Suitable for digitizing FM radio.[citation needed]
44,056 Hz	Used by digital audio locked to NTSC color video signals (245 lines by 3 samples by 59.94 fields per second = 29.97 frames per second).
44,100 Hz	Audio CD, also most commonly used with MPEG-1 audio (VCD, SVCD, MP3). Originally chosen by Sony because it could be recorded on modified video equipment running at either 25 frames per second (PAL) or 30 frame/s (using an NTSC monochrome video recorder) and cover the 20 kHz bandwidth thought necessary to match professional analog recording equipment of the time. A PCM adaptor would fit digital audio samples into the analog video channel of, for example, PAL video tapes using 588 lines by 3 samples by 25 frames per second.
47,250 Hz	world's first commercial PCM sound recorder by Nippon Columbia (Denon)
48,000 Hz	The standard audio sampling rate used by professional digital video equipment such as tape recorders, video servers, vision mixers and so on. This rate was chosen because it could deliver a 22 kHz frequency response and work with 29.97 frames per second NTSC video - as well as 25 frame/s, 30 frame/s and 24 frame/s systems. With 29.97 frame/s systems it is necessary to handle 1601.6 audio samples per frame delivering an integer number of audio samples only every fifth video frame.[9]  Also used for sound with consumer video formats like DV, digital TV, DVD, and films. The professional Serial Digital Interface (SDI) and High-definition Serial Digital Interface (HD-SDI) used to connect broadcast television equipment together uses this audio sampling frequency. Most professional audio gear uses 48 kHz sampling, including mixing consoles, and digital recording devices.
50,000 Hz	First commercial digital audio recorders from the late 70s from 3M and Soundstream.
50,400 Hz	Sampling rate used by the Mitsubishi X-80 digital audio recorder.
88,200 Hz	Sampling rate used by some professional recording equipment when the destination is CD (multiples of 44,100 Hz). Some pro audio gear uses (or is able to select) 88.2 kHz sampling, including mixers, EQs, compressors, reverb, crossovers and recording devices.
96,000 Hz	DVD-Audio, some LPCM DVD tracks, BD-ROM (Blu-ray Disc) audio tracks, HD DVD (High-Definition DVD) audio tracks. Some professional recording and production equipment is able to select 96 kHz sampling. This sampling frequency is twice the 48 kHz standard commonly used with audio on professional equipment.
176,400 Hz	Sampling rate used by HDCD recorders and other professional applications for CD production.
192,000 Hz	DVD-Audio, some LPCM DVD tracks, BD-ROM (Blu-ray Disc) audio tracks, and HD DVD (High-Definition DVD) audio tracks, High-Definition audio recording devices and audio editing software. This sampling frequency is four times the 48 kHz standard commonly used with audio on professional video equipment.
352,800 Hz	Digital eXtreme Definition, used for recording and editing Super Audio CDs, as 1-bit DSD is not suited for editing. Eight times the frequency of 44.1 kHz.
2,822,400 Hz	SACD, 1-bit delta-sigma modulation process known as Direct Stream Digital, co-developed by Sony and Philips.
5,644,800 Hz	Double-Rate DSD, 1-bit Direct Stream Digital at 2x the rate of the SACD. Used in some professional DSD recorders.

 Table 1 : Sampling Rate (Source : Wikipedia) 

The other component of sampling is audio resolution, this is dependent on the wordlength or bit depth of the sample. It is common in recording to use 24wordlength sample; which is 2^24 = 16777216. This is done via using pulse-code modulation (PCM). 

Variations in bit depth affects the noise level from quantization error. 

In simple terms, increase in sampling rate will present the audio file more accurately.

Reflections
I am not that familiar with DAW hence, I have choose this topic. Definitely I am getting a DAW. Knowing the Analog to Digital Conversion process will defintely help in using a DAW more efficiently. I hope you have enjoyed reading these information. Cya Next Week!

Type and Usage of Important Studio Cables

Introduction

Hi, My name is Tan Qin Han and I came from the little red dot otherwise known as Singapore in South East Asia. It is a tropical country where every day we get either the sun or the rain. I took up this course mainly due to self-interest to learn more about music production.

Topic

The topic that I will be talking about in this assignment will be the type and usage of important studio cables. This is as because studio cables are an integral part of the music production process. And they are also the main reasons when things go wrong, it is mainly due to a faulty connections

1/4 Inch TS Cable

The first cable I am going to talk about is the 1/4 Inch TS Cable otherwise known as the Single Conductor Cable. It is a single conductor cable comprises of a tip and a sleeve. It is otherwise known as an unbalanced cable because it doesn't rejects noise from the surrounding. 

 1/4 Inch TRS Cable

The next cable I am going to talk about is the 1/4 Inch TRS cable. It is a duo conductors cable with a tip, a ring and a sleeve. It differs from the TS cable in that it can rejects noise from the surrounding or cable be use as a stereo cable like your headphone. It is also known as a balanced cable.

XLR Cable

The next cable I am going to touch on is the XLR Cable. It is similar to the TRS Cable in that it has 2 conductors. It has the chasis, which is mainly used as the shield and a positive and negative terminals. It is typically connected to your microphone. It also has a locking device at its side.

Direct Box

I am going to touch on the direct box next. The direct box is a very useful device for converting a 1/4 inch TS Cable to a XLR Cable. This is very useful in making long runs of connections and hence reduces the noise of the connection. The direct box is can be also used to have 2 output, from a TS cable (Input 1) to a XLR Cable (Output 1) and a TRS Cable (Thru 1).

8 Inch Cable

There are other connections such as the 8 inch cables which is similar to the TRS cable and we see it frequently in our headphones and phones.

RCA Cable

The RCA Cable shown here is typically used for home consumer devices such as your TV, DVD players etc. However, do take note of the gain setting of these devices as most are set to work at -10dBv.

Other Connectors

There are other connections that allows us to interconnect digital devices. Devices such as S/PDIF in which signals is transmitted via fibre optic cables with TOSLINK connections. It is mainly used in home theatres.

The MIDI which allows a large variaty of electronics musical instruments, computers and other devices to connect and communicate with each other.

There are also other connections such as the Fire Wire and your typical USB cable that allows connections to your computer.

Reflections

I am not your typical music professional and but I do enjoy singing and playing the piano for quite a bit. I am learning a lot at this course and I hope that you do the same and enjoy the course!

Cya Next Week!