MBUS 3550 ANALOG TEST

Three elements of analog recorder

Electronics, Transport, Heads

Heads

recording, playback, erase head

Recording Head

- An electrical signal is routed to an individual region of the record head that has a "gap" in it.

-The magnetic tape medium completes the electrical circuit as it passes over the gap and the audio is stored when the particles of magnetic oxide are aligned on the tape to represent the waveform

- generates magnetic field from audio signal and imprints it onto the tape

Playback Head

-When the tape is run back over the "playback head" the magnetic flux stored on the tape medium creates the same electrical current in the system that was stored on it in the reverse process.

- How all tape recorders and magnetic media work in essence.

- reads magnetic info on the tape

- the magnetization generates an electrical signal that converts into sound

Erase Head

creates magnetic field to "wipe" the tape- essentially neutralizing the previous recording

Rule of Thumbs for Heads

-The more magnetic particles available to align on the tape whether by wider tape or smaller head count

- the wider the available dynamic range

- the lower the noise floor and the higher the fidelity of the recording

Transport

- The electronic controls and mechanisms that control the tape speed and direction across the heads

- play, rewind, fast forward, record, edit

Tape speed

Usually 7 1/2, 15, or 30 inches per second

- most modern are 30 IPS with 16 tracks on 2 inch reels of tape

- mixdown decks are 30 IPS with 2 tracks on 1/2 inch of tape

What do tape speed and width determine

how many particles of magnetic oxide are available to capture the electronic signal

Electronics

The elements of the ATR that convert and facilitate the transition of the input signal to and from the head stacks

Flaw in the electronics component

-Due to the phenomenon of frequency wavelengths getting shorter and shorter as they increase, there is an occurrence of the higher frequency sounds not being captured as well on tape since their wavelengths are equal to or smaller than the width of the head gap on the heads

Solution to electronics component

-there is an EQ curve automatically applied that boosts the high frequencies by 6 dB per octave to achieve a flat playback response

Variation in Fidelity

-Depends on the electronics, tape speed, tape type, track count and tape width

-varies from low fidelity with a high noise floor and low dynamic range, to extremely high fidelity, low noise floor and fantastic dynamic range

Why would someone choose a 15 IPS setting

-the sound is more "vintage"

- alternatively - It would be "bigger", more "compressed" and "bassier" with a slightly higher noise floor.

Sample Rate

The number of samples taken per second

- effects bandwidth (freq range)

- 44.1 kHz= 44,100 samples per second

Sampling

- takes periodic samples of an analog audio waveform over time

- calculates each sample into grouped binary words that digitally represent the voltage levels

Bit

Affects dynamic range

- higher bit, higher dynamic range

- ex: 16 bit, 96.33 dB

24 bit, 144.49 dB

Quantization

The signal level component

- used to translate voltage levels of a analog signal into binary digits (bits)

- effects volume, resolution, and stereo image

Nyquist Theorem

For the desired frequency to be faithfully encoded, the selected sample rate must be at least twice as high as the highest frequency recorded

Dither

-A process used during the recording or conversion process to increase the overall bit resolution (and therefore low-level noise and signal clarity) of a recorded signal, when converting from a higher to a lower bit rate

- adds small amount of randomization to increase precision of digital to analog converter

Normal Dither

added to mask artifacts at EVERY stage of recording and mixing

Noise- Shaped Dither

Used at the end stage of mixing or mastering if the bit depth must be reduced from higher to lower resolution

Vinyl final format

48 kHz + 24 bit

CD final format

44.1 kHz + 16 bit

- can have a volume ceiling digital 0

Streaming final format

48 kHz + 24 bit

- -14 LUF and -1 and -2 dB true peak

Mastering chain

1. corrective EQ: overall inconsistencies are addressed

2. compression stage: dynamic range is reduced to achieve desired dynamic range and volume

3. tone shaping EQ: track is "sweetened" tonally

4. limiting phase: dynamic range is reduced more drastically

LUFS

Loudness Units Relative to Full Scale: a volume reading based on momentary, short term and integrated RMS levels

Momentary (LUFS)

Reads a 400 ms window of audio, and each 400 ms window must overlap the previous by 75%

Short Term

A moving average of the last 3 seconds of momentary values

Integrated

Takes the short-term reading and averages it over an entire "program"

Loudness Range

Determines how much of the entire program is "loud"

True Peak

The peak level that will come out of a digital to analog converter

Codecs

compressed audio data

- can encode audio in a manner that reduced data file size and bandwidth requirements and decode the information upon playback (perceptual coding)

Perceptual Coding

- the principle that the human ear will not always be able to hear all the information that's present in a recording

- coding schemes filter out noises and sounds that can't be heard by ear

- this process is said to be "lossy" because once the data is filtered out it can't be replaced

- higher bandwidth will remove less data, while low will greatly reduce data stream

CBR

constant bit rate- designed for streaming where end user's bandwidth is in consideration

VBR

variable bit rate- when you want to create a downloadable file that has a smaller file size and bit rate without sacrificing sound and video quality

Perceptual Coding Schemes

MP3

MP4

WMA

AAC

RealAudio

FLAC

AAC

Advanced Audio Coding- multichannel friendly formal for secure digital distribution

- default audio backbone for all Apple products

FLAC

Free Lossless Audio Codec

- used by Tidal

- can reproduce up to 32 bits and up to 655.350 kHz

ALAC

Apple Lossles Audio Codec

- apples own proprietary

-apple's entire catalog is now encoded with this