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100 Cards in this Set
- Front
- Back
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Dynamic Range=
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Wordlength X -6
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How do you get 20 Bit resolution from 16 bit Recording
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Noise Shaped Dither and a High Sample Rate
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Wavelength=
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1130/freq
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Frequency
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1130/wavelength
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1/time
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Frequency
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1 Vari Mu
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Slow Attack Long Release
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Optical
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Slow Attack long Release
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Fet
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Fast Attack Fast Release
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VCA
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Fast Attack Fast Release
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DCA
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Can emulate older devices
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Digital/PWM
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Look-Ahead Attack, Fast Release
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Plug in Modeling
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Functional, but often lacking character
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Feed Forward vs FeedBack
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Most older compressors are Feedback design output signal triggering reduction unit.
Newer VCA DCA and PWM use a feed forward. |
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What has the hardest knee?
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Limiter- forms absolute ceiling.
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WHat is more musical soft or hard knee?
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SoftKnee
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What controls the high frequency response on a compressor?
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Attack Time
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What controls the resonant (low/mid) frequency response?
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Release Time
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What is the feedback based design of Filter called? How does it create a cut or boost?
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Infinite Impulse Response (IIR)- Routes a signal back onto itself slightly out of time either in standard or reverse polarity to create a cut or boost.
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If your finding yourself having to boost more than 3-4dB of any frequency with an EQ in recording consider adjusting what instead?
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The source Tonality
The microphone selection/design The microphone polarity pattern Microphone placement The acoustics of the environment |
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Analog tape has how much dynamic range?
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70dB
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What is the ideal signal processing chain for recording?
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Filters
Subtractive EQ Compression Additive EQ |
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Microdynamics
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Are automatic processors, like compressors
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Macrodynamic
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Are manipulated by faders, or "manual compression".
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Downwards Compression
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Brings High Levels Down
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Upwards Compression
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Raises levels of low passages (parallel compression. Dolby Encoding,)
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Upwards Expansion
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Brings High Levels Up Further
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Downward Expansion
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Brings Low Levels Down (Gates, Noise reduction.)
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Attack Times for mixing/Recording
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pg121-122
15ms-100ms |
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Attack times for mastering
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50ms-300ms
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Common Release times for musical content.
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50ms to 500ms often times longer for mastering.
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What is an example of upwards compression?
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Parallel Compression
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What is an example of upwards expansion?
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Compressor with ratios under 1:1 Often has a brightening effect by increasing level of transients
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Types of Non traditional Dynamics Processors
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Tape Saturators/ Simulators
Harmonic Enhancers ADSR Envelope Modifiers Reampers |
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What is dither?
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Randomized Noise which averages 0 Volts DC (having an equal number of1's and 0's).
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What is the LSB?
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Least significant bit in the word length.
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WHen Should Dither be applied?
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As the last step before creating the final master.
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Rules for Dithering
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Always add dither when reducing word lengths.
Avoid dither to 16 bit more than once in a project Audition to find the right dither SRC before Redithering Drop gain of peak limited material by .1dB |
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Why do higher sample rates sound "better" when most of the content captured by them is either inaudible or not reproducible with standard transducers?
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Problem with digital low-pass filters used in oversampling A/D and D/A converters. Causes distortion, Ripple/Aliasing artifacts heard as time smearing or short echoes.
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What are the three Bands of a LPF?
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Passband: Unfiltered Range below LPF
Transition: Beginning of cutoff frequency Stop: point at which maximum loss of the filter is reached |
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WHat is the minimum freq for an anti aliasing LPF to get rid of pre echo aliasing?
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50K
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When recording in digital What levels are best for peaks and average amplitude?
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Peaks should be under -3dB and the Average should be under-6db.
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What is the crest factor?
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The difference in dB between the average and peak amplitudes.
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What is the average crest factor for each recording medium.
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Digital=20dB
Analog=14dB |
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What is oversampling?
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Using a Gentle LPF with a High sample rate.
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What does Oversampling do?
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moves the filter distortion above the audible range.
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What does peak normalization do? and what does average do?
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Works for multiple songs for mastering but is very invasive for song by song basis. adds quantization distortion to already mixed material and does not help loudness or improve dynamic range.
Average is better than peak but still causes unwanted artifacts. |
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What is Jitter?
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Timing error between converter and another device.
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What is the minimum timing fluctuation an ear can hear?
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10 pico seconds
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What are two types of jitter?
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Interface Jitter: present in the interconnections between equipment.
Sampling Jitter: present in the clock that drives the converter |
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What causes interface jitter?
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Resistance found in any cable regardless of quality.
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What causes sampling Jitter?
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Clock irregularities.
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what is a PLL?
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Phased Lock Loops generate a frequency that is a multiple of the input frequency.
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What is clock recovery?
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When the PLL realigns incoming asynchronous clock to "clean" internally generated clock as the clock pulse land within the acceptance time of each incoming bit
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what is an ASRC?
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asynchronous sample rate converter
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Internal Clock
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built-in stable crystal clock to directly drive circuitry
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External Clock
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not preferable to internal. utilizes a PLL and cabling.
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Set peak meters to overload at what value?
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-.3dBFS
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when setting your VU with a sine wave what value should you set it to?
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-20dBFS=0VU
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For proper headroom use what level for your PPM?
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-5dBFS
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What is the main causes for bad digital audio?
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Poor ADC/DAC LPFs
Bad conversion technology Low sample rates Low bit resolution Improper dither Jitter Clock Leakage Inferior power supplies and internal sheilding |
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Advantage and disadvantage of analog summing bus.
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Has a musical distortion that can seem like an improvement in separation and depth. Worse actual fidelity than digital.
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What is the Golden Source quality Rule?
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Start with the highest resolution possible and maintain that quality for as long as possible in the production process.
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What is the wavelength of 250hz
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4.52 ft
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What is the wavelength of 500hz
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2.26ft
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What is the wavelength of 1khz
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1.13ft
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What frequency has a wavelength of 5ft?
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226hz
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what is the frequency that has a wavelength of 4 ft?
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282.5hz
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what is the frequency that has a wavelength of 3 ft?
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376.6hz
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what is the frequency that has a wavelength of 2 ft?
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565hz
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what is the frequency that has a wavelength of 1 ft?
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1130hz
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What is the equation to find time from frequency?
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1/freq=time
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What is the equation to find frequency from time?
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1/T=f
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Where is the first comb filter null?
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1/2 the fundamental frequency
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Where is the first comb filter null?Distance 4ft
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Distance 4ft f=250
nulls at 125, 375, 625,875 crests at 250,500,750,1k |
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Where is the first comb filter null?Distance 1ft
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f=1khz
Nulls at 500, 1500, 2500, 3500 Crests at 1k, 2k, 3k,4k, |
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What does engaging phase inversion do to the signal of two mics when comb filtering?
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it switches the placement of the crests and nulls.
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what is the first null of the comb filter with phase inverted and mikes set 2 feet away.
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f=565
Nulls at 565, 1.13k, 1.7k Crests at 282.5, 847.5, 1.4K |
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Depth
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governs the amount of ambiance or reverberation on a recording.
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Height
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governs the brightness and "front to back ratio" of the recording.
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Recommended Placement for Coincident pair
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Near Field Placement
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Recommended Placement for Near-Coincident pair
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Mid Field Placement
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Recommended Placement for Spaced Pair
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Far Field Placement
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Recommended Placement for Baffled Omni
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Binaural/ headphones
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Coincident Patterns such as x/y, m/s, and Blumlien use what to create a stereo image?
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Interaural Level Differences (ILD)
Best technique for mono compadability. |
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How do you setup a M/S?
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1 cardioid facing forward and 1 Bi-Directional facing perpendicular to it. You must bring the side mic back on two channels and hard pan them, with one side placed in reversed polarity.
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What does ORTF stand for?
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Office de Radiodiffusion Television Francaise.
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How do you set up an ORTF?
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Place two cardioid microphones Spaced 17cm between capsules at a 110 degree angle. Utilizes Interaural Timing Differences and ILD
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How do you set up an NOS?
How do you set up an DIN? |
Cardioid Mics
NOS capsules 30 cm apart 90 degree angle DIN capsules 20 cm apart 90 degree angle |
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How do you setup a baffled omni?
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2 Omni mics setup on either side of a 35cm disk about 2cm thick and covered with absorbent material. Mics placed with capsules 36cm apart and at a 40 degree angle from each other.
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What does a spaced pair rely on for stereo image
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ITD
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What is the 3-1 rule?
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The distance between the spaced stereo pair should be 3 times the distance of either microphone to the source. the minimum distance of the spaced pair should be 21.6 inches from the source.
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What are 3 rules of using spot mics with a stereo pair?
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Spot Mics should:
Never be louder than the array. Match the panning. Match the timing within 20ms |
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Things that kill depth.
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Multitrack recording
Multi-mic Recording Dead Acoustics in the record environment Overapplied compression Improper Dithering LowRes Processing |
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What is the slew rate?
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the maximum speed at which an amplifier can change states. Usually expressed in V/µs (volts per microseconds),
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What is Bob Katz first secret in digital audio?
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Word Lengths Expand
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Explain how a jeklin disk increases the separation of a spaced pair?
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It creates greater separation between the two channels.
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What are the three types of masking?
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Temporal, Directional and Amplitude.
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what is another name for a Multi-band compressor?
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Dynamic EQ
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What compressor has the fastest attack time
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VCA, they have a feed forward system. not to be confused with look ahead which allows for a zero attack time compressor on digital systems
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What is the purpose of the ribbon test?
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Makes the phantom center versus direct speakers even to accurately represent the mono instrument signals.
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