AUdIoCoUrSeS
Joined: 31 Oct 2002
Posts: 2014
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| Week 6 - Equipment 2 |
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Here we go guys a busy week for you, please answer these fuly.
1. Why is it often considered better to use an integrated disk recording system rather than one that uses a personal computer as the user interface?
Comment on the presentation of some disk recorders as replacements for tape multitrack recorders.
2. If a tape recorder has 24 inputs and 24 outputs, how many tracks will it have?
How many inputs and outputs would a disk recorder need if it was to be a replacement for a 24-track tape recorder?
3. If a disk recording system had two inputs, two outputs, and was capable of twenty-four tracks, what would be its main limitations?
4. What information is stored in the session file?
5. Are session files usually transportable between different systems?
Comment briefly on the suitability of SCSI, ATA and Firewire disks for audio recording.
6. What is 'fragmentation'?
7. Comment on archiving to CD-ROM.
8. What are 'virtual tracks'?
9. What is meant by 'edit density'? What are the implications of high edit density?
10. Does the editing and trimming of regions delete audio data from the disk?
11. In editing, what is the difference between 'slip' and 'grid' modes?
12. When might it not be possible to create a crossfade?
13. What is 'bouncing', in the context of mixing?
14. What is meant by 'latency'?
15. What is the difference between DSP processing and host-based processing?
16. Was DAT originally intended as a professional or a domestic recording medium?
17. What is the sampling rate of standard DAT?
18. What is the resolution of standard DAT?
19. What is 'azimuth recording'?
20. Describe the head wheel in DAT recorder.
21. What is SCMS?
22. Describe in what conditions a DAT recorder may be capable of near-simultaneous off-tape recording?
23. What is the sub-code area of the DAT tape used for?
24. What is 'interleaving'?
25. What is the width of the tape used for 24-track DASH?
26. What is the width of the tape used for 48-track DASH?
27. Describe how 24-track and 48-track DASH machines are compatible.
28. How are DASH tapes edited?
29. In DASH, why does a playback head come before the record head in the tape path?
30. Comment on the cleaning requirements of DASH
31. How many tracks does a modular digital multitrack (MDM) have?
32. How can more tracks be obtained?
33. Comment on the types of usage of ADAT and DTRS machines?
_________________
It's all in the ears. - Learn the concepts not the software.
Audio Courses is a way into the music business for you
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Mon Oct 11, 2004 4:14 am |
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Rico1210
Joined: 03 Aug 2004
Posts: 39
Location: Newcastle, UK |
| Week 6 answers |
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Hi,
here are my answers for this weeks questions.
1. Why is it often considered better to use an integrated disk recording system rather than one that uses a personal computer as the user interface? Comment on the presentation of some disk recorders as replacements for tape multitrack recorders.
It is often considered better to use an intergrated disk recording system rather than a medium that uses a PC as the user interface. This is because the performance of an integrated system can be guranteed by a manufacturer and if there is a problem, you go back to the manufacturer. In a PC based system if you encounter a problem, there could be a number of factors to consider. It could be the software, the hardware, the computer, the operating system, the hard disk, the list goes on.
2. If a tape recorder has 24 inputs and 24 outputs, how many tracks will it have?
How many inputs and outputs would a disk recorder need if it was to be a replacement for a 24-track tape recorder?
If a tape recorder has 24 inputs and 24 outputs, it will have 24 tracks. Tape recorders always have an equal amount of in inputs,outputs and tracks. A disk recorder being used as a replacement for a 24-track tape recorder could have as little as 2 inputs and 2 outputs. Although this would mean that no outputs other than the main stereo output could be used, and only 2 tracks could be recorded at once. If the recorder is to be used with a normal mixing console it would need 24 inputs and 24 outputs.
3. If a disk recording system had two inputs, two outputs, and was capable of twenty-four tracks, what would be its main limitations?
As above. If a disk recording system had two inputs, two outputs, and was capable of twenty-four tracks, it's limitations would be that it can only record 2 tracks at once and would not be able to take any outputs other than the main stereo output.
4. What information is stored in the session file?
The session file contains information including the project title, audio files used, any edits, track assignments and mix and plug-in data.
5. Are session files usually transportable between different systems?
Comment briefly on the suitability of SCSI, ATA and Firewire disks for audio recording.
Session files can be transported between different systems provided the systems are compatible. For instance, if a session file is recorded and edited on a system with 16 inputs and outputs and mixed with a particular set of plug-ins. It will be very difficult to recreate the session on a system with only 8 inputs and a different combination of plug-ins. Session files are highly incompatible between manufacturers. SCSI is a parallel interface, therefore is faster than Firewire. SCSI disks are attached to a computer via an external interface for convenience. ATA(IDE) is the most common disk interface, although expansion is limited as this is strictly an internal interface but some systems allow an ATA disk to be mounted in a removable cartridge. There is no such thing as a 'Firewire disk' as Firewire is a medium that transfers data, therefore a 'Firewire disk' is an ATA disk with a Firewire bridge. The advantage of Firewire is that it is hot-swappable(connected/disconnected without pc shutdown) unlike SCSI.
6. What is 'fragmentation'?
Fragmentation is when a file is stored in several 'chunks' instead of all together. Files are split and saved into separate clusters on a disk.
7. Comment on archiving to CD-ROM.
Archiving to an optical medium like CD-ROM is considered to be one of the most stable methods of storing data. Unfortuantely the space available for storage is only 700MB on a standard CD-ROM.
8. What are 'virtual tracks'?
A Virtual Track or V-Track, represents a workspace that can be used to hold recordings. A recorder may have lots of v-tracks but only the number of actual tracks allowed by the recorder can be played back at once. This means that on an 8 track recorder, an engineer is not limited to only 8 tracks of recording, but only 8 tracks can be played back. Tracks can be moved to v-tracks to enable more recordings to be made.
9. What is meant by 'edit density'? What are the implications of high edit density?
When audio is recorded it is placed in a long continuos section of the disk. This makes it easy for the disk to read. When the audio is edited, the regions that are to be replayed are not continuous. This makes it more difficult for the disk to read, potentially enabling less tracks to be replayed simultaneously. 'Edit density' describes the number of regions, their length and proximity to each other. If the regions are shorter and more densely packed, this is said to be high edit density. The problem caused by high edit density is that fewer tracks can be played simultaneously.
10. Does the editing and trimming of regions delete audio data from the disk?
Editing and trimming of disk regions does not delete audio from the disk. Editing and trimming is used to separate useful audio from non-useful audio. The audio is silenced but not deleted, as it may be required later.
11. In editing, what is the difference between 'slip' and 'grid' modes?
In grid mode of editing a grid is defined to enable regions to be snapped to a grid position when they are moved. They can then be given a time stamp to enable them to be found if moved. In slip mode there are no fixed time relationships between tracks, therefore any region or track may be 'slipped' in relation to others.
12. When might it not be possible to create a crossfade?
It is not possible to create a crossfade if audio is not beyond the region boundaries of the disk. If the audio does not extend beyond the region boundaries or if there is insufficient audio extended for the duration of the crossfade, a crossfade cannot be created.
13. What is 'bouncing', in the context of mixing?
Bouncing is when a number of tracks are grouped together onto a smaller number of tracks. For instance, a drum kit may have been recorded separately onto 5 or 6 tracks. These tracks can be grouped together into smaller tracks, maybe 2 tracks. This enables more playback tracks to be available for other instruments, instead of taking up 5 or 6 tracks they now only take up 2. V-tracks of the original recordings can be kept incase it is later felt that individual changes are needed. These can again be grouped or 'bounced' down to the required number of tracks.
14. What is meant by 'latency'
Latency can be defined as the time it takes a packet of data to get from one designated point to another. The time it takes the data to reach the designated point then return to the sender is considered to be the latency. In other words, latency is delay.
15. What is the difference between DSP processing and host-based processing?
Host based processing uses a PC's processor to complete the calculations needed for using plug-ins such as reverb effects. The amount of plug-ins that can be used at any one time is limited by the power of the host based processor, although more can be added if the buffer is increased. DSP (Digital Signal Processing) uses specially designed DSP chips that use audio signals in a different structure to host based processors. They tend to be very expensive but improve latency problems dramatically.
16. Was DAT originally intended as a professional or a domestic recording medium?
DAT was originally intended as a consumer-recording medium. It was to replace the cassette recorder.
17. What is the sampling rate of standard DAT?
DAT recorders offer a range of sampling rates that include professional rates of 44.1 and 48 kHz. An original consumer DAT recorder operates at 48 kHz to avoid digital copying of CDs, whereas professional and modern machines offer both.
18. What is the resolution of standard DAT?
Standard DAT resolution is 16 Bit.
19. What is 'azimuth recording'?
Azimuth describes the orientation of the head gap with respect to the tape. The gap should be perpendicular to the edge of the tape otherwise high frequencies are not efficiently recorded or replayed because the head gap becomes wider. If the azimuth is incorrect, the relative phase between tracks is changed.
Azimuth of the replay head is adjusted quite reqularly, especially when replaying tapes that have been recorded on a different machine with a different azimuth. Azimuth of the recording head is not modified unless there is reason to believe that it has changed.
20. Describe the head wheel in DAT recorder.
A DAT recorder uses a rotary head (hence the name R-DAT) like a video recorder. When recording, it lays the tracks diagonally across the width of the tape unlike analog tape which records the signal parallel to the tape edge. Unlike a video recorder, on which tape is wrapped almost all of the way around the head so that there is always contact between the two, tape on a DAT is only wrapped a quarter of the way around the head. At times the tape does not touch the head, this is compensated for by collecting data in a buffer to be read out at a constant speed. The head wheel in a DAT recorder spins at 2000 rpm.
21. What is SCMS?
SCMS(Serial Copy Management System) is a system used to enforce copyright laws of certain material. It enables copyrighted material to only be copied once. DAT recorders in professional use are exempt from SCMS as they accept a different type of digital input.
22. Describe in what conditions a DAT recorder may be capable of near-simultaneous off-tape recording?
If an extra pair of heads is mounted on the drum, simultaneous off-tape monitoring can be performed during recording just like a three-head analogue tape recorder
23. What is the sub-code area of the DAT tape used for?
The sub-code area of the DAT tape is where the time is recorded. The time from the beginning of the tape is recorded in every track, therefore if you start recording in the middle of a tape, the machine reads the time at that spot and keeps recording time sub-code appropriately. ID's are also recorded in the sub-code. These are points that contain digital code that can be found easily. They are Start ID's, Skip ID's (instruct the deck to find the next start point) and End ID's. Program numbers can also be recorded in the sub-code. These are numbers searched for during previous play operations. Sometimes Program numbers are included with each Start ID.
24. What is 'interleaving'?
Interleaving is when the order of samples is shuffled. Samples that were previously adjacent to each other in real time, are separated from each other on the tape. Interleaving is used in digital recording to rearrange the original order of samples, which can convert burst errors into random errors when the samples are de-interleaved. This helps to conceal errors.
25. What is the width of the tape used for 24-track DASH?
The width of the tape used for 24-track DASH(Digital Audio Stationery Head) is half an inch.
26. What is the width of the tape used for 48-track DASH?
The width of the tape used for 48-track DASH(Digital Audio Stationery Head) is half an inch.
Apparently there are two tape widths 1/2 inch and 1/4 inch, but what i've read says both machines use the same width tape. I don't understand why there are two tape widths. Can someone point me in the right direction, maybe i am wrong with my tape widths.
27. Describe how 24-track and 48-track DASH machines are compatible.
24-track and 48-track DASH machines are compatible because they use the same tape. If the tape is originally recorded on a 24-track machine it will leave guard bands between the tracks. If it is decided that more tracks are needed the tape can be moved to a 48-track machine which will record tracks in the 24 guard bands.
28. How are DASH tapes edited?
There are two ways to edit DASH tapes. The first is the cut-and-splice technique. The tape should be edited with a 90 degree butt joint. Circuits are incorporated in the machine to detect a splice and perform an electronic cross-fade from one side to the other, to conceal the edit. The other method of editing is Electronic editing. This is achieved using two machines plus a control unit. A master tape is assembled from takes of the player machine copied in real time.
29. In DASH, why does a playback head come before the record head in the tape path?
The playback head comes before the record head in the tape path because where an analog process will happen instantaneously, a digital process takes a little time. The playback head comes first to overcome the delay that would be created whilst the signal is being processed, when recording overdubs. There must be a playbaxk head upstream of the record head otherwise multitrack recording wouldn't work.
30. Comment on the cleaning requirements of DASH
DASH machines should be cleaned by an expert in this field as thousands of pounds worth of damage can be done by someone who doesn't know what they are doing. The heads are cleaned with a chamois-leather cleaning tool, wiping in a horizontal motion only. Cotton buds which are used for analog cleaning will clog the head with their fibers. The alignment of a DASH machine should be done every 6 months.
31. How many tracks does a modular digital multitrack (MDM) have?
A modular digital multitrack (MDM) has 8 tracks.
32. How can more tracks be obtained?
More tracks can be obtained by synchronizing multiple machines.
33. Comment on the types of usage of ADAT and DTRS machines?
ADAT machines are very affordable and are popular in budget music recording studios. DTRS machines are used in broadcasting and post-production of films. |
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Sat Oct 16, 2004 9:08 am |
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seanm
Joined: 06 Sep 2004
Posts: 20
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| wk 6 equipment 2 task |
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Hi Chris
here's my answers for this week.
1. Why is it often considered better to use an integrated disk recording system rather than one that uses a personal computer as the user interface? Comment on the presentation of some disk recorders as replacements for tape multitrack recorders.
Integrated disk recording systems are designed and built to record audio. Should any problems arise it’s a relatively simple matter to contact the manufacturer. They are also considered to be more hands on, allowing the user to access one or more parameters at once with the traditional feel of Knobs and faders. DAW’s with a PC as the user interface are attempting to emulate this with a variety of hardware “controller” interfaces.
Integrated disk recording systems commonly offer the basic transport, operational and remote control of a traditional (tape-based ) multitrack recorder and the speed and flexibility of random access audio. The number of tracks which can be recorded on a tape multi-track recorder is finite. With Disk recording systems the number of tracks is limited only by the size and speed of operation of the components, which can be easily upgraded.
Tape is expensive, bulky to store and requires careful handling.
2. If a tape recorder has 24 inputs and 24 outputs, how many tracks will it have? How many inputs and outputs would a disk recorder need if it was to be a replacement for a 24-track tape recorder?
24 tracks.
24 to truly emulate a 24-track tape recorder.
3. If a disk recording system had two inputs, two outputs, and was capable of twenty-four tracks, what would be its main limitations?
The inability to record more than two tracks simultaneously.
The inability to route tracks to dedicated channels of a mixing desk.
Most audio processing would need to be carried out off-line routing tracks to processors individually.
4. What information is stored in the session file?
A Session file contains all the information necessary to reconstruct a mix. It tells the system:
the audio files required and where they can be located.
All audio edits, crossfades, fades etc.
Mixer settings, plug-ins and inserts and their setting.
5. Are session files usually transportable between different systems? Comment briefly on the suitability of SCSI, ATA and Firewire disks for audio recording.
No not usually. It depends a great deal on the software being used and the platform.
SCSI is relatively fast, cheap and it’s an established reliable method used in audio recording. It can be internal or external (commonly external) and allows daisy chaining of up 15 devices (depending on specification).
ATA is the original name for IDE which stands for Integrated Drive Electronics. ATA’s or newer SATA’s (Serial AT Attachment) are the motherboard’s connection for a hard drive. Different ATA and SATA models operate at different speeds allowing users to upgrade with faster and bigger drives.
Firewire or IEEE-1394 is not a type of drive rather it is a high speed serial standard with a maximum bandwidth of around 400Mbits a second. It has a reputation for causing fewer “hiccups” during data transfer. Firewire supports hot swapping of devices and has peer to peer topology (you can plug firewire devices directly into each other without a PC). Firewire operates with a maximum cable length of around five metres.
6. What is 'fragmentation'?
Each file stored on a hard drive is stored in a group of clusters. These clusters contain references to each other making retrieval of the whole file easier, clusters however are stored to a drive randomly in order to optimize the time taken to write them to disk. Subsequently audio files (which are large) are spread all over the drive. This makes finding them cumbersome and time consuming. Use of these files, particularly any permanent alteration and re-writing increases this fragmentation. Fragmentation slows down the retrieval of audio files and increases the possibility of data loss. Regular de-fragmentation of a hard drive physically brings together these improving the drives performance.
7. Comment on archiving to CD-ROM.
CD-R capacity is around 750megabytes. This is a relatively small amount of data particularly when archiving 24bit projects. CD-R’s are considered to be reasonably safe but their longevity is yet to be tested fully. They are however cheap and since they contain no moving parts they have some advantages over drives as an archiving tool.
8. What are 'virtual tracks'?
Some disc recorders can store extra tracks (alternative takes for example) which are not available for playback, due to limits in the number of tracks, which can be played back simultaneously. They are still stored and can be recalled at any time as replacements for example.
9. What is meant by 'edit density'? What are the implications of high edit density?
Edit density refers to the number of audio edits made and the resultant size of the regions created from a single audio file. When all such edits are combined for all of the tracks in a project this is measured as edit density.
A project with an already high edit density might develop difficulties with audio streaming and further processing due to the problems caused by continually retrieving small pieces of audio fast enough for smooth playback.
10. Does the editing and trimming of regions delete audio data from the disk?
No as disk recorders employ “non destructive editing” where alterations to regions (audio segments) does not affect the source audio file originally.
11. In editing, what is the difference between 'slip' and 'grid' modes?
They refer to moving regions of audio. In slip mode a region can be placed anywhere within the project. In grid mode the region can only be placed in a position pre-defined by the user usually a rhythmic position but others can be specified (frames, seconds etc.)
12. When might it not be possible to create a crossfade?
Crossfades are not possible where regions of audio do not overlap.
13. What is 'bouncing', in the context of mixing?
Bouncing is a process used to free up tracks for further use. One or more tracks are "bounced" (recorded) to either a single track (mono) or a stereo pair. Once recorded to this new track(s) the source tracks can then be used for further recording.
14. What is meant by 'latency'?
Latency in DAW’s is simply the time it takes a DAW to move audio from one place to another. Each time a signal is altered, the DAW needs time to carry out calculations and since the signal is transferred in “chunks” rather than a continuous stream, this introduces a time delay equivalent to the size of the chunks. Latency is the time delay between triggering a signal through a soundcard and actually hearing it. Latency also affects the general responsiveness of applications.
15. What is the difference between DSP processing and host-based processing?
DSP (Digital Signal Processing) is carried out by a dedicated processor, leaving the host processor free for other tasks.
Host based processing simply involves the host processor carrying out all functions.
16. Was DAT originally intended as a professional or a domestic recording medium?
A domestic recording medium.
17. What is the sampling rate of standard DAT?
44.1 and 48KHz commonly on professional machines with some deviations by manufacturer, e.g. Pioneer machines offering 96KHz and Sonosax offering 44.1/48/88.2/96KHz. Less commonly some older machinesoffer 32/44.056KHz in addition to 44.1/48KHz sampling rates.
18. What is the resolution of standard DAT?
16bit most commonly with some exceptions e.g. Tascom 24 bitword option
19. What is 'azimuth recording'?
To reduce interference (crosstalk) between neighbouring tracks during replay, the head wheel is at a slightly different angle to the tape (plus or minus 20 degrees). This angle is known as the azimuth. During playback any unwanted signal from neighbouring tracks will be picked up at too low a level to be interpreted as part of the signal.
20. Describe the head wheel in DAT recorder.
DAT is described as a 16bit rotary-head digital recording system. Two or more magnetic heads are mounted inside a rotary drum. DAT stores data in “bursts” onto the tape. The heads rotate at 2000rpm in the same direction as the tape motion. Tracks of digital data are written diagonally, producing long, narrow slanting tracks of information on the tape. The angle of the head to the tape is 90 degrees reducing friction and wear on the tape.
21. What is SCMS?
Pronounced SCUMS, SCMS is a digital protection flag encoded into many consumer digital devices to prohibit the unauthorised copying of digital audio at the 44.1KHz sample rate.
22. Describe in what conditions a DAT recorder may be capable of near-simultaneous off-tape recording?
Professional DAT recorders often have four heads rather than just two.
This enables off-tape monitoring whilst recording.
23. What is the sub-code area of the DAT tape used for?
The subcode area is used to store information such as track start positions, sampling rate, timecode information, number of channels, and copyright information. This non-audio information can be recorded and deleted and edited without affecting the audio recorded.
24. What is 'interleaving'?
Interleaving is the process of rearranging streams of digital audio in order to spread any burst errors out making errors easier to correct.
25. What is the width of the tape used for 24-track DASH?
½ inch open reel
26. What is the width of the tape used for 48-track DASH?
½ inch open reel
27. Describe how 24-track and 48-track DASH machines are compatible.
Using a unique system, tapes recorded on a 24 track DASH machine can be recorded and reproduced on a 48 track Dash machine with no signal degradation using tracks 1-24 whilst tracks 25-48 can continue to be recorded onto the same tape with no compatibility problems.
28. How are DASH tapes edited?
DASH tapes can be spliced due to the interleaving of even and odd words. Also as error correction encoding and decoding is done independently on each track, any dropouts can be rectified without affecting other tracks and cross fading, punch in/out and electronic editing functions are all available.
29. In DASH, why does a playback head come before the record head in the tape path?
On an analogue recording system the sync playback signal comes from the record head, but with DASH there is a slight delay while the playback signal is processed (105 ms or 75mm of tape). To perform a synchronous overdub the record head needs to be slightly after the playback head to account for this delay in processing.
30. Comment on the cleaning requirements of DASH
A Dash machine should only be cleaned by an expert. The heads can be cleaned with a special chamois leather cleaning tool, wiping in a horizontal motion only. Cotton buds, commonly used on ATR machines should not be used as they can clog the Dash machines heads with fibres.
31. How many tracks does a modular digital multitrack (MDM) have?
MDM’s are compact multitrack digital audio recorders which can record up to eight tracks of digital audio onto standard video cassettes.
32. How can more tracks be obtained?
As MDM’s are “modular” they can be synchronously linked together (in groups of eight) to obtain more tracks.
33. Comment on the types of usage of ADAT and DTRS machines?
ADAT machines are cheaper than DTRS (Digital Tape Recording System) machines and are more likely to be found in project or home recording setups. DTRS machines are more commonly found in post production studios as they locate faster using a finding servo and can record more than twice as much as an ADAT machine (108 mins compared to 40)
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Sat Oct 16, 2004 11:14 am |
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