Alesis ADAT HD24
Encyclopedia
The Alesis
HD24 is a 24-track hard-disk audio recorder. It is the successor to the hugely successful tape based Alesis ADAT
.
s. Primarily, the use of hard disks as storage medium rather than tape allows for random access of audio, whereas tape based solutions only allow sequential playback.
The built in Ethernet
port allows users to transfer the audio files to a computer, which could only be done with a specific PCI
card with the previous ADAT. This feature permits users to transfer the audio to a Digital Audio Workstation
for editing, after which the audio can be transferred back to the HD24. However, transfer speed of the Ethernet port is limited to 10 Megabit per second.
For recordists who work mainly in analog realm, using digital recorder only as capture medium, the 1/4" line ins and outs on each channel make analog processing, such as re-amping, easy (using a reamp box, that is). The reamp box (which converts line-level signal to guitar signal) can also feed pre-recorded rhythm guitar chords to harmonizer unit, allowing sung harmonies to be added later, with no guitar playing needed at that session.
issues, it greatly reduces them. This prevents many seek operations, allowing the HD24 to use cheap IDE drives for 24 track audio storage.
Disks formatted with Alesis' proprietary FST
file system are not currently recognized by today's operating systems. Therefore, to permit interoperability between computers and the Alesis ADAT HD24, the HD24 recorder is equipped with a built-in FTP
server. This does not require any additional hardware, but is generally considered slow, and many users have experienced dropped connections (which has been attributed to expired DHCP
lease).
The combination of low transfer rates and dropped connections of the built-in FTP server has driven many HD24 users to opt for an external file transfer solution. The available options are the Alesis Fireport in combination with Alesis' FST/Connect software, or an HD24-compatible drive bay with the third-party HD24tools suite. Either combination allows for file transfers with a theoretical transfer rate of 400 megabit per second. However, in reality, this rate is seldom achieved as the throughput of the hard drive itself can be a limiting factor.
The HD24 has MIDI in and out and can transmit MTC
(MIDI Time Code), which allows for easy synchronization to other hardware, however it cannot synchronize to incoming MTC. The HD24 supports MMC
(Midi Machine Control) in two directions. It also features three Alesis Lightpipe
ins and outs (tape based had one of each), which each can transfer eight tracks of digital audio at once.
The HD24 also has 9 pin synchronization ports, dedicated to sync with other ADAT machines. An HD24 can easily be integrated into an existing tape based ADAT system, although there are a few issues with compatibility between the two; for instance, by default HD24s start each song from zero (although the zero-offset can be moved), whereas the tape based ADATs continue to the end of the tape no matter how many songs are recorded.
The built-in FTP server permits transferring files to and from computer-based Audio Workstations.
The connector-side of the original Alesis HD24 drive caddies reveals that they were designed by a company called ViPowER. Users on the HD24 Yahoo forums have confirmed that the Alesis HD24 caddies are interchangeable with ViPowER caddies, as well as with some no-name brands.
Alesis' FST/Connect fireport software only supports drives that are connected via FireWire and will therefore not work with USB drive bay
s. Even firewire versions of alternative drivebays have yet to be confirmed to work with the original FST/Connect software. Alesis has not released any updates to FST/Connect for several years. As such, no native 64-bit versions of FST/Connect exist. On 64-bit operating systems, this means the transfer software needs to be run in 32-bit compatibility mode. Yahoo group users have determined that FST/Connect no longer works on Windows 7 nor MacOS 10.6. Audio transfers are still possible using third-party software and using the FTP server of the HD24.
The HD24 was originally designed to work with IDE (PATA) drives, but efforts are on the way to support SATA to make the recorder more future-proof. Although natively the HD24 does not support SATA drives, the HD24 community on Yahoo groups have determined that the caddies can be fitted with a PATA-to-SATA conversion board. The HD24 community has found that when using conversion boards that use the JM20330 chip, the HD24 does not recognize the drives, whereas drives are recognized when using boards employing the Marvell (88SA)8040 chip. However, stability is still a concern. The US-based company Magicsound has developed a working SATA-to-IDE converting caddy, based on a chipset from an industrial application.
embedded
real-time
operating system
, running on a Motorola
MCF5206 EFT54 processor
, which combines a Coldfire
processor core with several peripheral
functions such as a DRAM controller, timers, parallel and serial interfaces.
A 26-pin port on the mainboard labelled 'Motorola BDM Port' permits background debugging using a Background Debug Mode interface
adaptor.
There are two IC41LV16256 chips in the HD24: according to the data sheets, they are 256kx16 bit Dynamic RAM with EDO page mode,
giving the HD24 a total of 1 megabyte of RAM.
The Ethernet chip is a CrystalLan CS8900A-CQ3, a 10BASE-T
LAN chip.
For recording, the original HD24 uses 12 stereo Wavefront AL1101G A/D converters
, and for playback it uses 12 stereo AL1201G D/A converters
. The HD24XR model uses the higher-quality AKM 5393 A/D and AKM 4393 D/A converters.
The HD24 is equipped with an Analog Devices ADSP 21065L KS-264 digital signal processor. There is an ALTERA ACEX EP1K30QC208-2 FPGA (Field Programmable Gate Array) in there as well.
The HD24 little remote control (LRC) is almost identical to older ADAT LRC's. The buttons are labeled differently, but internally the remote controls are identical: a simple resistor network.
Power outages during recording may result in lost recordings, leaving the drive in a corrupt state. This is due to the allocation information of a song only being written to disk when STOP is pressed. The power loss problem can be addressed by powering the HD24 recorder via a UPS. It would be possible to pre-record silence with the expected length of the recording or longer, however Yahoo forum users have reported that this increases drive activity during recording, which increases sensitivity to write errors due to high SPL. Often, it is possible to recover the audio that was lost due to power outages.
The HD24 stores adjacent tracks in adjacent sectors. This guarantees minimal drive head movement across the platters of the drive, but fragmentation in the time domain can still occur. As there is a limit on the number of fragments that a song can contain, heavily fragmented drives may cause data loss. This can be prevented by always recording to a freshly (quick)formatted drive. This best practice will also make it easier to recover from power outages.
Hard drives that are kept on a shelf unused for a long period of time may stop functioning and no longer spin up. This is due to the lubricant of the drives setting, and not a problem inherent to the Alesis ADAT HD24 recorder itself. The problem can be overcome by regularly spinning up the drives and by making regular backups.
The Macintosh version of the FST Connect software has only been released for the PowerPC architecture and not universal binary to support the Intel architecture. This was not an issue until Apple released the 10.4.9 update to its operating system.
Some users have reported the HD24 recorder to fall out of record mode when used in extremely noisy environments due to sonic vibrations. This has reportedly been overcome in several ways, among others fixing the hard drive to the chassis of the recorder; placing the recorder on a soft surface (such as a blanket); or simply shielding the recorder from the loud sound. A solution that was reported successful by HD24 users on Yahoo Groups is to insert washers (thin metal rings) under the connector screws. This will slightly push out the connector, allowing it to make better contact.
There is a possible design flaw in the HD24 where the connector is firmly attached by the two screws leaving no tolerance, which means that the caddy remains in tension and can pop out spontaneously or as a result of vibration. It is possible to work around this by loosening the two retaining screws for the D type connector at the back of the disk caddy. See picture.
A frequently reported issue on the HD24 groups is IDE drives not mounting. There is some speculation about why drives would not mount, and this issue has been discussed extensively by the HD24 group. Alesis confirmed (in thread "WD PATA drive not recognized" in the Yahoo HD24 forum) that larger WD drives do not mount because "their RPM speed is reportedly not as fast as advertised". Other possible causes are believed to be:
The IDE connector inside the caddies does not always exactly fit with the IDE connector of the drive. Symptoms are a constantly-lit LED on hot-swappable ViPower drive bay, slow booting and the drive not being recognized, either by the HD24 or by the computer. If this occurs, swapping the drive to another caddy may help.
Alesis
Alesis is a company based in Cumberland, Rhode Island, that designs and markets electronic musical instruments, digital audio processors, audio mixers, digital audio interfaces, recording equipment, drum machines, professional audio and electronic percussion products...
HD24 is a 24-track hard-disk audio recorder. It is the successor to the hugely successful tape based Alesis ADAT
ADAT
Alesis Digital Audio Tape or ADAT is a magnetic tape format used for the simultaneous digital recording of eight analog audio or digital audio tracks at once, onto a Super VHS tape that is used by consumer VCRs.- History :...
.
Advantages over tape-based ADAT
There are numerous advantages that the HD24 has over the tape-based ADATADAT
Alesis Digital Audio Tape or ADAT is a magnetic tape format used for the simultaneous digital recording of eight analog audio or digital audio tracks at once, onto a Super VHS tape that is used by consumer VCRs.- History :...
s. Primarily, the use of hard disks as storage medium rather than tape allows for random access of audio, whereas tape based solutions only allow sequential playback.
The built in Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
port allows users to transfer the audio files to a computer, which could only be done with a specific PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...
card with the previous ADAT. This feature permits users to transfer the audio to a Digital Audio Workstation
Digital audio workstation
A digital audio workstation is an electronic system designed solely or primarily for recording, editing and playing back digital audio. DAWs were originally tape-less, microprocessor-based systems such as the Synclavier and Fairlight CMI...
for editing, after which the audio can be transferred back to the HD24. However, transfer speed of the Ethernet port is limited to 10 Megabit per second.
Advantages and disadvantages compared to computer-based recording
Although it is possible to edit audio within the HD24, computer based systems offer a lot more editing power. The additional benefits of computer based recording mean that the HD24, or any stand alone multi tracker, is now not the preferred choice of many audio engineers. However stand-alone solutions are often perceived as being more reliable than computer based solutions.For recordists who work mainly in analog realm, using digital recorder only as capture medium, the 1/4" line ins and outs on each channel make analog processing, such as re-amping, easy (using a reamp box, that is). The reamp box (which converts line-level signal to guitar signal) can also feed pre-recorded rhythm guitar chords to harmonizer unit, allowing sung harmonies to be added later, with no guitar playing needed at that session.
File storage and transfer
Alesis developed their own method of writing to disk which interlaces the audio of the various tracks on disk. Although this does not entirely resolve fragmentationFile system fragmentation
In computing, file system fragmentation, sometimes called file system aging, is the inability of a file system to lay out related data sequentially , an inherent phenomenon in storage-backed file systems that allow in-place modification of their contents. It is a special case of data fragmentation...
issues, it greatly reduces them. This prevents many seek operations, allowing the HD24 to use cheap IDE drives for 24 track audio storage.
Disks formatted with Alesis' proprietary FST
File Streaming Technology
File Streaming Technology is the term used by Alesis for the proprietary file system used for their ADAT HD24 recorder which was released in 2001...
file system are not currently recognized by today's operating systems. Therefore, to permit interoperability between computers and the Alesis ADAT HD24, the HD24 recorder is equipped with a built-in FTP
File Transfer Protocol
File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
server. This does not require any additional hardware, but is generally considered slow, and many users have experienced dropped connections (which has been attributed to expired DHCP
Dynamic Host Configuration Protocol
The Dynamic Host Configuration Protocol is a network configuration protocol for hosts on Internet Protocol networks. Computers that are connected to IP networks must be configured before they can communicate with other hosts. The most essential information needed is an IP address, and a default...
lease).
The combination of low transfer rates and dropped connections of the built-in FTP server has driven many HD24 users to opt for an external file transfer solution. The available options are the Alesis Fireport in combination with Alesis' FST/Connect software, or an HD24-compatible drive bay with the third-party HD24tools suite. Either combination allows for file transfers with a theoretical transfer rate of 400 megabit per second. However, in reality, this rate is seldom achieved as the throughput of the hard drive itself can be a limiting factor.
Compatibility
The Alesis ADAT HD24 offers good out-of-the-box compatibility, both with existing ADAT systems and PC-based solutions.The HD24 has MIDI in and out and can transmit MTC
MIDI timecode
MIDI time code , or MIDI time division, embeds the same timing information as standard SMPTE timecode as a series of small 'quarter-frame' MIDI messages. There is no provision for the user bits in the standard MIDI time code messages, and SysEx messages are used to carry this information instead...
(MIDI Time Code), which allows for easy synchronization to other hardware, however it cannot synchronize to incoming MTC. The HD24 supports MMC
MIDI Machine Control
MIDI Machine Control, or MMC, a subset of the MIDI specification, provides specific commands for controlling recording equipment such as multi-track recorders....
(Midi Machine Control) in two directions. It also features three Alesis Lightpipe
ADAT Lightpipe
The ADAT Lightpipe, officially the ADAT Optical Interface, is a standard for the transfer of digital audio between equipment. It was originally developed by Alesis but has since become widely accepted, with many third party hardware manufacturers including Lightpipe interfaces on their equipment...
ins and outs (tape based had one of each), which each can transfer eight tracks of digital audio at once.
The HD24 also has 9 pin synchronization ports, dedicated to sync with other ADAT machines. An HD24 can easily be integrated into an existing tape based ADAT system, although there are a few issues with compatibility between the two; for instance, by default HD24s start each song from zero (although the zero-offset can be moved), whereas the tape based ADATs continue to the end of the tape no matter how many songs are recorded.
The built-in FTP server permits transferring files to and from computer-based Audio Workstations.
The connector-side of the original Alesis HD24 drive caddies reveals that they were designed by a company called ViPowER. Users on the HD24 Yahoo forums have confirmed that the Alesis HD24 caddies are interchangeable with ViPowER caddies, as well as with some no-name brands.
Alesis' FST/Connect fireport software only supports drives that are connected via FireWire and will therefore not work with USB drive bay
Drive bay
A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed....
s. Even firewire versions of alternative drivebays have yet to be confirmed to work with the original FST/Connect software. Alesis has not released any updates to FST/Connect for several years. As such, no native 64-bit versions of FST/Connect exist. On 64-bit operating systems, this means the transfer software needs to be run in 32-bit compatibility mode. Yahoo group users have determined that FST/Connect no longer works on Windows 7 nor MacOS 10.6. Audio transfers are still possible using third-party software and using the FTP server of the HD24.
The HD24 was originally designed to work with IDE (PATA) drives, but efforts are on the way to support SATA to make the recorder more future-proof. Although natively the HD24 does not support SATA drives, the HD24 community on Yahoo groups have determined that the caddies can be fitted with a PATA-to-SATA conversion board. The HD24 community has found that when using conversion boards that use the JM20330 chip, the HD24 does not recognize the drives, whereas drives are recognized when using boards employing the Marvell (88SA)8040 chip. However, stability is still a concern. The US-based company Magicsound has developed a working SATA-to-IDE converting caddy, based on a chipset from an industrial application.
Internal
The HD24 operates on a NucleusNucleus RTOS
Nucleus OS is a real-time operating system and toolset created by the Embedded Systems Division of Mentor Graphics for various central processing unit platforms. Nucleus OS is an embedded software solution and is in an estimated 2.11 billion devices worldwide.Development is typically done on a...
embedded
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
real-time
Real-time computing
In computer science, real-time computing , or reactive computing, is the study of hardware and software systems that are subject to a "real-time constraint"— e.g. operational deadlines from event to system response. Real-time programs must guarantee response within strict time constraints...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, running on a Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
MCF5206 EFT54 processor
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
, which combines a Coldfire
Freescale ColdFire
The Freescale ColdFire is a microprocessor that derives from the Motorola 68000 family architecture, manufactured for embedded systems development by Freescale Semiconductor .-Instruction set:...
processor core with several peripheral
functions such as a DRAM controller, timers, parallel and serial interfaces.
A 26-pin port on the mainboard labelled 'Motorola BDM Port' permits background debugging using a Background Debug Mode interface
Background Debug Mode interface
Background Debug Mode interface is an electronic interface that allows debugging of embedded systems. Specifically, it provides in-circuit debugging functionality in microcontrollers...
adaptor.
There are two IC41LV16256 chips in the HD24: according to the data sheets, they are 256kx16 bit Dynamic RAM with EDO page mode,
giving the HD24 a total of 1 megabyte of RAM.
The Ethernet chip is a CrystalLan CS8900A-CQ3, a 10BASE-T
10BASE-T
Ethernet over twisted pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. Other Ethernet cable standards employ coaxial cable or optical fiber. Early versions developed in the 1980s included StarLAN followed by 10BASE-T. By the 1990s, fast, inexpensive...
LAN chip.
For recording, the original HD24 uses 12 stereo Wavefront AL1101G A/D converters
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
, and for playback it uses 12 stereo AL1201G D/A converters
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
. The HD24XR model uses the higher-quality AKM 5393 A/D and AKM 4393 D/A converters.
The HD24 is equipped with an Analog Devices ADSP 21065L KS-264 digital signal processor. There is an ALTERA ACEX EP1K30QC208-2 FPGA (Field Programmable Gate Array) in there as well.
The HD24 little remote control (LRC) is almost identical to older ADAT LRC's. The buttons are labeled differently, but internally the remote controls are identical: a simple resistor network.
Known issues and how to deal with them
FTP transfers are known to be slower than real-time and not very reliable; this has been attributed to lost DHCP lease. Both of these issues can be overcome by switching to an external file transfer solution. The FTP server of the HD24 is known to hang on occasion; this has been attributed to the HD24 not understanding some of the newer FTP commands (RFC 1639, RFC 2228, RFC 2428) and can be resolved by using an older FTP client or by switching to an external file transfer solution.Power outages during recording may result in lost recordings, leaving the drive in a corrupt state. This is due to the allocation information of a song only being written to disk when STOP is pressed. The power loss problem can be addressed by powering the HD24 recorder via a UPS. It would be possible to pre-record silence with the expected length of the recording or longer, however Yahoo forum users have reported that this increases drive activity during recording, which increases sensitivity to write errors due to high SPL. Often, it is possible to recover the audio that was lost due to power outages.
The HD24 stores adjacent tracks in adjacent sectors. This guarantees minimal drive head movement across the platters of the drive, but fragmentation in the time domain can still occur. As there is a limit on the number of fragments that a song can contain, heavily fragmented drives may cause data loss. This can be prevented by always recording to a freshly (quick)formatted drive. This best practice will also make it easier to recover from power outages.
Hard drives that are kept on a shelf unused for a long period of time may stop functioning and no longer spin up. This is due to the lubricant of the drives setting, and not a problem inherent to the Alesis ADAT HD24 recorder itself. The problem can be overcome by regularly spinning up the drives and by making regular backups.
The Macintosh version of the FST Connect software has only been released for the PowerPC architecture and not universal binary to support the Intel architecture. This was not an issue until Apple released the 10.4.9 update to its operating system.
There is a possible design flaw in the HD24 where the connector is firmly attached by the two screws leaving no tolerance, which means that the caddy remains in tension and can pop out spontaneously or as a result of vibration. It is possible to work around this by loosening the two retaining screws for the D type connector at the back of the disk caddy. See picture.
A frequently reported issue on the HD24 groups is IDE drives not mounting. There is some speculation about why drives would not mount, and this issue has been discussed extensively by the HD24 group. Alesis confirmed (in thread "WD PATA drive not recognized" in the Yahoo HD24 forum) that larger WD drives do not mount because "their RPM speed is reportedly not as fast as advertised". Other possible causes are believed to be:
- Drives drawing too much current- to address this, a drive compatibility list has been compiled in the files section of the HD24 Yahoo group. Additionally, Alesis/Numark have issued a design update, which adds a capacitor to the drive bay daughterboard (part number 9-79-0238, previously 9-40-0238). This design update is available in the files section from the HD24 yahoo group.
- Removing the drive before unmounting it (unmounting the drive powers it down); This is thought to possibly cause damage on the IDE daughterboard .
- The electrolyte capacitors of the daughterboard drifting out of spec. This could be addressed by replacing the daughterboard or just the capacitors.
- A problem with the drive detection algorithm ("HD reset failed check jumper" error message), mostly with brand new drives. Members of the HD24 Yahoo groups have worked around this issue and had success mounting such drives by formatting them on a PC prior to using them in the HD24.
The IDE connector inside the caddies does not always exactly fit with the IDE connector of the drive. Symptoms are a constantly-lit LED on hot-swappable ViPower drive bay, slow booting and the drive not being recognized, either by the HD24 or by the computer. If this occurs, swapping the drive to another caddy may help.