There are still quite a few specialised digital recording formats out there that are either capable of high quality recording and playback or have other redeeming qualities but are not popular or common, noticeably there are quite a few semi-pro and pro digital formats that use enough common technology to be viable for use today. There are also current and/or recently discontinued professional recorders that record onto computer media such as PCMCIA (PC Card), Magneto Optical and SD.
There is a number of companies that provide professional and semi-pro recorders that record on to on of the DVD blank media available, usually DVD-RAM since that is a hard sectored format while + & - are soft sectored, this has nothing to do with DVDA but is rather the case of using the DVD media simply as a recording medium, the resulting masters are usually only playable black on the recording device itself and on PC's utilising pro audio recording software. The reason that people are recording onto DVD media and not onto hard disks, especially in the location sound sector is the limited durability and lifetimes of hard disks but even the recordable optical disk, itself not a secure archiving format by any means, beats a hard drive for storage purposes, note though that some of the recorders here offer optional hard drives for scratching or mirroring purposes. Also note that almost all recorders use a caddy system.
Fostex Makes the PD-6 but that is a portable 6 channel recorder that utilises a mini - DVD-RAM media (8cm) that records utilising an UDF format. Recording bitrates can be up to 24 bits and resolution up to 96KHz, the unit is oviously geared for location film recording since it features a built in timecode generator, fully balanced I/O and a simple 6 channel mixer. There is also an optional docking ststion called EX-12 that can house a full size DVD recorder and or a hard drive. The DV40 is however a rack mount unit intended to be a mastering recorder although if features a .
Akai Electric Co. Makes 3 types of 8 track MO recorders, unlike the Otari units here below that are geared towards the broadcast market, the Akai range is aimed towards the video post production market even to a degree were their standalone models can become a plug in replacement for TEAC DA-88's with a superset of the features and interfaces that it offers. They offer 2 standalone models, the DD-8 and the DD-8 Plus, both of them are rack mounted units with fairly simple editing options, the Plus version offers 24 bits recording at 96KHz. More interestingly the company has a modular system called the 1500 range, it consists of an tabletop editing unit named DL-1500 that can in turn control multiplies of the rack mounted DD-1500m recording units and DD-1500x11 MO storage units
In the early 90's the company had a line of 4 track MO recorders also intended for AV post production applications, they were 16 bit, with very good editing capabilities for the time and were called DD-1000 and you could get a slave unit called DD-1000s if you needed more tracks. An improved version called DD-1000i was introduced in 1994.
Genex Makes a 8 track MO recorder that is intended for classical music recording, has editing capabilities and can store DSD format recordings if an external bitstream converter is used.
Otari Made 2 lines of MO recorders and editors mostly intended for the broadcasting and duplicating market but they have also seen some use with the audio book industry due to the archival quality of MO media. They all use a standard 90mm (3.5") Fujitsu standard MO disks and the DX line stores the data as IBM OS/2 Wav files so you can use them with just about any computer editor that has been equipped with a MO drive, the DX units also support the BWF format, the PD units however format the disk in a proprietary way as the DOS format is to slow to handle multitrack or sampling rates above 44.1kHz. The DX-5050 is the lowest cost version of the Otari MO recorders, it has only simple editing functions but allows you to connect an external MO drive to extend the recording time capability of the unit. The DX-5 is a mono unit intended for use with voice recording such as is the recording of audio books and uses a reduced 22 KHz sampling rate to give you up to 4 hours of recording time. SCSI connector allows the unit to use external storage or to be used as a slave to a computer.
The PD-20 rack unit supports recording up-to 48 KHz and has exhaustive editing capabilities built in, simpler editing can be done from the front panel, but more advanced functions become available once you hook an optional remote to the unit and connect a VGA compatible monitor to the built in VGA connector. The unit has Video, digital and word clock sync options as standard and as SCSI interface. The PD-20B is a console version of the PD-20 that has exhaustive editing capabilities, built in VDU and AES/EBU interfacing in addition to the what the rack unit has. The PD-80 is an 8 track version of the PD-20 that sports DSP processing and frame sync in addition to the usual..
Sony In the early 90's they introduced the PCM-9000 a Magneto Optical stereo mastering recorder that had the unique (at the time) capability of being able to record 20 bit signals. Editing facilities, good I/O section and great sound meant that it sold a bit to the rich pop stars and to the classical recording industry, and may indeed be the inspiration for the Genex here above, but the scary price of the unit (more than most 24 track recorders at the time) meant that it never sold in any numbers to speak of.