This information should address both Jim Nollman and Douglas
Douglas makes a very good point in distinguishing between the analog
response and the digital sample rate. In fact, some of the
24-bit/192 kHz stand-alone digital recorders and firewire interfaces
have an analog frequency response of only 40 kHz. The Edirol FA101 is
one example of a computer interface that can sample at 192 kHz but
which only has an analog bandwidth of 40 kHz. The Sound Device 722
and 744 may also be in the same category, but we won't know until they
are independently tested. Two months ago, I asked with one of the
owners of Sound Devices about the frequency response of the 722 and
744. He told me that they only have the capability to test up to 40
kHz, therefore he didn't know what the frequency response of the
devices will be when sampling at 192 kHz.
If you're looking for a computer interface with a 24-bit/96 kHz sample
rate and a 40 kHz bandwidth, the new Edirol UA-25 works well. I just
installed one on a hydrophone system for the American Cetacean Society
and it's been performing quite nicely.
Regarding Jim's comments, there are devices that record to hard disk.
Gianni mentioned a few of them. The Sound Devices 722 and 744
mentioned above are two and the new Edirol R-4 is another. The Sound
Technology ST400 to be release later this year is also a hard disk
recorder that will be able to withstand much higher shock than pro
consumer devices like the 722 and R-4.
Jim's idea about using a PCMCIA interface to a standalone hard drive
with the Fostex FR-2 was very interesting, so I talked with the
professional products manager at Fostex. Unfortunately, his answer
was that the idea will not work. However, Fostex does make a
combination hard disk recorder and DVD RAM recorder called the PD-6.
It's a six channel device that can record simultaneously to DVD RAM
and a 40GB hard drive. It currently only records at 24-bit/96 kHz,
but the head engineer said the reason for that was the size of the DVD
RAM when the device was first released. He believes that it should
only take a software upgrade to allow the device to record at
24-bit/192 kHz with an analog bandwidth of 80 kHz.
Besides memory capacity, there are two other factors that I believe
are important when considering what type of portable digital recorder
to use. The first is the ruggedness of the device. Hard drives are
great because they can hold a lot of data. However, they are
susceptible to shock and humidity, and you are much more likely to
lose data when recording to a mechanical medium than to a solid state
medium such as compact flash. Therefore, if you think you'll be in
rough conditions and might bang up your recorder, get the CF recorder
and spend a bit more on the recording medium.
The second thing to consider is the overall price of the device. The
Fostex FR-2 has a list price of $1499 with a MAP (Minimum Advertised
Price, that is dictated by the manufacturer) of $1299. The Sound
Devices 722 has a MAP of $2375 and I'm not sure what the list price
is. The Edirol R-4 has a list price of $1895 and a MAP of $1595. The
Fostex PD-6 lists for $9995 and has a MAP of $8500 (this device has
lots of bells and whistles like two radio microphone outputs, built-in
mixer, etc.) High speed 1GB to 2GB Compact Flash cards sell for $100
to $200 each.
It should be noted that all of these devices are relatively cheap when
compared to research grade equipment that are required for most
research done in the physical sciences. My biggest caution to anyone
doing acoustic research is not to be burned by using cheap consumer
electronics when trying to make high-quality scientific measurements.
Joseph R. Olson
Cetacean Research Technology
PO Box 70186
Seattle, WA 98127
877-824-5432 (outside the Seattle local calling area)
Cetacean Research Technology is a strategic partner of
Sound Technology, Inc.
Spectra Group - Signal Analysis Division