Sound Devices USBPre Review (for linguists)
Sound Devices is a company based in Reedsburg, WI specializing in professional field recording equipment. They cater primarily to the news and motion picture industries, but their products are certainly versatile enough to be of tremendous value to field linguists. I own two pieces of Sound Devices gear, but I certainly find myself lusting after their entire product line. The single most useful piece of audio gear I have ever owned is the USBPre, a "Swiss Army knife" of computer audio interfaces.
Figure 1. USBPre, courtesy http://www.sounddevices.com
The USBPre is a small, but sturdy USB-powered unit that has an impressive spec sheet. It can be properly interfaced with microphone, line, instrument, and tape analog devices, as well as S/PDIF digital audio data streams. It offers an on-board phantom power supply, responsive LED levels metering, and no-latency headphone monitoring. The full specifications can be found here. Figure 2 shows a schematic of the workflow that I have been using with the USBPre.
Figure 2. USBPre workflow
If you want an all-in-one laptop recording solution, look no further. I have been periodically trying other, newer USB or FireWire microphone interfaces (e.g., M-Audio, Tascam, etc.) and have not found anything near the quality and reliability of the USBPre. It offers drivers for Windows XP (they also work with Vista and Windows 7) and Mac OS X. The Windows drivers are extremely stable. The device has never crashed on me, not even once! If you are still not convinced, please read on.
Why use a USB audio interface?
Over the last decade or so we have witnessed significant progress in the area of digital audio. However, the standard audio interface built into personal computers (including workstations and laptops) has changed very little since the original Sound Blaster 16. A typical Macintosh or Windows computer has a simple 1/8-inch audio interface consisting of (1) stereo line-out, for powered speakers or headphones, (2) mono microphone-in, for electret desktop or headset microphones and headsets, and (3) stereo line-in. Laptops these days are typically limited to (1) and (2), while some more sophisticated desktop motherboards come with a surround output system - see Figure 3 below. Such an interface may be sufficient for gaming and/or home theater purposes, but it is not suitable for professional audio applications.
Figure 3. Audio inputs and outputs of an Intel DP55KG motherboards (photo courtesy Intel)
The USB (and FireWire) bus provides a fast and efficient protocol for transferring digital audio data and interfacing professional audio hardware with PC software. A wide variety of USB devices are available, ranging from simple microphone pre-amplifiers to sophisticated multi-track control surfaces. It is often difficult to find just the right type of device for linguistic research. I have tested several of the popular brands (M-Audio, Digidesign, Tascam, etc.) and found the Sound Devices USBPre to provide the right type of solution. It is sturdy, solid, reliable, stable, and provides enough audio quality to satisfy even the most discerning linguists and speech scientists. Additionally, the USBPre is powered by the USB bus itself, thus facilitating portability and convenience in the field.
The USB 2.0 standard is fast enough for multi-track uncompressed PCM streams, but the USB 3.0 specification promises a ten-fold increase in speed and less CPU-intensive operation. The future, especially for laptop computers, is certainly in the USB technology.
There is not a compelling alternative to USB. Most high-end laptops have an available PCMCIA slot that can be used for audio add-on cards, but while such cards offer a size advantage over USB devices, they fall short on professional features, such as XLR microphone interfaces.
The USBPre - what I like a lot
The unit has an all-metal chassis. The input and outputs are solid. The knobs are smooth. The LED lights are highly responsive. You'd be hard-pressed to find a similarly priced unit that's better built.
The USBPre has the Sound Devices signature high-gain, low-noise microphone pre-amplifiers. They're certainly good enough to obviate the need for an external pre-amplifier, such as the MixPre. The only time when I bypass the pre-amplifiers and use the line interface is in the lab where I can use the state-of-the-art Tucker Davis unit. In all other recording situations, the USBPre works perfectly well.
Phantom power supply
The phantom power is solid. It powers well even the most finicky condenser microphones, such as the Earthworks measurement microphones. It will, however, increase overall power consumption of your laptop, so you should make sure to carry a spare battery with you.
Line and tape interface
As I mentioned, in the lab, I sometimes use the Tucker Davis pre-amplifier whose output I route through the USBPre's line interface. The performance is great, as expected. The USBPre also makes a great tape digitization unit. I used it to digitize all of my old analog recordings.
A/D and D/A converters
The A/D and D/A converters are first-rate. They offer pristine 24-bit, 48,000 PCM audio. There is really little practical need to go any higher for field speech recordings. Also, I often use the USBPre as an audio playback device for my speech perception and hearing experiments. The unit has a great dynamic range and nearly perfectly linear gain. Certainly better than most internal computer sound cards. Because the Windows drivers install as standard WDM drivers, I am even able to use my legacy Rothenberg nasometer, which otherwise requires an stereo line-in interface, which is no longer available on modern laptop computers. ASIO drivers are also available.
I only have two complaints about the USBPre. First, 64-bit drivers are not available for Windows 7. Second, the unit cannot function as a stand-alone microphone pre-amplifier. Yes, I know it would be crazy to expect that, but it would make a superb pre-amp in its own right.
I have chosen to use two completely different types of microphones to test the USBPre with. Each microphone poses a different set of challenges to the unit. The degree to which USBPre can handle both microphones will be indicative of its ability to provide adequate acoustic and electronic performance for a wide variety of microphones that can be used in the field.
The Sennheiser HMD25 is a professional, dynamic headset microphone that is ideal for recording speech in noisy environments. Being a dynamic microphone, the HMD25 requires a pre-amplifier with low noise and high gain. It is problematic for many field recorders, but the USBPre handles the microphone really well. Figure 4 shows a spectrogram of a Polish phrase "Czarna krowa" recorded at approximately -12 dBFS (a reasonably high level). You can see very good spectral detail with very little noise, and virtually no distortion. DOWNLOAD ORIGINAL FILE.
Figure 4. Spectrogram of a phrase "Czarna krowa" with the Sennheiser HMD25 microphone
Similarly, a narrow-band FFT spectrum of the vowel /a/ in "czarna" (Figure 5) shows a very natural spectral envelope and sharply defined formant peaks.
Figure 5. FFT of the vowel /a/ with the Sennheiser HMD25 microphone
Beyerdynamic Opus 55 Mk II
The Beyerdynamic Opus 55 Mk II is my microphone of choice for the most demanding recording applications. The microphone has a highly flat and wide frequency response, as well as medium sensitivity, which allows it to record really high spectral detail and achieve very favorable signal-to-noise ration (SNR) with close placement.
Being a condenser microphone, the Beyerdynamic Opus 55 Mk II requires phantom power supply of 48 V. It is rather uncommon to have a reliable, quality phantom power supply on a portable filed recording unit, but the USBPre handles the Beyerdynamic Opus 55 Mk II without much effort. Figure 3 shows a spectrogram of
a Polish phrase "Czarna krowa" recorded at approximately -12 dBFS (a reasonably high level). You can see very good spectral detail with very little noise, and virtually no distortion. DOWNLOAD ORIGINAL FILE.
Figure 6. Spectrogram of a phrase "Czarna krowa" with the Beyerdynamic Opus 55 Mk II microphone
Similarly, a narrow-band FFT spectrum of the vowel /a/ in "czarna" (Figure 7) shows a very natural spectral envelope and sharply defined formant peaks.
Figure 7. FFT of the vowel /a/ with the Sennheiser HMD25 microphone
If you prefer to record audio directly to a laptop computer, USBPre is going to provide a solid solution. I have also found the Sound Devices tech support to be very friendly and helpful. You actually get a really technician on the line who is able to understand your questions and help you troubleshoot our issues and find appropriate solutions. I have owned two USBPre units over the years and neither has ever failed me.