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Applications for Pocket Recording
  • Live recordings of musicians and group rehearsals
  • Recording your friends' band to show them what they really sound like
  • Lecture and theatrical recording
  • Nature ambient recording
  • Recording musicians' and composers' works in progress for demos
  • Sampling sounds for keyboards and computer samplers
  • Ambient effects recording
  • Recording film and video ambient stereo sound
  • Recording sound design, catalogued ambient sound and EFX library, and foley effects for film
  • Radio and TV journalism, documentary ambient, interview, linguistic study, spoken history study
  • Sound research and SFX for interactive game projects
General Web Resources for DAT and MiniDisc Recording

The MiniDisc Community
A gathering point for everything about MD—news, reviews, tech info, discussions
http://www.mini-disc.org/

MiniDiscussion.com
Offers message boards, FAQs, MD unit reviews, and resource lists
http://www.minidiscussion.com/

DAT Heads
A general resource for portable DAT recording
www.eklektix.com/dat-heads

Miniature Stereo Microphones and Accessories

The Sound Professionals
Miniature stereo mics, preamps, AD converters, accessories
123 Creek Road #10
Mt. Laurel, NJ 08054
1-800-213-3021
856-638-0008
fax: 856-638-0151
sales@soundprofessionals.com
http://www.soundprofessionals.com/

 


Reposted with permission from the October 2000 Issue.

 


by Pat Kirtley

My dad told me the story of a recording he made in 1954 of a piano recital given by his sister when she was graduating from music college. It was a special event in a big hall with a full concert-size Steinway grand. His rig was one of the most portable recorders available at the time—a one-channel Magnecorder reel-to-reel tape machine in a two-piece travel case weighing 65 pounds. That was portable recording then—now, we can carry around a miniaturized digital recorder, complete with stereo microphones, in a coat pocket. The entire package weighs less than 10 ounces, and is about the size of the level meter on the 1954 Magnecorder. High quality “pocket recording” is now a reality.

The size reduction in portable recording equipment has been an incremental process. For years the smallest battery-operated pro audio recording machine you could get was made by Nagra in Switzerland. It weighed six or seven pounds and cost around $5,000. Electronics companies made valiant efforts to miniaturize and improve portable recorders using the familiar compact cassette format, and brought the size down to impressively small dimensions. But even with Dolby or dbx noise reduction built in, these units failed to deliver pro-level recording quality, except in a few voice-only or sound effects gathering applications. If you wanted portability for master quality music recording, machines like the Nagra remained the only weapon of choice.

Miniature DAT
The introduction of the diminutive Digital Audio Tape (DAT) format in 1988 changed everything for miniature field recording. With a tape cartridge size of only 2"x23¼4"x3/8", it was only a matter of applying existing design and manufacturing techniques to come up with tiny handheld machines capable of storing up to two hours of master-quality digital recording. Nearly every major recorder manufacturer offered a miniature battery-powered DAT recorder.

I bought my first “pocket DAT” around 1993—a one-pound unit by Denon—and it immediately changed my approach to recording. Freed from the need for an AC power source (the unit had a NiCad battery with more than two hours run time), I could record just about anywhere, as long as there was ample blank tape. The mic preamps in the unit were nothing to get excited about, but weren’t too bad, either. After building adapters to mate the standard mic connectors to the recorder’s 1/8" miniplug inputs, I was ready for action.

I took the recorder into environments where I wouldn’t have bothered trying to record before—small clubs to capture an Irish acoustic band, construction sites for environmental sound effects gathering, my own concerts, where I began getting the best “board tapes” ever—and even made casual recordings of my own guitar playing. I realized that the ease of doing it made all the difference. My entire kit of equipment was in a bag weighing a few pounds (though the cost was a few thousand dollars).

It also made a difference that I wasn't scaring anyone with formidable-looking gear. How many times do subjects, even professional performers and actors, change their attitude and/or freeze up when a photographer, videographer, or recordist shows up? With my pocket DAT setup, I raised no eyebrows, and even if they knew I was recording, it just didn't look like a rig that would give master-quality results. (Note: I do not make recordings of musical or theatrical performances without explicit permission.)

The DAT format is fairly robust, with the tape protected inside a sturdy plastic shell, but it's still tape, and tape with always have the downside of being fragile. DAT tape is thin, and must move accurately across a rapidly spinning head-drum assembly. Anyone who's used DAT for any period of time has seen tapes "eaten" due to wayward transport problems.

With portable DAT machines, another nagging problem shows up—moisture. Any moisture or condensation buildup on the head drum assembly causes the tape to bind and snarl, and when transports are moved from a cold environment to a warm one, condensation can easily occur inside the machine. Many DAT machines have internal moisture sensors that will shut down the machine if condensation occurs, but they you could find yourself without a recorder at a critical time.

Then Came MiniDisc
In 1992 Sony introduced a new recording format called MiniDisc. With specifications rivaling the DAT format, and with almost none of the problems associated with fragile tape, it looked too good to be real. Now after eight years and five generations of refinement, MiniDisc (MD) is a prime format for portable recording. Some field recordists are totally sold on its virtues, and in broadcast work, for both radio and TV sound, the MiniDisc format has firmly taken hold. If, after grueling technical trials, these hard-core professionals (including the BBC and US national networks) have embraced the format, it has to be good.

While DAT takes criticism for potential mechanical and tape problems, the mechanically stable MD format has been called into question for audio quality issues, regarding its use of data compression. The MD data compression system, known as ATRAC, is probably the most sophisticated audio data compression technique ever created. It compresses digital audio data at a 5:1 ratio, meaning that about 80 percent of the original data is thrown out. It would seem impossible to preserve audio quality with that much missing, but actually the data isn't thrown out—it's recoded by a special computer processor into a much more compact form.

As another real-life example, data compression is used in digital cameras, too, and in that application they get away with using huge compression ratios of up to 25:1 but the loss is barely perceptible in the resulting images. The ATRAC system yields recordings that sound equivalent to DAT or CD quality in almost every way, and few discerning listeners—in double-blind listening tests—can tell the difference.

MiniDisc Portables
DAT tapes are small, but MiniDisc media is even smaller. The disc itself is encased a square protective package just 2.2" on a side. The MiniDisc recorder can be made amazingly small because the mechanical parts (a moving laser head and rotating drive motor similar tow hat's found in a CD player) are much simpler than those of a digital tape transport. In fact, the average pocket MD recorder is just 3"x3 1/2"x1" and weighs about nine ounces! Inside this wondrous gismo are (typically) a decent mic preamp, optical and analog line inputs, a 24-bit A/D converter, and a complete set of editing functions. Where miniature DAT machines can record for around two hours on a set of batteries, MD portables get four to 10 hours for a couple of AA rechargeables.

Beyond sheer portability, MD has a strong advantage in portable recording that comes from the inherent random-access nature of digital disc recording. With tape machines, before making a new recording on a tape you've already used, you have to make sure that you are at the end of the old recorded material, or you will obliterate it with the new material. In most MD machines, this process has been made completely foolproof—when you press record, a new track is automatically created and that's where the new recording goes. (Most manufacturers' designs work this way, but ironically, Sony, inventor of the MD format, persists with including an "end search" button that you must press when making a new recording on a previously used disc.)

Mics and Plug-In Power
To make good recordings, you gotta have good microphones. Although the history of microphone development is many times longer than the quick evolution of miniature recording machines, the best microphones are still fairly large items, and the recent trend has been toward larger, not smaller, designs. Add in the required hefty mic cables and paraphernalia required to supply phantom power, and you can easily end up with the microphone kit being many times the size and weight of the recorder itself. For successful, self-contained pocket recording, we need miniature microphones.

Most truly miniature high-quailty mics are going to be of the electret condenser variety. Why? because these are the designs that can be shrunk to the smallest dimensions. Standard condenser mics need a considerable amount of internal electronics to create a polarizing voltage for the element, and circuitry to match the high impedance of the capsule with the input electronics of consoles and recorders. Electret condenser mics need no polarizing voltage, and just a couple of volts to run an internal buffer amplifier. Many portable recording nits, both DAT and MiniDisc, supply this "bias" voltage via a feature called plug-in power. It is a standardized system, with specifications agreed upon by both the recorder and microphone manufacturers. Here is the spec: The microphone connector will be a 1/8" stereo (tip-ring-sleeve) mini-jack , and the machine will supply approximately 1.5 volts DC to that input. Most machines won't like it if you try to use microphones that don't conform to the specification (e.g., older miniature electret condenser mics that have their own self-contained battery power sources, or standard dynamic mics). The good news is that there are numerous affordably priced plug-in power mics that will yield excellent results with the new recorder designs.

On higher end DAT and MD recorders, you will often find quality built-in mic preamps with standard XLR microphone connectors, which can directly accept a wide range of microphones. These are not exactly "pocket" machines, though, and are the size of a medium hard-cover book with a weight of around three to four pounds. The minuscule dimensions of pocket recorders rules out using rugged XLR connectors, and we must learn to live with relatively fragile 1/8" jacks if we want pocket portability.

The Right Microphone
There are times when full-size, discrete microphones are appropriate to use with a pocket recorder, but more often, specialized miniature microphones are best. The most important thing to remember is that the quality of the mic and preamp determine the quality of the recording. There is no way to make a bad mic sound good, and post-processing of recordings is much easier if the initial quality of the recording is high.

Several small specialty companies have developed miniature stereo microphones designed specifically for live recording with miniature DAT/MD machines. In general, their designs are based on miniature microphone modules form sources like Audio-Technica and Panasonic. The best of these mics are excellent, and the companies have created many special-purpose mics as well as general purpose stereo pairs.

One of the most crafty and useful designs is the "T"-style microphone from Sound Professionals. This ingenious little stereo mic is about the size of a drum-tuning key, and fits directly into the mic jack on a portable recorder, with no cable at all. The recorder/mic combination becomes a one-piece handheld "soundgrabber," unencumbered by cables. For about $50, this mic is great for general recording and excels at lecture/interview applications.

At the other end of the micro-mic price range is the DSM series from Sonic Studios. These mics feature a pair of miniature premium omni mic capsules adaptable to a number of interesting configurations. The applications include attachment to the earpieces of a user's sunglasses, and attachment to an available dummy-head for binaural/stereo perspective recording. These mics have gotten rave reviews for their performance in acoustic concert and classical music settings.

In the middle range are versatile mics like the Sound Professionals SP-CMC4 Premium Cardiods, a set of two matched miniature units based on the Audio-Technica AT-853 capsule. These microphones are available with integral miniature clips that allow them to be used in many different ways, and boat impressive specs (frequency response of 30-20kHz and a signal-to-noise ratio of 67 dB).

High SPL Options and Filters
Sometimes you need to record sources that are very loud. While plug-in power connections provide adequate voltage to microphones under most conditions, upping the voltage to the mic gives more headroom, and the ability to deal with truly intense sound sources, such as rock bands in large venues. The tool that's available is called a battery box or auxiliary battery supply. Most provide power from a 9-volt battery, and allow mics to handle sound pressure levels up to 145 decibels. Some of these battery supplies feature bass roll-off filters to help control the low frequency environmental rumble that is often encountered outdoors and in large buildings. The battery boxes are easy to use—just plug the mic set into the box, and the box into the recorder input, and voilà, no more blown-out, distorted concert tapes. Some recorders, including those from Sony, feature built-in attenuator pads that can be switched in to tame excessively loud levels before reaching the microphones.

Pocket Recording Communities
While portable DAT and MD recorders have not caught on with the general public , the niche market for pro and amateur recordists is healthy and thriving. On the Internet, through web sites and mailing lists, several communities of portable recording enthusiasts have formed. There are may subsets of this group, ranging from audio professionals to "stealth" concert tapers who trade copies of their illicit recordings via the net. In general, the online pocket recording communities are just groups of people interested in the concept of portable recording, and fascinated by the jewel-like miniature gizmos we use to accomplish it. Some recordists are interested only in making compilation recordings of their favorite albums to listen to in the car, while others are pushing the envelope of live recording.

DAT fans congregate at a site called DAT-Heads (www.eklektix.com/dat-heads), and MiniDisc proponents find tons of information at sites like The MiniDisc Community (http://www.mini-disc.org/) and The MiniDiscussions Page (http://www.minidiscussion.com/). Besides publishing lots of equipment reviews and opinions, they feature focused, topical mailing lists and discussion groups where you can air your views and seek advice from others.

Get Out There and Record
Nearly every home recording enthusiast can utilize the unique capabilities of portable recording devices. It's been said that you never understand how playback systems really sound until you make a live recording of a musical performance, then go back and listen to it at home. You begin to understand the huge disparity between real life, and the attempt to recreate it with amps and speakers. Making a good live recording with minimal equipment is one of the most rewarding projects you can undertake. If you've never done it, you're in for a thrill.

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Copyright © 2000 Cherry Lane Magazines
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