CASSETTE Cassette decks are the most prevalent in planetaria, primarily because they're the least expensive, and it's not too difficult to drop a cassette in the deck and hit PLAY. But the tape is only an eighth of an inch wide, which means the tracks are less than 1/32 of an inch wide, and it crawls along at 1-7/8 inch per second. With Dolby noise reduction, passable audio quality can be obtained.

"Mono" cassette

There are still some ancient monaural cassette decks out there, mostly installed as part of a control console. Even these "mono" decks usually have two channels -- one holds the audio, the other holds the data for the automation. The output of the audio channel is piped into the sound system, the data goes to the controller. This is sometimes called the "inaudible beep tone", but it's plenty audible, it's just not sent to the amplifier. If you flipped over a cassette recorded on one of these systems and played it, you'd hear the data playing backward out the speakers, and you'd get the audio playing backward into the controller (which undoubtedly would not be too happy).

Even if you played a stereo tape in this deck, the mono head would pick up both tracks and blend them together.

Fortunately, there aren't many of these decks around any more.

Stereo cassette

Technics RS-BR465

More common are consumer-model stereo cassette decks. These have a limitation for most planetarium use, because they only play two channels at a time. There are actually four channels on the tape; when you flip the cassette over, the offset of the heads picks up the other two. If you've ever wondered how auto-reverse decks work, they physically slide the head over to pick up the other two channels, while reversing the drive motors and swapping the left/right signals to the electronics. Tricky!

In theory, you could record a monaural audio track on the left channel, and put controller data on the right. In practice, the noise of the data will leak into the audio channel -- those tracks are physically THISCLOSE, and there's a lot of high-frequency energy in SMPTE time code. Besides, no one does mono these days. This is the new millennium; even pre-school kids have stereo Walkmans and such.

Multi-track cassette

Tascam 134

To provide two audio channels for stereo and the necessary separate data channel, there are 3- and 4-channel cassette decks. The 3-channel variety is primarily designed for audio-visual work; the 4-channel decks (usually containing a built-in mixer) are aimed more at the home musician market, but for all practical planetarium purposes, they work the same way. The first two channels are identical to standard audio cassettes. Channel 3 is usually left blank as a "guard band" -- again, to keep the noise of the SMPTE time code on track 4 from leaking into the audio. For obvious reasons, you don't flip one of these cassettes over to play "the other side"; there isn't one.

We should note that standard cassettes play at 1-7/8 inches per second. In an effort to improve the sound quality, some multi-track cassette decks run at 3-3/4 inches per second. Unless the slower speed can be selected, regular cassettes will play at double-speed on these decks, and tapes recorded on them will play at half-speed on conventional decks.

REEL-TO-REEL While cassettes are primarily a consumer medium, reel-to-reel decks are what the professionals use, or at least they did until the advent of digital. Some still prefer the "warm" sound of the analog tape over the "coldness" of digital. Regardless, the basic track layouts on the tape are the same as the cassette, mostly.

Half-track stereo

Otari MX-5050 MkIII-2

This is the "broadcast standard", the one radio and TV stations use. The tape is one-quarter inch wide, and as the name implies, the format uses half the tape to record a track. Thus, you get two channels, both going the same direction. These decks typically can run at a selectable high/low speed of 15/30 or 7.5/15 inches per second. 7.5 ips is the usual speed for planetarium use, a reasonable compromise between the ultimate in fidelity and the ability to fit a show on one 7-inch reel of tape. Since it uses a wide area of tape to record the signal, it offers the best sound quality. But there's no channel to record the SMPTE time code. Actually, Sony did invent a way to squeeze a little thin channel between the two audio tracks, but these specialized "center-channel time code" decks tended to be more expensive than typical planetarium budgets would allow.

Quarter-track stereo

The quarter-track format was developed primarily as a consumer medium, for home tapers who didn't mind "flipping a tape over" to record on "the other side". It uses a quarter of the tape to record a track. However, the reel-to-reel manufacturers chose to separate the two heads instead of putting them side by side like cassettes, so the tracks INTERLEAVE when the tape is flipped over. But you still get only two channels at a time.

Quarter-track 4-channel

Teac 3340S

So they invented the 1/4-inch 4-channel tape deck. If you play a conventional quarter-track stereo recording on a 4-channel deck, the audio will play out of channels 1 and 3. Many planetarians have adopted this as their standard, so they'll be assured of compatibility with other quarter-track recordings.

As with the multitrack cassette, the proximity of the SMPTE time code to an audio channel can be a concern, so a better track layout consists of audio on channels 1 and 2, a guard band on 3, and the SMPTE time code on 4.

The quarter-track format was designed for the consumer, and thinking the consumer wouldn't be rich enough to afford lots of reels of tape, they designed these decks to run at slower speeds. Most still have a high/low selectable choice, but it's usually 3.75/7.5 inches per second.

8-track reel-to-reel

Otari MX-5050 MkIII-8

Double the quarter-track 4-channel format, and you have the 8-track. Its tape is usually 1/2-inch wide; most decks run at 7.5/15 inches per second. Here at Loch Ness Productions, we've used ours for assembling shows, or like a planetarium, for playing stereo soundtracks with SMPTE time code. Ordinarily, we don't provide show soundtracks on 1/2-inch 8-track tape; most planetarians will copy the stereo soundtrack in our show package onto two or more channels of their 8-track, add their SMPTE time code, and that becomes the show tape.

In the 1980s, digital audio tape decks became affordable. One obvious benefit of digital over analog is the elimination of tape hiss, wow and flutter, allowing for "cleaner" recordings. You can make copies that are identical to the original, and bounce audio from track to track without building up generations of noise each time. Digital being the language of computers, you can also manipulate the audio in a computer, and save the resulting mix or edit to digital tape.

These digital decks use transports that are based on video and camcorder technology. They pull the tape out of its shell, in a convoluted path, to wrap around a spinning drum head, which writes helical tracks of data on the tape as it passes by.

Still, the planetarian is faced with the same situation when it comes to the number of channels: you need two channels for stereo audio, and another for the SMPTE time code.

DAT

Panasonic SV-3700

DAT (which stands for Digital Audio Tape, even though the other formats are digital audio tape too) is the digital equivalent of the analog cassette. Most have only two channels of audio. While some DAT decks do have SMPTE time code capability, they cost about the same as a digital 8-track, so most planetarians prefer getting the additional channels for their money.

Digital 4-tracks

In passing we'll mention digital 4-track decks, which like the multi-track cassette, are designed primarily for the home musician. Most record on MiniDisc, a format that only holds 34 minutes of compressed stereo audio -- without time code. This doesn't seem to be the optimal choice for planetarium use.

Digital 8-tracks

ADAT

Fostex RD-8

The first affordable digital 8-track was invented by Alesis, the A in ADAT. It uses S-VHS cassettes for tape, though you'll want to use a tape formulated specifically for digital audio, not just any S-VHS cassette you can buy at the local supermarket. The tapes come in 42- and 62-minute lengths. Some decks have a separate SMPTE channel, so you can get 8 audio channels without having to devote one for the time code, though the prudent planetarian will record a backup channel of SMPTE on an audio channel, just in case.

It should be mentioned that the International Laser Display Association has established the ADAT format as the standard for laser shows, and even have a track specification for storing the laser, audio and SMPTE information.

DA-88

Tascam DA-88

There are two competing tape formats for home camcorders -- 8mm and VHS -- so naturally we have to have the same format war for digital 8-tracks. Tascam came up with the DA-88, which uses Hi-8 type cassettes. Of course the encoding method used to store the digital data on tape is incompatible with the ADAT. The tapes come in 30, 60, 90, and 120 minute lengths, not that you'd want to present a two-hour planetarium show. It too offers a separate "ninth" channel for SMPTE, though it requires an additional card to be installed.

What this all means for the Loch Ness Productions planetarium show soundtracks we provide

We provide our planetarium show soundtracks in stereo -- that is, with two audio channels, left and right.

When we initially produce a show, we mix our original multi-track down to a stereo master. We then simply dub (copy) that stereo master onto the tape or disc we send to you in the show package you order.

Even though you may have a multi-track deck, and multi-channel audio playback in your theater, there are still only two channels of audio on our soundtrack, so you aren't going to get better than stereo (unless you want to pay us to remix the entire show on a custom basis for your theater).

Given that we're providing a stereo soundtrack, you should get it in the form that will provide the highest quality reproduction. This may or may not be the same format as your theater playback deck.

We expect and encourage you to make a copy of the show soundtrack, and use the copy for your show presentations, not our original.

It only makes sense to archive our soundtrack; if anything unfortunate happens to your show tape, you can make another one from the original, which has been stored safely on your shelf.