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Microphone Details

[Craig O’Donnell is the author of Cool Mac Sounds (ISBN 1-56830-067-0), the second edition of which was recently published by Hayden Books. We reviewed the first edition in TidBITS #155, and if the second edition improves on the first as I suspect it does from the information Craig provides below, it’s worth checking out for those who work with sound on the Macintosh. -Adam]

Mark Anbinder wrote in TidBITS #204:

Purchasers of Apple’s new low-end Macintosh systems will be surprised if they try to use a borrowed Apple microphone in the computers’ microphone jacks. The Performa 475 and 476, LC 475, and Quadra 605 computers require the new PlainTalk microphone in order to record sounds using the microphone port, but don’t include it. Microphones bundled with previous Macintosh models won’t work, because the PlainTalk microphone has a longer plug (.75" rather than .5") and the old plug doesn’t properly seat inside the new jack.

Mark’s on the right track but unfortunately microphones are now a little more complicated than that. Maybe this time next year things will be simpler; or perhaps, with the PowerPCs coming out, things won’t be simpler. You never know.

First of all, the new PlainTalk mic ($29 – part #M9060Z/A or service #922-0867) has a longer connector unique to Apple. Why? Because the input is stereo, but at the same time the mono PlainTalk mic requires power, and the Mac requires something to let it know a PlainTalk mic is plugged in.

The new dual-purpose input jack accommodates:

  • mono 1/8-inch plugs
  • stereo, or "TRS" 1/8-inch plugs
  • the PlainTalk mic plug. When this longer plug is in, it feeds power to the mic and signals the Mac that a PlainTalk mic is plugged in, rather than an External Line input.

As far as the Macintosh hardware itself? There are several sets of variables which I’ll discuss briefly below:

  • mic-level input vs. line-level input
  • one-channel input vs. two-channel input
  • stereo output vs. mono output
  • internal mics vs. external mics
  • old Performas vs. new Performas
  • internal CD-ROM

Apple has three kinds of audio inputs on recent Macs. Let’s say you need to use a mic sometimes, or a stereo Hi Fi VCR.

  1. Line-level and stereo/16-bit INPUT (AV Macs only). You can plug a Hi Fi VCR directly into this input. You need the PlainTalk Mic, or a line-level input from a mic preamp or mixer.
  2. Line-level and mono/8-bit INPUT (the sound architecture in the Performa 475/LC 475, Performa 550/LC 520, or Quadra 605). Although these Macs can play back stereo sound files, they cannot record stereo sound files. Any two-channel input is mixed into mono upon recording. L and R = (L+R). You can plug a Hi Fi VCR directly into this input, but the resulting soundtrack will be mono.
  3. Mic-level and mono/8-bit INPUT (all Macs with the sound input port beginning with the IIsi, including the Quadras, LC, LC II, and LC III, Performa 400-450 series, Duos, and "Fat PowerBooks"). This is the one we’re all most familiar with. You can plug a Hi Fi VCR into this input if you have a Radio Shack attenuating adaptor.
  4. Stereo OUTPUT? Stereo, of course, is two-channel sound on both input and output; L=L and R=R; Apple spec sheets constantly fudge this. Most Macs have been able to play back stereo since the Mac II debuted. (The exceptions are any SE-based or LC-based machine).

    Only the AVs actually record stereo. The new Performa 550/LC 520/MacTV records in mono by mixing the input channels; they are the only Macs so far to have stereo speakers built in.

  5. Internal CD-ROM. The internal CD ROM drives have nothing to do with the Apple Sound Input or Output hardware. They play stereo out the rear panel jack just like an audio CD player would: this mixing process of CD-ROM sound and beeps is analog.

    On all Macs with an internal CD-ROM, except the 550/520 machines, the two channels of CD ROM audio are mixed into mono when played through the internal speaker. The hydrocephalic Macs have two small stereo speakers built in.

    When the "Internal CD-ROM" has been selected as the audio source in the Sound CDEV, you can record the output of any audio CD. The levels are corrected internally. For example, the Performa 550 will record a 22k, L+R-to-mono sound file. The 660AV will record a 44.1k, stereo sound file. (Actually, the AVs’ input sample rate settings are a shade more complicated than that but it’s not worth going into here).

  6. Sound Manager 3.0. One nice thing about Sound Manager 3.0 is the fact that it causes any stereo sound files played on the "mono" LC-based machines to come out the speaker mixed to mono. Without Sound Manager 3.0, you get only the left channel at the output.

    This is nice for the day (whenever it comes) when LC owners are faced with QuickTime movies with two, three, or four tracks of audio.

Model by Model — Here’s how it breaks down. It’s probably easiest to group the information by product line. PTM is my code for "PlainTalk Mic required" and "SDM" is my code for "the older Silver Dollar Mic only."

Old Performas: Performas prior to October 1993: SDM. The line of recently discontinued Performas based on the LC II and LC III included the old "silver dollar" Apple mic, and were the last Macs to include an external mic (sigh… except the two AV Macs).

New Performas: PTM. The newer Performas (460s, 470s, 550) do not include a mic, except that the 550 has a built-in front panel mic.

LCs: All SDM, with a few exceptions. The LC 475 is PTM. The LC 520 and the Color Classic (which is LC-based) have a built-in, front panel mic.

Quadra/Centris line: All SDM, except for the AV Macs, and the Centris 605 (which does not record stereo).

PowerBooks: All SDM, including the Duo Docks. Duos have a built-in mic.

Substitutes? — There is no substitute for the PlainTalk mic, although you can use any mic through a mic preamplifier or mixer as a "line-level" input to the PTM Macs.

Of course, this costs you at least $200, right on up to $5,000, for a mic preamp and microphone of any quality at all. A typical low-cost AV-compatible setup would include the Mackie 1202 mixer ($325; a great bargain) and an Audio-Technica, Shure or EV mic ($75 to $200). You can try to use a Radio Shack mixer and cheap mic but I don’t recommend it.

No Silver Dollar Mic? — Not to worry. Radio Shack carries three or four "electret condenser" mics in the $18-$28 range and any of these work in lieu of the old Silver Dollar on the SDM Macs. I personally like the $28 Tie Tack Condenser because it’s small, it has a long cable, and it has a nice, balanced sound. But the sound on all three of these mics is close.

Part Numbers (from pages 145-147 of Cool Mac Sounds):

     Omni Electret #33-1060       $18
     Tie Clip Omni #33-1052       $22
     Tie Tack Omni #33-1063       $29
     "Radio Shack PZM", just over $50.

     Apple's Silver Dollar Mic lists for $19.

However, on these older Macs, to record a "line input" from a tape, VCR, CD, and so on, you need an attenuator. Radio Shack makes two (an attenuating "dubbing cable" and a simple attenuating adaptor). Either works fine. Part #274-300 or 42-2461.

Scurrilous Rumors — There is a rumor going around (unfortunately reinforced in print) that you need an extra-special adaptor for a Silver Dollar Mic Mac’s sound input port, and it isn’t true. The standard mono 1/8-inch plug on Radio Shack’s adaptors and electret mics functions perfectly; there is no danger to your Mac’s input hardware.

The only time you might endanger anything is if you plug a stereo cable from your CD player or VCR into the rear-panel input without an attenuator. There’s a very small DC voltage for Silver Dollar mic power on what is normally the Right Channel of a stereo input. This could damage your hi fi (but it’s unlikely).

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