CD Playthrough is a program that no owner of a 660AV, 840AV, or Power Mac with internal CD should do without. The ﾒuserﾓ mode of this program bypasses the Sound control panel to do three things, if possible:
1) set the sound input source to the internal CD,
2) maximize playthrough volume level, and
3) change the sound out rate to 44.1 kHz (thanks a million to Gary Anwyl)
CD Playthrough can also reset to what I call the ﾒsystemﾓ mode, whose various settings are required for PlainTalk Speech Recognition, GeoPort Express Modem, and Apple Phone operation:
1) microphone as the sound input source,
2) playthrough turned off, and
3) sound out rate at 22.050 kHz on a Power Mac, or 24.000 kHz on a 660AV or 840AV.
Finally, the ﾒuserﾓ mode is so named since copies of CD Playthrough can be redefined with different settings, as desired by the user ﾑ you.
requirements (what it needs)
Sound in requires a computer capable of multiple sound input sources ﾑ
Centris/Quadra 660AV, Quadra 840AV, any Power Macintosh with an internal Apple CD300i or CD300i Plus CD-ROM drive. Third party internal CD drives must be hooked up to the internal audio mixer on the motherboard via a dedicated analog 4-pin stereo header ribbon cable. To playthrough an external CD on the internal Mac speaker, connect the driveﾕs line-out to the microphone port.
Caution: only the above and new Macs have microphone ports that accept line-level audio directly, which is why they require the new PlainTalk microphone with a built-in preamplifier. If your Mac uses the original round disc mic, the sound input circuitry can only handle mic-level signals. When piping in line audio to these Macs, use the Apple Y-adapter with a built-in attenuator to avoid damage. This adapter (part number 590-0618-A) should have been bundled with your CPU and microphone.
CD Playthrough isnﾕt very useful for single input source computers, including the LC I/II/III, IIsi, PowerBook, and other Centris/Quadra models. The program will beep at various stages of its execution when it doesnﾕt find what itﾕs looking for and then quit, but it shouldnﾕt blow up.
Sound out requires the Component Manager ﾑ
System 7.1 (or 7.0 with QuickTime 1.6), and Sound Manager 3.0. These happen to be the minimum components built-in to every AV and Power Mac configuration.
functionality (what it does)
As strange as it may sound, CD Playthrough is doing its work if you open this program and it quits right away. It is a fire-and-forget application. I recommend placing a copy in the Startup Items folder with an alias in the Apple Menu Items folder.
Opening the program with no modifier keys sets the Sound options to ﾒuserﾓ mode. Hold down the Command key for ﾒsystemﾓ mode instead.
To program the ﾒuserﾓ mode, first select the desired settings with the Sound control panel, then duplicate a copy of CD Playthrough and open the copy while holding down the Control key. The program will display the settings and ask for confirmation. If confirmed, the new settings will be written to the application itself and remembered.
The ﾒsystemﾓ mode cannot be redefined.
limitations and bugs (what it does not do)
CD Playthrough is powerless to change the sound settings when another program locks it first, including:
1) Video Monitor (both sound in and sound out are locked)
2) Fusion Recorder (both locked)
3) GeoPort Express Modem, connected or in auto-answer (data/fax) mode (both locked)
4) Apple Phone (sound out locked)
5) PlainTalk Speech Recognition (sound out locked)
6) Any program playing continuous sound in the background (sound out locked)
7) Sound Effects (all effects lock sound out, Electric Guitar and Vocals can also lock sound in)
Some of the above may only apply to the 660AV and 840AV (Apple Phone, for example). You must quit the offending program or activity before any change can take place.
The self-modifying bit breaks all Apple Human Interface Guidelines, and probably raises hell with virus checkers. If this behavior offends anybody, you are invited to change the program to use preference files instead. Let me know when you get drag-n-drop working. :-)
The input source cannot be changed on single input source CPUﾕs, but I discovered that playthrough is enabled, but only if you click the alert Add button in the Sound control panel. Apparently there are other programs that can handle playthrough for older Macs. If you understand the problem (my sources are included), drop me a line.
legal mumbo jumbo
CD Playthrough is provided free of charge but remains copyright (1994) by jwang@csua.berkeley.edu <James Wang>. The complete archive, which must include this documentation, is encouraged to be redistributed freely, as long as it is not sold for profit and no part of the archive modified.
This program is provided as is, with no warranty of any kind, expressed or implied. James Wang and neg.active.productions cannot be held responsible for damages incurred from using CD Playthrough.
Developed using Symantec C++, Think Reference, ResEdit, and Resorcerer.
Tested on a Centris 660AV 16/230/CD running System 7.1/SU 3.0.
Sample code and additional testing thanks to anwyl@apple.com <Gary Anwyl>.
Products mentioned herein are trademarks of their respective holders.
Full sources to CD Playthrough are included with this archive, including the setSoundSRC.c sample code written by Gary Anwyl. Gary has been absolutely instrumental in the creation and continued evolution of this program. If you intend to use these sources in your project, please include an appropriate attribution. It would also be nice if you send me a copy of the final product.
