Constant high-pitched humming, buzzing, whining

[billw58]

Based on this I can't help but wonder what the rest of the internet is doing for their screencasting, because I couldn't recommend using a Mac for recording audio based on these tests.

There must be something wrong with your methodology.

1) Lots of people are using Macs with no such problems.

2) How did you transfer the MP3 files from the Sony to the Mac? Via USB? If so, then the USB port on the Mac must be "acceptably noisy".

3) I did a number of tests using my G5 dual 2GHz (an antique machine, these days).
Audacity set to 32-bit quality, Mac line in volume set to maximum
a) Line in port on Mac open circuit (nothing plugged in), record 10 seconds:

Spectrum open circuit.png (47.18 KiB) Viewed 1077 times

b) LIne in port on Mac short circuit (dual-RCA > mini-plug cable plugged in, RCAs shorted), record 10 seconds:

Spectrum short circuit.png (47.41 KiB) Viewed 1076 times

Saved project and quit Audacity. Plugged AT2020USB mic into front panel USB port. Selected AT2020B in System Preferences > Sound > Input. Re-opened project.
Set Audacity > Preferences > Devices > Input > Devices to AT2020USB.
Put mic in a camera bag in a futile attempt to reduce room noise.
c) Record 10 seconds from AT2020USB:

Spectrum AT2020USB.png (46.36 KiB) Viewed 1076 times

The line-in port is noisy when open-circuit, as expected. When shorted it is dead quiet. With the mic, the pre-amp noise and room noise dominate the internal noise from the USB port. There's also some hum (60 Hz and harmonics) with the mic, which is probably a limitation of the mic, or EMI floating around my computer room (lights are on a dimmer).

Based on these observations, I would dispute your claim that Macs are not suitable for recording audio.

-- Bill

[kozikowski]

<<<On all Macintosh equipment the line-in port was unsuitably quiet using a variety of powered and non-powered microphones. >>>

Doesn't surprise me. Macs do not have a Microphone Input, and nobody will give the built-in microphone any awards.

<<<On all Macintosh equipment the USB port was unsuitably quiet using a variety of microphones.>>>

As was the PC, I'll bet. All the sound amplification in a USB microphone is in the microphone and once you have a bitstream, the volume is stuck unless special provision is made to amplify it. Further, USB microphones are universally quiet because they have no provision to adjust volume during overload. Live Performances are really hard to deal with.

Macs do have a terrific analog and digital optical Line-In suitable for connection to a mixer or other Line-Level device.

http://www.kozco.com/tech/LRMonoPhaset4.wav

Any trouble hearing that? That was a straight recording done with my mic, mixer, and Mac on the duvet atop my bed. The last segment is intentionally damaged as a test, but there is no other processing.

We've made really good use of one of these mixers for simple podcasts and instructional videos...

http://www.peavey.com/products/browse.c ... 29%206.cfm

The stereo Line-Out will plug straight into a Mac or a PC Line-In. It gives you the ability to mix and control several microphones and other sound sources and feed the computer and feed the headphones of the performers.

PC Laptops have designed their way out of simple, one-microphone podcasting. Cheap sound cards do not have enough volume boost to deal with cheap microphones -- everybody designed down at the same time, so it also doesn't surprise me that you found an external sound manager that works enormously better than either of the computers. Zooms will do that, too.

PCs are business computers and Macs are designed to be connected to external mixers.

Koz

[kozikowski]

The forum put together a review/comment section for External Sound Cards.

http://forum.audacityteam.org/viewtopic.php?f=27&t=9477

Koz