Audio Equipment: USB audio interface

A small USB audio device – sometimes referred to as an external sound card or USB Audio Interface – is a good way to get audio into your computer… and out of it, too. Usually, getting audio in is the greater challenge, so I’ll concentrate on that. The USB devices tend to be versatile, too– accepting a microphone, a line-in, and maybe an optical connection, and providing a line out (or headphone) connector to export sound.

In the last week, I used two different USB devices to get audio into the computer. Yesterday I used my boyfriend Doc M’s M-Audio Transit USB connector to import and digitize a cassette tape (the tape deserves its own post). A few days before that I used my Griffin iMic to connect a microphone to my computer in order to talk to a friend using Gizmo Project – a Voice over IP (VoIP) application. I could have used that same setup to record directly into the computer– what I was doing was getting sound from the microphone IN to the computer in order to send that signal over the internet to my friend so we could chat.

These are devices that convert the signal from analog to digital. Sound enters the device through an analog connection (an audio miniplug). The device converts the sound to digital audio and delivers the digital information to the computer through the USB port.

First, an introduction to the devices themselves, and then how I used each one. Though I used these with Macs, they work on Windows, too. Doubtful that they work on Linux.

The devices:

Griffin iMic.

It’s a lower-cost, low-frills basic USB audio interface. Street price is just under 50 bucks. Plug one end into your USB port, and the other end will accept a couple of mini-plugs. For sound IN, either a line-in or microphone plug, and for sound OUT, a line out (headphone jack) plug. The iMic has a switch on its size to select whether the audio IN plug is a microphone or a line-in. (note: I have an older version of the iMic; Griffin has since come out with a newer version, which is shown here. The newer version is much clearer about which switch position is mic-level or line-level.)

M-Audio Transit USB

M-AUDIO Transit USB Audio Interface
The Transit USB has more features than the iMic, and comes at a higher price ($78-83 street price). The electronics inside the device are very quiet—It is praised for not introducing any background hiss or noise at the point of conversion from analog to digital. As for plugs and ports, the Transit USB includes the standard sound IN mic and line in—and also offers optical line in, to transfer sound from digital sources such as CD players and some minidisc decks that include optical out ports.

To use the Transit USB, you install driver software onto your computer; what’s installed is a software control panel that gives you some options for converting from analog to digital. Change the sound level (gain/volume) going into or out. Set the bit depth. Adjust latency (um, no clue there what that is. Didn’t fiddle with it.)

One thing going against the M-Audio Transit USB is a flakey USB driver. I used the unit with an Intel-based MacBook. Though it worked perfectly yesterday, the computer wouldn’t “see” the device when I tried it again today. Restarting the computer solved that.

Uncharted (for me) territory: Edirol USB Interface.

Edirol UA-1EX USB Audio Interface
Uncharted because I haven’t used it. The Edirol seems comparable to the MAudio Transit—in price and functionality. It includes an optical in line, too. The big unknown: How does the driver work, and is there a good software interface on the computer to set volume/gain for incoming audio signal?

Here are the two ways I used the two devices:

Microphone to USB

Using this kind of interface, you can bypass a portable recorder and record your audio directly to computer (using an application such as Audacity).

Microphone—> USB Device—> Computer

On a lark, I decided to use my small microphones [two mics on a Y-style connector to a stereo miniplug] connected via iMic to USB for a voice call to a friend using Gizmo Project. I hooked up the microphone (stand, holder, cable from mic to iMic, iMic to USB port.) Using the computer’s sound control panel (sound input), I made sure that the voice signal was going in. Then plugged in my headphones to the computer (Using the iMic for simultaneous sound IN and sound OUT is not adviseable; the sound is choppy) Once I began the call, I could just talk toward the mics.

I could have as easily recorded audio directly into the computer this way.

Cassette Playback to Stereo Amplifier to USB

Yesterday, I finally worked up the gumption to digitize a cassette tape. Reason for delay: The tape was made in the early 1980s the morning after the big birthday bash of my Great Great Uncle Frank Fox’s 100th birthday party. (I did not attend.) My mother gave me the tape, and I hemmed and hawed over whether to do it myself or, since 20 years had gone by, to send it to an expert. Yesterday, I just upped and did it. I’m very glad I did. Success! My grandfather and his brother told some old stories that they remember from Granddad (Uncle Frank’s Father) and a number of people present sang some old songs from Ireland. The transfer was a success.

Here’s how things were connected:

Cassette Deck—> Receiver—> RCA stereo cable to miniplug—> USB Transit Line In—> USB to computer

I just began to play the tape right where it was (turns out it was full on side A and only partly recorded on side B, so the tape was stopped where side B stopped). The right channel was much louder than the left. The USB Transit’s ability to adjust sound levels for each channel meant that I could boost the softer channel coming in. Sweet.

It was a major treat to hear the sound of my grandfather and his brother, my Great Uncle, telling some old stories. A big and wonderful payoff. And I have the basis of a sound master to attempt to clean up a bit, and audio CDs to burn for other family members who, I assume, would also appreciate hearing the sounds of those voices. The sound of their voices—that’s the whole reason for going through this digitizing exercise.


Enjoy this post? Share it with others.

  • Google+
  • StumbleUpon
  • Tumblr
  • Evernote

Posted by Susan A. Kitchens on May 06, 2007 in • AudioAudio: Hardware
2 CommentsPermalink

« Previous An Old School Mystery | Oral History as A Narrative Form Next »


Hi, Susan,

Thanks for the mention…one thing I’d like to mention is that while using the tape recorder output of the receiver is convenient, it is certainly not necessary. You can plug the same RCA-stereo miniplug cable directly into the cassette deck and then into the USB Transit. It would remove things from the signal path—something I’m in favor of.

Glad you got the transfer to work. It’s not hard. Optimizing the high-frequency playback is a bit harder. I have posted an azimuth adjusting example and notes on my blog. and search for “azimuth” in the WordPress search box.



Richard L. Hess  on 05/07  at  07:53 AM

Richard, you may yet see that tape. wink (My mom was uncertain about sending it to Canada. Spoke with her about it again on Saturday after I’d uploaded a Q&D MP3 of her dad telling one of his favorite stories. (But Mom, he’s a friend. He used  to live the next city or two over. I visited his workspace there. And he’s got the best cassette deck—it’ll get every last bit of signal off of the tape, thanks the the magic of Auto Azimuth Adjustment!) With one copy made, she’ll consent to allowing it to make the trip. The tape is in surprisingly good shape for sitting for years in a partially wound state, and being a 1980-era thing. 90 minute. No stretching to speak of. Sound quality is boomy low with background noise (recorded in living room w/ big group around). Not pristine or sparkly, by any means, but okay, serviceable. Comprehensible and therefore precious.

re: removing steps from the path. Good point.

Susan A. Kitchens  on 05/07  at  08:11 AM

Add a comment





Remember me.

Please let me know if someone else comments here.