M-Audio Transit S/PDIF Interface Is Bit Accurate

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We've been testing the M-Audio Transit with an Apple Mac iBook [an 800
MHz G3 iBook running OS X (10.2.8) running the latest Transit OS X
driver (1.5.8f2 build 101)] to determine if the Transit is a bit-for-bit
accurate S/PDIF interface.

For a recording application, at M-Audio's suggestion we used Amadeus II
v3.7. (They also suggested Sound Studio but we haven't tried it yet.)

PROCEDURE

We have a suite of four test files that we use for testing our own
products. Each of the files lasts at least one hour. The four files
were recorded at 16/44.1, 24/44.1, 24/48 and 24/96. Each consists of a
3:13 song followed by 2 seconds of silence that is looped continuously.

We outputted each file from our PC to an Alesis Masterlink recorder via
an M-Audio Audiophile 2496's S/PDIF output. When we send the
Masterlink's file back into the PC via the Audiophile 2496's S/PDIF
input and then use Adobe Audition to Mix/Paste an inverted version of
that file with the original, we get perfect cancellation (complete
silence). This procedure confirms that the digital audio path from the
PC to the A2496 to the Masterlink and back again preserves bit-for-bit
accuracy.

We then sent the files from the Masterlink to the Apple iBook via an
M-Audio CO2 (to convert coaxial to optical) to the Transit. All iBook
services that might have interrupted the recording were disabled,
including screen savers, local area networks (AirPort), sleep functions,
energy savers (e.g., hard disk shutdowns) and alarms.

RESULTS

For all combinations of word widths and sample rates that we tested,
we're pleased to report that the Transit was bit-for-bit accurate in
preserving the data stream.

The Transit, with our Mic2496 Dual Mic Pre/A-to-D and a Mac laptop
(e.g., iBook or Powerbook) would make a fine, compact laptop recording
system.

We will start stocking the Transit immediately. Price will be around
$70.

--
Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio
Core Sound http://www.stealthmicrophones.com
Teaneck, New Jersey USA http://www.core-sound.com
moskowit@core-sound.com Tel: 201-801-0812, FAX: 201-801-0912