Inside the 882 (1996)

[supernova777]

http://www.soundonsound.com/sos/1996_articles/sep96/applesep96.html

INSIDE THE DIGIDESIGN 882

Since I had a captive Digidesign system for the purposes of writing this month's Digital Performer review, I took the opportunity to have a closer look at it. I always open up hardware boxes, and the Digidesign's 882 Audio I/O box was no exception, even though I needed to find some Imperial Allen Keys to get inside!

The inside of an 882 is more or less filled with a large double-sided PCB. The design and construction is of a very high quality -- there were no visible corrections or modifications, and the audio/digital areas were clearly defined by the ground planes used for the audio sections. The majority of the board components were surface-mounted, with just a few through-hole components. The BNCs for the clock I/O were hand-soldered.

The main Analogue-to-Digital Converters (ADCs) were eight Philips SAA7360Ps, with PMI Op-amps buffering and filtering the audio inputs. On the output side, eight AK4318 Asahi Kasei Digital-to-Analogue Converters (DACs) were used, with PMI SSM2142 VCA, and an Analogue Devices ADG412BR DAC was used to control output level. An Actel gate array forms the bulk of the control logic; the remainder was made up of small gate-count DIL packages.

The umbilical cable that connects the 882 to the host computer is buffered using standard 26LS31 and 26LS32 line drivers, whilst the power cable to the external power supply unit has RF filters plus 2 large chokes and several 220µF electrolytic capacitors around the 5V regulator.

Overall, this is a very nicely constructed and designed unit. Having the audio inputs and outputs remote from the computer enables a much more flexible placement of the computer, and provides high-quality audio conversion.