Processing and Control for Professional AV Installations
Legacy Hardware

ADA8824 (ADAT) 24-bit Eight Channel A/D-D/A Converter

The Lucid ADA8824 (ADAT) Audio Interface is an eight-channel, 24-bit, A/D and D/A converter intended for use with digital audio workstations. The 8824 provides ADAT lightpipe connections, eight analog I/O channels, and eight AES/EBU digital I/O channels.

FAQ

No, there is no dithering on either the AES3, S/PDIF or ADAT digital outputs. It is recommended that dithering be performed (by external equipment) subsequent to bit depth reduction. In practice, truncating to 20-bits produces very low levels (<114dBFS) of truncation distortion, which is beyond the SNR of the converters, and can often be performed without audibility. Truncation to 16-bits can product audible distortion, and is not recommended.

These connectors allow sending and receiving ADAT-specific information between daisy-chained ADAT machines or other hardware capable of sending or receiving ADAT Sync. The ADAT sync cable carries machine control, Word Clock, and timecode signals. These connectors, or the MIDI connectors, may be used for controlling the 8824. The only signal in the ADAT sync connection that matters to the 8824 is the machine control signal.

Note: If you are using the 8824 with the Alesis PCR card, the 8824 must be the first device connected after the PCR card. Doing so ensures that the 8824 can always receive commands (ADAT machines do not always pass ADAT Sync information through themselves.)

This can be accomplished using the provided 8824 Configuration application via MIDI System Exclusive messages.

The analog I/O level sliders of the 8824Config app provide gain control in 1dB increments from -96dB to +31dB for each of the 8 analog inputs or outputs. With the input gain set to -8dB, a +4dBu input translates to approximately 20dbFS (i.e. 20dB digital headroom). With the input gain set to +4dB, a -10dBV input translates to approximately -20dbFS (again, 20dB of digital headroom). Similarly, with the output gain set to +1dB, a -20dBFS input translates to approximately +4dBu into 600 ohms. With the output gain set to -11dB, a -20dBFS input translates to approximately -10dBV. In both of these cases, the actual headroom before clipping depends on the inputs of the mixer, power amplifier, etc, that the 8824 is driving.

This could be caused by a couple of scenarios:

A) If the 8824 is configured for the analogue outputs to get their source signal from the ADAT (optical) digital inputs and no signal is present the ADAT chip can act erratically and produce noise and digital garbage.

B) If the 8824 is configured for the analogue outputs to get their source signal from the ADAT (optical) digital inputs and the ADAT is turned off. Always power up ADATs and/or external clocks connected to the ADA 8824 first then power up the 8824 last.

The ADA8824 (ADAT) works with the Alesis ADAT Connect and ADAT Edit software using their PCR PCI card. We’ve also tested the ADA8824 with the SonorusStudi/o card using Cubase VST. Virtually any PCI card which has either ADATLightpipe, AES or S/PDIF digital audio I/O should work.

Yes. While Digidesign encourages its customers to use their own proprietary hardware it is possible to make digital audio transfers to and from ProTools using industry standard AES or ADAT (lightpipe) connections. If you are a ProTools user and have a Digi 888(24) interface you can bypass the converters in the 888(24) and connect to a Lucid ADA8824 (ADAT) or other external converter via the 888(24)’s AES inputs and outputs. If you have a Digi ADAT Bridge you can make direct digital connections to the Lucid ADA8824 (ADAT) via the lightpipe connectors on each device. Note: Older versions of the Digidesign ADAT Bridge only support 20-bit audio transfers. The newer ADAT Bridges are 24-bit and are what we recommend to work with the Lucid 8824 (ADAT). The ADA8824 (ADAT) also makes a great front end for the Digi001 and Digi002 via their ADAT Lightpipe connections.

The analog outputs from the 8824 are fed by either the Optical or AES digital inputs, there are no connections between the A/D and D/A. If you just want to get signal looping through the unit for test purposes, attach an ADAT loopback cable (connect the ADAT OUT to ADAT IN directly with a single cable).

Determine which external clock (AES1 thru 3, S/PDIF, WORD, ADAT optical) is causing clicks. Its entirely possible the ADA8824 is working correctly but that the clicks are occurring somewhere else in his system, or that there is a sync issue with the system (master/slave stuff, etc). There can be only one master device in a clocking system, all others must slave to it either directly or indirectly. Additionally, when using AES input, ensure that all AES sources are in sync (referencing the same clock source themselves).

The 8824’s A/Ds can be synchronized to the first 3 AES3 inputs, and also the S/PDIF input. Simply connect a valid AES3 or S/PDIF signal to the desired input (24kHz-48kHz only), and select that input as the A/D Sync Source, using the dip switch (local mode) or configuration application (remote mode).

Connect the external Word Clock signal to the Word Clock input. If the cable run is longer than approx 6ft, external 75ohm termination is required (it is recommended at all times). Then, simply set the A/D sync source to “Word Clock” using either the dip switches (local mode), or the PC or Mac configuration application. The Word Clock frequency range is approx. 22kHz-48kHz.

The optional configuration utility for the ADA8824 (ADAT) which runs on a Macintosh computer (Classic OS) or Windows PC, found below, is used to configure the ADA8824 (ADAT) via MIDI.

Note: There is no version of the Configuration Applet for Mac OS X and there will not be. This Applet is optional, the ADA8824 (ADAT) can be fully configured via the DIP switches on the rear of the unit. Refer to the User’s Guide for more information

.ADA8824 (ADAT) Config – Mac OS Classic

ADA8824 (ADAT) Config – Windows

In both local modes (+4) and remote (+4/-10), the default headroom is set to 20dB. Therefore, setting the unit to +4 means the maximum input is +24dBu, and that the maximum output level is +24dBu (+/- 0.5dB). By using the variable I/O) gain control from the remote mode configuration applications (PC or Mac), the user can alter the unit’s input and output headroom.

This is normally accomplished by the hardware/software connected to the AES or Light Pipe connections. For example with an ADAT connected to the optical in/out, the ADAT will make the connection between the A/D and D/A and determine if the analogue output signal(s) are derived from either the source (A/D) or from the tape.

Mac OS 7.1 thru 9.1, also the application requires OMS (Opcode Music System) version 2.X or higher. The latest version of the ADA8824 Config application program is 2.0. (check in “about” under the Apple menu for the version number).

External equipment should have no problems syncing to the 8824 AES outputs – they are all phase aligned (unlike some equipment), and as long as they are receiving a good clock they will work. If not setup properly then it is possible they won’t work – i.e. if the 8824 AES outputs are set to get data (and hence clock) from the ADAT (optical) inputs, and there is no ADAT input, then its not going to work.