888/24 bit DACs (Digital-Analog Converters) Upgrade

888/24 bit DACs (Digital-Analog Converters) Upgrade

Taken from the 888/24 I/O Interface FAQ:


  1. How do I know if I have 24 bit DACs (Digital-Analog Converters)?

  2. How do I upgrade my DACs to 24 bit?

  3. What are the specifications of the 888/24?

  4. How do I change the operating level of the 888/24 from +4 to ­10?

  5. Why would I want to change the operating level? What’s the difference?

  6. How can I use the 888/24 in Stand Alone mode & How can I tell if it is in Stand Alone mode?

  7. The default sample rate in Stand Alone mode is 44.1 kHz, how can I change that?

  8. How do I enable/disable DAC muting when using Stand Alone mode?

  9. Why are the inputs on my 888/24 distorting when connected to my Mix Farm card, but operate correctly when connected to another audio card?

  10. I set the Infinite Peak Hold preference in Pro Tools, but the meters on my 888/24 haven’t changed, why?

  11. Why am I getting clicks and pops when recording a digital input?

  12. When or why should I calibrate my 888/24’s inputs and outputs?


1. How do I know if I have 24 bit DACs (Digital-Analog Converters)?

The affected serial number cutoff is DH17130. Any unit carrying a serial number higher than this or displaying " Rev J" or higher on the external FCC label already has 24 bit DACs installed. return to top

2. How do I upgrade my DACs to 24 bit?

Customers who own 888|24's with 20-bit DACs may upgrade their units for a fee. The upgrade price covers all parts and service, as well as return shipping to the customer. Customers who purchased 888|24's after June 1st, 1998 are eligible for free upgrades. Contact Digidesign for upgrade pricing.

Upgrades require the return of the 888|24 to the Digidesign Service Center.

An advance replacement program is also in place. For an additional fee an upgraded unit with 24-bit DACs will be sent to the customer and they would then send in their original unit(s).

Contact Digidesign Technical Support for the upgrade.

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3. What are the specifications of the 888/24?

General

  • Analog Inputs/Outputs: Actively balanced XLR connectors; internally switchable between +4dBu

  • and -10dBV operating levels. Factory set to +4 dBu.

  • Analog Level Trimming: Accessible from front panel, via recessed trim pot

  • Digital I/O's AES/EBU: 8 channels: balanced XLR connectors

  • Digital I/O's S/PDIF: 2 channels: coaxial RCA connectors

  • Sample Rate: 44.1kHz or 48kHz ±10ppm

  • Clock Reference: Super Clock 256x sample clock; In/Out; BNC connectors; additional clock references supported via Digidesign's Universal Slave Driver, SMPTE Slave Driver, Video Slave Driver and other optional synchronizers

  • Nominal Operating Level: +4dBu; factory calibrated at -18dB headroom

A/D Specifications

  • SNR (signal-to-noise ratio): Ž-113dB (balanced, A-weighted), Ž-110dB (unweighted)

  • THD: 0.003% -0.01dB @ 1kHz 20Hz-20kHz (band-limited)

  • Maximum Input: +26dB

  • Frequency Response: 20Hz-20kHz ±1db

  • Clock jitter: <40pS RMS 22Hz-22kHz BW

D/A Specifications

  • SNR (signal-to-noise ratio): Ž-110dB (balanced, A-weighted), Ž-107dB (unweighted)

  • THD: 0.003% -0.01dB @ 1kHz 20Hz- 20kHz (band-limited)

  • Maximum Output: +26 dB/channel (bridging loads)

  • Frequency Response: 20Hz-20kHz ±1dB

  • Output Impedance: 50ý typical (45 min, 55 max)

Physical Specifications

  • Power requirements: 90-260 VAC, 47-63 Hz; 30 VA; auto-switching

  • Weight: 7 lbs, 9 oz (4.1 kg)

  • Dimensions: 2u external rackmount device; 19" x 3.5" x 9.75" (48.26 cm x 8.89 cm x 24.77 cm) black anodized finish

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4. How do I change the operating level of the 888/24 from +4 to –10?

The 888/24 I/O is factory set to +4 dBu operating levels for input and output. You can individually switch any of the analog inputs or outputs to either a +4 dBu or –10 dBu operating level by moving internal jumpers on its circuit board.

This requires careful removal of the 888/24's top cover physically moving the jumpers corresponding to each input and output.

Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance.

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5. Why would I want to change the operating level? What's the difference?

It is important to determine which line level is appropriate for you studio equipment. Setting the +4 or –10 dBu operating levels help determine the input and outputs loads a particular piece of equipment can handle or deliver. +4 dBu is generally considered "professional" and –10 dBu "consumer". Some processors, etc. can be toggled manually between +4 and –10 dBu via an external switch or internal jumper (such as the 888/24). However, many are permanently set. Check the owner's manual for you mixer, amplifiers, or effects processors to determine the correct operating level for you studio's equipment.

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6. How can I use the 888/24 in Stand Alone mode & how can I tell if it is in Stand Alone mode?

To use your 888/24 as a ‘stand alone' 24 bit Analog-Digital or Digital-Analog converter:

  • Quit Pro Tools if it is launched.

  • For Analog-Digital conversion, be sure to disconnect or turn off any external digital devices (DAT machines, effects processors, etc.) that may be providing word clock information to the 888/24's AES/EBU or S/PDIF channel 1 & 2 inputs.

  • An AES/EBU (or S/PDIF — see below) word clock signal is necessary for Digital-Analog conversion in Stand Alone mode. Be sure to have a digital device providing word clock connected to the AES/EBU inputs 1 & 2 of the 888/24 interface.

In Stand Alone mode, the 888/24's default word clock input port is AES/EBU, unless changed to S/PDIF via the corresponding internal jumper setting. Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance.

To verify that the 888/24 is in Stand Alone mode:

  • Check to see that the "analog" LED display for meters 1 & 2 is flashing. The LED flashes between a half-lit state to full display.

  • Turn off your CPU.

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7. The default sample rate in Stand Alone mode is 44.1 kHz, how can I change that?

The factory default sample rate of the 888/24 is 44.1kHz. You can change this default sample rate to 48 kHz by moving an internal jumper on the circuit board. This requires careful removal of the 888/24's top cover and physically moving the jumper corresponding to the desired sample rate.

Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance.

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8. How do I enable/disable DAC muting when using Stand Alone mode?

In certain cases, you may wish to mute the 888/24's Digital-Analog Converters when in Analog-Digital Stand Alone mode. This is useful if, for example, you need to eliminate potential external analog feedback through a console. This procedure requires careful removal of the 888/24's top cover and physically moving the jumper corresponding to Stand Alone DAC muting.

Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance.

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9. Why are the inputs on my 888/24 distorting when connected to my Mix Farm card, but operate correctly when connected to another audio card?

This is due to a change made in Revision N of the 888/24 that affected all interfaces through Revision Q.

Revision R fixes the problem. Contact Digidesign Tech Support for repair information.

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10. I set the Infinite Peak Hold preference in Pro Tools, but the meters on my 888/24 haven't changed, why?

In the Display Preferences, the Peak Hold options only affect the meters within Pro Tools (on screen).

The Peak Hold and Level Sensitivity settings for the 888/24 meters are available in the Other Options dialog box from within the Hardware Setup window:

  • Setups > Hardware > Other Options

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11. Why am I getting clicks and pops when recording a digital input?

When 2 digital devices are connected via AES/EBU or S/PDIF and recording in either direction, a common clock is required (For example: 1 device's clock must be slaved to the other's)

If you are recording into Pro Tools via the AES/EBU or S/PDIF inputs (such as a DAT or any other digital device), the Sync Mode in the Hardware Setup window should be set to DIGITAL.

  • Setup > Hardware > Sync Mode > Digital OR Windows > Show Session Setup > Sync Mode > Digital

When you are finished recording the digital signal, you should set your Sync Mode to Internal for Pro Tools playback.

There are exceptions to these guidelines, especially when working with expanded systems, external synchronizers, and optical devices. Please refer to the appropriate installation guide when using expanded systems or additional devices.

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12. When or why should I calibrate my 888/24's inputs and outputs?

The 888/24 is factory calibrated so that it's operating level is +4 dBu with 18 dB of headroom nominal at full code, unity gain, making calibration unnecessary for most professional applications. However, you may want to calibrate the inputs and outputs of the 888/24 to the operating level of your mixing console, so that the output meters of the 888/24 match the levels of your console. Additionally, you may want to re-calibrate you interface if you feel that the inputs or outputs of your 888/24 are not recording or playing back at equal levels.

Please refer to the 888/24 I/O Installation Guide for specific instructions and guidance..

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