Benchmark DAC1 Instruction Manual
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Benchmark DAC1 Instruction Manual

2-channel 24-bit 192-khz audio digital-to-analog
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Benchmark Media Systems, Inc.
DAC1
Instruction Manual
2-Channel 24-bit 192-kHz
Audio Digital-to-Analog Converter

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  • Page 1 Benchmark Media Systems, Inc. DAC1 Instruction Manual 2-Channel 24-bit 192-kHz Audio Digital-to-Analog Converter...

  • Page 2: Revision History

    Benchmark Media Systems, Inc. Revision History: Revision Filename Date PCB Rev. Author DAC1 – Manual – Rev A. Doc 10/01/02 John Siau, Allen Burdick DAC1 – Manual – Rev B. Doc 11/27/02 John Siau DAC1 – Manual – Rev C. Doc...

  • Page 3: Table Of Contents

    Benchmark Media Systems, Inc. REVISION HISTORY: SYSTEM OVERVIEW: FEATURE SUMMARY: FRONT PANEL: REAR PANEL: CALIBRATION: REMOVING TOP COVER: JUMPER LOCATIONS: JUMPER SETTINGS: COMPLIANCE AND SAFETY INFORMATION: CERTIFICATE OF CONFORMITY: CONTACT INFORMATION: WARRANTY: ULTRALOCK™ … WHAT IS IT? DAC1 PERFORMANCE CURVES:...

  • Page 4: System Overview

    The DAC1 is designed to interface directly to power amps and powered studio monitors in order to provide the cleanest and shortest path from digital to monitor output. 10, 20, and 30 dB pads are provided for interfacing to studio monitors having high input sensitivity.

  • Page 5: Feature Summary

    Analog output mute function on rear-panel switch Preset output levels use multi-turn trimmers – one 10-turn trimmer per output, 20 dB Range, 2 dB/turn Total jitter immunity with Benchmark, phase-accurate UltraLock™ technology Two Error LED’s, (no digital input, non-PCM digital input) Power Indicator LED THD+N = -107 dB, 0.00045% @ -3 dBFS input, -105 dB, 0.00056% @ 0 dBFS input...

  • Page 6: Front Panel

    The width of the DAC1 panel is exactly ½ that of a standard 19” panel. The DAC1 is one rack unit high. Either ear of the DAC1 can be mounted directly to a standard 19” rack. A machined junction block connects the other ear to a ½...

  • Page 7: Rear Panel

    DAC1 converters produced after 12/01/02 are equipped with internal jumper-selected 10, 20, and 30 dB attenuators. DAC1 converters produced prior to 12/01/02 were shipped with external 20 dB attenuator cables. Most powered monitors will require 20 dB attenuation when connected directly to the DAC1 XLR outputs. Caution: Do not set the ‘Output Level Switch’...

  • Page 8: Analog Outputs

    Note: The RCA outputs should not be used to drive cables exceeding 1360 feet (see Table 1). DIGITAL INPUTS: There are three digital inputs on the DAC1. These inputs are selected from a front-panel toggle switch. All of the inputs can decode AES/EBU and S/PDIF input signals in either professional or consumer formats. The DAC1 will...
  • Page 9 The AC input has a very wide input voltage range and can operate over a frequency range of 50 to 60 Hz. At “110”, the DAC1 will operate normally over a range of 90 to 140 VAC. At “220”, the DAC1 will operate normally over a range of 175 to 285 VAC.

  • Page 10: Specifications

    Benchmark Media Systems, Inc. SPECIFICATIONS: DIGITAL INPUTS: Number of Digital Inputs (switch selected): 3 (XLR, Coaxial, TOSLINK) Number of Audio Channels: Input Sample Frequency Range: 28 to 195 kHz Maximum Input Word Length 24 bits Digital Input Impedance on XLR input:...

  • Page 11: Audio Performance

    +/- 0.5 degrees at 20 kHz – any sample rate Interchannel Differential Phase (Between DAC1 Units Fs<110): +/- 0.5 degrees at 20 kHz – Fs < 110 kHz Interchannel Differential Phase (Between DAC1 Units Fs>110): +/- 4.1 degrees at 20 kHz – Fs > 110 kHz Delay (Digital Input to Analog Output): 1.01 ms + (48/Fs)
  • Page 12 9.33” (237 mm) Overall depth including connectors but without power cord or BNC-to-RCA adapter. 9.5” (249 mm) Wide 1.725” (44.5 mm) High WEIGHT: DAC1 only: 3.5 lb. DAC1 with power cord, BNC-to-RCA adapter, and manual: 4.5 lb. Rack mount kit (blank panel, junction block, and rack-mount screws): 0.32 lb. Shipping weight: 7 lb.

  • Page 13: Removing Top Cover

    Benchmark Media Systems, Inc. REMOVING TOP COVER: The DAC1 has a removable cover. This cover provides access to the jumper settings on the PCB. The DAC1 contains static sensitive components and should only be opened by qualified technicians. Static discharge may cause component failures, may affect the long-term reliability, or may degrade the audio performance.

  • Page 14: Jumper Locations

    Benchmark Media Systems, Inc. JUMPER LOCATIONS: JP7 - 75 ohm BNC Termination P5-P8 Position Function Position Attenuation Switchable input 0-dB Optical only 10-dB BNC only 20-dB XLR only 7-8v 30-dB Figure 1. – DAC1 Jumper Locations Page 14 of 39...

  • Page 15: Jumper Settings

    A 2-pin jumper on header P2 (see Photo 1) can be used to disable the front-panel source-selection switch. This feature is useful when the DAC1 is in a critical audio path, and only one of the three digital inputs will be used. In such an application, the digital source selection can be made using the jumper on header P2.
  • Page 16 JP7 (see Photo 2). This termination is required for normal operation, but may be removed if the user wishes to loop a single coaxial feed through several other pieces of equipment (using a BNC “T” adapter on the DAC1). A termination must be applied at the last device on the loop, and there should be a combined total of less than 6 feet of cable between the first and last receive device.
  • Page 17 Benchmark Media Systems, Inc. XLR Output Attenuation Jumpers (P5, P6, P7, and P8): One pair of 8-pin headers controls the output level at each XLR jack as follows: 0 dB - (Attenuator disabled) – (Jumper plug between pins 1 and 2 of each header) •...

  • Page 18: Compliance And Safety Information

    For continued fire hazard protection, fuses should be replaced ONLY with the exact value and type as indicated on the rear panel. Do NOT substitute parts or make any modifications without the written approval of Benchmark Media Systems, Inc. Doing so may create safety hazards and void the warranty.

  • Page 19: Certificate Of Conformity

    Benchmark Media Systems, Inc. CERTIFICATE OF CONFORMITY: Page 19 of 39...

  • Page 20: Contact Information

    Benchmark Media Systems, Inc. CONTACT INFORMATION: Benchmark Media Systems, Inc. 203 E. Hampton Place, Ste 2 Syracuse, NY 13206 (315) 437-6300 Phone (315) 437-8119 Fax http://www.benchmarkmedia.com mailto:sales@benchmarkmedia.com Page 20 of 39...

  • Page 21: Warranty

    In the event of failure of a product under this warranty, Benchmark Media Systems, Inc. will repair, at no charge, the product returned to its factory. Benchmark Media Systems, Inc. may, at its option, replace the product in lieu of repair. If the failure has been caused by misuse, neglect, accident, or, abnormal operating conditions, repairs will be billed at the normal shop rate.

  • Page 22: Ultralock

    AES/EBU signal that can be decoded by the AES/EBU receiver will be reproduced without the addition of any measurable jitter artifacts. The DAC1, DAC-104 and the ADC-104 employ Benchmark’s new UltraLock™ technology to eliminate all jitter- induced performance problems. UltraLock™ technology isolates the conversion clock from the digital audio interface clock.
  • Page 23 Benchmark Media Systems, Inc. Jitter creates “new audio” that is not harmonically related to the original audio signal. This “new audio” is unexpected and unwanted. It can cause a loss of imaging, and can add a low and mid frequency “muddiness” that was not in the original audio.
  • Page 24 It is therefor important to attack jitter at both ends of the audio chain. The DAC1 is a great start, as it will allow accurate assessment of various A/D converters.

  • Page 25: Dac1 Performance Curves

    Frequency Response at Fs = 48 kHz The above graphs show the frequency response of the DAC1 when it is operating at a 48-kHz sample rate. The top graph shows that the differential phase is better than ± 0.5º at 20 kHz. The bottom graph shows the amplitude response on a highly expanded 0.05 dB/division scale.
  • Page 26 Frequency Response at Fs = 96 kHz The above graphs show the frequency response of the DAC1 when it is operating at a 96-kHz sample rate. The top graph shows that the differential phase is better than ± 0.5º at 20 kHz and better than ± 1º at 43 kHz. The bottom graph shows the amplitude response on a highly expanded 0.05 dB/division scale.
  • Page 27 Analysis of Idle Channel Noise The above graph demonstrates that the DAC1 is free from idle tones and clock crosstalk. The highest spurious tone measures –128 dBFS and is AC line related hum. The highest non-line related tone measures –138 dBFS.
  • Page 28 110 kHz. The above graph shows the differential phase between 10 audio channels using 5 DAC1 converters operating at 96 kHz. The DAC1 converters were chosen from stock at random, and measurements were made using a random combination of Coaxial, XLR, and Optical inputs. The type of digital interface used has no measurable effect on the phase.
  • Page 29 20 Hz to 20 kHz is very slight). Note that at worst case, the distortion is 109 dB less than the – 3 dBFS test tone (and 112 dB less than the full scale output of the DAC1). This implies that the distortion created by the DAC1 should be below the threshold of hearing unless playback levels exceed 112 dB peak SPL.
  • Page 30 Benchmark Media Systems, Inc. THD+N vs. Level at 1 kHz – Balanced Outputs Below –4 dBFS, distortion is lower than the noise floor of the converter. Above –3 dBFS, distortion reaches a maximum value of only –107 dBFS. Page 30 of 39...
  • Page 31 This graph shows the output of the HPA2™ headphone amp driving a 60-Ohm load at a very high level (+14 dBu). Even under these conditions, the HPA2™ delivers the full rated performance of the DAC1. Compare this to the performance of the balanced outputs (see previous graph).
  • Page 32 Benchmark Media Systems, Inc. THD+N vs. Level at 1 kHz - Unbalanced Outputs This graph demonstrates the performance of the unbalanced outputs. Note that the performance is nearly identical to that of the balanced outputs. Page 32 of 39...
  • Page 33 Benchmark Media Systems, Inc. THD+N vs. Sample Frequency The above graph shows that the DAC1 provides consistent performance at all sample rates. Distortion is not a function of sample rate. The minor variations in the above plots are due to measurement limitations.
  • Page 34 The graph above shows the results of a standard AES jitter tolerance test. The top (red) curve shows the amplitude of the jitter applied to the inputs of the DAC1. The scale for the top curve is on the right hand side of the graph and is calibrated in UI of jitter.
  • Page 35 We set the interface jitter amplitude to its maximum value of 12.75 UI (2075 ns) of jitter. We then swept the jitter frequency from 2 Hz to 9 kHz and plotted the THD+N from the DAC1. Absolutely no change in THD+N was observed at any test frequency, and the DAC1 performance did not change when the jitter was turned off.
  • Page 36 Benchmark Media Systems, Inc. DAC1 Cable Jitter Immunity The above FFT plots demonstrate that the performance of the DAC1 is not degraded in any way when long cables are used to transmit digital audio to the DAC1. Page 36 of 39...
  • Page 37 XLR Digital Input Sensitivity The above graph shows that the performance of the DAC1 is not a function of the signal level at the XLR digital input. When the signal is too low to decode (< 160 mVpp), the converter mutes gracefully.
  • Page 38 Coaxial Digital Input Sensitivity The above graph shows that the performance of the DAC1 is not a function of the signal level at the coaxial digital input. When the signal is too low to decode (< 120 mVpp), the converter mutes gracefully.
  • Page 39 AES. In addition, the above plots show that while the AES minimum eye pattern specifications are barely met at the end of 1000 feet of Category 5 UTP cable, the DAC1 receivers have enough sensitivity to allow reliable operation. The jitter produced by this connection is removed entirely by the Benchmark UltraLock™...

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