Benchmark Media Systems, Inc.
Benchmark Media Systems, Inc. Revision History: Revision Filename Date PCB Rev. Author A B C D E F G H DAC1 – Manual – Rev A. Doc DAC1 – Manual – Rev B. Doc DAC1 – Manual – Rev C. Doc DAC1 – Manual – Rev D. Doc DAC1 – Manual – Rev E. Doc DAC1 – Manual – Rev F. Doc DAC1 – Manual – Rev G. Doc DAC1 – Manual – Rev H.
Benchmark Media Systems, Inc. REVISION HISTORY: 2 SYSTEM OVERVIEW: 4 FEATURE SUMMARY: 5 FRONT PANEL: 6 REAR PANEL: 7 CALIBRATION: 7 REMOVING TOP COVER: 14 JUMPER LOCATIONS: 15 JUMPER SETTINGS: 16 COMPLIANCE AND SAFETY INFORMATION: 19 CERTIFICATE OF CONFORMITY: 20 CONTACT INFORMATION: 21 WARRANTY: 22 ULTRALOCK™ … WHAT IS IT? 23 DAC1 PERFORMANCE CURVES: 27 DAC1 - Manual - RevH-05-01-04 (2).doc Page 3 of 39 Ed.
Benchmark Media Systems, Inc. SYSTEM OVERVIEW: The DAC1 is a reference-quality, 2-channel 192-kHz 24-bit audio digital-to-analog converter featuring Benchmark’s UltraLock™ technology. The DAC1 is designed for maximum transparency and is well suited for critical playback in studio control rooms and in mastering rooms. A compact and rugged enclosure makes the DAC1 an excellent choice for location recording, broadcast facilities, and mobile trucks.
Benchmark Media Systems, Inc. FEATURE SUMMARY: y y y y y y y y y y y y y y y y y y XLR balanced, BNC coaxial, and TOSLINK optical digital inputs – front-panel switch selectable High level, +4 dBu balanced analog outputs, +29 dBu maximum output level Jumper-selected 10, 20, or 30 dB pads on balanced outputs -10 dBV unbalanced outputs, +13.5 dBu maximum output level, factory set to +2vRMS @ 0dBFS (8.
Benchmark Media Systems, Inc.
Benchmark Media Systems, Inc.
Benchmark Media Systems, Inc. ANALOG OUTPUTS: Balanced Analog Outputs: Left and Right balanced outputs are provided on Neutrik™ gold-pin male XLR jacks. The output levels may be controlled from the front panel, or may be set to fixed levels using the rear-panel Calibration Potentiometers. The output impedance of the XLR outputs is 60 Ω when the output pads are disabled. The low output impedance makes these outputs well suited for driving up to 680 feet of cable (assuming 32 pF/foot).
Benchmark Media Systems, Inc. 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 not decode AC3 signals. A red Non PCM Error LED will illuminate when AC3 or other non-PCM input signals are connected to the selected digital input. Internal jumpers can be used to disable the front-panel selector switch.
Benchmark Media Systems, Inc.
Benchmark Media Systems, Inc. AUDIO PERFORMANCE: Fs = 44.1 to 96 kHz, 20 to 20 kHz BW, 1 kHz test tone, 0 dBFS = +24 dBu (unless noted): SNR – A-Weighted, (0 dBFS = +20 to +29 dBu): SNR – Unweighted, (0 dBFS = +20 to +29 dBu): SNR – A-Weighted at low gain, (0 dBFS = +9 to +18 dBu): 116 dB 114 dB 114 dB THD+N, 1 kHz at 0 dBFS: THD+N, 1 kHz at –1 dBFS: THD+N, 1 kHz at –3 dBFS: THD+N, 20 to 20 kHz test tone at –3 dBFS: -105 dBFS, -105 dB, 0.00056% -107 dBFS, -106 dB, 0.00050% -110 dBFS, -107 dB, 0.
Benchmark Media Systems, Inc. GROUP DELAY (LATENCY): Delay from digital input to analog output is a function of sample rate: 2.72 ms at 28 kHz 2.51 ms at 32 kHz 2.10 ms at 44.1 kHz 2.01 ms at 48 kHz 1.55 ms at 88.2 kHz 1.51 ms at 96 kHz 1.45 ms at 108 kHz The delay can be calculated using the following formula: Delay = 1.01 ms + (48/Fs) Where Fs = the sample rate in Hz.
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. Use a static control wrist strap when changing jumper settings.
Benchmark Media Systems, Inc. JUMPER LOCATIONS: JP7 - 75 ohm BNC Termination P5-P8 Right Function Switchable input Optical only BNC only XLR only Position 1-2 3-4 5-6 7-8v Attenuation 0-dB 10-dB 20-dB 30-dB Left Position N O C X Figure 1. – DAC1 Jumper Locations DAC1 - Manual - RevH-05-01-04 (2).doc Page 14 of 39 Ed.
Benchmark Media Systems, Inc. JUMPER SETTINGS: Jumpers are provided for special applications. A 2-pin jumper plug at header P2 can be moved in order to disable the front-panel input selection switch. A jumper at JP7 can be removed to disable the 75-Ω termination on the coaxial digital input. Four 8-pin headers (P5, P6, P7, and P8) allow selection of the output level at the XLR jacks. Caution: Do not change any jumpers other than P2, P5, P6, P7, P8, and JP7. All other jumpers are for test purposes only.
Benchmark Media Systems, Inc. Coaxial Input Impedance Jumper (JP7): The Coaxial (BNC) input has a 75-Ω internal termination that may be disabled by removing the 2-pin jumper at 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).
Benchmark Media Systems, Inc.
Benchmark Media Systems, Inc. COMPLIANCE and SAFETY INFORMATION: FCC Class B Compliance: This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) This device must accept any interference received, including interference that may cause undesired operation. Safety Information: Do NOT service or repair this product unless properly qualified. Only a qualified technician should perform repairs.
Benchmark Media Systems, Inc. CERTIFICATE OF CONFORMITY: DAC1 - Manual - RevH-05-01-04 (2).doc Page 19 of 39 Ed.
Benchmark Media Systems, Inc. CONTACT INFORMATION: Benchmark Media Systems, Inc. 5925 Court Street Road Syracuse, NY 13206-1707 USA (315) 437-6300 Phone (315)437-8119 Fax http://www.benchmarkmedia.com mailto:sales@benchmarkmedia.com DAC1 - Manual - RevH-05-01-04 (2).doc Page 20 of 39 Ed.
Benchmark Media Systems, Inc. WARRANTY: The Benchmark 5 Year Warranty Benchmark Media Systems, Inc. warrants its products to be free from defects in material and workmanship under normal use and service for a period of five years from the date of delivery. This warranty extends only to the original purchaser. This warranty does not apply to fuses, lamps, batteries, or any products or parts that have been subjected to misuse, neglect, accident, or abnormal operating conditions.
Benchmark Media Systems, Inc. UltraLock™ … What is It? Accurate 24-bit audio conversion requires a very low-jitter conversion clock. Jitter can very easily turn a 24-bit converter into a 16-bit converter (or worse). There is no point in buying a 24-bit converter if clock jitter has not been adequately addressed. Jitter is present on every digital audio interface. This type of jitter is known as “interface jitter” and it is present even in the most carefully designed audio systems.
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. Jitter induced sidebands can be measured using an FFT analyzer. Problem #2: Jitter can severely degrade the anti-alias filters in an oversampling converter. This is a little known but easily measurable effect.
Benchmark Media Systems, Inc. What UltraLock™ converters cannot do: UltraLock™ converters cannot undo damage that has already been done. If an ADC with a jitter problem was used to create a digital audio signal, then there is nothing that can be done to remove the damage. Jitter-induced sidebands are extremely complex and cannot be removed with any existing audio device. It is therefor important to attack jitter at both ends of the audio chain.
Benchmark Media Systems, Inc. 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. Note that the amplitude response is down by only 0.
Benchmark Media Systems, Inc. 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. Note that the amplitude response is down by only 0.22 dB at 20 kHz and only –1 dB at 43 kHz.
Benchmark Media Systems, Inc. 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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 27 of 39 Ed.
Benchmark Media Systems, Inc. Multi-Unit Phase Response Multiple DAC1 converters may be used to create a multi-channel playback system that maintains phase accuracy across all channels. The above graph shows the differential phase between 10 audio channels using 5 DAC1 converters. The DAC1 converts were chosen at random from stock 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.
Benchmark Media Systems, Inc. THD+N vs. Frequency at –3 dBFS The above graphs demonstrate that the THD+N specifications for the DAC1 are not frequency dependent (the variation from 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.
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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 30 of 39 Ed.
Benchmark Media Systems, Inc. THD+N vs. Level at 1 kHz – Headphone Outputs 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). DAC1 - Manual - RevH-05-01-04 (2).doc Page 31 of 39 Ed.
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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 32 of 39 Ed.
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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 33 of 39 Ed.
Benchmark Media Systems, Inc. DAC1 Interface Jitter Tolerance 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. The bottom (green) curve shows the THD+N of the DAC1 as the jitter amplitude and frequency is varied at the inputs of the DAC1.
Benchmark Media Systems, Inc. DAC1 THD+N vs. Jitter Amplitude and Jitter Frequency The above graph shows the results from the most severe jitter test that we could create with an Audio Precision System 2 Cascade test set. We selected a 10-kHz audio test tone in order to maximize the sensitivity of the test. 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.
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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 36 of 39 Ed.
Benchmark Media Systems, Inc. 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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 37 of 39 Ed.
Benchmark Media Systems, Inc. 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. DAC1 - Manual - RevH-05-01-04 (2).doc Page 38 of 39 Ed.
Benchmark Media Systems, Inc. DAC1 Minimum Eye Pattern The above graph demonstrates that the DAC1 can operate with an eye pattern considerably smaller than specified by the 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.
