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Benchmark DAC1 PRE, Инструкция по эксплуатации

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DAC1 PRE

 Instruction Manual         Rev J                       

Page 28 

THD+N Tests 

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. Distortion should still be well masked at 

higher playback levels. 

Содержание DAC1 PRE

Страница 1: ...Benchmark DAC1 PRE Instruction Manual 2 Channel 24 bit 192 kHz Digital to Analog Audio Converter with Preamp Functions and USB Input ...

Страница 2: ...RLY QUALIFIED ONLY A QUALIFIED TECHNICIAN SHOULD PERFORM REPAIRS Fuses CAUTION FOR CONTINUED FIRE HAZARD PROTECTION ALWAYS REPLACE THE FUSES WITH THE CORRECT SIZE AND TYPE 0 5A 250 V SLO BLO 5 X 20 MM LITTELFUSE HXP218 500 OR EQUIVALENT Modifications CAUTION DO NOT SUBSTITUTE PARTS OR MAKE ANY MODIFICATIONS WITHOUT THE WRITTEN APPROVAL OF BENCHMARK MEDIA SYSTEMS INC MODIFICATION MAY CREATE SAFETY ...

Страница 3: ... 2 3 and 4 Coaxial 11 Output Level Switch 12 Balanced XLR Analog Line Outputs 12 Unbalanced RCA Analog Outputs 13 Low Impedance Passive Pads 13 Calibration Trimmers 14 AC Power Entry and Fuse Module 14 Internal Settings 15 Removing Top Cover 15 Jumpers 15 Rack Mounting 17 System1 Universal Rack Adapter 17 Blank Rack Panel 17 Benchmark Technologies 18 HPA2 Headphone Amplifier 18 UltraLock Clock Sys...

Страница 4: ... compatible with Windows and Mac computers without driver installation Coaxial digital inputs support professional AES and consumer S PDIF data formats at up to 192 kHz 24 bits Optical digital inputs support professional AES and consumer S PDIF data formats at up to 96 kHz 24 bits Benchmark s UltraLock technology eliminates jitter on all digital inputs including USB Jumper selected low impedance 1...

Страница 5: ...ncy and is well suited for critical playback in studio control rooms mastering rooms and high end audiophile applications Benchmark s AdvancedUSB Audio interface makes the DAC1 PRE an ideal primary output device for digital audio workstations desktop audio editing applications computer based media playback home media servers and computer based radio broadcast systems A rugged rack mount adapter ma...

Страница 6: ...nsequently no audio is lost when an audio transient follows full silence Furthermore the DAC1 PRE signal to noise specifications represent the true system performance not just the performance of an output mute circuit The DAC1 PRE will operate even when sample rate status bits are set incorrectly Sample rate is determined by measuring the incoming signal Lack of sample rate status bits or incorrec...

Страница 7: ...DAC1 PRE for the input sensitivity of virtually any load amplifier preamp etc Most power amplifiers and powered monitors require the 20 dB pad setting The DAC1 PRE is factory set with the 20 dB pad enabled Source Selector and On OFF Switch A rotary Source Selector control selects any of the 6 inputs to the DAC1 PRE Pressing the Source Selector toggles the DAC1 PRE on and off The on off function fe...

Страница 8: ...p outs due to a bad cable Incompatible data type AC3 ADAT etc Non Audio data If the error is not resolved within 15 seconds the DAC1 PRE will enter Standby Mode The DAC1 PRE will resume normal operation when it detects a valid input signal at the last chosen input There is no error indication on the analog input Source and ON OFF Switch The rotary Source Selector control is located directly to the...

Страница 9: ...tly The Volume Control adjusts the level for both jacks The original gain range of the HPA2 such as in the original DAC1 is often too high for the headphones of many users The DAC1 PRE features three gain ranges for the HPA2 to suit the sensitivity of any particular headphones These gain ranges are set using internal jumpers The jumpers reduce the input to the HPA2 by 0 10 or 20 dB These jumpers a...

Страница 10: ...eo analog input via a pair of RCA connectors The analog inputs can be used for devices such as Phono preamplifiers FM Tuners Tape Transports Analog VCR outputs iPod and MP3 devices Outputs from analog mixing consoles Computer Input USB The USB input accepts a B type male USB 1 1 or USB 2 0 connector An A B type USB cable is provided with the DAC1 PRE The USB cable connects the DAC1 PRE directly to...

Страница 11: ...e rates between 28 and 195 kHz are supported The Coax inputs are DC isolated transformer coupled current limited and diode protected The RCA body is bonded directly to the chassis to prevent currents in the internal ground systems This direct bonding also maximizes RF shielding TIP Shielded 75 Ohm coaxial cable is required for stable performance Do not use 50 Ohm cables or twisted pair cables or a...

Страница 12: ... PRE is being used in a critical signal chain such as a broadcast facility or theater the headphone mute switch should be defeated using the internal jumpers See Internal Settings section for instructions Balanced XLR Analog Line Outputs The Left and Right balanced outputs use Neutrik gold pin male XLR jacks The XLR shell and pin 1 ground are both directly bonded to the chassis to prevent currents...

Страница 13: ...due to ground loops We highly recommend using balanced interconnects for long runs Low Impedance Passive Pads The XLR outputs are equipped with low impedance passive pads that may be used to reduce the output levels while preserving the full dynamic range of the DAC1 PRE The DAC1 PRE ships with the 20 dB pads enabled TIP When directly driving power amplifiers and powered speakers use Variable mode...

Страница 14: ... preset levels may be increased by 5 dB or decreased by 15 dB in order to conform to other studio reference levels This range of levels is also well suited for direct connection to the balanced line level inputs on most power amplifiers Most professional equipment will work well at these levels Note The Calibration Trimmers have no effect on the output levels when the Output Level Switch is set to...

Страница 15: ... any screws on front or rear panels Never remove the power entry safety cover in the rear corner of the DAC1 PRE Always connect a static control wrist strap to the chassis before touching any internal component Jumpers The following functions are jumper configured Headphone Gain Range Adjustment Headphone Switch Disable XLR Output Pads XLR Output Pad Selection P5 P6 P7 and P8 Four 8 pin headers P5...

Страница 16: ...e JP1 and JP2 Headphone Gain Reduction JP3 and JP4 The gain range of the HPA2 can be set using jumpers JP3 and JP4 When jumpers are installed at position A the headphone amplifier gain is decreased by 20 dB When jumpers are installed at position B the headphone amplifier gain is decreased by 10 dB The ideal gain setting permits the user to set the front panel Volume Control above 40 10 o clock wit...

Страница 17: ... are available from Benchmark Call us visit our website http www BenchmarkMedia com or contact your dealer to purchase these accessories System1 Universal Rack Adapter The Universal Rack Mount Adapter is a tray that mounts up to two System1 products in a single race space The tray accepts any combination of System1 products with or without rack mount type faceplates Blank Rack Panel The Blank Rack...

Страница 18: ...A2 does not change when headphones are driven THD N measurements for no load 30 Ohm resistive loads 30 Ohm headphone loads and 600 Ohm headphone loads are virtually identical The HPA2 will substantially improve the sound of 30 and 60 Ohm headphones It will make very noticeable improvements with 600 Ohm headphones UltraLock Clock System Accurate 24 bit audio conversion requires a very low jitter co...

Страница 19: ...stem insures that interface jitter can never degrade the quality of the audio conversion Specified performance is consistent and repeatable in any installation with cables of any quality level How does conversion clock jitter degrade converter performance Problem 1 Jitter phase modulates the audio signal This modulation creates sidebands unwanted tones above and below every tone in the audio signa...

Страница 20: ...d to understand these effects Is it possible to eliminate all of the effects of jitter in an entire digital audio system Interface jitter will accumulate throughout even the most carefully designed digital audio system Fortunately interface jitter can only degrade digital audio if it affects the sampling circuit in an analog to digital or digital to analog converter Any attempt to cure jitter outs...

Страница 21: ... the resulting sequence is always identical to the original the path is bit transparent Benchmark s USB technology is the first native USB solution capable of streaming 96 kHz 24 bit audio with full bit transparency Beware of Custom Drivers Until now high resolution USB audio devices required custom drivers These drivers may compromise the stability of the operating system and may cause conflicts ...

Страница 22: ...e to play 16 bit 44 1 kHz music files The reason is that digital volume controls and digital mixers increase the word length of the audio The longer word length is a result of multiplication and addition These arithmetic operations produce long word lengths that must be squeezed back into a shorter word length Word length reduction adds noise and or distortion to the audio The amount that is added...

Страница 23: ...that bit transparency can be maintained It also forces Kmixer into a 24 bit output mode so that the Windows volume control does not degrade the audio quality if it is used Benchmark s AdvancedUSB Audio solution offers users the convenience of simultaneous high quality playback from more than one Windows application Kmixer s sample rate conversion is disabled as long as all applications are playing...

Страница 24: ...s 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 The amplitude response is down by only 0 22 dB at 20 kHz The bass response extends well below the 10 Hz limitation of the measurement equipment ...

Страница 25: ...e 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 The amplitude response is down by only 0 22 dB at 20 kHz and only 1 dB at 43 kHz The bass response extends well below the 10 Hz limitation of the measurement equipment ...

Страница 26: ...FFT 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 ...

Страница 27: ...he 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 Please note that no reference or synchronization cables are required to create a phase accurat...

Страница 28: ...e 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 Distortion should still be well masked at higher playback levels ...

Страница 29: ... Instruction Manual Rev J Page 29 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 ...

Страница 30: ...ne 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 ...

Страница 31: ...ruction Manual Rev J Page 31 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 ...

Страница 32: ...ge 32 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 ...

Страница 33: ...he 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 There is absolutely no change in the DAC1 THD N measurement over the entire range of jitter test frequencies and amplitudes In fact the DAC1 can tolerate much higher levels of jitter withou...

Страница 34: ...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 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 The same test was conducted using FFT analysis to look fo...

Страница 35: ...uction Manual Rev J Page 35 Immunity to Cable Induced Jitter 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 ...

Страница 36: ...Sensitivity Tests 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 ...

Страница 37: ...e 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 clock circuits and the DAC1 operates at full specified performance ...

Страница 38: ...38 Volume Control Curve Volume Control 80 0 70 0 60 0 50 0 40 0 30 0 20 0 10 0 0 0 10 0 0 5 10 15 20 25 30 35 40 Rotation Steps Gain dB Volume Control Step Size 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 25 30 35 40 Rotation Steps Step Size dB Step ...

Страница 39: ...2 dB at 10 Hz 0 20 dB at 20 kHz 0 85 dB at 40 kHz 2 5 dB at 45 kHz Frequency Response at Fs 48 kHz 0 1 dB 20 to 20 kHz 0 02 dB at 10 Hz 0 20 dB at 20 kHz Crosstalk 100 dB at 20 kHz 125 dB at 1 kHz 130 dB at 20 Hz Maximum Amplitude of Jitter Induced Sidebands 10 kHz 0 dBFS test tone 12 75 UI sinusoidal jitter at 1 kHz 141 dB Maximum Amplitude of Spurious Tones with 0 dBFS test signal 126 dB Maximum...

Страница 40: ...Automatic in Consumer Mode De Emphasis Method Digital IIR De Emphasis Supported at Fs 32 44 1 48 and 96 kHz Group Delay Latency Delay Digital Input to Analog Output function of sample rate The delay can be calculated using the following formula Delay 1 01 ms 48 Fs Where Fs the sample rate in Hz 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...

Страница 41: ...o 13 dB RCA in to Headphone Factory Set Analog Input Gain In Calibrated Mode 0 5 dB RCA in to RCA out 4 0 dB RCA in to XLR out Digital Audio Inputs Number of Digital Inputs switch selected 5 1 USB 1 Optical 3 Coaxial Number of Channels 2 Input Sample Frequency Range 28 to 195 kHz Coaxial 28 to 96 kHz Optical 44 1 48 88 2 96 kHz USB Maximum Input Word Length 24 bits Digital Input Impedance on XLR i...

Страница 42: ...lerance With no Measurable Change in Performance 12 75 UI sine 100 Hz to 10 kHz 3 5 UI sine at 20 kHz 1 2 UI sine at 40 kHz 0 4 UI sine at 80 kHz 0 29 UI sine at 90 kHz 0 25 UI sine above 160 kHz Jitter Attenuation Method Benchmark UltraLock all inputs ...

Страница 43: ...d Output Level at 0 dBFS 4 dBu Attenuator 20 dB Output Level Range at 0 dBFS In Variable Mode Off to 27 dBu Attenuator off Off to 17 dBu Attenuator 10 dB Off to 7 dBu Attenuator 20 dB Off to 3 dBu Attenuator 30 dB Output Level Variation with Sample Rate 44 1 kHz vs 96 kHz 0 006 dB Unbalanced Analog Outputs Number of Unbalanced Analog Outputs 2 Output Connector RCA Output Impedance 30 Ohms Analog O...

Страница 44: ...Front Panel Output Level Range at 0 dBFS into 60 Ohm Load Off to 21 dBu Maximum Output Current 250 mA Overload Protection independent per channel Current limited at 300 mA Thermal Bandwidth 500 kHz THD N 106 dB 0 0005 into 30 Ohms at 18 dBu 1 26W Status Display Indicators Type and Location 3 Blue LED s on Front Panel Selection Status Indication Solid Digital Input Selection Flashing Signal Error N...

Страница 45: ...8 Watts Idle 8 Watts Typical Program 16 Watts Maximum Fuses 5 x 20 mm 2 required 0 5 A 250 V Slo Blo Type Dimensions Form Factor Rack Wide 1 RU High Depth behind front panel 8 5 216 mm Overall depth including connectors but without power cord 9 33 237 mm Width 9 5 249 mm Height 1 725 44 5 mm Weight DAC1 PRE only 3 5 lb DAC1 PRE with power cord extra fuses and manual 4 5 lb Shipping weight 7 lb ...

Страница 46: ...to radio communications However there is no guarantee that interference will not occur in a particular installation If this equipment does cause harmful interference to radio or television reception which can be determined by turning the equipment off and on the user is encouraged to try to correct the interference by one or more of the following measures Reorient or relocate receiving antenna Inc...

Страница 47: ...DAC1 PRE Instruction Manual Rev J Page 47 CE Certificates of Conformity ...

Страница 48: ...DAC1 PRE Instruction Manual Rev J Page 48 ...

Страница 49: ...rs will be billed at the normal shop rate In such cases an estimate will be submitting before work is started if requested by the customer Attempts to deliberately deface mutilate or remove the product s label will render this warranty void Any DAC1 PRE returned from the European Union for warranty repair must have the required RoHS logo on the product label otherwise repairs will be billed at the...

Страница 50: ...edia Systems Inc optionally extends the standard one 1 year warranty to a period of two 2 years from the date of delivery For the extended warranty to become effective the original purchaser must register the product at the time of purchase either by way of the prepaid registration card or through the product registration section of the Benchmark Media Systems Inc website This optional warranty ap...

Страница 51: ...opyright 2007 2009 2010 2012 Benchmark Media Systems Inc All rights reserved Benchmark Media Systems Inc Benchmark Media Systems Inc 203 East Hampton Place STE 2 Syracuse NY 13206 1633 USA 1 315 437 6300 FAX 1 315 437 8119 www benchmarkmedia com ...

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