Specifications

• USB, XLR balanced, BNC coaxial, and TOSLINK optical digital inputs
• Compatible with Windows Vista/XP/2000 and Mac OS X without driver installation
• Elected low-impedance 10, 20, or 30 db pads on bal- anced outputs
• Jumper-selected low-impedance 10, 20, or 30 dB pads on balanced outputs
• -10 dBV unbalanced RCA analog outputs, +13.5 dBu maximum output level
• Two HPA2™ high-current, 0-Ohm, high-output 1/4″ headphone outputs
• HPA2™ gain jumpers to match gain to headphone sen- sitivity
• Front-panel volume control for headphone outputs Front-panel volume control of all analog outputs (in “Variable” mode)
• Rear-panel “Variable/Calibrated” mode switch enables volume control of analog outputs
• Rear-panel “Variable/Calibrated” mode switch includes a mute position
• XLR outputs are preset to +4dBu at 0 dBFS in “Calibrated” mode (20-dB Pad enabled)”
• Automatic “Standby Mode” -activated after 15 seconds of loss of digital input signal
• Instant wake-up from “Standby Mode” –
• THD+N = -107 dB, 0.00045% @ -3 dBFS input, -105 dB, 0.00056% @ 0 dBFS input
• Automatic de-emphasis in response to consumer pre-emphasis bit (44.1, 48, 88.2, and 96 kHz)
• 115 V, 230 V, 50-60 Hz international power supply
• Low radiation toroidal power transformer Dimensions: 9.5in W x 1.725in H x 9.33in D Weight: 7 lbs
• Price: $1,275.00
• Manufactured in USA

For several years the world of digital audio has been going through a metamorphosis. Audio enthusiasts have seen the creation of several high resolution encoding formats. However, the state of these formats is uncertain, and it is quite probable that all of the current high-resolution formats will fade from the audio landscape. Still, the standard compact disc soldiers on, and comprises large portion of most enthusiast’s music library. Even though it is a mature technology, the audio community is still finding ways to tease higher levels of performance from this format. One of the recent trends in digital audio is the storage of music on large computer hard drives. In these systems, the traditional CD transport is completely eliminated. The cost of large hard drives have fallen dramatically over the last few years, and have become a cost effective way to feed a high quality signal to a digital to analog converter. From a practical standpoint, the hard drive will rival the signal quality of a very expensive stand-alone transport. The tricky part of this process is interfacing the hard drive with the audio system.

There are a several products on the market that facilitate the marriage of computer technology and traditional two channel audio systems. The first-generation of interface units are USB to SPDIF converters. These converters are still a viable method to interface an older DAC to a computer system. However, there are more elegant solutions to this issue, such as building a DAC that has a USB input port. I spent a bit of time on the Internet, and was able to find a sizable number of USB capable D to A converters. These units tend to fall into two camps, such as inexpensive units manufactured in Asia, or pricey boutique converters that the average audio enthusiast would be reluctant to purchase. At this time, there is a significant shortage of high quality USB capable digital to analog converters that fall between the two price extremes.

Earlier this year, Benchmark Media Systems brought to market a reasonably priced DAC that has an innovative USB interface circuit. This unit is built upon the basic architecture of the highly regarded DAC1 D to A converter that has been a prominent player in the $1000 price category. The upgrades in the DAC1 USB extend farther than the USB option. There have been refinements added to the preamp and headphone portions of the unit, which improve both the sound quality, and user friendliness of the piece. Even though the DAC1 USB fills the role of more than one component, it does an excellent job in all areas. For an audio enthusiast who is watching where the pennies are being spent, the Benchmark unit represents a good value due to its multi-function design.

Benchmark DAC1 USB review

A Dell Inspiron 1100 laptop computer was pressed into duty for this review. The laptop is a few years old, however it will function quite nicely as platform for a music server. The first issue I had to resolve in this project is the fact that the internal hard drive to the Dell is too small, and therefore I had to acquire an outboard unit. Fortunately, I was able to purchase a Western Digital 250 gig external drive for $80 at the local Best Buy. The final concern I needed to address is which program to install on the laptop for downloading and organizing the music library.

There are several different music server programs that can be downloaded on the net for free. I decided to speak with the technical department at Benchmark in order to get an understanding of which programs would work well in my application. While sound quality was the most important consideration, I also needed a program that would be easy to install and use. Benchmarks technical department assured me that iTunes would be an acceptable program for my application. I found it to be quite straightforward to set up and use. The technician at Benchmark walked me through a couple of adjustments to the program, and in a matter of minutes I was able to start burning discs to the hard drive. There are a number of programs that will work equally well as iTunes. I encourage you to do some research into the subject, and select one that allows you to configure the server in a manner that meets your personal needs. Benchmark did an excellent job on the USB interface on this unit. The interface is designed to work with all the mainstream operating systems. You can use Microsoft XP, 2000, or Vista operating systems. Macintosh users are not left out either, since the USB1 is designed to work with the OS X platform. No matter which operating system you have, the DAC1 USB should directly interface with your computer. The input is USB 1.1 and therefore it can be used with older generation of computers. When I hooked the DAC up to my laptop, the XP operating system found it in a matter of seconds. From my experience, this is a well-designed interface, and I never had an issue with installing it on a computer.

The USB input on this converter is capable of passing 24-bit word length. While this word length is necessary for 24/96 encoded discs, there is also an important element for playing standard 16 bit data. Quite often the programs in music servers will manipulate the data during the burning process. Many of the server programs have features that will repair disc errors, while others have an equalization feature that operates in the digital domain. All of these options manipulate the data stream, and result in a word length that is greater than the original 16-bit string. If the USB interface is not capable of 24-bit word length, than the data stream is being truncated, and the end result will be degradation in audio performance. Benchmark has gone the extra mile, and developed an interface option that does the job right. The DAC 1 USB has been designed from the ground up to work correctly with a computer based audio system.

At the heart of the Benchmark DAC is the Ultra Lock jitter control circuit. The people at Benchmark make bold claims for this circuit, and believe that the DAC1 USB is virtually immune to jitter issues. I spoke with a tech from Benchmark, and asked for a layman’s explanation of how their anti-jitter system worked. Elias gave me the following explanation that outlines the broad details of what is occurring in this DAC. When the D to A converter receives an incoming signal, the first thing it does is separate the clock signal from the data stream. The clock information from the source unit is completely abandoned. The data stream is then passed onto the Delta/ Sigma converter, where it is up-sampled to 110 KHZ, and optimized for the internal architecture of the unit. When the data stream leaves the Delta/Sigma converter, a new clock signal must be generated and synched to it. Benchmark employs a high precision clock in order to create a properly synchronized data stream. The digital to analog conversion stage is the next stop, and this is the point where the data stream is transformed into a conventional audio signal. The analog output stage is the last stage in the unit, and this is where a set of op-amps are responsible for generating the final gain portion of the DAC.. Since the Benchmark DAC creates its own clock signal, the quality of the transport is not as important to the overall sound. Benchmark claims that the DAC1 USB will sound the same with different types of transports. From a practical standpoint, a traditional CD transport or DVD player will sound just like a hard drive based source. Now the sole purpose of the transport is to provide a data stream to the DAC1 USB.

Benchmark has included a couple of refinements to the USB version of the DAC1. For instance, the pre-amplifier stage has been beefed up, and is now capable of driving difficult impedance loads. The high current output drivers can drive any load down to 300-ohms, so it will match up with virtually any amp that has been produced. Long cable runs, or high capacitance designs do not affect the high current output stage of the DAC1 USB.

For those individuals who are familiar with the original DAC1 know that it also contains a high quality headphone amplifier known as the HPA 2. The HPA 2 is capable of driving a pair of headphones through the quarter inch jacks located on the front of it. The USB version of the DAC 1 has added a feature that mutes the signal of the output stage when the left headphone jack is in use. The output level of the HPA 2 has been reduced by 10DB in order to give the user more range on the volume control. An internal set of jumpers that can be removed if the user wishes to increase the output level of the HPA 2. . The output muting function is a refinement that makes the DAC a little more user friendly. The headphone amplifier built into the DAC1 USB is a high quality unit, and not a cheap add-on feature. Discriminating headphone listeners should appreciate the sonic abilities of the HPA 2.

The Benchmark DAC1 USB and Dell laptop took up residence in my main system. I also removed the Electra-Print PVA pre-amplifier for the majority of my listening sessions. A pair of Monarchy SM 70 PRO amplifiers fed the Audio Nirvana Super 12 speakers. Audio Magic Illusions 4D interconnects and speaker cable were responsible for making the connections between components. Electrical connections were made with Audio Magic Extreme power cords. Now that the preliminary descriptions are taken care of, it’s time to relate how the DAC1 USB performed during my listening sessions.

Benchmarks claim that the Ultra Lock clock system will make different transport sources perform at the same level is quite bold. In order to verify this, I decided to compare the computer-based system against a Phillips DVP-642 DVD player. I decided to use “North Dakota” [Joshua Judges Ruth; MCA MCAD 10475] by Lyle Lovett for this evaluation. There are many subtle cues within this song that should easily bring to light the differences between the two source units. I played the cut several times, and listened to the texture of the percussive instruments, the timber of the piano, the decay of the steel guitar, and the interplay between Lyle Lovett and Rickie Lee Jones vocal duet. I entered this evenings listening session with a fair degree of skepticism about Benchmarks claim regarding the Ultra Lock system. At the end of the evening I have to say that I could not reliably identify either source component. There were times I thought the computer based system sounded slightly better than the Phillips DVD player, but the differences were so miniscule that I can not guarantee that my own listening biases were coming into play. To verify what I was hearing, I decided to install a JVC TL-Z1050TN CD player into the system and make one more comparison. For all practical purposes, all three units sounded the same. I have to agree that the Ultra Lock clock system levels the playing field for different source components. Potential buyers for the DAC1 USB should realize that a hard drive based music server does not automatically result in a higher quality digital source.

There are certain functions that can be found in music server programs that can result in sonic improvements. For instance, many programs have digital equalization features, or the ability to repair damaged data during the burning process. Of course there are certain convenient playback features that also come with the music server format. The convenience factor of having access to an entire digital library is a significant factor in many audio enthusiasts decision to build a computer based music system. The ability to tailor a music play-list is another worthwhile feature. The storage of digital media on a hard drive also means that loading music onto another audio device such as an iPod becomes quite simple. Really, from just an ergonomic standpoint, there are several advantages to a computer based audio system for today’s audio enthusiast.

For the next step of my evaluation process, I needed to get a handle of the abilities of the pre-amp stage of the Benchmark DAC. At this point I removed the Electra-Print PVA from the system and drove the amplifiers with the RCA outputs of the DAC1 USB. The Electra-Print pre-amplifier is a passive unit based on a pair of nickel core transformers. At it’s price point, I am not aware of another until that can exceed it’s level of neutrality and detail. However, the pre-amp stage of the DAC1 USB turned in a fine performance, and came close to matching the overall sound quality of the Electra-Print. I scrolled down to John Gorkas “Joint of No Return” [The Company You Keep; Red House Records RRHR CD 151] on the computer, and just double clicked on the track. The vocals on this song were not quite as rich and full with the Benchmark pre-amp in the system. There was also a small amount of shortening of soundstage depth to the song. On the positive side, the drive and dynamics of the bass guitar and drum set is improved with the Benchmark pre-amps stage in the system. Overall, I would say that the pre-amp portion of the DAC1 USB turned in a highly respectable performance. It has certain limitations, which should be expected at its price point, but its sonic abilities far outweigh any limitations. From a practical standpoint, the DAC1 USB would make a fine pre-amplifier in most affordably priced two channel systems.

Every audio system has an overall sonic personality, which is determined by the specific mix of components, room characteristics, and set up abilities of the owner. It also stands to reason that certain recordings will have a synergy with a specific system, and the music will result in a memorable listening session. “Walking On Eggs” by Nighthawks at the Diner [Walking on Eggs; Nighthawks at the Diner Populair Recordings AL 75002] is the track that highlighted the abilities of the DAC1 USB in my system. This song is a quirky blues number that probably has limited appeal outside of its genre. Since my musical tastes sometimes stray from the beaten path, I found it to be quite an interesting performance. There is a double bass and saxophone duet in the middle of this piece that made me sit up and take notice. The bass has excellent texture and pitch, and each plucked note had the correct sounding decay. The saxophone sounded quite believable, with the distinctive aural signature of the brass and reed components of its design. The lead singer for the Nighthawks has a gruff and gravelly textured voice that sounded quite natural through the Benchmark DAC. I have listened to this track in many different system configurations, and the DAC1 USB reproduces this cut better than the majority of the digital to analog converters I have had in my system. The Benchmark DAC1 USB is one of those rare components that can meet a wide variety of needs. In my mind, it is the equivalent of a Swiss army knife in the world of audio. Without a doubt, this DAC is the most straightforward method of creating a high-resolution computer based digital playback system. The DAC1 USB is literally a plug play component. The pre-amplifier stage of the unit is quite capable, and can drive a wide array of amplifiers. The headphone amplifier is the same basic unit that is found in the original DAC1, although a few features have been upgraded. I am not an aficionado of headphone listening, and therefore cannot directly comment on the abilities of the HPA 2. Headphone enthusiasts have held the HPA 2 in high esteem, and readers can find several reviews of the original unit in the audio press. The DAC1 made quite a splash in the audio world, and I have no doubt that the DAC1 USB will successfully follow the footsteps of its predecessor.

Review Equipment

• Monarchy SM 70 Pro amplifier
• Monarchy Audio AC Regenerator
• Audio Nirvana Super 12 speakers w Lovecraft Design cabinets
• Dell Electronics Inspirion 1100
• Audio Magic Illusions 4D interconnects Audio Magic Illusions 4D speaker wire Audio Magic Extreme power cords

from affordableaudio,  By John Hoffman