Purelink by Dtrovision HDS-41R HDMI 4x1 Switcher 
Home Theater Video Processors & Switchers Video Switchers
Written by Jeremy R. Kipnis   
Monday, 01 May 2006

Home theater enthusiasts are now most certainly in a digital world, both audio and very recently video. It is becoming increasingly important to be able to add new components and switch seamlessly between a wide variety of digital sources. These now include DVI (digital visual interface) and HDMI (high-definition media interface) as an interface, providing a one-cable digital solution for both picture and sound, as opposed to the multiplicity of analog cables required to watch HDTV, such as RGBHV or YPrPb.

Unfortunately, because of a continuing desire by the motion picture and television industries to control the dissemination of their intellectual property (the movie, television show or video game itself), we now are all subject to varying degrees of digital connection irritation brought about by the inclusion of HDCP (high-definition copy protection). This copy management system inhibits the ability of any digital recorder (such as a Blu-Ray or HD-DVD disc recorder) to legally or illegally make copies of copyrighted material. As a music and film producer, I understand and appreciate the issue of offering up a CD or DVD product, which may have taken many years and many millions of dollars to create, only to see bits and pieces of it for sale over the Internet without any permission and without compensation for any effort required to create something worth stealing.

At the same time, I also believe that everyone has a right to enjoy copyrighted material easily and view or copy any software that they own or rent for the sole purpose of their continued enjoyment (with family and, I suppose, friends and acquaintances). In any case, if I spend money on a software product, I think it should be possible to watch, listen to, copy and/or manipulate that purchased software in any way I desire, so long as it does not violate copyright and generate a profit for someone other than the owner of the original work. This includes time-shifting, a concept that still remains a debatable security.

Notwithstanding this HDCP copyrights use issue, an HDMI switcher is of the greatest importance to the home theater owner with a digital display, and these devices must switch quickly and effectively between sources to be desirable. It seems that many new A/V sources have HDMI and/or DVI outputs, but most surround receivers and even new televisions like the Sony 40XBR1 Bravia LCD HDTV (review coming soon to AVRev.com) only feature a single HDMI input. On very high-end equipment like Sony’s $30,000 Qualia 004 projector, there are only two digital inputs available. It is very reasonable to suggest people buying HDTVs today may be currently using HDMI sources such as HD-DVRs and HD Satellite Receivers/Cable Boxes. It is also reasonable to suggest that they will in the next few months be adding sources such as Blu-ray, HD-DVD and Playstation 3. With only one or two inputs and today’s lower-priced receivers not 100 percent reliable for HDMI switching, what are you to do?

Thankfully, along comes the $549 HDS-41R from PureLink. This four HDMI input to one HDMI output switcher is compatible with both DVI sources and HDCP encryption. This new unit is small, 13 inches (W) x 1.5 inches (H) x 4 inches (D), black, sleek and has an input cycling selection button on the front panel, which I found very helpful, in addition to the included miniature remote control.

Equally as interesting is the $949 PureLink Modular OBC-010 DVI Optical Transmission System with a 33-foot fiber optic cable (with an industry-leading maximum possible length of 330 feet with the OBC-100 at an MSRP of $1,649). This system features a pair of optical modules that extend the usable transmission distance for DVI signals well beyond the 15-foot length restriction imposed by conventional copper wire. PureLink's OBC system is HDCP-compliant, so such sources can be used over the very long distances found in many newer home theaters, where the video projector or display can be many meters or more away from the source and/or switching equipment. This can also be the case in a house-wide system, where video sources are frequently placed in a single central control room some distance from the displays they feed.

Finally, for those worried about integrating digital sources into a home theater that features only displays that have an analog HDTV input, the DC-DA1 ($349 MSRP) converts an unprotected and unencrypted DVI input to analog VGA available on a D-Sub 15 connector. I found that HDCP-compliant sources, such as satellite receivers, cable DVRs, Blu-Ray and HD-DVD players could be seen on various analog monitors, such as my Sony 40XBR700, which only has analog 1080i inputs, or various HDTV-capable CRT projectors like the Runco DTV 1201 nine-inch front projector.

Set-Up and Testing
The PureLink HDS-41R HDMI switcher is designed to sit on one shelf of a rack, with HDMI inputs on the back in pairs on either side of the HDMI output located in the middle. There is sufficient space between inputs to accommodate the use of DVI to HDMI converters for each and every input and also the output simultaneously, if necessary. There is, however, another device made by Dtrovision, the PureLink DVI 4x1 switcher DS-41R (not reviewed here, also priced at $549 MSRP) and a wealth of other fine products available to address many if not all of the major digital connection concerns. Their DS-1818M (18 in/out) DVI digital matrix router ($29,995 MSRP) is becoming a broadcast industry standard.

With its external “wall-wart” power supply attached, all inputs filled and the output connected to a monitor or projector, the HDS-41R switcher worked almost perfectly with every source and display. In effect, this switcher worked very much as its analog counterpart should: quietly, quickly and seamlessly. This level of performance should be routine for almost any A/V device, but it is especially nice with a peripheral, since it adds value and performance to an existing system, rather than taking anything away. Indeed, the picture and sound quality switched through the Dtrovision products, being digital signals, always appeared almost identical to the straight signal path without the switcher in the signal path.

I say almost identical because jitter, even in digital video as with digital audio, can cause small differences in the absolute quality of the reproduced image and sound. Such differences are extremely small and very difficult to measure, but can be observed reliably on the largest, highest-resolution playback systems in the world. In this context, the Dtrovision products, including the 4x1 switcher, were among the best I have tested and used, as they do not appear to adulterate the signal they are passing in any meaningful way.

As an aside, I was able to perform several key comparisons using three Scientific Atlanta 8300 HD-DVRs running the newest SARA 1.18 operating system. After recording the same digital broadcast of the James Bond film “Goldeneye” on all three DVRs simultaneously, and syncing the playback of all three recordings, I was able to switch between DVR playbacks with only a short pause while the display’s HDCP handshake was validated. Strangely, some displays seem to have a longer handshake time (Qualia 004 – six seconds, Qualia 006 – five seconds, Bravia 40XBR1 – four seconds, all Sony brand), but your results may be slightly different. Using the HDS-41R HDMI Switcher, I was able to discern a small and mostly insignificant loss of apparent detail between the DVR playbacks of “Goldeneye” (Cinemax HD) using different-quality HDMI cables. The PureLink cable was in each test among the subjective best in a group that included mostly more expensive cables from well-known and reputable brands like Cardas and Kimber.

The PureLink switcher also allowed me to discern tiny but visible losses of detail and color with increasing lengths of the same brand HDMI to HDMI cable. The longer the length, the less immediate images appeared to be. This was seen on all lab displays, including, surprisingly, the Sony 40XBR700, which has a resolution of only 920 x 1080i. Switching the cables around between DVRs showed that the losses in quality were directly attributable to the cables used. Clearly, such differences among identical digital sources are solely due to jitter.

The DVI Fiber Optic Extension Kit
Next in the trio is the fantastic Dtrovision OBC-010 33-foot Modular DVI Optical Transmission System. This product utilizes two optical modules that are set up with DVI connections at either end, fueled by a quad fiber optic network and an RJ-45 Ethernet connection for the HDCP handshake portion of the connection; this must be two-way and is what makes the HDCP handshake happen so seamlessly. Together, these components provide a way of connecting DVI (or HDMI with a changer) over lengths longer than 15 feet.

In theory, a source could be as far away as 330 feet from the display with no change in picture quality. I found that I could easily view Windows Media Video (WMV) HDTV movies, such as “Hero” or “The Gangs of New York,” using an Apple G4 laptop via its DVI output to any of the monitors on hand here in my lab. Just as simply and easily, I was able to view any of my HDCP-encrypted sources, like my JVC-HM-DR5U or Scientific Atlanta 8300 HDTV DVRs, from well across the room, with sound available as long as the source contained digital audio.

This is certainly a breakthrough product, which establishes a new level of performance in signal handling quality for an after-market accessory. HDTV and D-VHS recordings like those I watched of the delightfully funny Universal film “Amazon Women on the Moon” or Fox’s “Silver Streak” with Gene Wilder and Richard Pryor were resolved almost exactly the same as with a straight run of two-meter HDMI or DVI cable. Picture and sound quality were exceptional, but again, jitter plays an important role in changing picture quality very, very subtly. Still, this was only really perceptible on 1080p displays like the Sony Qualia 005 46 inch tri-color stimulus LCD display. Otherwise, the fiber optic extension system did nearly everything that was asked of it.

The DC-DA1 DVI to VGA Converter
The previous two PureLink accessories should be more than sufficient, but what can one do if the display only has analog inputs? Like so many color televisions sold over the last 53 years, both my Sony 40XBR700 and GDM-FW900 HD computer displays accept only analog signals, just like most front and rear three-gun CRT projectors and most of the plasma TVs sold before 2005. Until recently, there were almost no solutions to this problem outside of broadcast and professional equipment. But now the $349 Dtrovision DC-DA1 DVI to VGA converter has made this problem a thing of the past.

If the converter is used along with the fiber optic extension kit mentioned earlier, digital DVI (and HDMI) sources can be sent over long distances without apparent loss of fidelity. This is an impressive combination that can also be used with the PureLink HDMI switcher for a complete system approach. This is where I found a special symmetry about the design of the PureLink products – they all work and they all work well together to create a nearly seamless switching and transmission system for HDMI and DVI sources.

The Downside
For otherwise nearly perfect products, there are always a few minor problems to consider as we tiptoe near the cutting edge of HDTV technology, content protection and overall digital connectivity, the most important of which is how the HDCP handshake does not always work through the 4 x 1 HDMI switcher. Several major incidents occurred (just using the switcher with the DVRs and a monitor) when I was greeted with the “Snowscreen of Death,” which would not go away without rebooting the DVRs. DVDs never had a problem on the Sony, Samsung or Theta DVD players I used for this review.

I also found that the unit would switch inputs with certain Sony and Scientific Atlanta remote control codes. This could be somewhat confusing, as it was not always clear whether the HDCP handshake had failed and was trying to reinitialize or I was suddenly on the wrong input. I am assured by Dtrovision president Minsoo Park that any conflicts will be dealt with as they are reported to the company.

The timing of the HDCP handshake is not entirely standardized, so there were also instances with all of my D-VHS recorders when I lost picture and sound and received a “your monitor or television is not HDCP-compliant – please use the analog connections” message, an angering event to say the least. Prerecorded copies of “Galaxy Quest,” “Butch Cassidy and the Sundance Kid” and “Alien” all showed occasional handshake problems through the PureLink that did not occur with a direct connection. Interestingly, I found the FireWire 400 iLink IEEE 1394 direct connection to several of the 1080p monitors to produce a slightly less jitter-laden signal, resulting in a slightly better and more three-dimensional image with both the SA DVRs and the JVC D-VHSs. I wonder if we should reinstate iLink in all consumer displays as a simpler, more reliable way to distribute content up to 1080i.

The fiber optic extension kit worked, fine except for some occasional hanging pixels. I saw this only with still desktop images and still pictures at resolutions at or above 1280 x 1024p @ 60Hz. This problem only appeared occasionally, indicating that it is likely the result of a ground loop or other interference that has sufficient force and frequency to upset certain pixels, but not destroy the result as a whole.

The Dtrovision PureLink products bridge a great gap in our ever-growing world of digital audio and video frontiers. The HDS-41R HDMI 4 x 1 HDMI switcher is a great addition to any system that has more digital sources than available inputs. Its small size and ease of operation made it a pleasure to use for a variety of switching assignments. It comes with a small remote control and RS-232 interface, so that control of switching operations can be done seamlessly for the most part, aside from a few errant responses to other companies’ IR codes. It is also clear that Dtrovision offers a number of other switchers, including DVI, that allow for additional simplicity and ease in setting up many digital sources for a single system.

The OBC-010 Modular DVI Optical Transmission System also works wonderfully, making long-distance digital audio and video connections for a home theater or even a whole house-wide system a breeze. No other product can carry 1080p sources over a length up to 330 feet without objectionable degradation or no signal at all. The simplicity of set-up is plug and play. Make no mistake - this is a breakthrough product.

Finally, the DC-DA1 DVI to VGA converter worked precisely and repeatedly with all sources presented to it. In general, I enjoyed the versatility and simplicity of the PureLink components, so much that I will most likely purchase the review pieces for use at home and in the lab, rather than lose one of the only opportunities to configure our systems so directly and easily. And when reviewers start writing checks – you know the products are good.
Manufacturer Purelink by Dtrovision
Model HDS-41R HDMI 4x1 Switcher
Reviewer Jeremy Kipnis

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