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