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Pricing at publication
  MSRP Street Amazon.com
HM-31 $99.00 $99.00 $99.99

Serial #: HM0735940367
Warranty: 1 year, parts and labor

Summary: A full featured 3x1 HDMI switch at a very competitive price

OPPO has garnered a solid reputation with their upconverting DVD players and seeks to expand their market with the HM-31 HDMI switch.


  • 3x1, 3 inputs, 1 output (supports DVI with adapters)
  • Remote control
  • Auto switching and priority switching
  • Hot plug and play for HDMI
  • External IR input and RS232C serial port for custom installations
  • HDMI 1.3 supporting 1080p video, Deep Color, bit stream and PCM HD audio
  • HDMI Cable EQ circuit
  • External power supply
  • Optional wall mount capability

Optional Accessories

  • External IR remote sensor, IR-ES1

OPPO has a great website with oodles of information about their products. For the HM-31 you will find everything from specs and a wall mount template to RS 232 codes: HM-31 Advanced 3x1 HDMI Switch.

Opening the Box

OPPO enhances even the simple things with quality packaging. The switch box comes in a cloth envelope along with stick-on rubber cushions for set top applications versus wall mounting. When you take it out of the bag you find this cute and appealing little plastic box with piano black on the sides, a sleek silver trim on the top beveled edge along with a black brushed aluminum top that can easily compliment other visible products in your system. A card-type remote provides one button for switching to the next active input or 3 individual buttons for each input. All of this is packed in a nice velvet plastic divider along with the power supply.

Hooking It Up

It's just a switcher; there is nothing to set up so installation is a newbie breeze. The power supply wall wart is offset to the side to avoid taking up two outlets. That seems like a great feature but that will depend on the orientation of your outlets. Oddly enough for me my outlets and strips made that the most difficult part of this installation. It supports hot plug and play and auto switching as evidenced when I hooked it up. I simply inserted the HM-31 in between a Toshiba HD-A35 HD DVD player and a Denon AVR-3808Ci receiver while in the midst of a movie. I looked up at the screen and within a few moments there was Phantom of the Opera in 1080p24 with sound. A quick look at the receiver confirmed my bitstream DTS True HD was still engaged. From there I connected a Sony PS3 and switched over finding a picture and "PCM" displayed on the receiver.

Priority, Auto and Remote Switching

Priority and Auto switching logic can easily make remote control unnecessary. Auto switching logic detects live HDMI connections automatically selecting the active source if the other two sources are turned off. Simply by turning sources on and off you can automatically switch without doing anything more. There is a catch though; this logic will not work if one of your sources leaves the HDMI output active even though you have turned it off, such as cable or satellite receivers. To turn off the HDMI on these devices requires pulling the AC power. In this application, Priority Switching logic becomes your auto switching best friend. Input 1 has the highest priority and input 3 the least. By connecting your always active HDMI source to input 3 you can switch to input 2 by turning on that source. You can leave input 2 on along with input 3, but when you turn on input 1 it will switch to that. Conversely, if input 1 is on then you can't auto switch to input 2 or 3 without turning it off. If you have more than one HDMI source always active you can toggle through the three inputs via the front panel or use direct input select via the remote. If the HM-31 can't be easily accessed or will be hidden from view, OPPO provides an external IR sensor accessory to get the IR detector in view of your remote(s).

HDMI Cable EQ Circuit

HDMI has problems with long distances because it is based on DVI, and that was developed for the typical PC user application where the display and PC are near each other; long DVI cable runs were not even considered during development. HDMI does not specify cable length, only a minimum performance standard which can be extended by the quality of materials used. Due to this anomaly, manufacturers have stepped forward with chip sets that incorporate Transition Minimized Differential Signaling Equalization (TMDS EQ), which samples the signal and automatically tunes the connection impedance for maximum signal integrity supporting output or input tuning. This is what OPPO calls Cable EQ. This is a very beneficial feature, but should be taken with a grain of salt. The OPPO website documents a successful 100 foot HDMI application, two 50 foot cables with the HM-31 in between, yet provides a disclaimer that your mileage may vary. The best general advice is that once you hit 30 feet, you are pushing the tolerance of the HDMI system design. At 40 feet you have reached design limitations so going beyond that can open yourself up to problems. How much further you can go will depend on the integrity of the source, cable and display HDMI design.

Putting it in Perspective

The most interesting aspect of the HM-31 is that for $99 you can expand the HDMI inputs on a new HDMI-equipped A/V receiver for less than what you would be charged to upgrade to the next model up; typically a $200-300 additional charge for just one or two more HDMI inputs.

Final Conclusion

If you need to expand the HDMI inputs on your display or A/V receiver OPPO has provided a highly competitive and wonderful $99 solution that covers newbie to custom home theater applications.

For More Information

When it comes to cable lengths and the HDMI specification, you can find more information in the HDMI FAQ at HDMI.org. However, I find that their site tends to gloss over the finer points of the specification. For a thorough analysis of the HDMI specification and dealing with it in the real world, I recommend Blue Jeans Cable.

Posted by Richard Fisher, April 29, 2008 9:20 AM

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About Richard Fisher

Richard Fisher is the President of Mastertech Repair Corporation, serving north east Atlanta, Georgia, and has been servicing, calibrating and reviewing audio video products since 1981. Tech Services USA, a division of Mastertech, creates sites, communities and libraries for consumers and professionals to share their technology knowledge and learn from each other. These include The ISF Forum and HD Library. HDTV Magazine exclusively publishes HD Library and Forum for Tech Services USA.

Richard is ISF and HAA certified providing calibration and A/V reproduction engineering services. Richard is a technical consultant and also provides performance ISF and HAA home theater systems and calibration via Custom HT. Mastertech Repair Corporation is a factory authorized service center for Hitachi, Mitsubishi and Toshiba and a member of the National Electronics Servicing Dealers Association, NESDA, and the Georgia Electronics Servicing Dealers Association, GESDA.