Sunday, June 2, 2013

Plasma TVs and Audio Interference

We have had a Samsung LN52A650 LCD TV for almost 5 years now and it was time to upgrade this technology to something a little more current. This old 52" LCD TV was a choice based on a few requirements: HDMI inputs, flat panel technology, low power consumption, and good to excellent video reproduction capabilities.  While we pretty much got what we wanted from these requirements, LCD panels are just slow (think of the "L" in Liquid Crystal Display like the thick viscosity of molasses, or rather S-L-O-W) and deep blacks, well, we won't go there.

Now comes the challenge: what requirements should we use for the new set? After hearing about the Pioneer Elite Kuro and its well-touted virtues, we decided plasma technology would be a really good choice while waiting for UHD and OLED technologies to stabilize. But unfortunately, Pioneer decided to abandon its television line and we missed out on getting one of these amazing sets by waiting just a little too long. Oh well, such is life.

Fortunately, Panasonic purchased the rights to this technology and has introduced the VT60 and ZT60 series sets, both of which I hear are indeed stunning. However, our home theater room is not dark in the daytime and we are unwilling to buy blackout coverings for the six windows in this room (the view is far more important to us). So the compromise is to get a brighter screen plasma TV than the Panasonics could offer. Enter the Samsung F8500 series plasma TVs.

There was one other requirement my wife imposed on this deal and that was to get as large of a screen size as possible so this meant the 64" version as the only choice.  Memorial Day weekend is always a good time to search for coupons, discounts, and special offers and finding one to our liking we placed our order.

Now the problem with Plasma is that the screen looks best in darker rooms and this television lived up to that need. Blacking out the windows in our living room proved to be one issue that we managed to overcome with the aid of some bubble insulation and soon we found the room and the television to our liking. But then reared something for which I was unprepared - the dreaded plasma BUZZ.

I have a toroid power conditioner (PowerVAR HBC1200-11 hospital grade, balanced output) and a toroid transformer in my OPPO BDP-105 and my McIntosh MC2100 power amplifier (a conversion after a lightning strike). All of this gear is located directly underneath the television (within 36" or 1m).  Because of their proximity to this huge plasma screen, something strange occurred with the interaction between the TV and the toroid transformers: all transformers began to hum with an increasing and decreasing "rrrr-eeee-OOOO-WWWW-oooo-mmmm" buzzing sound. Disconnecting every connection to the TV (LAN, antenna, HDMI, etc.) and turning on the set caused this annoying hum and I was also suspicious about this hum causing incidental damage to the toroids.

So the set went back and this blog note is a word caution to folks with similar gear in close proximity to their plasma flat screens: be aware that the high-voltage-induced RF interference generated by ALL plasma TVs may give you a similar headache. The only solution to totally eliminating the RF interference issue is to get rid of the plasma television (YIKES!).

Manufacturers spend serious thought in designing audio gear to be immune or at least resistant to such interference but the extreme level of RF noise generated by all plasma TVs is another whole ball game. Despite the efforts of the best designed plasma sets, the amount of RF interference generated by the plasma technology is huge. HAM radio operators report interference being so bad that plasma sets located 50 feet from their antenna totally trash the airwaves and make reception intelligibility next to impossible. See the following links to get an idea of how bad this RF noise is:

The buzzing noise you hear in these videos is a conversion by the radios and test equipment from the RF band to the audio band. This means that even though you cannot hear this noise from your plasma TV, this noise exists and it is so powerful it can penetrate your expensive shielded cables and shielded metal cabinets. I personally tried putting mumetal around my power conditioner with zero success.

Now just imagine what this amount of noise is doing to the signals in your stereo. Do you really want to deal with removing the noise such sets emit or would you rather not have to remove it in the first place? I chose to do the latter and I just want to let you know that this issue exists. This is something that no one in the audio or video field is talking about and it needs to be revealed, so there it is.

My recommendation would be to dump your plasma set and get a LED or better yet an OLED technology TV. Do yourself a favor: live with the lower-quality black levels and opt for lower RFI instead.
Yours for higher fidelity,

Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

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