General Asylum: PlasmaSonic a headphone that puts even the Orpheus to shame? itâ€™s what you think, a plasma HP. by cfb

There once existed a headphone even more exotic and unobtainable than the exalted Sennheiser Orpheus electrostatic is today, so rare you probably never even heard of it. Just to be clear this was a real product but with serious flaws, unfortunately....

The PlasmaSonic, this headphone was briefly introduced in the mid 1980's from the same engineers who would later go on to design the AHL Tolteque plasma (ion corona) speaker that was shown at the trade shows in the early 1990's. Only a few dozen Plasmasonics were ever produced and sold in Europe and Asia by Audio Reference. The main problem was the life of the electrode which needed service after as little as 50 to 100 hours, significantly worse than, but similar to the DuKane Ionovac problems back in the 1950's with the life of their quartz cell being shortened when overdriven. The PlasmaSonic headphone was not in fact one of the ion corona discharge designs sometimes labeled as a â€œcold plasmaâ€ such as their later AHL Tolteque speaker would be but instead utilized a RF hot plasma technique (see note below) similar to the designs that are currently out on the net. Do a search for DIY plasma tweeter to turn up several projects. Another of the PlasmaSonicâ€™s problems was the use of solid state devices for the high voltage circuit. This was mandated by size constraints, the entire HV circuit had to fit inside the headphone unit, no room for a PL519 vacuum tube here. Remember that the working voltage involved is a whole order of magnitude greater than the typical electrostatic headphone design. They should have marketed these with Alan Hillâ€™s Plasmatronic speakers (just joking here the rest of the post is serious), by the way Hillâ€™s Plasmatronic used helium as a shielding gas for the corona to prevent ozone generation, the main unwanted by-product was nitrous oxide not ozone, I wonder if that affected anyoneâ€™s perception of the sound! Please note that the PlasmaSonic design will produce some ozone as no shielding gas is used; that might make a good modification, gas shielding and ozone scavenging. In addition, the distortion of a plasma increases significantly at lower frequencies plus I doubt if it had much output below 50 Hz; this is a common fault with plasma designs, their inability to reproduce low frequencies. They are for the most part a high frequency driver only. The PlasmaSonic is one of the few attempts to utilize a plasma full range, for that alone it is worthy of note. This design poses two points, one it is interesting that the potential owners had no concerns over strapping a high KV source one inch from their ears, just try to get this CE approved today and two, why didnâ€™t the press ever mention them? I donâ€™t recall any of the audio magazines of the time ever printing anything about it. Does anyone have any references to this in the press of the time? I wonder if there are any still in existence? When you consider the short life of the electrode, I doubt that any are still in working order today, although the electrode could be replaced. Does anyone know of an audiophile who owns what must be the rarest of headphones?

The AudioCircuit has several links if you are interested in plasma high frequency drivers. Some commercial designs of RF ( radio frequency heating technique ) plasma tweeters were the Magnet in the 80's, the CORONA Acoustic GmbH in the 90's and the Acapella currently.

P.S. Please no jokes about none of the original owners being in existence due to electrocution. I have never heard of a report of someone being injured by an electrostatic or in this case a plasma headphone before.