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DuKane Ionovac Information


jackpod
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Hello,

I thought I would pass this information along. My name is Jack and I am one of the 2 people behind www.ionovac.com which is a very informative site about the history of the DuKane Ionovac and the only place available to accquire cell kits and other unique parts. The Ionovac is a gas plasma tweeter that was first manfactured by Electro-Voice under license of DuKane, later to be manufactured by DuKane in 1961 to be soon dropped. I personally own 6 working pairs and I have a pair of prototypes. I just thought you might find it interesting reading.

Jack

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Speakerfritz, yes you are correct, the limiting factor is there is a stepup tranformer in the input circuitry which is the limits the response, the oscillator is capable of up to 50khz the plasma itself is unlimited. From my years of living with them, i have yet to find anything that has the response of the Ionovac. The fact that there is no mass makes it the fastest reproducer in existence. Roger Russel performed some test many years ago and he has that info available on his website. The drawback and eventual demise was the maintenance and cost of the unit. In 1961 the cost was $79, which back then was a lot of money. There was also a concern because there is ozone produced during operation. All i have noticed is that if the room is closed and the units (usualy 3 pair) are in operation for several hours, there is a light odor in the air. I have run them as long as a year without maintenance. DuKane recommended electrode replacement after 1200 hours but I have run them for several thousand hours with an occasional cleaning. Because the electrode is consumed during operation as a test I ran a pair until the tip of the electrode was completely burned away and they still worked, as long as the residue is cleaned from the orifice of the quartz cell which can cause hot spots and eventually crack the quartz cell. I was fortunate enough that the city I grew up in had a local hifi shop that was the west coast dealer for DuKane and I was able to accquire several of the original DuKane cell kits. When Daniel Schoo and I decided to have a small quantity of quartz cells and electrodes made I performed tests and the replacements have the same charateristics as the originals. From my understanding there are still a couple of companies in Europe and Japan that make plasma tweeters today, but they are very expensive. Some day I would like to see if i could modify the input stage to see if i can bypass the need for the input transformer, then i would truly have unlimited response well beyond what is otherwise available

Jack

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Very intresting, thanks.

Concerning the input transformer, whats was new, and now thought of as old, is now new again. More and more implementations of the transformer are creeping back into audio. Recently found an impediance matching transformer that has a bandwidth of 2hz to 2mhz, while being able to handle quite a bit of power.

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I would need to check the Ionovac transformer, wouldn't it be something if the impedances were close enough to be able to put one of those in an ionovac, imagine the response you could achieve, sure couldn't hear 50k but the subharmonics would provide top end like no one has ever heard before

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Hello Jack,

Its good to see you on the Forum. I picked up a pr of DUK 30s a few years back and I found lots of good info on your site. I especially enjoyed reading about the Ionovac's development and demise and the maintenance section was very helpful.

I originally wanted to try the Ionovac tweeters with the Khorn but found the endeavor to be a bit too much of a challenge - besides, I couldn't bring myself to take the speakers apart.

I'm delighted to see that you're offering the replacement parts and may hook 'em up again ( I only had a single replacement set of cells and electrodes and was wary of using them up). The 30's sound quite refined and the tweeters are phenomenal and plasma is very high on the "cool-factor" chart. Just wish I could keep from staring at that little plasma ball.

Thanks for the link and don't be a stranger -Bryan

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Speakerfritz,

Thanks, I have some info on the t3500, but what you posted is more complete. The big drawback with the T3500 was oscillator shift, because the plasma runs a little on the warm side, aprx 1000 degrees farenheit, the T3500 was hard to get the plasma started. they tried many ways to make the oscillator shift as the plasma warmed up but were never able to refine the process. At the same time in the UK I believe the Ionofane was in production, but it had its own set of problems. At one time the B&W line had an Ionofane. And then in the Netherlands I think it was the ionophone. Even with the incredible sound the technology was not "consumer" ready because of the problems. It has been a couple years since I gathered all the info and put the site together, amazing what you forget if you don't use it everyday.

Jack

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Hi Bryan,

I run (currently 3 pair) on top of my Belles, I left the Belles intact (tweeter connected) and use an electronic crossover to power the ionovacs. It really adds that "just right amount" of crispness. The Belles are a little more efficient and hence the reason I run 3 pair (and also because I have them and i can). I recently accquired speakercraft plans and will be starting construction on a pair of Khorns real soon (once I get a couple other projects out of the garage so i have the room).

I am glad you were able to use some of the info from the site. It makes both Daniel and myself happy to know we were able to help others with their Ionovacs. Discovering the info and especially having the opportunity to talk with Mr Ben Jewison (one of the original DuKane engineers) was an incredible experience. Ben was really surprised to find out people still had ionovacs and that they were still working now (45 years later). I totally understand about staring at the plasma, imagine 6 of them looking at you. I have had all 6 pair on simoustaneously quite the impressive sight [8-|] and sound!.

DuKane recommended replacing the cells every 1200 hours, but that was to prevent problems with the general public. While the speaker is operating, the tip is slowly consumed which leaves Kanthal deposits on the walls of the quartz tube (cell) which can cause hot spots. It is the hot spot that can damage the cell. If you take them out and use a toothpick or end of a paper clip and scrape the deposits out (best you can) you can run the electrode down to where the tip is totally gone without damage. I have run electrodes for several thousand hours. I still have i believe 7 cell kits available. I am not sure we are going to have anymore made. It is a large cash outlay that takes a while to get back. We have had 2 runs of 30 kits made (both cells and electrodes) in the last 2 years and a third of those were put in my personal stash for my units. I also have a handful of original unused DuKane elctrodes.

Turn on your Duk 30's and enjoy them, parts are no longer "unavailable" like they were for some 30 years

Jack

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In case it's not noted on the Ionovac site, the nice folks at Telex have made much legacy EV literature available on-line, including the T-3500's datasheet: http://archives.telex.com/archives/EV/Drivers/EDS/T-3500%20Ionovac%20EDS.pdf

There was an article a year or two ago in AudioXpress magazine on a DIY plasma tweeter. There are also several websites, including http://www.plasmatweeter.de/eng_plasma.htm and http://www.geocities.com/agalavotti/plasma.htm

Just be careful to use in a well-ventilated area. The plasma does produce some ozone (triatomic oxygen), which isn't good for us.

My apologies if all of this information is redundant to that on the Ionovac site.

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