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Old 11th March 2008, 01:46 AM   #121
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Yeah, now it's finally clicking in my mind, so the 0.1uf capacitors between the filament windings are shorting the RF to ground. Also I'm wondering if it's alright for me to have center tapped my transformers the way I did, I don't have center tapped filament transformers, so instead I have two 100 ohm resistors in between them and have a center tap at that connection is that alright?

If I'm understanding correctly, then I'm supposed to ground the grids and then apply a positive voltage to the center tap of the filament transformer as a bias?

here's a redrawn schematic as well.


http://www.flickr.com/photos/1403176...40744/sizes/l/
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Old 11th March 2008, 05:17 AM   #122
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Hill's Plasmatronic speakers used a DC powered glow discharge. No RF, crossover as low as 700 Hz (without horns), and if you search these forums (they have been mentioned numerous times, which indicates to me you haven't done much research even around diyaudio) you'll find the measured frequency response and waterfall, showing that nothing else comes even close. You can also find Hill's patent (now expired ) for the theory of operation. And no you don't really need helium
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Old 11th March 2008, 06:10 AM   #123
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Yeah, I've definitely done my research on this forum, I've looked at all the forum threads for plasma tweeters. The ones for plasmatronic type tweeters seemed mostly conceptual and if I recall there was much bickering on those threads and nothing too useful. Initially I thought about doing something like that mentioned in the Hill patent but it seems beyond the scope of my abilities.
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Old 11th March 2008, 07:24 AM   #124
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The difficulty is not in getting sound from it (been there done that), but shaping it to get the right frequency response, and designing the enclosure to minimize diffraction effects etc.
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Old 13th March 2008, 03:48 PM   #125
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Quote:
Originally posted by Serge66
Angsuman,
You are driving your 811 by the cathode (the grid being grounded).
The signal coming from the 807 is shorted to ground through these caps.
Shhhhh...

How the heck do you think people are going to learn anything if you spill the beans??

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Old 13th March 2008, 03:52 PM   #126
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Quote:
Originally posted by abzug
Hill's Plasmatronic speakers used a DC powered glow discharge. No RF, crossover as low as 700 Hz (without horns), and if you search these forums (they have been mentioned numerous times, which indicates to me you haven't done much research even around diyaudio) you'll find the measured frequency response and waterfall, showing that nothing else comes even close. You can also find Hill's patent (now expired ) for the theory of operation. And no you don't really need helium
If you say so...

The Hill is an excellent measuring device, gotta discount the HF noise though... and it sounds fantastic.

I'm sure Dr. Hill would have not have included the expensive and difficult to handle inert gas in his design because it was not needed, right?

And, I have a copy of the patent, fyi... thanks.

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Old 13th March 2008, 05:14 PM   #127
Paul W is offline Paul W  United States
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A few quick suggestions... At least in the new schematic, L4 is shorted by the second (lower) line coming from pin 1 of the right 811...delete that line. Pin 4 of the right 811 should go to the junction of L5 and R5. Delete R6 & R7 unless you want them for layout symmetry. Maybe add small RF bypass caps from the 6.3V secondary, and the junction of R4 & R5, to ground. Double check all component values.

This may be a dumb question, but is there a reason for biasing the heater/cathode rather than the grid? (I've never worked with heater only tubes.)
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Old 14th March 2008, 08:32 AM   #128
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Quote:
Originally posted by bear
gotta discount the HF noise though
What are you talking about? There is no HF. It's a DC-powered plasma--even if the patent mentions other types plasma, the actual product had a DC supply.

Quote:
I'm sure Dr. Hill would have not have included the expensive and difficult to handle inert gas in his design because it was not needed, right?
Wrong! He included it because a modern technology that was developed in plasma engineering which make it unnecessary did not exist during his time.
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Old 14th March 2008, 06:30 PM   #129
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Quote:
Originally posted by abzug

What are you talking about? There is no HF. It's a DC-powered plasma--even if the patent mentions other types plasma, the actual product had a DC supply.


Abzug,

Wonder why you don't mention your location or have contact buttons up? But anyway...

HF noise = High Frequency NOISE.
NOT RF noise. Ok?
...you misunderstood.

Ever listen to a Hill Plasmatronic? No?
It hisses... fwiw.

And yes, you are correct, he used HV DC to create the plasma, but he needed to strap on a tank of Helium to make it work.

Any other commercial products use DC?
Would be interesting to know...


Quote:
Wrong! He included it because a modern technology that was developed in plasma engineering which make it unnecessary did not exist during his time.

Ok, now we're getting somewhere.
What "modern technology" are we talking here?
Or are you the same guy who posted under another login who was on about "platinum catalysts" a year or more back??
Actual information on this would be of interest.

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Old 14th March 2008, 06:56 PM   #130
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Hè guys look to this http://www.hardcoreaudio.de/plasmatweeter.htm
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