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Registered Member #1642
Joined: Sun Aug 17 2008, 11:36PM
Location: Black Canyon City
Posts: 96
I was playing around with my Multimode Prototype VTTC Coil the other day and thought it would be interesting to show you the results of some of my experiments. The first video is about a year old and was taken at Dr. Spark's house. One can see that the coil is literally spread from one side of the garage to the other. This was my first attempt at audio modulation. A Sony Walkman CD player was used for the experiment.
Video at:
The next video describes just some of the fun you could have with a VTTC.
Video at:
So far I have achieved the following:
-CW mode (AC level shift and pure DC) -Stacatto mode (AC level shift and pure DC) -Pulse mode (Cathode Modulated) good for keyboard, guitar, theremin and Audiotesla MKIIc Tesla Coil Controller. -Grid Drive mode (Both AM and FM) great for audio from an IPOD or CD player-but is really a power hog! I use a 100W 30~500khz mosfet power amp to drive the grids.
In the future I will be experimenting more with grid phasing, etc.
Registered Member #1642
Joined: Sun Aug 17 2008, 11:36PM
Location: Black Canyon City
Posts: 96
I was wondering if you can also change grid leak resistor to achieve longer sparks when running in low BPS staccato mode?
I have to be honest, my expertise is not with the 833C tube, but rather the 811A. On the 811A I was able to drop the grid leak resistor to somewhere around 400 ohms in stacatto mode. This doubled the spark length. Dr. Spark has much more experience with the 833C, and we optimised it around 4K ohms. I'm not sure whether reducing this value is good...I tried...but did not notice any appreciable difference in spark length, so we left it at 4K.
I am not hammering the tubes with excess plate voltage...I try to keep it at around 3kv max.
BTW: When operating in grid drive mode (for audio), I do not use the tickler coil at all. I use the 100W mosfet amplifier at around 30~40 watts with high bias. I noticed that the higher the bias, the better the sound. The max so far has been only -150 volts. I am planning to increase this several fold and use a much larger coupling xfmr for about a 400~500 volt swing. This should bring the tubes well into a class C operation. Am curious about the results. With -100 to -150 volts, the tube are operating class A to AB. This tends to eat alot of current with only 1 1/2" spark output. I am hoping class C operation will net me a larger output without too much distortion.....your thoughts?
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Multimode VTTC Tesla Coil
