I like to experiment
DIY trasducers. For long time I've been searching news on plasma tweeters
in the web.
Some months ago
finally I found a full detailed project in the web in Ulrich Haumann page:
http://members.aol.com/uhaumann/eplasma.htm
Hulrich gave me a
lot of helpful advices and also make me a gift: two philips 100uH - 1A coils (that without value in the schemat.)
to get the oscillator work.
Thank for your help Hulrich!!!.
Here is a partial scheme. More details can be found in Ulrich's page.
The 100k pot. on
the Bu208's base set the bias current of the 509 and thus the flame size.
The most difficult
stage to me was finding the ceramic supports for the tesla coils.
Diameter is not
so important. Actually my support is 1 cm. larger than suggested but with
no noticeable effect on performance. To expedite the costruction I didn't
build the high pass filter.
I arraged quickly
the circuit on a wood table warm up the tube, switch the HT on and.....
It has been
very nice to hear the sound coming up from this little "dancing" flame.
Here are some
photos of the tweeter. for the entire project please refer to Hulrich's
pages.
Here is a close shot of the flame:
The flame could double
the size, but the distortion arises. There is a best position for the size
potentiometer.
In this point the
modulation of the flame is "simmetrichal" and the distortion reduced to
the minimum.
Plasma start at about 5-6ma consuption. The flame increases the size with the consumption. I've reached 10-15ma for a couple of seconf but the tube start glowing hot red.
The highs that come out from this tricky little hot spot are among the best that I've heard.
In the future I hope I'll devote a little more time to this project, to try to eliminate the main disadvantage that are:
