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Re: PWM Controller question

Original poster: Sue Gaeta <sgsparky-at-prodigy-dot-net> 

...and that was with a lousy modulation transformer!
I showed my project to a friend of mine who is a broadcast engineer, and a 
high fidelity freak. He is also an amateur radio operator with a home 
brew  high fi AM transmitter. Just for sh**s and grins, he connected his 
modulator and power supply to my VTTC. The quality of the audio was 

The mod transformer that I have in there now is out of an old military 
transmitter which is known for poor quality audio (an ART 13). If I wanted 
good fidelity I would have to use a transformer that was 4 times as heavy, 
and would not fit in my modulator deck! Good high side modulation makes for 
a very bulky, and heavy rig, but the results are indeed cool!

I have this crazy idea that bigger sparks will give better bass response, 
so I would love to see Steve Ward give his interrupter a rest, turn down 
the rail voltage half way, and high side modulate that sucker! People say 
it can't be done, but it is done with 50, 60, 100, and 120 Hz all the time. 
Finding a suitable mod transformer that can handle that much current, and 
has the correct impedance match would be challanging, and maybe even 
impossible though. Someone once suggested substituting the mod transformer 
with an SCR or something. If someone could come up with a way of high side 
modulation with active power devices in place of a modulation transformer 
it would be great! Even if he settled with driver side modulation, I would 
love to see what kind of audio comes out of a 10 foot arc! The nice thing 
about high side, high fidelity modulation is that throbbing base will 
produce long streamers if you are fully modulating (ie: the rail voltage 
will peak at double the! supply voltage with no modulation, and then dip to 
0 volts during an audio cycle).

Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: "Eastern Voltage Research Corporation"

 > > I think Dan's PlasmaSonic design is good, but I could see some
 > > improvements in using (possibly) rail modulation. Real high power
 > > audio modulation will be seriously cool! I have seen it while arcing
 > > something "semi-grounded" to a AM radio station tower many years past
 > > (don't ask!). My grid modulated VTTC has been the closest I have seen
 > > yet, but quality was unreliable.

Absolutely. This *is* the way to do it, although high-side modulation is
more involved and requires a lot more

Sue Gaeta's high-side audio modulated VTTC was stunning and definitely out
performed the PlasmaSonic as far as audio quality goes.