Re: Successful SSTC Audio Modulation - SWEET!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Hey Dan,

Question, Do you need the goofy deadtime settings????  Ive got lots of 50A 
parts that dont heat up too easily, and im also building my next SSTC right 
now (its going to use a 494).  I would love to be able to crank some audio 
into it if i only have to add a cap and lift a pin from the board!  That 
would be really awesome!  Is that all that is necessary for audio modding?
I really want to do this.

Thanks

Steve Ward


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Successful SSTC Audio Modulation - SWEET!
>Date: Thu, 29 May 2003 07:46:39 -0600
>
>Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><dhmccauley-at-spacecatlighting-dot-com>
>
>After a day of extreme frustration (yesterday gate drive problems) and a
>simple re-design of my gate drive topology, i finally got my SSTC to run
>from the push-pull outputs from the
>TL494.  So now, I have 25% on-side1, 25% deadtime, 25% on-side2, 25%
>deadtime.  This is required as operating in CW mode consumes mucho power, so
>by running the coil
>this way, you can reduce total output power and improve reliability of the
>h-bridge switch.
>
>Audio was provided by a CD player (high impedance output) and fed into the
>deadtime comparator pin of the TL494 through an 0.1uF capacitor.
>
>Audio output was very clear and almost zero noise otherwise from other
>harmonics in the arcs.  Very impressive, similar to Sue Gaeta's high side
>modulation audio quality on her 811A
>VTTC.  Also, with fan cooling, the heatsinks and FETs never even really get
>warm.
>
>One note to add, is that to improve audio quality, it is necessary to
>draw-out a continuous white flaming arc from the toroid.  This can be done
>by any metallic object and permanently set at about
>a 2-3 inch gap depending on output power levels.  The result is stunning
>audio.  (at least stunning when considering its coming from a hot flaming
>multi-kilovolt arc ! ! !)
>
>Also, volume control can be provided by adjusting this discharge gap
>distance.  To get really loud audio, just try to stretch the arc as long as
>possible.  I guess this provides much more heating of the air and therefore
>more volume.
>
>Awesome!
>
>The Captain
>