Re: VTTC provisional results

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

Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>


David Trimmell wrote:

> How were you going to do the Audio mod, Screen or Grid?

David,

I will use control grid modulation as plate/screen grid modulation 
would need much more modulation power. 

> I have never tried Screen mod, think it may be even more
> difficult than grid.
- Using this kind of modulation you would have to take the dc 
current into consideration as well. If you choose series modulation 
(dc current flows through modulation transformer)  you would need  
a modulation transformer with air gap. For parallel modulation you 
would need a rf choke suitable for HV.....I agree that things may 
me become much more difficult.

> With grid you need to get your dc bias resistance up
prety high, so that may drop spark output somewhat, but the 
pulsing action of the Audio will increase the spark also.
- A-mode instead of C-mode? 

> Sugest filtering <100 Hz Audio signal, as that seems to distort 
like something awfull.
- In previous tests I have used a booster with built-in equalizer. So I 
could set the audio response easily.

> I have tried a Audio output transformer from a old tube amp (15 
watt), and that worked ok with a 833 tube, aslong as I bypassed 
the DC component as sugested by Dunkan. 
- I shall use this approach as well with the large torodial core audio 
transformer I have borrowed from a friend.

> My setup:  
http://216.36.6.9/webdoc2.htg/Tube_coil/Audio/New_Audio1.jpg
- I shall have a look at it.

> Great work Herwig, and keep these reports flowing!
- Thank you. I'll keep you updated.

Regards,

Herwig