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Re: VTTC - audio modulation

Original poster: "David Trimmell by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davidt-at-pond-dot-net>


At 03:59 PM 5/23/01, you wrote:
>Original poster: "Dr. Duncan Cadd by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <dunckx-at-freeuk-dot-com>
>Hi Herwig, All!


> >>>Wouldn't modulation cause the oscillation to stop?
> >> It all depends on the modulation depth
> >- So overmodulation would cause the oscillations to stop and a low
> >modulation depth means low loudness?
>Basically yes, you've got it!  However, I recall those who have built
>these things do not complain of low loudness despite the necessarily
>low modulation depth, a couple of websites I've visited say it's
>plenty loud enough, even with pipsqueak power to the TC.  "Low"
>loudness is thus very much a relative term :-)

My experience with grid mod showed that very loud sound can be produced 
from a small plasma, *but* as Herwig thinks, the larger plasma does 
increase the frequency response in the lower end. It doesn't seem to be 
neat and linear, though. Of course many other factors complicate the issue. 
I have had serious issues with over modulation cutting the tube off, flat 
line on the scope, but if I turned volume (grid mod V) down, the output 
would drop too much. I was modulating 100%. I have hopes that a new circuit 
(one that Dunkin suggested, bypassing DC from mod Trany) will work well 
with a pair of 833's, did some quick tests a while ago. Someday I will get 
back to it...


David Trimmell

>Geek#1113 (G-1)