[AMRadio] 813 tx (EL-34 comment)


W7QHO at aol.com W7QHO at aol.com
Sun Nov 28 17:52:48 EST 2004


In a message dated 11/28/04 1:12:38 PM, bcarling at cfl.rr.com writes:


> I am not sure how you quantify a lot more audio, but we probably
> could not hear the difference unless you could squeeze at least
> an extra 25-30 watts out of them, and even then it would be barely
> perceptible.
> 

Guess you've had no experience with a Viking 2.   Stock, these run a pair of 
807s AB1 in the modulator which just barely puts out enough audio to   fully 
modulate the rig, even with a pair of hot tubes and the screen voltage and grid 
bias adjusted just so.   More typically one gets flat-toping and distortion.  
 One way to solve this problem is to modify the rig to add a proper AB2 
driver (6AQ5 with negative feedback, etc.) along with regulating the screens and 
bias supplies.   Dropping in a pair of 
EL-34s works just as well and is an easier mod.   Never measured just exactly 
how much more headroom the 34s provide, but one can definitely hear the 
difference (believe me).

Dennis D. W7QHO
Glendale, CA



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