|[AMRadio] Re: Ranger... good news, bad news|
ne1s at neandertech.com
Thu Nov 9 13:18:35 EST 2006
Jack Schmidling writes:
> Gary Schafer wrote:
>> So unless you have some higher gain tubes in the amp 12 to 15 watts drive
>> will not be enough drive.
> I have contended all along that it takes about 20w drive. Everything
> seems to work well including 100% mod when I drive with 20w. Only >problem being that the tubes redden.
The low-voltage B+ modification may not be practical for you, Jack. Any
class AB2 grounded-grid linear I've ever played with (and I've designed and
built two) had a power gain between 10 - 15. Someone said the power gain of
you amp was only around 6. So after reducing the Ranger power to 12W and
feeding the amp, you'll only be getting ~70W carrier out, not quite double
what the unmodified Ranger puts out (~40W). Hardly worthwhile.
> As a point of interest, I am using 6L6's in the modulator but assume they
> just won't last as long and not effect the amount of modulation. Is this > a good assumption?
Kinda depends. From memory the original metal 6L6 only had a maximum plate
voltage rating of 350V, so voltage breakdown at the socket may be a problem.
The maximum plate voltage of the 6L6GC was 400 or 450V. I can't remember if
there was a difference in the maximum plate dissipation. Anecdotally, I am
running 5881s in my Ranger that gets used reqularly, and they've been in
there at least 10 years. They may be a bit soft by now but still give me
nice sharp peaks in excess of 100%. As long as the tubes survive, though,
they should be equivalent to the 1614 electrically, and thus in terms of
their ability to modulate.
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