On Jul 18, 2006, at 9:28 AM, Tom W8JI wrote:
>> The tubes (3-500z`s) were from RF Parts. I replaced (Henry
>> 3K repair
>> job)some low hr Eimacs that one had developed a grid to
>> filament short. Gain
>> was compared to a nos pair of Eimac`s.Higher zsac for a
>> given Ep and close
>> to 10% more output for a given value of drive.Jim..
>
> The trend is generally this:
>
> Higher quiescent current for fixed bias and HV generally
> indicates lower mu, not higher.
correct.
> It takes more negative bias
> to reduce anode current as mu is increased.
the opposite is true. Example -- With higher Mu Amperex tubes in a
SB-220, the 5V bias zener needs to be shorted (0V) to increase the ZSAC.
>
> Lower mu generally indicates higher input impedance, more
> negative feedback, and less gain in a g-g amplifier.
correct
> In a
> g-g amp gain is mostly determine by the ratio of load
> impedance to driving impedance, and higher mu tubes
> generally have a lower cathode drive impedance.
>
> It would be interesting to see what the Chinese are doing
> differently when they make the tubes. Maybe the tubes are
> lower mu and lower driving impedance?
In g-g configuration, lower Mu means higher driving Z, and higher Mu
means lower driving Z.
>
> 73 Tom
>
>
>
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|