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[Amps] ALPHA 77

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Subject: [Amps] ALPHA 77
From: (Guillermo)
Date: Sun, 04 Aug 2002 22:28:42 -0300
Hello Phil:

Phil Clements escribió:
> > Why would one need to tune for grid-current ?  Minimal grid current does
> > not give a correct tune.  Maximal grid-current does not give a correct
> > tune.  A correct tune is max out with the drive needed to produce 1A of
> > anode current per 8877 -- which coincidentally results in c. 100mA
> > grid-current per grid, which could be seen on a 0-500 scale.  However,
> > there is no need to measure  grid-current on a cathode-driven amp.
> > Grid-driven, yes.
> When I tune an 8877 amp, I tune everything for maximum power out.
> I then tweak the PA loading cap slightly to give a needle-width decrease
> on the wattmeter. I need to see the grid current at this time to make sure
> it goes down and not up when making this adjustment. This slight reduction
> in suds makes a nice increase in clean.

        I've read in a book to decrease output nearly 2% (may be the same
thing) to achieve better linearity, but, do you increase or decrease
capacitance of loading control?.

Best regards
Guillermo - LU8EYW.

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