[Amps] SB220 Improvements

[Pete Smith]

At 10:53 PM 2/11/03 -0800, Tom and Linda Hellem wrote:
>Gentlemen:
>
>The information I have read concerning improvements to the SB220 contain a
>recommendation to replace the grid chokes-to-ground with resistors and to
>replace the stock 200 pf mica capacitors from the grid to ground with 1800
>pf of capacitance per tube socket. My Digikey catalog lists some ceramic
>disc 680 pf @ 1KV for .31 each and some silver micas, same value @ 500V for
>1.86. Since I have two amps to modify, the cost is an issue and I am
>wondering if the ceramic discs will do the job. Also, is the 1800 pf a
>critical value, as I will end up with 2040 pf per tube using the 680's. Any
>thoughts would be appreciated.

Hmmm ... I have also read repeatedly on this reflector the recommendation 
to ground the grids directly, removing all of those components.  In the 
absence of problems with my amplifier, I have not changed it from 
stock.  The disparity in these recommendations tends to make me believe 
that this area is a good candidate for "if it ain't broke, don't fix it."


73, Pete N4ZR
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