R.Measures wrote:
> On Oct 1, 2005, at 3:59 AM, almacottage wrote:
>
>
>>i have the AL811 with 3 tubes , i directly swapped the 811a tubes for
>>572B tubes and run the high voltage at 1900v [ie in the red segment of
>>HT meter] .
>>
>>i found that on these amps the original anode parasitic chokes
>
>
> In a HF/MF amplifier, R//L VHF parasitic suppressors are not "chokes".
> They are a device that reduces the VHF Rp* presented to the anode.
> Less Rp means less VHF amplification, which in turn means more
> stability at the anode's unavoidable parasitic resonance. (typically
> from 43MHz to 160MHz)
>
> * Rp = Parallel-equivalent R. Achieving less VHF Rp requires less VHF
> suppressor Q.
Also, don't forget that the Rp seen by the tube is the Rs (series
equivalent resistance) of the suppressor network at the vhf frequency in
question.
Steve
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