[Amps] AL-811H etc

[Steve Thompson]

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