[Amps] Parasitic suppressor resistor

Steve Thompson g8gsq at eltac.co.uk
Mon Jan 2 04:04:55 EST 2006



Bill Turner wrote:
> ORIGINAL MESSAGE:
> 
> At 04:22 PM 1/1/2006, R. Measures wrote:
> 
>>**  A problem with a resistor that is c. 120mm long is that has more 
>>L than would be optimal for a parasitic suppressor.

> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> I thought about that, but the L would be there anyway. The 8877 sits 
> low on the chassis and the top of the plate choke is six inches above 
> the chassis, so the wire would be that long anyway. I guess I could 
> have mounted the choke horizontal but it's too late now.  :-)
Having the L in the resistor is different from having it in series with 
the resistor/inductor suppressor. Whether the difference matters is 
unique to your amplifier and its gain/phase characteristics. If you can 
measure them, you can design a suppressor that's spot on for the job - 
if you can measure them, you might find that you can make an amp that 
avoids oscillation without needing a suppressor.

Steve


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