On May 31, 2006, at 7:10 AM, Steve Thompson wrote:
>
>
> R L Measures wrote:
>>
>> On May 30, 2006, at 11:07 PM, Steve Thompson wrote:
>>
>>>
>>>
>>> R L Measures wrote:
>>>
>>>> Just how the AL-1500's designer came to the conclusion that 5000-
>>>> ohms
>>>> of feedback XC at the tube's max freq rating could not cause
>>>> oscillation is a mystery.
>>>
>>>
>>> Maybe he didn't. Feedback C is but one of many factors
>>> contributing to
>>> oscillation, and one over which the designer has no influence.
>>> Perhaps
>>> he believed/designed/intended that other elements of the circuit
>>> prevented gain>1 and phase=0 without the need for an anode
>>> auppressor.
>>
>>
>> It must have have been a wishful intention, Steve, since there is
>> nothing unique about the 8877 -- in fact, its extraordinary gain-
>> bandwidth product should have been a pretty good clue that
>> oscillation
>> was something it could probably do.
> Indeed - but anode suppressors are not the only way to prevent
> oscillation.
True, however, prayer cloths are not all that reliable. The main
reason for going after a parasite in the anode circuit is that it's
where the damped wave VHF ringing takes place - whenever anode
current changes - that starts the snowball rolling downhill.
>
> Steve
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>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
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