[Amps] Overdrive protection

Roger (K8RI) k8ri at rogerhalstead.com
Thu Jul 26 13:50:26 PDT 2012


On 7/26/2012 3:11 PM, Joe Subich, W4TV wrote:
>
>> My question -- and maybe there's an Alpha employee on the list who
>> wants to answer -- is "isn't it possible to make an overdrive
>> protection circuit that will cause the amplifier to fault fast enough
>> to protect the tubes and components?"
>
> Of course there is but such a protection circuit would make the amp
> almost impossible to use with the many rigs have have a horrendous ALC
> spike on initial key-down.  Many of the most commonly used rigs produce
> a full power (or higher) 2-5 ms long even when cranked back to 30 or
> 40 watts.
>

Only one brand that I know of and do all of theirs do that?  I never had 
a problem with my 756 Pro and I believe they are one of those that 
supposedly have the spike.

My FTDX5000MP does not create a spike like that although I normally run 
it class A as it has way more than enough power to dive the amp to full 
output even in class A, let alone the legal limit.  Class AB1 runs about 
4 times that power and even backed off I notice no problems.

73

Roger (K8RI)



> 73,
>
>      ... Joe, W4TV
>
>
> On 7/26/2012 12:36 PM, Vic K2VCO wrote:
>> Alpha's email newsletter talks about damage to amplifiers as a result of overdrive -- the
>> example is given of amplifiers designed to produce 1500w output with 40w drive being
>> driven with 150w. They say that there is a log maintained by the firmware which records
>> overdrive incidents and that they won't repair damage caused by this kind of abuse under
>> warranty.
>>
>> I am sympathetic to their attitude and don't approve of the philosophy that all knobs
>> should always be set to 11. But sometimes it's unintentional.
>>
>> My question -- and maybe there's an Alpha employee on the list who wants to answer -- is
>> "isn't it possible to make an overdrive protection circuit that will cause the amplifier
>> to fault fast enough to protect the tubes and components?"
>>
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