"Eeyore" <rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote in message
news:480EFA3D.CD27BC9F@[EMAIL PROTECTED]
>
>
> Iain Churches wrote:
>
>> "keithr" <keithr@[EMAIL PROTECTED]
> wrote
>> > "Iain Churches" <IainNG@[EMAIL PROTECTED]
> wrote
>> >>
>> >> This whole idea of the usefulness of current regulation
>> >> came to me when I was running a prototype amp
>> >> from a bench power supply, and noticed the huge
>> >> current drawn by the cold heaters.
>> >>
>> > Same as any hot piece of wire, it is the reason that incandescent
light
>> > globes blow at switch on 99% of the time.
>> >
>> > If you feel that this is im****tant, then (assuming parallel feed) you
>> > either need a current limiter for each tube or a single voltage
>> > regulator
>> > that ramps up the voltage over a second or two at switch on.
>>
>> Hi Keith. I am not sure it is *that* im****tant. But I have some very
>> good but fragile Tesla KT88s which I would like to give the best
>> possible chance.
>
> Is there any evidence that the heaters are especially vulnerable ?
Yes indeed. In the case of the Teslas they do not travel well, and
may arrive DOA. A colleague of mine who was travelling to Prague
for an orchestral recording session took an extra cello case, which
contained only a couple of rolls of bubble wrap. The packed the
KT88s well. When orchestras travel they usuually hand over the
instruments to the tender care of the airline baggage master, who
signs for them, and takes very good care indeed that they are treated
with the greatest care. Repair to a Magini cello might cost the insurance
company five times the baggage master's annual salary!
>
> I suspect the simplest way to go is just to ramp the heater voltage
rather
> than
> limit the current actually. It'll be simpler to make and have a lower
> overhead.
How should this be done?
Iain
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