Yeah I was just thinking of wiring two filaments in series and feeding them 
with a 7805, that means a 10 ohm 1 watt resistor. That way I'll have the 
best of both worlds; minimal gradient effect, easy DC and resistor 
protection

So now I only have to figure out wether my two transistor driver is a good 
way to drive my IV-11 tubes :)

A big thank you for all the help until now, I've only got my driver 
question remaining :)

Op dinsdag 19 november 2013 21:15:05 UTC+1 schreef Gideon Wackers:
>
> Yeah I think I'll go for a 
>
> Op dinsdag 19 november 2013 21:07:42 UTC+1 schreef jrehwin:
>>
>> > Do any of you use some sort of protection circuit for the filaments? 
>>
>> I just use a higher voltage supply and a series resistor.  That way, the 
>> difference in current between a cold filament and a hot one is less, so the 
>> starting surge is minimized.  It's less efficient than just driving the 
>> filaments at their rated voltage directly, but safer.  Another approach is 
>> to use a current regulated supply instead of a voltage regulated supply - 
>> then you can skip the resistor. 
>>
>> Note that if you're using a 7806 anyway, the efficiency is the same - 
>> it's a linear regulator, so the heat shows up in the regulator instead of 
>> the resistor.  In this case, I'd either use a 7808 and a resistor (reducing 
>> the heat on the regulator and gaining some protection), or wiring it up as 
>> a current source: 
>>
>> http://www.circuitstoday.com/fixed-positive-voltage-regulators 
>>
>> As it happens, the 7806 does have the ability to limit current, so it 
>> won't give the cold filament more than 1.5A or so anyway, which helps a 
>> little (it's still more than 3x the rated current, however). 
>>
>> - John 
>>
>>

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