By now, some of you may be getting tired of my continuous questions regarding valve amps. My apologies to those.
Based on the kind assistance I have received so far, I feel this is a good place to ask questions, and hopefully kind-hearted souls will take pity
So I have a good amp design in mind, but I don't like the choice of pre-amp/phase splitter/driver tubes as they are ugly (6SN7)! Looks like an "ugly dumpling in a knee length dress with gum boots on" and will detract from the beauty of my KT88s. Yes. I realize this is hardly a technical reason. I would prefer to use something like the 6CG7. It appears to me to be technically very similar, however the maximum plate voltage is much lower, 300V as opposed to 450V.
I do my calculations and the operating points for the three stages are well below the 300V point, so all seems good. Right? Wrong? What happens before the tubes warm up? The plate current doesn't flow, so the potential divider action with the anode resistor doesn't take place and initially the full voltage (477V in my case) will appear across the valve. Will this short duration overvoltage damage the valve? Assuming so, what stops me from clipping the initial voltage to 300V with a trio of series connected Zeners? They will move "out of circuit" so to speak, once the tubes start conducting.
If anybody can recommend an alternative tube with a 450V rating, please do. I have looked. Alternatively, one only applies the HV once the heaters have warmed up, an option, but not fool proof.
Please comment if you are knowledgeable in this regard.
My thanks.
Based on the kind assistance I have received so far, I feel this is a good place to ask questions, and hopefully kind-hearted souls will take pity
So I have a good amp design in mind, but I don't like the choice of pre-amp/phase splitter/driver tubes as they are ugly (6SN7)! Looks like an "ugly dumpling in a knee length dress with gum boots on" and will detract from the beauty of my KT88s. Yes. I realize this is hardly a technical reason. I would prefer to use something like the 6CG7. It appears to me to be technically very similar, however the maximum plate voltage is much lower, 300V as opposed to 450V.
I do my calculations and the operating points for the three stages are well below the 300V point, so all seems good. Right? Wrong? What happens before the tubes warm up? The plate current doesn't flow, so the potential divider action with the anode resistor doesn't take place and initially the full voltage (477V in my case) will appear across the valve. Will this short duration overvoltage damage the valve? Assuming so, what stops me from clipping the initial voltage to 300V with a trio of series connected Zeners? They will move "out of circuit" so to speak, once the tubes start conducting.
If anybody can recommend an alternative tube with a 450V rating, please do. I have looked. Alternatively, one only applies the HV once the heaters have warmed up, an option, but not fool proof.
Please comment if you are knowledgeable in this regard.
My thanks.
