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I have some ILC5 pentodes I'm trying to connect up in series in my pre-amp, and everything seems to be fine until I connect the cathode. The voltage is supposed to be 1.4 volts across each tube and it reads this, as long as the cathode is not connected. I guess what I didn't realize is that the cathode is actually connected to the heater internally... I was running it for about 2 hours having a play around and never realized it had double the heater voltage on it... surprised it didn't just stop working.
Is there any way I can connect these in series (as it would stop me having 2 separate regulators >.> and taking precious board space). I'm running most things in my preamp in grounded cathode operation (fixed bias is applied at the grids) if this somehow offers a workaround. On a separate note... if I biased with an unbypassed cathode resistor, wouldn't cathode-current feedback be much less, and the gain wouldn't suffer hugely? Since the heater current is actually flowing directly through the cathode (the heater draws something like 50mA, with the quiescent plate current at about 0.5mA)
Datasheet: http://tubedata.milbert.com/sheets/127/1/1LC5.pdf
Is there any way I can connect these in series (as it would stop me having 2 separate regulators >.> and taking precious board space). I'm running most things in my preamp in grounded cathode operation (fixed bias is applied at the grids) if this somehow offers a workaround. On a separate note... if I biased with an unbypassed cathode resistor, wouldn't cathode-current feedback be much less, and the gain wouldn't suffer hugely? Since the heater current is actually flowing directly through the cathode (the heater draws something like 50mA, with the quiescent plate current at about 0.5mA)
Datasheet: http://tubedata.milbert.com/sheets/127/1/1LC5.pdf
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