Hi,
I built some amplifiers using lower than standard voltages with not common tube types and wanted to know if someone knows something about limitations regarding the minimum anode current.
For example, I am running a 5678 in triode mode at 65v, biased at -1.5v (fixed bias) and I am using a very large anode resistor (the usually used 100k resistor).
The anode current, however, is around 0.3 mA, far away from the 1.8 mA suggested for the class A operation in the datasheet.
Is it detrimental to the signal? Is it more prone to noise interference? What is your experience in the field?
Any negative effects of low anode current?
Moderators: pompeiisneaks, Colossal
Re: Any negative effects of low anode current?
It's possible you can get cathode poisoning if you're running tubes with very little current. See: https://valvewizard.co.uk/standby.html
The fourth paragraph under the second section describes the process.
The fourth paragraph under the second section describes the process.
Re: Any negative effects of low anode current?
Good to know, I had not thought about that and always associated that with no current at all.
I thought the low current could make it susceptible to any vibration of the grid or even Noise emitted from other wires.
I thought the low current could make it susceptible to any vibration of the grid or even Noise emitted from other wires.
Re: Any negative effects of low anode current?
That is a nice article about using tubes at low voltages. To think that the valvecaster did something like this so long ago.