0v grid allows tubes to draw "humongous" currents limited of course by what is available from the psu and any dc resistances in series...if left unattended/unchecked will cause magic smoke to come out..
so the use of the term "humongous" here is along these contexts,
meaning that cathode currents are as huge as can be without anything to hold it back..
so the use of the term "humongous" here is along these contexts,
meaning that cathode currents are as huge as can be without anything to hold it back..
The anode current hits the peak signal or 'cranked' level of current that flows when the plate voltage signal starts to clip or flat top in to a square wave. That is 'normal' operation for a guitar amp, and when the loadline has hit the 0V grid curve (preferably near the knee of the 0V grid curve for a pentode). That is the design peak operating current of the anode - is that what you refer to as 'humongous'?
Even a diode has resistance (on state V-I), which is circa 400 ohm for a 5Y3 and circa 185 ohm for a 5U4 at nominal 50V.
A 6L6GC has a circa 200 ohm resistance characteristic below the knee. Above the knee, the incremental resistance is huge as the characteristic turns to constant-current, and the max current through the anode is not going to go above 250mA even if you can somehow keep the screen at say 300V. Is 250mA 'humungous'?
The tube effective plate resistance on the Vg=0 line is typically much higher than an OPT half-winding resistance which is likely to be under 100 ohm for 50W'ish OPT rating.
A 6L6GC has a circa 200 ohm resistance characteristic below the knee. Above the knee, the incremental resistance is huge as the characteristic turns to constant-current, and the max current through the anode is not going to go above 250mA even if you can somehow keep the screen at say 300V. Is 250mA 'humungous'?
The tube effective plate resistance on the Vg=0 line is typically much higher than an OPT half-winding resistance which is likely to be under 100 ohm for 50W'ish OPT rating.
And what I'm trying to indicate is that the peak current value during normal operation is effectively the same as the continuous 'humongous' current you are referring to.
Operating continuously at the peak current level may or may not exceed plate or screen dissipation limits, depending on the sagged B+ and screen voltage rail levels. Plate dissipation on the saturation curve out to at least the knee is generally no worse than idle plate dissipation, due to the constant power curve. Adding in a power transformer secondary fuse with just enough margin on its current rating, would provide the cheapest, and good chance to protect the OPT in that situation.
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