Just reading through Morgan Jones 3rd edition of Valve Amplifiers page 197
"in this circuit Ia for the 6C45Î is set purely by the constant current sink, so considerations of thermal runaway caused by excessive grid leak resistance are irrelevant."
Consider that when studying for example Aleksadar's RH amplifier methods of using a CCS (hold whatever you think of his use of 3 legged regulators for this purpose aside) shared with a resistor (to absorb extra voltage).
Alexandar gives other benefits to this otherwise pointless ccs, but for this benefit Morgan Jones shared with his readers, it introduces new beneficial criteria to our designs.
In theory one could use a 1 mΩ grid leak resistor anywhere and so get more amplification and facilitate use of smaller coupling caps. In practice
might be safer to box clever and not take it to extremes.
Definitely not good for A2 operated output valves.
Keep in the armoury for A1 operation.
Grid resistor : exceeding the spec
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Paul Barker
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#1 Grid resistor : exceeding the spec
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
#2
Yep the CCS in the cathode will control the current through the cathode, but it doesn't set if it passes through the grid or the anode.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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Paul Barker
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#3
Yes, so the free extra resistance would have a limit before distortion set in, but the valve won't run away. Depends on valve choice and biasing clear of A2.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
#4
please excuse the OT Paul......
the 16th century jesuit brothers relied on just this maxim....I believe....doesn't it form the basis of every witch trial?"there is no theoretical way to distinguish between Truth and an extremely accurate and reliable misunderstanding."
There's nowhere you can be that isn't where you're meant to be
#5
And modern science.ed wrote:please excuse the OT Paul......
the 16th century jesuit brothers relied on just this maxim....I believe....doesn't it form the basis of every witch trial?"there is no theoretical way to distinguish between Truth and an extremely accurate and reliable misunderstanding."
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.