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Original Message
RE: What I like about the Crowhurst analysis
Posted by Ralph on June 16, 2021 at 12:51:56:
Is the way he depicts the two tubes (ignoring for now the cathode resistor).
We can clearly see that the first tube is driving the 2nd via its cathode.
We also know that the greater the mu of a cathode follower, the less signal voltage loss there will be on the cathode.
So in the scenario where only one tube is driven by the grid, we can see that the other tube will always have less output, as a function of its mu.
The better the CCS becomes, the more this difference is reduced. If both sides are driven by opposite signals, it becomes no concern. Since our circuits are all balanced anyway that is why we use matched resistors.
Put another way, if you're driving this circuit single-ended, there will be a slight difference at the outputs, especially if your CCS is questionable.