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RE: Funny though, I knew there was something wrong with your argument

So I did some measurements. The problem is that the *signal* voltage on the cathode of the tube is likely to be about 1/20th that of the grid! I did this measuring actual signal on one of our MA-1s, which use differential amplifiers with a very effective vacuum-tube CCS.

The other half of the diff amp gets its signal not so much from the cathode, but *the effect that that cathode has* on the total current through *both* tubes, which is constant.

So the effect is that for all intents and purposes, a differential amplifier has if anything, very slightly less gain (certainly *way* more than half). With a higher mu tube the gain gets closer to being identical.

I recall measuring this about 10 years ago, so I was a little hazy on it and just accepting my recollection. Hard measurements work better.


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