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RE: basic analysis of the S.E.X. amp

75.144.182.145

Hello again,

This is wonderful, and I've learned a lot already. I have a probably dumb question about the first part. when you said:

"...This creates a voltage below ground, which biases the grid of the output triode to a negative voltage."

Is this because the high negative voltage below Rg yields a positive voltage at the Cc-Rg-Rstop node which then gives you a negative bias at the second tube's grid because of Rstop?

This next bit I understand (and i like your thought process here, very logical):

"Weird, I agree..."

except does Cpf stand for parafeed capacitor?

And the last part is a little confusing to me, and I'm sure it's because I'm still getting my feet wet here:

"Another complication - every triode is slightly different due to
manufacturing variability. That's why cathode bias is used - the bias
depends on the triode's current in a way that stabilizes the operating
point for that particular triode through negative feedback. The feedback
only operates at DC and frequencies below audibility. For this to work,
each triode needs its own feedback, so there must be dual independent power supplies."

I guess I understood "cathode bias" to be a certain voltage applied to the cathode, but it is grounded, so maybe my understanding is wrong. Also, I guess I'm just lost when you start talking about negative feedback. I think I need to learn more about how the tube operates to get it, but could you explain where in the circuit the feedback comes from?

As always, I really appreciate you taking the time to explain these things to me, it's been very helpful, thanks!


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  • RE: basic analysis of the S.E.X. amp - Anthony 06:56:18 09/30/09 (1)

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