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previous: bobCT I am about to start collecting the ... -- 7/13/1999 1:46 PM

Re: Dumble Build - Any schematic errors?

7/13/1999 2:55 PM
Jim S.	Re: Dumble Build - Any schematic errors? I too am planning to build this circuit soon. Looking at the circuit and component values, 22M sounds like a reasonable value for the feedback resistor on the 2nd gain stage. Assuming the jazz/rock switch is in the "rock" position and taking into account the 1M volume control and the 220K grid resistor between its wiper and the 2nd stage grid, I see that the resistance to ground from the bottom of the 22M resistor varies between 220K (min. volume) and 1220K (max. volume). Doing some basic voltage-divider calculations tells me that the signal level at the junction of the 22M and 220K resistors will vary between 1% to 5% of the signal coming off the .05u cap. Actually, this seems to me like a significant amount of negative feedback. Or am I missing something here?

7/13/1999 2:55 PM

Jim S.

Re: Dumble Build - Any schematic errors?

I too am planning to build this circuit soon.

Looking at the circuit and component values, 22M sounds like a reasonable value for the feedback resistor on the 2nd gain stage. Assuming the jazz/rock switch is in the "rock" position and taking into account the 1M volume control and the 220K grid resistor between its wiper and the 2nd stage grid, I see that the resistance to ground from the bottom of the 22M resistor varies between 220K (min. volume) and 1220K (max. volume). Doing some basic voltage-divider calculations tells me that the signal level at the junction of the 22M and 220K resistors will vary between 1% to 5% of the signal coming off the .05u cap. Actually, this seems to me like a significant amount of negative feedback. Or am I missing something here?