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10-11-2019, 11:50 PM
Hi liquidair
The 68k in the bias reg is the culprit as it sets the ratio of raw bias voltage to the bias-set network. We generally never use more than 56k, with 47k being the lowest noise point and quite useful, although 51k is a bit better for large-bottle tubes.
The 100k on the output of the bias reg is of no concern and is included in our kits.
Regarding using DC Power Scaling of the Super Budget style: It is good to have 330k-1W off each mosfet source to ground. This provides a tether that helps keep the mosfets stable.
The bias adjust range at minimum Power Scale setting is also of no concern except that in your case the whole tracking proportion was off. The output stage is biased at full voltage and then left alone for the Power Scale circuit to do what it's designed to do.
Note that were you using different tubes, some luw-mu triode or other, then a bias reg feeback resistor of 68k or higher could be appropriate. For example, 6080 et al are mu=2 and need typically -120V of grid control to keep from melting down. Even that sets a reasonably warm condition for the plate.
The 68k in the bias reg is the culprit as it sets the ratio of raw bias voltage to the bias-set network. We generally never use more than 56k, with 47k being the lowest noise point and quite useful, although 51k is a bit better for large-bottle tubes.
The 100k on the output of the bias reg is of no concern and is included in our kits.
Regarding using DC Power Scaling of the Super Budget style: It is good to have 330k-1W off each mosfet source to ground. This provides a tether that helps keep the mosfets stable.
The bias adjust range at minimum Power Scale setting is also of no concern except that in your case the whole tracking proportion was off. The output stage is biased at full voltage and then left alone for the Power Scale circuit to do what it's designed to do.
Note that were you using different tubes, some luw-mu triode or other, then a bias reg feeback resistor of 68k or higher could be appropriate. For example, 6080 et al are mu=2 and need typically -120V of grid control to keep from melting down. Even that sets a reasonably warm condition for the plate.
