Hence the golden rule: high Z bias supplies - with bias voltage derived from a HV winding thru a large resistor - should use small caps, typically 10µF; low Z supplies - with bias derived from a dedicated tap, winding or transformer thru a small resistor - can use larger caps, typically 100 µF.With 100K preceeding a 100uF cap in a simple 'Dumble-like" bias circuit with bias derived off a dedicated low VAC secondary winding, it would take about 47 seconds (5 RC time constants) for the cap to charge up to 99%. Fortunately, that resistance is typically 1 to 10K (the bias range resistor), and 99% charge typically occurs in roughly 0.5 - 5 seconds.
Bias Supply Filtering
Moderators: pompeiisneaks, Colossal
Re: Bias Supply Filtering
Re: Bias Supply Filtering
In future builds using this type bias circuit, I'm thinking of using 50uF up front, with another 8-10uF on the actual bias voltage feed.FYL wrote:Hence the golden rule: high Z bias supplies - with bias voltage derived from a HV winding thru a large resistor - should use small caps, typically 10µF; low Z supplies - with bias derived from a dedicated tap, winding or transformer thru a small resistor - can use larger caps, typically 100 µF.With 100K preceeding a 100uF cap in a simple 'Dumble-like" bias circuit with bias derived off a dedicated low VAC secondary winding, it would take about 47 seconds (5 RC time constants) for the cap to charge up to 99%. Fortunately, that resistance is typically 1 to 10K (the bias range resistor), and 99% charge typically occurs in roughly 0.5 - 5 seconds.
Re: Bias Supply Filtering
The largest cap will set the time constant. Using 50µF is OK with a low Z supply.In future builds using this type bias circuit, I'm thinking of using 50uF up front, with another 8-10uF on the actual bias voltage feed.