NewYorkDave
Well-known member
For a designer, one nice thing about a forum like this is that even when you're capable of weighing your options and deciding on your own, it can be enlightening to present the choice to others and see which route they would choose.
I have a tube circuit that can be broken down into three major sections. The first requires approx. +130V regulated at 0 to 14mA. The second section needs +130 to +150V at 6mA and the third requires +130V to +150V at 18 to 20mA. (The B+ for sections 2 and 3 must be well-filtered, but not necessarily regulated). I intend to provide the regulated supply with a TL783. My raw DC input is about 175V, capable of up to 100mA.
My first inclination was to split the supply after the input filter and feed sections 2 and 3 off a simple R-C filter, and section one off the regulator. Since section 1's current draw varies, the voltage divider resistors on the 783 must be sized for a fairly large standing current (15mA, IIRC).
Then, it occurred to me, why waste that 15mA? If I fed the entire circuit off the regulated supply, there would always be ample current (24mA minimum) flowing from the 783's output pin to assure proper regulation--unless all the tubes were removed, of course. And one less filter cap would be needed. On the downside, the regulator would have to dissipate more heat at maximum load (40mA max vs. 14mA max).Sections 1 and 3 are push-pull, so along with the low output impedance of the power supply, cross-coupling through the supply seems pretty much a non-issue.
What do you think?
I have a tube circuit that can be broken down into three major sections. The first requires approx. +130V regulated at 0 to 14mA. The second section needs +130 to +150V at 6mA and the third requires +130V to +150V at 18 to 20mA. (The B+ for sections 2 and 3 must be well-filtered, but not necessarily regulated). I intend to provide the regulated supply with a TL783. My raw DC input is about 175V, capable of up to 100mA.
My first inclination was to split the supply after the input filter and feed sections 2 and 3 off a simple R-C filter, and section one off the regulator. Since section 1's current draw varies, the voltage divider resistors on the 783 must be sized for a fairly large standing current (15mA, IIRC).
Then, it occurred to me, why waste that 15mA? If I fed the entire circuit off the regulated supply, there would always be ample current (24mA minimum) flowing from the 783's output pin to assure proper regulation--unless all the tubes were removed, of course. And one less filter cap would be needed. On the downside, the regulator would have to dissipate more heat at maximum load (40mA max vs. 14mA max).Sections 1 and 3 are push-pull, so along with the low output impedance of the power supply, cross-coupling through the supply seems pretty much a non-issue.
What do you think?