Choke loaded power supply

[TUBEDUDE]

The 6DQ5 is a tough tube. I have a silicon allergy so i'll have to rely on the 800V inductor and the 1000V cap ladder to hold out. If anything, the 630V metalized poly caps paralleling them will start arcing. That's my defect detector.

[Roe]

That sounds low to me. 300V÷ 150 mA = 2H?

Ok, so 500v/167ma = 3h and 500v/25ma = 20h

[TUBEDUDE]

And possibly twice those values as optimum, if Landee, as Tony Bones mentioned, is correct.

[Astronomicum]

The whole trick with inductive input filters is then to make sure that the load stays high enough (or the inductor/capacitor are sized correctly) to keep the output load current above the critical loading current for that inductor and cap.

It will take some calculation to ensure that the choke you have is run under the correct conditions for a choke input filter and give the desired output voltage and ripple reduction.

Where can I find the information and formulas to do the calculations to determine the "critical loading current"?

Thanks.

[Roe]

The whole trick with inductive input filters is then to make sure that the load stays high enough (or the inductor/capacitor are sized correctly) to keep the output load current above the critical loading current for that inductor and cap.

It will take some calculation to ensure that the choke you have is run under the correct conditions for a choke input filter and give the desired output voltage and ripple reduction.

Where can I find the information and formulas to do the calculations to determine the "critical loading current"?

Thanks.

https://ampgarage.com/forum/viewtopic.p ... 2&p=109098
https://www.diyaudio.com/community/thre ... er.385661/
https://www.turneraudio.com.au/audiofilterchokes.html
https://www.diyaudio.com/community/thre ... er.365295/

[Roe]

The whole trick with inductive input filters is then to make sure that the load stays high enough (or the inductor/capacitor are sized correctly) to keep the output load current above the critical loading current for that inductor and cap.It will take some calculation to ensure that the choke you have is run under the correct conditions for a choke input filter and give the desired output voltage and ripple reduction.

Where can I find the information and formulas to do the calculations to determine the "critical loading current"?

I did calculations, but the empirical test require less current than the calculations. A zobel network helped greatly. 3h choke 110ohms, with 100R and .1uf in paralell

[Astronomicum]

The whole trick with inductive input filters is then to make sure that the load stays high enough (or the inductor/capacitor are sized correctly) to keep the output load current above the critical loading current for that inductor and cap.

It will take some calculation to ensure that the choke you have is run under the correct conditions for a choke input filter and give the desired output voltage and ripple reduction.

Where can I find the information and formulas to do the calculations to determine the "critical loading current"?

Thanks.

https://ampgarage.com/forum/viewtopic.p ... 2&p=109098
https://www.diyaudio.com/community/thre ... er.385661/
https://www.turneraudio.com.au/audiofilterchokes.html
https://www.diyaudio.com/community/thre ... er.365295/

Thanks.

[R.G.]

I did calculations, but the empirical test require less current than the calculations.

This is likely because real inductors have higher inductances at low flux densities. Some inductors that were designed for inductor input applications had special core and winding techniques to make this much more pronounced just to lower the minimum load current. Just as in most other electronics, knowing the imperfections can let you use them to your advantage.

The screaming, crying case for not using inductor-input filters is the wild voltage change from low currents, where it acts like a capacitor input filter, to the critical current, where the inductor action forces the rectifiers to conduct for full half cycles; past that critical point, the voltage doesn't drop radically like it does during the changeover from effectively capacitor input to loaded inductive. The minimum loading criteria often required load resistors to keep that minimum current going.

[Roe]

I did calculations, but the empirical test require less current than the calculations.

This is likely because real inductors have higher inductances at low flux densities. Some inductors that were designed for inductor input applications had special core and winding techniques to make this much more pronounced just to lower the minimum load current. Just as in most other electronics, knowing the imperfections can let you use them to your advantage.

The screaming, crying case for not using inductor-input filters is the wild voltage change from low currents, where it acts like a capacitor input filter, to the critical current, where the inductor action forces the rectifiers to conduct for full half cycles; past that critical point, the voltage doesn't drop radically like it does during the changeover from effectively capacitor input to loaded inductive. The minimum loading criteria often required load resistors to keep that minimum current going.

Yes but in this case the minimum current was relatively modest. Without a Zobel network, it was ca 24ma, but the voltage already dropped greatly with 10-14ma, which works for a screen supply. With a Zobel network, the voltages dropped quicker.

[Roe]

I've started testing w. two kt88s at 4k 515v anode and Zobel network to get earlier screen sag.

It works very well. Amp keeps its basic tone and response. The attack is relatively fast yet dynamic. Tone has more harmonics than I can remember.

Max screen current per tube is 25ma at 305v, i.e. 7.6w peak.

[R.G.]

Kewl - and interesting. What value of filter cap after the inductor were you using?

[Roe]

Kewl - and interesting. What value of filter cap after the inductor were you using?

Only 16uf. And a .22uf before the inductor