What are the pros/cons of starting out a pi filter chain with an RC stage as opposed to a C stage? Right after the rectifier stage. Would you do this simply to obtain some needed/desired voltage drop? Is the waveform pre-conditioned in any way like an LC or otherwise? Would you do it because it makes things easier on the diodes and first capacitor? What is the difference in how the whole filter is operating, if any? Drop, regulation, conduction angle, inrush, ripple, shape, etc...
You'd do it for voltage drop - has little effect on filtering, slight reduction in ripple current in the first capacitor, slight increase in conduction angle and power factor. Using a transformer with the correct voltage will give you better regulation.
Main issue is that the math is hard - voltage drop is considerably more than the DC current would indicate, due to the complex peaked waveform, and dissipation is likewise higher than you might expect. No big deal if you simulate it in SPICE or PSUD - use RMS current to calculate dissipation.
Main issue is that the math is hard - voltage drop is considerably more than the DC current would indicate, due to the complex peaked waveform, and dissipation is likewise higher than you might expect. No big deal if you simulate it in SPICE or PSUD - use RMS current to calculate dissipation.
Thanks! That answers it, best to adjust the desired final voltage drop using the subsequent RC stages where those resistors are already present.
If you are using a vacuum tube rectifier there will be a peak plate current spec which is often translated into a minimum transformer DCR in the tube manual. Often modern cost reduced (less wire and iron) transformers are used to build an old vacuum tube design. These transformers have a lower DCR than what the schematic designer had available so a resistor must be added between each rectifier plate and the transformer, in series with the transformer CT or between the rectifier cathode and the first cap.
The TSE and TSE-II adds a 270 ohm resistor between the SS diodes and the first filter cap to reduce the peak current through the diodes. This is done to prevent the current spike from propagating through the transformer into the audio, though I never determined the exact mechanism of this action. That 270 ohm resistor sees very short, but high current pulses and must be capable of eating them without failure. Oddly the only kind of resistor that failed was one specifically rated for that purpose.
The TSE and TSE-II adds a 270 ohm resistor between the SS diodes and the first filter cap to reduce the peak current through the diodes. This is done to prevent the current spike from propagating through the transformer into the audio, though I never determined the exact mechanism of this action. That 270 ohm resistor sees very short, but high current pulses and must be capable of eating them without failure. Oddly the only kind of resistor that failed was one specifically rated for that purpose.