We don't use the cap reactance for DC filtering/charging . Initially it is like a dead short 🙂 So without limiting resistors the current is much higher
True.
The reactance of the capacitor is not a constant, it is dependent on frequency.
So not many consider that, when analyzing the turn on impulse.
An impulse is not a frequency, it is many frequencies.
The start up.
In the real world, there is no zero ohms voltage source, and no zero ohms capacitor load to cause infinite current.
And, the wiring, and capacitor itself have parasitic inductance, not to mention the power mains, and the power transformer.
There is a shape, a rise time, and how that initial impulse charges the capacitor.
The initial charging of the capacitor causes a broad spectrum.
Now we get to the operating characteristics.
Even after the B+ has reached its final voltage, the capacitor is constantly charging and discharging.
But again, the spectrum of the charging impulse is very broad.
Any un-controlled ground loop here, might cause low frequency hum in the amplifier, but might also high frequency hash in the amplifier.
Capacitor input filters do that.
A Choke input filter does not cause a transient of such broad spectrum, we may be left with hum ground loop, but not the high frequency hash.
All generalizations have exceptions.
The reactance of the capacitor is not a constant, it is dependent on frequency.
So not many consider that, when analyzing the turn on impulse.
An impulse is not a frequency, it is many frequencies.
The start up.
In the real world, there is no zero ohms voltage source, and no zero ohms capacitor load to cause infinite current.
And, the wiring, and capacitor itself have parasitic inductance, not to mention the power mains, and the power transformer.
There is a shape, a rise time, and how that initial impulse charges the capacitor.
The initial charging of the capacitor causes a broad spectrum.
Now we get to the operating characteristics.
Even after the B+ has reached its final voltage, the capacitor is constantly charging and discharging.
But again, the spectrum of the charging impulse is very broad.
Any un-controlled ground loop here, might cause low frequency hum in the amplifier, but might also high frequency hash in the amplifier.
Capacitor input filters do that.
A Choke input filter does not cause a transient of such broad spectrum, we may be left with hum ground loop, but not the high frequency hash.
All generalizations have exceptions.
| There is any advantage in use the Half Wave diode 30 sec slow warm-up 6D22S instead the 5C8S? https://datasheetspdf.com/pdf-file/1039289/Svetlana/6D22S/1 SVETLANA TECHNICAL DATA 6D22S High Performance Half-Wave Rectifier T he SvetlanaTM 6D22S is a glass-envelope power diode for use as a half-wave B+ rectifier in high-quality audio amplifiers. Originally intended for colorTV damper-diode service, the 6D22S is similar to the 6DL3 except for base connections and some ratings. The 6D22S features very slow warmup (30 seconds typical), making it an excellent, rugged power-on delay device for audio amplifiers. Its warm-up time is longer than that of common rectifier tubes (such as the 5AR4/ GZ34), and it is lower in cost than electronic delay relays. |
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Most slow warm-up rectifiers have relatively massive filaments and massive cathodes.
That is what causes the slow warm-up.
Caution:
That also means that once the filament and cathode have reached final operating temperature, they have a slow cool-down.
Slow cool-down might be a liability if your power mains company briefly interrupts power, and then brings power on again.
That is called a Hot-Start.
At the 2nd power-up, the cathode is still Hot, and now there is No delay of B+.
2 steps forward, and 2 steps back.
Just saying.
That is what causes the slow warm-up.
Caution:
That also means that once the filament and cathode have reached final operating temperature, they have a slow cool-down.
Slow cool-down might be a liability if your power mains company briefly interrupts power, and then brings power on again.
That is called a Hot-Start.
At the 2nd power-up, the cathode is still Hot, and now there is No delay of B+.
2 steps forward, and 2 steps back.
Just saying.