Phantom power and capacitor

[mkruger]

is using this cap normal?

my phatom power supply doesn't have one... should it? and why?

Another question - if i have a switch in series with my signal path and it pops when i turn it off and on, what would be the simplest way to cure this?

 

[CJ]

Are you sure your supply dosen't have one?
If you have a standard pi filter, you have that cap there.
It's not a bad idea to have a cap there just in case some garbage gets on your supply line downstream from the last filter cap. It's always better to squash noise at the source, wherever that is.

Use a bleeder on your phantom supply so that cap dosen't hold it's charge.
Keeps you from spiking your mics.

 

[mkruger]

can you explain to me a little more about bleeder resistors... I understand their purpose but im not sure what values I would need for resistance and wattage.... how is that calculated?

 

[CJ]

High voltage supplies (250-300 volts dc): 220k at 2 watts
Low voltage supplies: (12 to 48 vdc) 10 k at 2 watts
that will get you in the ballpark.
you want about 1 to 5 milliamps to flow through the bleeder, depending on the cap size.
power is current squared times the resistance.

the time required for the cap to discharge to 68.9957 or whatever the first time constant is:
resistance times capacitance in farads, so a 10k on a 1000 uf cap gives
10000 times .001 equals 10 seconds .
so a 30 volt supply will be at about 10 volts in ten seconds, and about 3 volts at twenty seconds.