Stupid cap question...

[Bogie]

When modding/adding power supply caps, can one use multiples to replace singles? For instance, replacing a pair of 10,000 µf caps with a dozen 2,000 µf caps? I've got a friend who has some, and hey, I've got some old amps that could probably use a bit more capacity...

 

[edl]

Yeah, you can do it, the overall result will be even better (paralell caps > lower equivalent serial resistance).
But be aware of old caps! How old are them? What brand?

Regards,

On the margin it's not a that stupid question...

 

[mrshow4u]

The short answer is yes. You'll need more room. Things get less ideal. There's additional resistance and more inductance in using the longer leads, but probably not too much of a problem.

 

[Bogie]

They're made by Nippon-Chemicon...

 

[Leolabs]

They're made by Nippon-Chemicon...

Great.Good caps.

 

[Bogie]

Okay... They're new appearing 25 volt dealies... Now, if I understand correctly, I can get 75 volts by making a series of 3, which gives me a 700ish mike unit... Then I take umpty units per side, and parallel 'em? Seems like fairly easy wiring, but could be bulky... Definitely gonna have to move some transformers...

 

[mrshow4u]

Okay... They're new appearing 25 volt dealies... Now, if I understand correctly, I can get 75 volts by making a series of 3,

Ahhh, so they'll be in series?? I'd recommend wiring a high value resistor (1Meg) across each cap. This will create a dominant leakage path down the resistor chain, setting a up a voltage divider which will ensure that each cap gets a third of the voltage dropped across it.

 

[quasi]

Okay... They're new appearing 25 volt dealies... Now, if I understand correctly, I can get 75 volts by making a series of 3, which gives me a 700ish mike unit... Then I take umpty units per side, and parallel 'em? Seems like fairly easy wiring, but could be bulky... Definitely gonna have to move some transformers...

Using series capacitors whilst can be done as suggested by Mrshow4u is not an ideal solution. The ESR will effectively be tripled and the effective capacitance reduced. Also the inductance will increase 3 times.

In your case 3 x 2000uF caps in series will give you an effective capacitance of only 667 uF. So your dozen caps (4 banks of 3) will only give you about 2,670uF.

The only way to use multiple caps in audio is in parallel and then you do achieve the benefits mentioned earlier.

Cheers
Quasi

 

[AndrewT]

Hi,
I have a commercial amp (German) which uses multi parallel smoothing caps.

They have 32 2.2mF 50V giving +-35.2mF.

The only designs errors are using 50V caps on a +-51Vdc power supply and sharing this cap bank between both channels.
Sounds not too bad as well.