Voltage rating on capacitors

[Erlend_G]

I'm gonna have to change all the electrolytics in my amp. What I'm unsure of, is the voltage rating on them, i.e "22uF 10V". Does this mean that the replacement cap needs to be the same voltage rating, or is it okay (or even better) if I use one rated for higher voltages?

 

[GoldenVulture]

Re: Voltage rating on capacitors

In most cases around the same voltage.EG:If it's a 10volt cap, a 16 volt should be alright;maybe a 25 volt;a 35 volt probably won't.Don't go under though.If you do they stand a good chance of frying themselves.

When it comes to high voltage [100 volt+] they also have temperature ratings[105C].High temp versions are best in Power Supplies and other HV applications.

For battery powered devices ,keeping them as close as possible to their original rating is best.A bigger voltage cap will draw more from your battery and maybe make the circuit " wonky" due to overdraw of power and uneven supply to other components.A lot of battery powered stuff is designed within fairly critical limits ,in regard to power draw.


:kabong:

 

[Erlend_G]

Re: Voltage rating on capacitors

Ok, thanks alot mate!

 

[GoldenVulture]

Re: Voltage rating on capacitors

PS: Don't get them round the wrong way[Polarity]They'll go bang!/pop! Even the low voltage ones .

 

[Fresh_Start]

Re: Voltage rating on capacitors

I don't know solid state amps at all, but in an all-tube amp you can replace a 25 volt cathode bypass cap with a 50 volt version no problem. Probably not a bad idea actually.

Increasing the value of an electrolytic can have unintended tonal consequences though, or worse. It's logical to think that if a 22uf cap is a good filter, a 50uf cap must be better. Might be in some amps, but randomly upping the filter cap values in a Tweed amp made it more bass-ey and did something to the touch response. Very important, each rectifier tube has a maximum first cap value IOW the cap between the rectifier and the rest of the power rail.

One last point on voltages - even if your power rail typically doesn't exceed 400 volts, the caps may need to be rated for 500v. Part of any initial start-up procedure is powering up without any tubes installed. No tubes, no current draw, significantly higher voltages all along the power rail.

Sorry for the overkill - I'm planning a new build and have filter caps on the brain this morning.

HTH

Chip

 

[GoldenVulture]

Re: Voltage rating on capacitors

a 50uf cap must be better

Where do you find a 50uf. cap?
The closest to that value that is available is 47uf.That's been the case for decades,unless you know of some custom ones @ 50uf



:kabong:

 

[Sporky McGuffin]

Re: Voltage rating on capacitors

Wouldn't a 50 mega-Farad cap be about the size of Finland?

 

[jeremy]

Re: Voltage rating on capacitors

nah, about the size of espoo

 

[Fresh_Start]

Re: Voltage rating on capacitors

Where do you find a 50uf. cap?
The closest to that value that is available is 47uf.That's been the case for decades,unless you know of some custom ones @ 50uf

:kabong:

The point was that bigger is not always better. : popworm:

How about this 50uf cap?

Or this cap can with two 50uf sections?

Besides, with +/- 20% specs there's no practical difference between "47uf" and "50uf".

Chip

 

[GoldenVulture]

Re: Voltage rating on capacitors

Besides, with +/- 20% specs there's no practical difference between "47uf" and "50uf".

Yes, agreed.


:kabong:

 

[GoldenVulture]

Re: Voltage rating on capacitors

How about this 50uf cap?

- http://www.tubesandmore.com/ -. [FONT=Arial, Helvetica, sans-serif][SIZE=+3]Antique Electronic Supply - :wizard:

[/SIZE][/FONT]

 

[GoldenVulture]

Re: Voltage rating on capacitors

Wouldn't a 50 mega-Farad cap be about the size of Finland

nah, about the size of espoo

Capacitor uF - nF - pF Conversion Chart When reading schematics, repairing radios and buying capacitors, you often must convert between uF, nF and pF.
Paper and electrolytic capacitors are usually expressed in terms of uF (microfarads). Short forms for micro farad include
uF, mfd, MFD, MF and UF. Mica capacitors are usually expressed in terms of pF (micromicrofarads) (picofarads).
Short forms for micromicrofarads include pF, mmfd, MMFD, MMF, uuF and PF. A pF is one-millionth of a uF. In
between a pF and a uF is a nF which is one-one thousands of a uF. Converting back and forth between uF, nF
and pF can be confusing with all those darn decimal points to worry about. Below is a uF - nF- pF conversion chart.
Just print a copy and tape it to your workbench....it will come in handy.

:kabong: