Author Topic: Question about buying capacitors  (Read 1229 times)

Lgmlgm76

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Question about buying capacitors
« on: November 29, 2022, 05:52:12 PM »
Quickish question. I've noticed that most of the mbp builds have a 16v minimum for caps but when buying these, for example, there will be a 47uF cap with 16v, 35v, 50v, 63v, 100v, up to 400v ratings.

-Does it matter which voltage I get as long as it's the minimum rating?
-Is there a range I should stay in, like is 400v super overkill?
-Should all caps be around the same voltage or can I mix and match depending on what's available?
-Also, is it good practice to get the cap that has the higher life expectancy? Usually they're around 2000-5000 hours, up to 10,000 hrs. I've noticed the higher voltage caps can have a higher life expectancy.

Thanks in advance. Too many options have confused this newb.

Aleph Null

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Re: Question about buying capacitors
« Reply #1 on: November 29, 2022, 06:15:20 PM »
As long as the cap meets the minimum voltage rating it should work (without burning up). Beyond that, the voltage rating shouldn't matter too much. The next most important thing is the lead spacing. Most PCBs assume a 5mm lead spacing for most caps. Not all capacitors have the same lead spacing. Box caps are all 5mm, but not all green mylar caps are. Green mylar caps will work, they're just harder to fit into the PCB sometimes as the lead spacing varies depending on the value.

Lgmlgm76

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Re: Question about buying capacitors
« Reply #2 on: November 29, 2022, 06:42:41 PM »
As long as the cap meets the minimum voltage rating it should work (without burning up). Beyond that, the voltage rating shouldn't matter too much. The next most important thing is the lead spacing. Most PCBs assume a 5mm lead spacing for most caps. Not all capacitors have the same lead spacing. Box caps are all 5mm, but not all green mylar caps are. Green mylar caps will work, they're just harder to fit into the PCB sometimes as the lead spacing varies depending on the value.

Awesome thank you. Regarding the green mylar caps, would you use those in place of box caps? Is there a difference in sound? I've only used ceramic, box, and electrolytic caps.

madbean

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Re: Question about buying capacitors
« Reply #3 on: November 29, 2022, 07:01:18 PM »
As long as the cap meets the minimum voltage rating it should work (without burning up). Beyond that, the voltage rating shouldn't matter too much. The next most important thing is the lead spacing. Most PCBs assume a 5mm lead spacing for most caps. Not all capacitors have the same lead spacing. Box caps are all 5mm, but not all green mylar caps are. Green mylar caps will work, they're just harder to fit into the PCB sometimes as the lead spacing varies depending on the value.

Awesome thank you. Regarding the green mylar caps, would you use those in place of box caps? Is there a difference in sound? I've only used ceramic, box, and electrolytic caps.

Green mylar can get fairly large when the value goes up. Really no reason to use them over box caps, IMO.

As far as electrolytic caps, for values 47uF and lower [edit] the 16v-50v are usually the same physical size and lead spacing. When you get into 100uF and above, a 35v cap is going to be larger in size and have a larger lead spacing than a 25v. For for 220uF and up I recommend sticking the minimum voltage rating required by a build.
« Last Edit: November 29, 2022, 07:43:06 PM by madbean »

Bio77

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Re: Question about buying capacitors
« Reply #4 on: November 29, 2022, 07:13:21 PM »
For 47u, 100u, which are electrolytic, I'd recommend choosing 25V, 35V, maybe 50V.  Not a a rule, but in general larger voltage caps are much bigger (footprint size). They may not fit comfortably on the PCB.  Not really a problem for box film caps, they are usually rated for much higher voltages and are mostly similar in size, but you will see higher voltages (~250V) cost more.  You do have to be careful with them when they approach 1uF, those can get too big for boards sometimes above the 50V rating.   

Sound differences are rare with caps but I do see it mentioned from time to time.  I think tolerance will make more of a difference.  A cap meter can help with that.

Lgmlgm76

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Re: Question about buying capacitors
« Reply #5 on: November 29, 2022, 07:58:38 PM »
As long as the cap meets the minimum voltage rating it should work (without burning up). Beyond that, the voltage rating shouldn't matter too much. The next most important thing is the lead spacing. Most PCBs assume a 5mm lead spacing for most caps. Not all capacitors have the same lead spacing. Box caps are all 5mm, but not all green mylar caps are. Green mylar caps will work, they're just harder to fit into the PCB sometimes as the lead spacing varies depending on the value.

Awesome thank you. Regarding the green mylar caps, would you use those in place of box caps? Is there a difference in sound? I've only used ceramic, box, and electrolytic caps.

Green mylar can get fairly large when the value goes up. Really no reason to use them over box caps, IMO.

As far as electrolytic caps, for values 47uF and lower [edit] the 16v-50v are usually the same physical size and lead spacing. When you get into 100uF and above, a 35v cap is going to be larger in size and have a larger lead spacing than a 25v. For for 220uF and up I recommend sticking the minimum voltage rating required by a build.

For 47u, 100u, which are electrolytic, I'd recommend choosing 25V, 35V, maybe 50V.  Not a a rule, but in general larger voltage caps are much bigger (footprint size). They may not fit comfortably on the PCB.  Not really a problem for box film caps, they are usually rated for much higher voltages and are mostly similar in size, but you will see higher voltages (~250V) cost more.  You do have to be careful with them when they approach 1uF, those can get too big for boards sometimes above the 50V rating.   

Sound differences are rare with caps but I do see it mentioned from time to time.  I think tolerance will make more of a difference.  A cap meter can help with that.


Thanks fellas, that clears a lot up. Much appreciated!