Help! Do I really want to use 250volt capacitors in a DS-1 mod? They're huge!

[Jonesey]

I've been checking out all of the mods available for the Boss DS-1 and the links listed on this forum.

One list shows Mouser part numbers with 250 volt caps which are huge compared to the caps on the original Boss  board.

Am I missing something?  I really wonder if these guys are gonna fit?

Thanks for your help!

[343 Salty Beans]

In most situations, the voltage of a cap doesn't matter. 250V is how many volts the capacitor is rated to take before it blows. So the voltage won't matter.



EDIT: as an added note, since DS-1s run off of 9V, you want a voltage rating on your caps that is greater than 9V. pad the number a little bit, so don't use 10V caps. 16V is the next step up in electrolytic caps, so pretty much use anything bigger than that. So you don't NEED to use 250V...it's an excessive rating, but it won't harm anything. Just don't use any caps below 9V or they will blow.

As a future note, it's the same with resistor wattage rating. 1/4 watts are best to use, simply due to size constraints on the board. But a 1/2watt, 1 watt, even 5watt resistors will still do the exact same thing.

[LyleCaldwell]

I've been checking out all of the mods available for the Boss DS-1 and the links listed on this forum.

One list shows Mouser part numbers with 250 volt caps which are huge compared to the caps on the original Boss  board.

Am I missing something?  I really wonder if these guys are gonna fit?

Thanks for your help!

I can't think of any reason a non-tube pedal would need any cap over 35v, and 16v is usually more than adequate.  Some values of caps only come in higher ratings, but if you can use a smaller rated cap of the same value, go for it.

[deadsnake]

In most situations, the voltage of a cap doesn't matter. 250V is how many volts the capacitor is rated to take before it blows.

I didn't know that...... I always learn something everyday.

[Amblis]

I actually had the same exact question as the original poster. Now that the question has been cleared up, where can you get a 35v metal cap? The only place I really know to look is radio shack and they only carry the 1.0 uf 250v metal film caps. Can you use say a dipped tantalum cap? They also carry electrolytic caps at Radio Shack but the schematics I am using call explicitly for metal film not electrolytic. What is the differnce between the two anyways?
Thanks!

[343 Salty Beans]

You can use the 250V metal film and it will work just as well as the 35V. Like I said, it's the voltage that the capacitor is rated at.

Let's compare this to baseball. Suppose you need to hit the ball 150 feet to get a home run. Instead, you you hit the ball 500 feet. You'll still get a home run, and only one point on the scoreboard, whether you hit the ball 150 feet or 500 feet.

Cap rating is the same way. For a 9V circuit, you only need a 10V (although 16V would give you a little more wiggle room) cap. But using a 250V rated cap will work just fine.

[Paul Perry (Frostwave)]

It's a mistake to buy from radio shack. Even with postage, it's usally cheaper to go with Small Bear electronics (the guitar DIY specialist) or Mouser.

[tiges_ tendres]

I actually had the same exact question as the original poster. Now that the question has been cleared up, where can you get a 35v metal cap? The only place I really know to look is radio shack and they only carry the 1.0 uf 250v metal film caps. Can you use say a dipped tantalum cap? They also carry electrolytic caps at Radio Shack but the schematics I am using call explicitly for metal film not electrolytic. What is the differnce between the two anyways?
Thanks!

electrolytic caps are polarized, meaning they have a plus and a minus side.  the metal film are non polar so you can insert them any way with no problems.  

[Jonesey]

OK I understand that a higher voltage rating isn't really a factor.  My real concern is getting the 250volt caps to fit on the board and then in the box.  Are lower voltage .1 UF and 1 UF Metal Film Caps difficult to find?

[tiges_ tendres]

OK I understand that a higher voltage rating isn't really a factor.  My real concern is getting the 250volt caps to fit on the board and then in the box.  Are lower voltage .1 UF and 1 UF Metal Film Caps difficult to find?

no, not too hard, you can find them at jameco, or mouser  or small bear!

[343 Salty Beans]

or, if you want to go cheap and are willing to wait 2 weeks, Futurlec 

If you replace a nonpolarized (ceramic, metal film, poly film, mylar, silver mica, etc.) cap with a polarized cap (aluminum electrolytic, tantalum), then you will need to make sure that the + side of the polarized cap is connected to the connection point with the larger voltage. Use your multimeter to figure this one out.

To replace a polarized cap with a non-polarized cap is no problem.

As an added bit of extra reading, here's RG Keen's explanation on cap types. Just for the heck of it.

http://www.diystompboxes.com/pedals/rgcaps.html

[gulliver]

OK I understand that a higher voltage rating isn't really a factor.  My real concern is getting the 250volt caps to fit on the board and then in the box.  Are lower voltage .1 UF and 1 UF Metal Film Caps difficult to find?

The big caps fit no problem, just keep an eye on what's under them once the board is in place. Sometimes, it's better not to push them all the way to the board, as it eliminates any wiggle room.

Because they're bigger, they must be better ... those are the rules (for non-digital electronics).

[mac]

Imagine two metal square plates of area A separated by a small distance d with each plate connected to one side of a battery. The voltage difference between the plates is V, the battery voltage. Because electrons have a negative charge they flow to the +V side of the cap, so this side has a charge -Q and the other side +Q.
Capacity C is defined as Q/V, Q: the charge of any of the plates and V: the voltage difference between the plates. Looking the capacitor as a whole it has a neutral charge.
After some math one may calculate that for this example capacity is C = (eo*A)/d, eo: a constant. You may notice that C depends only on the geometry of the capacitor. This is also true for an inductor.

When you see that a capacitor has been rated 50V, it means that this is the maximun voltage that you can apply to the cap before it becomes a popcorn. For a DS-1 running at 9v a +16v rated cap is fine. A 250v does the same job

But... calling some elect eng.

I don't know exactly how a cap is made. As far as I read some electros are made of two thin Al plates separated by a thin dielectric material  instead of air. I was thinking that maybe a 1uf 25v cap and a 1uf 250v cap may have different dielectrics or the same dielectric with different thickness. I wonder if this differences may introduce some mojo...

mac

[Jonesey]

Follow up - I just got my order from DigiKey and the 50 v caps fit and look a whole lot better than those hugh 250 v caps.

[calpolyengineer]

To answer your question mac, the dielectric that is used is most often the name of the capacitor. Electrolytic caps use an electrolyte that forms an extremely thin dielectric. Mica caps use a thin piece of mica (a very soft, sheet like mineral) as the dielectric. Etc, etc.

-Joe

[gulliver]

I was using this from mouser (8mm x 15.5mm x 18.5mm): 5989-250V1.0-F

But this is smaller and only 69 cents (7mm x 14mm x 12.5mm): 5989-100V1.0-F

They're Metallized Polyester Film. I believe the polyester is part of the RoHS (reduction of hazardous waste) compliance.

[mac]

To answer your question mac, the dielectric that is used is most often the name of the capacitor. Electrolytic caps use an electrolyte that forms an extremely thin dielectric. Mica caps use a thin piece of mica (a very soft, sheet like mineral) as the dielectric. Etc, etc.

-Joe

yes. but do different dielectrics, ie different caps, react in the same way when a guitar signal passes through them or not?
I guess that being the dielectric very thin only at very high freqs one could notice some big difference, due to charge redistribution  when an audio signal is applied to the cap.
anyway some people do hear noticeable variations among caps. when i tested my mxr+, the ceramic caps made it sound different than the polyester caps. but i am not certain that this difference was due to the caps or to tolerance variaions.

mac