OIP caps

[Robert1950]

I was looking at OIP caps at various sites. I know what the different uf values do, but noticed other different values: 100v to 630v. What effect does this have? Which is right for a tone cap? (.047uf/100v? .047uf/400v?)

[Wheeman]

I may be way off base, but I think the voltage value is the maximum amount of voltage that can be safely passed though the component. Lower values should be fine (100V is still probably over kill for a tone control).

[drift_boat]

The voltage rating has probably more to do (practically) with how thick the wire coming out of each end of the cap is for soldering onto your pots. Generally under 300v would be fairly thin. People seem to stick with 400-600v for guitar cap applications.

From what I recall of reading threads at the Les Paul forum, the voltage rating has little to do with performance and tone..someone can correct me if I am wrong here.

For a humbucker, .022mf caps are preferable....some use a .015mf cap in the neck (to get a brighter tone) and a .022 in the bridge.

Single coil pickups usually call for .047mf caps.

[LowWatt]

Also, voltage affects the size of the cap. Usually I end up with 400v caps because that seems to be the standard (the wire point earlier sounds right for why this is). When you go bigger, often the cap will be too big to fit in a tight control cavity, like the one in my SG.

[dwagar]

voltage makes no difference for a guitar cap, other than sheer size of the cap as mentioned above.

[greco]

voltage makes no difference for a guitar cap, other than sheer size of the cap as mentioned above.

+1

As for the values of the caps, this topic has been discussed on the Seymour Duncan forum to the point of exhaustion.

In the end, most folks seem to go with what they feel sounds the best. The range used is from .010 to .047 with all sorts of values in between both for neck & bridge, humbucker & single coils.

Peace

Dave

[mhammer]

Some people swear they can hear the difference between so-called "bumble-bee" caps and other types. Me, I've never heard it.

As for voltage rating, very few, if any, pickups will ever put out a signal greater than 1V, so the odds of requiring a cap with a rating of even 10 volts is slim. Whatever voltage ratings are associated with OIP caps stem from the ratings they come in rather than any rating one needs. That is, if you can't even get one with a voltage rating lower than 100v, then people will say "get one with a 100v rating" to imply you don't need more than that, and people will eventually come to think you need a 100v rating.

I suppose if you use a low-value tone pot, then perhaps the type of cap may make a difference since they will vary in leakage. If the pot itself provides insufficient resistance to preclude leakage, then I suppose the leakage properties of the cap start to matter more....at least when the tone pot is turned up to full treble. Obviously when a tone pot is turned down to something like 50k resistance, it doesn't really matter what you started out with.If your tone pot is turned up full and you have, say, 500k between the volume pot input and the tone cap, I can't see why cap type should make a difference.

I've had a personal crusade going on for years to change attitudes about tone cap values. Specifically, to make the value used reflect the purpose of the pickup it is used for. I personally do not know anyone who would use their bridge pickup for a muted sound. Consequently, it makes no sense to use a tone cap value that could achieve that. It does make sense to have a higher value for the neck PU tone control, but not for the bridge PU. So, my recommendation is to use something around 1/2 to 1/3 the value of the neck cap for any bridge tone cap. If the neck value is .02uf, then consider .01uf or even .0068uf for the bridge pickup. That will let you use the bridge tone control to simply round things off a bit, while still leaving the squawk that you switched to the bridge pickup for largely intact.

If you have only one tone control, one trick I recommend is what I call a "bi-directional tone control". Here, one would use a 1M linear pot, with the wiper connected to the volume pot input lug. Soldered to one outside lug on the tone pot would be one cap value, and soldered to the other lug would be a different value (such as .02uf and .0068uf). Such a tone pot permits use of either of two rolloff points, with "flat" in the middle setting. If you can score a pot with a centre detente so that you can feel when you've hit flat instead of having to look for confirmation, even better.

One of the nifty perks of this arangement is that all the tonal change in either direction is squished into half the rotation that it normally is required to achieve that same amount of tonal change. This makes it a breeze to do "finger wah" by rotating the tone pot with your pinky, the same way you would do volume swells with your pinky on the volume pot.

[konasexone]

The capacitor is chosen based on the corner frequency you desire. The pot's resistance comes into play based on the formula fCorner= 1 / (2*3.14*Rpot*C).
The voltage of a guitar pickup is roughly 1Vrms so a cap with a voltage rating any higher is fine, 10 volts would be fine, any bigger a waste of space and money perhaps.