I use a Kyser style capo. I don't know any better, but are there better capos? I'm looking for a durable capo that wont drastically put my guitar out of tune when I use it. What kind of capos won't detune my guitar?
I don't think your problem lies in the capo. Have you checked your intonation on your guitars? If you don't know how to do that, there are many good advice in this forum for how to setup a guitar. You can also take it to your luthier.
You should tune your guitar after you put on your capo, this way you minimize the errors in intonation. (It's good to quicktune before as well)...
I had a quick look at your capo and in the description it says it's for thin necks, So if you have a very thick neck on your acoustic it might be that the spring is not enough.
Also if you have had your capo for long then the spring is probably too loose. Capos need to be replaced every now and then.
I use a very basic Dunlop capo and don't have any problems (I use it on both acoustics and electrics)
Don't leave your capo on after playing since this will wear out the spring as well.
Usually the reason a capo pulls your guitar out of tune is because it has too much force relative to the height of your frets. If you have super high frets, or jumbos, then you can test this by fretting a string, picking a note, and then alternating how much pressure you apply to the fretted note. You should hear the note bend in pitch slightly unless your frets are very low. There' also a chance that the capo isn't sitting on the neck correctly, which causes it to pull the strings to one side and consequently making them sharp. Here's a graphical representation of what's happening in both cases.
So to fix this with a Kyser style capo there are several alternatives. The first would be to purchase a capo that allows you to adjust how much force it has on the fretboard like this one by Kyser or this one by Schubb. The other alternative--and something I have been doing for years--is to wrap some rubber bands around the clamp handles of the capo. This will reduce the amount of force that the capo applies to the fretboard and consequently keep it from pulling your guitar out of tune.
Definitely check your intonation before you try anything else. However, it is possible to detune a guitar that has perfect intonation with a capo. My guitar has perfect intonation but the capo sharpens almost 20 hz to the tuning on my guitar, which is outrageous.
Try this, fret your guitar on the 12th fret of your 1st string, check the tuning there. It should be a perfect E if your guitar has decent intonation. Now, press onto the 12th fret as hard as you can, check the tuning again, and now it's sharp. You can try this test on other frets as well, say 7. Same thing happens.
Your capo is probably doing the same thing to your guitar, it's "fretting" your guitar too hard. So you need to somehow decrease the stiffness of the spring of your capo (I'm assuming you're using a normal capo).
To do that, you can try the rubber band method stated above. Or clamp your capo on something thick over night. That will force the spring into plastic yield. This sounds bad if you're a mechanical engineer, but that is exactly what we want. A spring that's not too stiff. After a night of stretching your capo, it should not be as stiff as before, which means the applied compressive force is lower. Your strings are now less stretched when capo'd. Keep loosen the capo with this method until it gets close to perfect.
However, if you go too much, there's no way of coming back. Note that you're stretching your spring plastically, so it's not gonna be restored to its original state. You'd have to buy a new capo.
Yes, the point about the Kyser design is that you can't adjust the amount of tension it applies.
The advantage of the Kyser design is that it's very quick to put it on or take it off with one hand, and its tension works pretty well for the average acoustic steel-string guitar.
A capo, like your fingers, should apply the minimal amount of pressure necessary to fret the strings, and no more, because too much pressure on all six strings can throw things out of tune.
Different guitar necks have different thicknesses overall, and any one neck will be thicker at one end than the other. Also, different players use different gauges of strings (heavy or light) and have their guitars set up for higher or lower action.
So optimally, you should be able to adjust the tension on your capo to suit your particular guitar neck, the part of the neck where you normally put the capo, and the type of strings you use and how high your action is.
With the Shubb design, you get less tension and better distribution of tension, but you need both hands to put it on or take it off, and it takes longer to get it into the proper position or move it.
There are some other designs on the market that attempt to provide "the best of both worlds".
The Planet Waves company sells a range of capos that incorporate different designs, all of which enable variable tension.