Saddle Shim Question

[AcousticFPicker]

Hi guys,
I have a quick question about adding a shim on an electro acoustic guitar. I recently added a shim to raise the saddle a tad and put it underneath the pick up rather directly under the saddle. The chap in the guitar shop advised me to do it this way.
After playing it through a PA System, one which I play through weekly, I was told the output of my guitar was really really low. Lower than it had ever been.
Before I start messing around with the shim again, my question is, is that because I put it underneath the pick up? Should I place it directly under the saddle? does that make a difference at all and does the problem of low output lie elsewhere?

Okay that's more than one question

Any help would be greatly appreciated! Oh, and yes it is a fresh battery

Thanks!

- Chris

[charles Tauber]

Under-the-saddle (Piezo) pickups can be very temperamental. The output is proportional to the amount the thickness of the element is squeezed. If the saddle is too tight in its slot so that it inhibits the change in pressure being transferred from the saddle too the pickup element, that can reduce output.

Another common problem is that the pressure on the element varies from one string to another. This is usually due to one or more of the surfaces between the bottom of the saddle and the bottom surface of the slot not mating well. The surfaces could be the bottom of the slot, the surfaces of the shim, or the bottom of the saddle. Adding a shim adds two additional surfaces that have to match.

It seems obvious that if you plug it in to the same amp with and without the shim and there is a large difference in output, the shim, and how it's surfaces match its neighbouring surfaces, is the problem.

[Fanatic]

What about a new saddle? a shim is just for an emergency, just sayin.

[AcousticFPicker]

I was just going to say, after reading what Charles has said, the best thing then would be to put in a new saddle.
I have another saddle but I am not sure I can put it in my self. It's just a blank piece of bone that needs shaping to the curve of the neck.

So as a quick solution, for now, it would make no difference putting shim on top of the pick up as opposed to below?

[John Arnold]

I don't think under/over the pickup would make a difference. But the shim material will make a difference.
In my expereince, the best way to shim saddles (either with or without an UST) is to glue a rosewood or ebony shim on the bottom of the saddle with CA.

[LouieAtienza]

I'd agree with what John mentioned about using a rosewood shim. It's entirely possible, if you use a piece of soft wood, you can get grain that goes from hard to soft to hard to soft and that can affect the output as well. I'd make sure your current saddle is a slip-fit, meaning it requires almost no force to put in and out without being sloppy. Also you can check if your saddle slot is truly flat as well as your shim.