MIMF

I have an acoustic guitar by LAG with was factory built with undersaddle piezo pickup and onboard preamp (fairly standard set up). Recently the pluggedg in sound has been difficult to use exhibiting the following symptoms:

1) A definite 'clacking' sound if the bridge is struck during strumming (this 'clack' is heard if the bridge or the soundboard is struck between the bridge and tail but not if the soundboard is struck on the upper bouts or waist areas which induces a pleasant low boom)

2) A tendency to break up with harder strumming

3) A tendency to feedback low frequencies at relatively low volume settings.

A visual inspection suggests no obvious damage to the pick up or connecting wires and my limited ability to inspect inside the guitar suggests nothing obvious there either. Apart from a fault with the electrics my thoughts were that perhaps the bridge or a brace is loosening allowing more flexibility in the top which might explain the feedback as well as the 'clacking' sound. My suspicion is increased by the fact that the clacking is more pronounced with the instrument is tuned up to concert pitch than when strings are off the guitar.

How likely is it that this problem stems from the fabric of the guitar rather than the electrics? How might I go about testing this before I spend on new electrics to find that the problem remains.

Further information - the bridge is a pinless design which in addition to glue (I hope they used glue!) is secured by two thin bolts with nuts through the bridge plate. I have tightened these to the full extent thinking this might help.

Thank you for any guidance you might give.

Rob

Do you hear the "Clack" acoustically (AKA not plugged in) ??

As Chuck said, eliminate all of the chances that it is something that happens even if the guitar is not plugged in before looking anywhere else.
If it does it only when plugged in, which I think will be the case- this sounds like it is not a problem with a loose brace or anything else with the guitar itself- then it is probably a bad fit with the pickup in the saddle slot. The slot must be dead flat, and the bottom of the saddle dead flat too so that it gives a solid and equal pressure on the pickup. this is the most important thing when messing with the piezo pickups, can't stress that enough.

Great replies guys. Chuck: no acoustic clacking only plugged in.

Confession time: I did attempt to lower the saddle by sanding the bottom of it with fine grit paper on a polished marble slab. I thought it was pretty flat but perhaps not. Any tips on getting this right?

I use a quality straight-edge and hold the saddle against it with a light behind it and this will show if there is any problem with the bottom of the saddle. It doesn't take much deviation at all to create a problem. Also look for any debris in the saddle slot or under the pickup itself.

If I spot a problem what's the best way to actually flatten the saddle. I was using fine paper on a marble slab. Assuming the marble slab is flat(!) should this be sufficient? How do you guy's avoid rocking on either axis when you sand?

Working on a flat surface should be sufficient as long as you check the flatness of the saddle against a known flat/straight edge or surface. The rest is practice.

Flat along the length is the primary concern. A little unintended rocking sideways doesn't seem to create problems. I'll typically use a belt sander for saddles but the heat generated can cause saddle material to soften and flex so you need to be aware of the potential to get a warp in the base. If I'm having problems, I'll resort to using fresh 220 grit sandpaper on a known flat surface and do gentle passes to avoid distortions from downward pressure. Bone is more brittle and less prone to distortions from heat and I think I can get a consistently flatter result. For anything other than bone, I'll always do a few passes along the 90 degree edge with a single edge trazor blade to eliminate any burr.

Getting the inside of the saddle slot clean needs to be on the to-do list. There can be flaws on the floor of the slot so inspect it closely. Piezo elements can also be defective and especially those than have a fragile plastic lamination or seal. I've had good luck with getting replacement elements from ebay on the cheap (sometimes under $2 an element). A cheap $2 element is better than an expensive one that is damaged so I've bought them in bulk to always have a selection on hand.

What I have done is get a nice square small block of wood. Set it on top of a shim that is the desired thickness(how much you want to lower the saddle) Stick the saddle to it with tape or something, belt sander on, Bubinga!!!, done and it stays square.