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Removing an under saddle transducer

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Removing an under saddle transducer

Postby Jay Menon » Sat Jan 11, 2014 1:37 pm

I wish to uninstall my Fishman under saddle transducer on my acoustic guitar.

This will obviously cause the saddle height to drop, and will require a shim.

How thick will the shim need to be? And what material should I use - paper?

Expert opinions most appreciated
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Re: Removing an under saddle transducer

Postby Kwackman » Sat Jan 11, 2014 1:47 pm

I'm no expert, but a new saddle of the correct height would be the best solution IMHO.
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Re: Removing an under saddle transducer

Postby zenguitar » Sat Jan 11, 2014 3:23 pm

Kwackman is right, the best option is ALWAYS a replacement saddle. My preference would be a nice piece of bone or fossil ivory if I can lay my hands on it affordably.

Next option would be to build up the existing saddle with a strip of bone or hard wood glued to the bottom. The extension should be the same thickness as the transducer you removed. You need to ensure the bottom of the saddle is perfectly flat (which it should be anyway) and glue the spacer on with epoxy or superglue. Once the glue has fully dried (that's at least 24 hours, even with superglue) you can shave/sand/file the spacer back to the same shape as the saddle itself. When you refit the saddle just make sure that the new base is perfectly flat again and it drops in with just the tiniest hint of friction (it shouldn't fall out but should not require force to pull out).

Final option is to make a separate shim to sit in the bottom of the saddle slot. However, paper is NEVER an option. Very stiff card will do at a push. But the best things are hardwood veneers, hard plastic strip (old bank cards/store cards/gift cards/iTunes cards can work well), metal sheet, bone veneers. The shim should fit cleanly in the bridge slot in the same way as the saddle and fractionally loose fit is better than a tight fit.

But a replacement bone saddle is by far the best, and if you aren't confident making and fitting one it should not be expensive to get a decent tech to do the job for you.

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Re: Removing an under saddle transducer

Postby Jay Menon » Sat Jan 11, 2014 11:35 pm

What you say makes sense...

However, there is currently a shim under the saddle, in the form of the under saddle transducer itself. The presence of the UST isn't noticeably compromising the tone, so why would another shim that substitutes for the UST make a negative difference?
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Re: Removing an under saddle transducer

Postby zenguitar » Sun Jan 12, 2014 2:09 am

JM-1 wrote:What you say makes sense...

However, there is currently a shim under the saddle, in the form of the under saddle transducer itself. The presence of the UST isn't noticeably compromising the tone, so why would another shim that substitutes for the UST make a negative difference?

Fair comment, and as such deserves answers.

The first point is that '... isn't noticeably compromising the tone' isn't the same as 'isn't compromising the tone'.

A well designed and manufactured saddle transducer is actually quite solid once installed. Piezo crystals respond to changes in pressure, so in a saddle transducer they are generally embedded in something like hard rubber. That hard rubber, once installed and under the downward pressure from the saddle, has a similar performance to a solid shim. In absolute terms there is a slight compromise in acoustic performance, but it is negligible and needs that slight flex for the piezo crystals to work.

For a saddle to work optimally the bottom of the saddle slot should be perfectly flat and the bottom of the saddle should be perfectly flat. So that the two surfaces mate perfectly. Of course, in the real world nothing is quite that perfect. So the inherent problem with any shim is that you have two sets of mating surfaces, neither of which are quite perfect in the real world.

A replacement saddle, or a well fitted glued extension to a saddle, eliminates one of the imperfect pairs of mating surfaces. A shim can work equally as well but has a lot more potential problems to address to get it working properly mechanically. Because of the thickness of a shim it is hard to get top and bottom both perfectly flat and parallel, it flexes when you try to sand it. So you tend to go for sheet material that is perfectly flat on both sides and parallel, which is usually thicker than required and results in you having to do extra work on the saddle to bring the action down to the right height.

So, shims are fine when you need to raise the saddle by a few 10ths of a millimetre, it is usually easy to source suitable material for that, but when you need a couple of millimetres it starts to require more work. And at that point it is no more work to make a replacement bone saddle which will eliminate a whole host of potential problems.

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Re: Removing an under saddle transducer

Postby Jay Menon » Sun Jan 12, 2014 1:55 pm

Thanks Andy.

Finally, would you tell me please - is bone, subject as it is to osteoporosis and a host of other biological factors (including being force fed with hormones), truly superior to a material such as TUSQ which can be standardised to a uniform density/consistency?
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Re: Removing an under saddle transducer

Postby zenguitar » Sun Jan 12, 2014 5:16 pm

I would put it the other way around JM_1

Tusq is indeed very consistent but it is no better than a good piece of bone from a reputable supplier. It is a lot more expensive, and it is not so easy to work as bone.

Of course, bones can be inconsistent with softer areas, but the cut bone blanks you buy are selected from material of the right grade and quality. And while Tusq(TM) has a massive marketing budget (funded by the high price - which extends to doing deals with guitar manufacturers to offer Tusq nuts and saddles to add to the perceived value of both brands), good old fashioned bone isn't a business's propriety solution so doesn't get nice large adverts in the guitar press.

Where Tusq has an advantage is not as an alternative to bone but as an alternative to ivory, which as the name suggests is what it was designed to be. Real ivory is illegal unless you have legitimate old stocks, and even then it can make it technically illegal to carry the guitar across international borders. The legal alternative is fossil ivory which is more expensive than Tusq.

And the difference between bone and ivory is very subtle, on a par with the difference due to a rosewood or ebony fretboard.

Bone, ivory, mother or pearl, abalone, carbon fibre, Tusq, fossil ivory and other materials are all perfectly acceptable for nuts and saddles. What matters most (and makes the largest material difference) is how well they made and fitted.

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