uneven piezo

[treguiers]

My acoustic guitar's piezo pup is uneven across the
six strings. I've established that the unevenness is in the
bridge itself and not the saddle.
Does anyone have any tips on evening out the
bottom of the saddle slot on the bridge of an
acoustic guitar?
Any nuggets of wisdom will be warmly welcomed.

[Yew]

My first question would be, Is it causing you a problem? If its not hindering your guitar playing, then why risk ruining a perfectly good instrument. Second, Would you want the action higher or lower, as you might be able to 'shim' the saddle, but if you want it lower then you will need to get more surgical. Also, If you can get a few photos that would be great

Regards, Yew

[4real]

Hey there Treguiers

I was not around when you and johnH et al developed the piezo/blender things, but embarking on the same, so a thank you in order right off the bat!

...

I also did an install on a pizo system and tested it for the first time on my prject...the brdige though was custom built, but I reffered to avoid pitfalls the "BIBLE"...

www.amazon.com/Guitar-Player-Repair-Guide-3rd/dp/0879309210



Guitar Player Repair Guide 3rd edition, dan erlewine

This is a bargain and absolutely a must have on everything...one can put aside the constant plugs for stew-mac tools and such, it has advice on everything for guitar maintenance, set up and repair

On piezo systems pp240-240 there is quite a bit of stuff...a lot depends on the type of bridge and piezo element you are using. Some are 'split' and work similar to an HB to reduce noise and often improve intonation.

When did this problem start to occur?

Generally though, it seems that a slight taper to the bridge saddle sides and that the saddle sits flat and even is important for getting the best out of each string.

If you installed it yourself, the bottom of the saddle slot with the piezo element in it must be routed 'flat' and account for perhaps a common bulge in the top and bridge under string pressure too. I imagine that failing the tools and jigs to route a fine slot accurately with a dremmel say, one might be able to gently fill the bottom of the slot with some light wood filler and improve things if this is the cause.

Basically, the piezos must have even pressure on them from the bridge saddle onto the bottom of the slot to get a proper response from the things. A none flat bottom is often the cause, which strings are effected can be something of a clue.

There are many tips, but DAn shows how to use a kind of turnbuckle prop (you could make one from wood) to keep the top 'flexed' as if under the pressure of the strings when the strings are off to get things 'flat' in the saddle, but the procedure is involved and could be tricky.

So, perhaps a little more info is required...I have the book handy when I know more about things perhaps.

...

Anyway, I read those posts and replicating some of what you guys worked out in my new project and it was a gold mine to find someone had gone there before and worked it out in advance...cheers...

[treguiers]

Hi
firstly 4real the blender was all JohnH. I'm a working musician with a little knowledge of electronics and some basic skills with a soldering iron. I would build whatever he said and test it at a gig. I had no creative input in the blender design.(I've just built on of his strat designs....the man is an absolute genius)

As for the problem with the piezo. Is it noticeably uneven? initially no. but once you become aware of it, it becomes amplified.
Its a good guitar so i don't want to go the route of routers and such.
The piezo itself is of the fishman variety(cylindrical with copper mesh/braid round the outside) as opposed to a martin thinline type of thing.

What I have been doing is using an old saddle in which i removed roughly a quarter of it's length. I then glue strips of very fine sandpaper(the same thickness as the saddle) to the underneath of the modified saddle and gently try sand out any small ripples in the floor of the saddle slot.
I believe this will eventually come good, but I was just wondering was there another less labourious, more accurate way of doing this. I am aware when it comes to what is essentially lutherie there often is no short cuts....but maybe in this case there is.

[4real]

gluing strips and trying to sand inside a small slot is going to be problematic.

My lateral thinking would go more towards using a 'plastic wood' to even out some unevenness in the slot as it is more like a putty and once could make an easy tiny scraper the size of the slot to smooth it in before it drys.

'plastic wood' is water-based and sands easily...in fact is soft enough that a 'scraper' should be enough I suspect and being a putty can go on pretty smooth anyway. You can also water it down and being water based I suspect easy to get out of their should that be required.

I've used the stuff for similar kinds of things at times with success.

Dan Erlewine though makes a good point. That a guitar top on an acoustic changes with all that string pressure and returns when they are off...so doing the slot without the conditions of the string on means that the slot might well end up curved under pressure no matter how flat it is relaxed.

I've no experience in doing this or know how great the effect is or on your guitar.

On my project I am using a more common hard 'thinline style'. I do though have a fishman like that in the parts boxes but have not used one and found it all a bit 'curious' and seemed not to be easy to get a good fit on something this flexible.

I imagine though, another strategy with such a pickup which is flexible is to modify the underside of the bridge saddle to better fit the slot shape rather than to try and alter the slot or risk the guitar in any way.

Following that thought, perhaps it might be possible to cut a saddle in divided sections, one for each string so that the pressure of each will be firmly on the piezo.

This is the way that ovations originally did thing and the kind of design I used in my archtop bridge...



You might see from this construction shot that each saddle sits on the piezo independently from the others...this avoids the kind of problems and other aspects that you describe...something along that principle could perhaps be devised by taking a blank saddle and cutting into sections that can vibrate independently from one another and apply it's own pressure on the piezo strip regardless of the slot under it.



(there are various aspects that I was exploring in this design, better intonation for instance by being able to shape each strings saddle rather than a conventional straight acoustic bridge)

hope that gives you a few ideas though, it does sound like you have identified the problem and working towards a valid solution...perhaps some of these ideas will help you think of something that is viable to you. I too would be a bit wary of hacking the guitar and would likely experiment with a replacement saddle so things can go back together the way they were...just in case you know.

...

Oh, i realize that John is not only good at these things but extremely generous to boot however this forum allows the sharing and exploring of ideas that only get expression when someone presents a problem or scheme of what they want to do. Then, it all goes into the resource and can be endlessly adapted to suit individual needs and built upon. Credit does go to people who step up with a desire and motivation to carry it through and prove the results, so kudos all the same...without your project and results, I'd not have the resource to draw upon is what I meant

[treguiers]

Love the idea of seperate saddles for each string. How would the plastic wood be as a conduit of sound? would it act as a sound muffler? I've never tried it but I would imagine it would absorb some of the sound....I'm only guessing here.
gonna pick up a saddle tomorrow and slice and shape it into six seperate individual saddles. I'll let you know how i get on.
BTW
very curious about your Jazzy strat!

[4real]

Well, just throwing some ideas out there, see what they might inspire for you...no guarantees...

"Plastic wood" is a brand name out here...water based wood putty. It dries hard but is not 'structurally' strong. In something like a slot, it would be as hard as wood generally and would have no ill effects as a thin layer to flatten that out.

If brave enough, separate saddle pieces in a divided saddle is an insteresting idea. I've not done it myself on an acoustic and ovations say, do that kind of thing traditionally...



Though some don't now it would appear. Some are divided for noise cancelling and better intonation. Dan erlwine says it is harder to make a split (in 2) saddle and advises against if not necessary...like making 2 saddles in terms of work. This idea is effectively six...so not sure if you are up for that particularly. It would need to be pretty tight fitting and well supported between and at the ends. A saddle built for the guitar will loose some length if cut as each cut is likely going to take a mm out of the length...it all adds up and these things need to be tight.

All suggestions are made without seeing the instrument, one could make a perfectly flat slot, but as Dan suggests, it may not be flat with the strings on and under pressure which is normal.

Chocking up as you have been trying with some paper is not a bad idea...but then, the same thing applies with the strings on or off being different. The worry there is that chocked up too far on say the high e will take pressure off of all the strings bar the low e in the process if excessive.

The only real advantage besides a lot more work, of the divided pickup is that each one will be forced onto the string below. What you need to check on though is that there is enough support that each 10mm bridge piece can't move about or fall over in you guitar...it is not something I'd ever seen recommended before.

...

The 'jazz strat' is a bit of a concept guitar to test out ideas like this. It is an arch-top so the bridge is very different from a flat. Testing it yesterday the ideas seemed to be born out with the results I was hoping for. Each saddle could be individually intonated (though is not adjustable), each saddle puts a constant pressure and sure footing on the piezo element, it picks up primarily the sound of the strings vibration and not the top or acoustic-ness of the host guitar. This last point was a wish to cut back on handling noise on the top or bridge. One can rest the heal of the hand on the bridge itself without any noise. Only if you bang on the actual bridge saddles do you really get any handling noise...not so good if you are hoping to play percussive parts by 'bongo-ing' the top and sides of the instrument that many do, but low on noise and what I was aiming for there.

It certainly is a unique instrument and very comfortable to play...it sounds quite ok acoustically too, so ideal for practice without an amp in front of the TV which is common here LOL.

Hope that helps, not seeing the instrument or knowing what you can do, all one can do is to throw ideas around and see what might suit or willing to try. If you keep the old saddle and make no major mods, likly everything can be returned to the state it was for the cost of a saddle blank...or, you might get improved performance, never know till someone tries it

[treguiers]

Hi everyone. Sorry I haven't been responding...but this is proving to be frustratingly difficult Still not satisfied with results.
I've tried individual pole pieces and there is still an imbalance. i have used a smidgen of isopon(automobile crash repair paste). I had some degree of success with that.

Above is a picture of the coax piezo ....... can i cut the frayed bit at the end, I have quite a bit of excess piezo?. My thinking now is the hole in which the piezo enters the saddle slot is too vertical and I may need to drill a 45 degrees hole( being very careful to avoid bracings!) to get the piezo to sit better in the slot.

Anyway i shall carry on........

[4real]

You should be ok opening up or changing the piezo lead hole a bit. Assuming that the bridge is not putting pressure on that part and creating a hollow below it.

I've not worked with this kind of flexible piezo, was this an original in this guitar or fitted later?

Looking again that book, it does warn that the piezo needs to be central under the bridge, not to one side of another and it occurs to me, is it possible that it can be twisted and this effect things?

Sorry that the individual string saddles did not work, it was an experimental suggestion and might well have some merits, worked well in mine but a completely different approach and design.

Can you identify which strings are lacking compared to others? Is it possible that the bridge stringing (pins and such) are putting enough an or even pressure down on the bridge saddle?

best of luck ~p

[treguiers]

I've looked all over the net and i can't find anything that says yes or no on whether you can cut(about 1 cm) off this kind of flexible coax piezo..... does anyone know if this can be done?

[treguiers]

Sorted it...... It was the angle the piezo was entering the saddle slot. the entry hole was at 90 degrees to the saddle slot....it should be around 45 degrees. I also drilled an exit hole at the other side of the slot, again at around 45 degrees......this solved the roblem of the piezo being frayed at one end(lucky i didn't cut it!!!!).
Thanks to everyone especially 4 real fr rowing in on this one........the guitar works a charm...better sundng than it ever was.