Piezo bridge question.

[Sambrook]

My Cort B4 fretless has a piezo bridge. It works perfectly with the Chromes it came with, also the TI flats and rounds I've tried on it. However, my LaBella white nylons are a different story. The E and A strings work fine (and sound really good), but there's almost no output from the D and G. The strings work fine on my other piezo fretless (so it's not the fault of the strings); I've tried raising the saddles to increase the tension on the piezo element, no good. I've had a thorough look at the wiring guts, can't see anything obviously amiss, though I'm no expert. There is some audible output, but barely...

Is there anything I'm missing? It plays well with the other strings, but semi-hollow, fretless, piezo, and white nylons are meant to be together...

Any help greatly appreciated.

Cheers, Sean 

 

Changed the battery as well, btw...

[ikay]

There are some threads on TB suggesting nylon strings don't always work that well with a Fishman piezo bridge (example below). Old thread alert (2016)! I have black nylons on a bass with Graphtec piezo saddles and that works fine. I did try white nylons once (on a non-piezo bass) and noticed that they were super light tension which certainly wouldn't help. There's not much that can go wrong with a piezo saddle - it either works or it doesn't. The contact pressure from the string is critical to how much of a signal it generates though. 

 

[Sambrook]

Thanks for that, it certainly fits the symptoms.

[Maude]

Try cutting a slip of thick paper or thin card and placing it under the piezo strip on the D&G side. 

If it works then it might need a bit of trial and error fine tuning with different size bits of paper to even out the volumes from the strings. 

[Andyjr1515]

Do you happen to know if your strings are the 750T set (50; 65; 85; 105) or the 760T (60;70;94;115)?

 

If they are the 750T's, then try tuning the A & D up 2 semitones.  Does it cure the balance?  Tuning up two semitones is going to be roughly equivalent to the tension difference of the two sets and if it sorts the volume issue then it would probably be worth the expense of buying the higher tension set.

[Sambrook]

Thanks to all of the above responders. This weekend is the first time I've had chance to attack the problem.

No joy, sadly. Bought a set of Rotosound Trubass to get as close to the double bass sound as possible. This time, the E and G are fine, with little output from the A and D! Tried the suggestions, but no improvement.

If I see a reasonably priced piezo bridge for sale, I will probably try that, cos the Trubass strings do give that lovely warm thwump.

Thanks again, chaps.

[Sambrook]

...as a side note, the quiet strings operate at full volume when I touch the piezo element, as if there were some kind of grounding issue...

[Andyjr1515]

1 hour ago, Sambrook said:

...as a side note, the quiet strings operate at full volume when I touch the piezo element, as if there were some kind of grounding issue...

Hmmm....that sounds important.  What happens to the louder strings?

[Sambrook]

Nothing, I think.

[Andyjr1515]

And no pressure applied anywhere?  Just touching it?  Hopefully some clever Basschatter can suggest why this would be and maybe even what could be done to make this the norm...

[ikay]

It could well be a grounding issue. I found the following post on the Line6 forum which seems to refer to a problem similar to yours:

 

If any of you want to diagnose your piezo as a ground issue, you should be able to hear the string, but it should be quiet and possibly crackly.

If it cuts out 100% with no sound at all then you have an issue with the signal wire, not the grounding connection.
 

The problem is that the piezo has lost contact with the saddle, which transfers all grounding to a wire connected to the bridge. 

You could try to use contact cleaner, but it might go out again, so I suggest you secure the grounding contact by inserting conductive material on the side/under the piezo between the saddle. It's working great.

 

 

[Sambrook]

Thanks again, chaps.

The connections between the PCB and the bridge plate are sound, as are the wires from the plate to the actual piezo elements. The bass working well with my Thomastiks tells me it must be the nylon coating.

SO...what I did was this:And it works! The copper tape is connecting the ball end of the string to the piezo element.

I will tidy it up (and hope I don't blow myself up), but I quite like the diy look...

Thanks for your input, I probably would have given up without it 

[ikay]

Excellent 👍   

 

I wonder why the other two strings don't have the same problem!

Edited August 1, 2022 by ikay

[Maude]

I still don't quite understand how it's doing what it's doing, but if that's fixed it then happy days. 

[Sambrook]

Happy days indeed. I bought a set of Trubass strings when I first got into fretless playing, and hated them. Really hated them- stiff, dull thudding.

Having been on a pilgrimage for the double bass tone without actually having said double bass, I tried them again, and they really do the trick- you have to attack them like you would an upright, which makes sense, I guess...