@inproceedings{ehrhardt_piezoelectric_2020,
address = {Royal Birmingham Conservatoire},
title = {Piezoelectric strings as a musical interface},
abstract = {Flexible strings with piezoelectric properties have been developed but until date not evaluated for the use as part of a musical instrument. This paper is assessing the properties of these new fibres, highlighting their strengths and weaknesses for nime applications.},
booktitle = {Proceedings of {NIME} 2020},
author = {Ehrhardt, Marcel and Neupert, Max and Wegener, Clemens},
month = jul,
year = {2020},
pages = {2},}
}
It can be powered either by two AAA batteries or via 48V phantom power (in the later case no batteries are necessary).
There is also an electrical simulation which you can see online at falstad.com
First batch are 10 kits.
If you want to be put on the list to reserve one, write me an email: max@ this domain.
We have 10 reservations now. Keep the reservations coming it will help us to determine the next batch size.
When researching how to power an amplifier from phantom power (P48) you’ll quickly discover the Schoeps circuit. Here are some links which we found when looking at schematics, but after some tests we finally decided not to use a Schoeps circuit at all. Our topology is instead based on a lightweight single channel op-amp which has an N-Channel JFET inside. We use the same opamp twice for two stages in our schematic. (I’m just parking these link here so I can close some tabs)
Test was successful. Now assembling the rest and making the casing (rectangular pipe segments).
We do however have to remake the first stage, which goes directly on the string itself due to mechanical reasons (Soldering holes for the cable were too small).
The PCB layout allows for two alternative assemblies: A) with Zener diode or B) with a linear regulator. Both works equally well, I can’t hear any difference. Probably because the power from P48 or batteries is super clean anyways. I’ve also compared ceramic capacitors with tantalum ones, and the ceramic caps don’t show any microphone characteristics even when I smack them with something.
Back features TRS and XLR ports, TRS is meant for battery power and XLR for use with P48 phantom power. Please don’t connect both at the same time, you will be getting 48V on the jack if phantom power is on the XLR.
The fist preamp stage (impedance amplifier) sits directly on the fiber on this tiny PCB. Since the fiber is heat sensitive it is braided on the board, not soldered. It is then connected to the preamp box with a 2.5mm TRS jack cable. Each preamp kit comes with two of these fibers and cables. The fibers are about 1m long (the one pictured is shorter) and braided with a 50µm steel-filament. The fibers can be shortened to the desired length.
This is the end of the fiber. The unshielded, exposed PVDF acts like a noise antenna. Feel free to just cut this part off where I put the red line. Don’t short it though, there can be no conductive contact between the inside rubber and the outside braided steel.
If you have the DevKit, you probably ask yourself how to to suspend the fiber without breaking it. Have you come up with solutions? I’m curious, please share your ideas. Something like this works OK for me:
Piezo fiber test with audio proessing by Richard Dudas.
Direct sound from piezo string on left channel, processed sound (echoes and transposition) on right channel.
awarded “Best Demo”)
