1 Topic by Intini (edited by Intini 2022-07-16 23:52:15)

  • Registered: 2022-03-22
  • Posts: 8

Topic: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

While trying to find an affordable way to integrate electronic drums in my setup I found an UK company (called Audiofront) that makes a VST plugin (called DSP Trigger) that translates audio to MIDI notes and can do that in real time (!) using piezoelectric sensors connected to the line input of audio interfaces. These piezoelectric sensors are the same ones found in electronic drum pads from Roland, Yamaha, etc. However, my idea is to make my own custom pads with these piezoelectric sensors.

I am a bit worried about possible implications to the UFX+ converters from the piezoelectric signal, peak voltage and di/dt from the transducer and I will not connect these sensors to my UFX+ without asking here first if this is an acceptable use of the interface.

A litle background: Piezoelectric, or simply piezo, are sensors that work as small "microphones" but create an electric field from the deformation of a material (crystal, ceramic, and others), converting vibration (from a drum stick) to a voltage (electric field).

Therefore, please, is it safe to connect these "piezo" to my UFX+ interface a/d converter's via the line inputs to be processed by this VST plugin?

Thanks a lot in advance.  Any input will be greatly appreciated.

Here are the links to the plugin manufacturer and to the said piezo:

Plugin manufacturer:
https://www.audiofront.net/dspTrigger.php

Example of piezo I intend to use:
https://www.ebay.com/itm/192251623333?m … media=COPY

2 Reply by Intini (edited by Intini 2022-07-30 03:42:16)

  • Registered: 2022-03-22
  • Posts: 8

Re: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

I am sorry to post again. It has been a week with no reply. I just would like to add that any input is welcome.

  • cyrano
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  • Registered: 2015-04-28
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Re: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

I think you would be better of using the instrument inputs.

I've tried piezos as a trigger. It works with the instrument inputs, but some piezos might clip those. Still works, depending on what you're triggering.

The impedance of the instrument inputs is 470k on my old FF400. I believe it's even higher on newer interfaces.

In the end, I used an instrumentation amplifier (10M impedance, 10X amplification) for audio, not for triggering. That was for vibration measurement though.

Experimenting will surely not break anything. There isn't that much energy in a piezo.

MB Pro - 2 X FireFace 400, FF800 & DigiFace USB
ADAT gear: Korg, Behri, Fostex, Alesis...

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  • Registered: 2022-03-22
  • Posts: 8

Re: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

cyrano wrote:

I think you would be better of using the instrument inputs.

I've tried piezos as a trigger. It works with the instrument inputs, but some piezos might clip those. Still works, depending on what you're triggering.

The impedance of the instrument inputs is 470k on my old FF400. I believe it's even higher on newer interfaces.

In the end, I used an instrumentation amplifier (10M impedance, 10X amplification) for audio, not for triggering. That was for vibration measurement though.

Experimenting will surely not break anything. There isn't that much energy in a piezo.

Thank you so much for sharing your experience. Were you triggering audio to midi, like the DSP Trigger VST Plug-in I mentioned? Or was it with something else?

The instrument inputs are 1MOhm on my Fireface UFX+. The line inputs are only 8 kOhm (unbalanced). But I guess I could use a potentiometer in series with the piezo as a variable voltage divider to avoid clipping. After I made my post, I investigated a bit further and piezos are very commonly used as a pickup for acoustic guitars. So, I am not actually doing anything out of the ordinary here. It is just an electric signal anyway.

I am now a bit curious about your use for of the FF400 for vibration analysis. I saw some research being made with vibration and an audio interface for spacecraft and airplane vibration -Fast Fourier Transform Analysis, etc. Did you use it for this kind of research?

  • cyrano
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Re: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

It was just a way to see the panel vibration of loudspeakers. In the end, you can also just use your hand. Touch the panel and see if it feels dead. I had hoped seeing the vibrations would make bracing easier.

But I also used it to listen bearings, trying to recognize worn ones. Worked beautifully, but a stethoscope is simpler.

I also tried triggering drums VSTis. Not for me, I'm not musical at all. Also worked fine.

I also tried speakers as input. Even a "Buttkicker" (a very low frequency speaker, aimed at people who want to feel the bass). Useful to measure road traffic intensity.

RME's DigiCheck is a very useful tool!

MB Pro - 2 X FireFace 400, FF800 & DigiFace USB
ADAT gear: Korg, Behri, Fostex, Alesis...

cyrano's Website

6 Reply by Intini (edited by Intini 2022-08-02 13:34:44)

  • Registered: 2022-03-22
  • Posts: 8

Re: Piezoelectric sensors into the line inputs of Fireface UFX+ ?

cyrano wrote:

It was just a way to see the panel vibration of loudspeakers. In the end, you can also just use your hand. Touch the panel and see if it feels dead. I had hoped seeing the vibrations would make bracing easier.

But I also used it to listen bearings, trying to recognize worn ones. Worked beautifully, but a stethoscope is simpler.

I also tried triggering drums VSTis. Not for me, I'm not musical at all. Also worked fine.

I also tried speakers as input. Even a "Buttkicker" (a very low frequency speaker, aimed at people who want to feel the bass). Useful to measure road traffic intensity.

RME's DigiCheck is a very useful tool!

Thanks for your reply! These interfaces are incredible indeed - so useful in such diverse fields!