Hey Guys,
As a fun little side project, I have been messing around with exciting vibrations in a guitar string using a coil of wire.
I got the idea from this post and the setup is very similar to what I am using: Fun with Magnets and Strings - MUFF WIGGLER
I have wound a few "exciter coils", mostly around 4 ohm DC resistance and have been using a few different off the shelf audio amplifier IC's to drive it.
Out of my parts bin, I had a Velleman 7W amplifier ( 7W Mono Audio Amplifier Kit ) and got very good results from this. I can get a string to vibrate pretty good with this amplifier only consuming about 3W of power from my benchtop PSU.
While experimenting/messing around.. I also had a PAM8403 amplifier ( PAM8403 Stereo Audio Amplifier Module- Features, Pinout, Datasheet, Working ) that I tried, thinking a class D amplifier would be more efficient. Unfortunately it wasn't for some reason, and while also consuming about 3W it was only able to vibrate the strings half as much.
My eventual goal is to have a bunch of strings and exciters, so that's why I'm looking for an amplifier that works "best" for this task and uses the least amount of power while still moving the strings a lot.
A friend suggested I look at some university research project called the "Electromagnetically Prepared Piano" ( Version 2 – The Electromagnetically-Prepared Piano ) that uses similar exciter coils to vibrate piano strings. Since the piano strings are way bigger than my little setup, they are using a lot more power. This paper ( http://vhosts.eecs.umich.edu/nime2012//Proceedings/papers/117_Final_Manuscript.pdf ) says they're using 22W audio amplifiers but the schematic shown on Page 4, Figure 4 shows the amplifier circuit has some additional components in the feedback loop to make it constant current output amplifier. Seems like this is done so the exciters still work good at higher frequency, which is a problem I've also noticed...
I'm wondering if there's any way to try this constant-current thing out in a smaller 3W-ish amplifier to benefit from the better high frequency response..
Or maybe if there's some other things I should try? I'm happy to breadboard a few things and report back. I also have some different gauge magnet wire so I can try other coil impedances.. Sorry for the long/rambling post, but it's been fun watching this string start vibrating with invisible forces I don't understand 🙂
As a fun little side project, I have been messing around with exciting vibrations in a guitar string using a coil of wire.
I got the idea from this post and the setup is very similar to what I am using: Fun with Magnets and Strings - MUFF WIGGLER
I have wound a few "exciter coils", mostly around 4 ohm DC resistance and have been using a few different off the shelf audio amplifier IC's to drive it.
Out of my parts bin, I had a Velleman 7W amplifier ( 7W Mono Audio Amplifier Kit ) and got very good results from this. I can get a string to vibrate pretty good with this amplifier only consuming about 3W of power from my benchtop PSU.
While experimenting/messing around.. I also had a PAM8403 amplifier ( PAM8403 Stereo Audio Amplifier Module- Features, Pinout, Datasheet, Working ) that I tried, thinking a class D amplifier would be more efficient. Unfortunately it wasn't for some reason, and while also consuming about 3W it was only able to vibrate the strings half as much.
My eventual goal is to have a bunch of strings and exciters, so that's why I'm looking for an amplifier that works "best" for this task and uses the least amount of power while still moving the strings a lot.
A friend suggested I look at some university research project called the "Electromagnetically Prepared Piano" ( Version 2 – The Electromagnetically-Prepared Piano ) that uses similar exciter coils to vibrate piano strings. Since the piano strings are way bigger than my little setup, they are using a lot more power. This paper ( http://vhosts.eecs.umich.edu/nime2012//Proceedings/papers/117_Final_Manuscript.pdf ) says they're using 22W audio amplifiers but the schematic shown on Page 4, Figure 4 shows the amplifier circuit has some additional components in the feedback loop to make it constant current output amplifier. Seems like this is done so the exciters still work good at higher frequency, which is a problem I've also noticed...
I'm wondering if there's any way to try this constant-current thing out in a smaller 3W-ish amplifier to benefit from the better high frequency response..
Or maybe if there's some other things I should try? I'm happy to breadboard a few things and report back. I also have some different gauge magnet wire so I can try other coil impedances.. Sorry for the long/rambling post, but it's been fun watching this string start vibrating with invisible forces I don't understand 🙂
Fantastic project!!! Question: would it be interesting to have a string with a winding (or multiple layers of winding) made of insulated wire so that the string itself could be fed with some kind of signal...?
You are just re-inventing the "e-bow" that dates back to the eighties if memories serve. I played with that gadget at the time, funny experience playing "Santana" on an acoustic guitar. 😉
This one worked with a single 9V-block.
This one worked with a single 9V-block.