Homemade Ebow?

[SeanCostello]

As far as lower battery voltages in the Ebow, I have found that a fresh battery is the most predictable. That said, at one point the battery was dying in my Ebow, and I started getting SUBHARMONICS out of my strings. In other words, the note being generated by the string was an octave below the fretted note, or an octave and a fifth. At the time, I knew very little about physics, and thought that I might have stumbled upon the key to get some type of Gyuto Monks chant of God voice out of my guitar. I still don't know much about physics, but I have programmed several nonlinear filters for digital audio, and have heard the subharmonic pheonomenon (sp? pheonomenonemenon?) enough times to not be as surprised that it can happen.

Sean Costello

P.S. An envelope filter with short enough attack/decay times can produce subharmonics out of an impulsive periodic signal. It sounds a lot like engine noises. Which would also be interesting, except that I spent a year and a half of my life creating physical models of engine sounds for video games, so I try to avoid having things sound like cars whenever possible now.

[lvs]

Hi, I'm glad the Logos Foundation site gets some attention. One of the main guys there is Godfried-Willem Raes, nonconformist musician and instrument builder, and from what I saw on TV, a skilled Tango dancer.

Here's a translation of that EBow page.

4047 Electromagnetically driven strings

It's a known fact that an electric guitar can produce sustained tones when we stand close enough to a loudspeaker that is supplied with enough volume.

Even without this rather brutal technique it is possible to play sustained notes on string instruments with magnetic strings. For this exists since many years an aid called EBow.

(links & photo)

Building such a little gem is within reach of any good DIYer.

To put experimenters on the right trail (study of chapter 2 is advised for a more in depth understanding of the project), here's a few practical directives and schematics.

In the following diagram we applied a LM386 chip. For somewhat more power you can also use an LM386-4, which you must supply with 15-16VDC instead of a 9V battery.

(diagram)

Voltage amplification of this little design is 200, or 46dB. For optimal functioning the electromagnet of the driver (at the output) must be low impedance (around 8 Ohms). You can use an output transformer from an old transistor radio, from which you remove the iron core and replace it with a permanent magnet. The input coil can have high impedance. For use as EBow the receiving and driving coils must be mounted close to each other, but so that they won't oscillate when resting. The easiest way to achieve this is using an oscilloscope, but it's also possible with a current meter in series with the battery. When the current is large (>10mA) while still no metal object is vibrating, then you can be sure that the whole thing is oscillating spontaneously. In that case the distance between both elements must be enlarged.

If you can't get it working at low frequencies then possibly an RC network has to be placed in parallel with the input.

[NaBo]

thanks a lot for the more coherent translation, lvs... that makes things quite a bit easier.

I can definitely see myself screwing around with this stuff for a while...  I just wish i was taking engineering instead of useless, useless english  :roll: