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Peter,
the PV cells are stacked so that the string casts an equal shadow on each and the center line of the shadow is also the joint between the PVs. On thin strings the PV nearly touch, on the fatter strings there is a slight gap between them. If the string excursion is too great then you will get a square wave.
I don't think LightWave was ever able to get a system to work for guitar. The .08" high E string is just too small to work with. I think probably a .025" string is about the smallest you can deal with comfortably.
The signal strength is dependent on the size of the change in the string shadow. You need to balance the output of each string. You could do this by using longer , narrower PVs for the small strings. Lots of finicky adjustments to get that just right. Instead LW chose to set the signal strengths electronically with a rather sophisticated circuit design.
I suspect you would need at least an oscilloscope to determine the DC offsets and then choose an appropriate capacitor to stop the DC but allow the lowest frequency through. The LW board does this for each string and you have to change components on the board if you are wanting to tune the subsonic filters for each string. Since it was all SMT components I found it to be a bit of a PIA. The nice thing about having separate string outputs was that you could connect to a midi controller via a 13 pin jack. I did this on a fretless bass but never heard the results myself.
If you follow up on this, just remember that you'll want to be able to adjust the string height and then will need adjust the sensor height too to get the shadow in the right place.
the PV cells are stacked so that the string casts an equal shadow on each and the center line of the shadow is also the joint between the PVs. On thin strings the PV nearly touch, on the fatter strings there is a slight gap between them. If the string excursion is too great then you will get a square wave.
I don't think LightWave was ever able to get a system to work for guitar. The .08" high E string is just too small to work with. I think probably a .025" string is about the smallest you can deal with comfortably.
The signal strength is dependent on the size of the change in the string shadow. You need to balance the output of each string. You could do this by using longer , narrower PVs for the small strings. Lots of finicky adjustments to get that just right. Instead LW chose to set the signal strengths electronically with a rather sophisticated circuit design.
I suspect you would need at least an oscilloscope to determine the DC offsets and then choose an appropriate capacitor to stop the DC but allow the lowest frequency through. The LW board does this for each string and you have to change components on the board if you are wanting to tune the subsonic filters for each string. Since it was all SMT components I found it to be a bit of a PIA. The nice thing about having separate string outputs was that you could connect to a midi controller via a 13 pin jack. I did this on a fretless bass but never heard the results myself.
If you follow up on this, just remember that you'll want to be able to adjust the string height and then will need adjust the sensor height too to get the shadow in the right place.
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