Re: Sustain

[Jim Coker <jcoker@interaccess.com>]

Hmmmm. a very complex set of problems, as I had also thought of 
getting a couple extra pickups and trying the DIY approach.  
Actually I think an interesting approach would be to buy 6
ebows, pull out the electronics, and mount them in a guitar
body, but that probably also be difficult, particularly in
terms of mounting the hardware.  It would allow one neat
thing, independent sustainability on each string...

jim


Matthias Grob wrote:
> 
> >>However, the guitar is going (used) for $900.  No way.  I've got to 
>build
> >>me one of these....  somehow!
> >
> >I've never gotten around to checking out the circuit in mine, but I 
>suspect
> >it is pretty simple. They just take the signal from the bridge pickup,
> >filter it, and use it to drive the neck pickup in reverse. Just as 
>strings
> >moving in the pickup's magnetic field produces an ac voltage at the 
>output
> >of the coil, applying a signal voltage to the coil output will cause the
> >motion of the magnetic field to move the string. NotRocketScience (tm). 
>You
> >need to make sure you get the pickup placement right so that you drive 
>the
> >string in phase.
> 
> Sure I tried it, years ago. There are problems I did not have the 
>patience
> to solve:
> 
> 1 To keep the correct phase for any note is not easy.
> 
> 2 To drive, you need power. Either a higher tension than battery or a low
> impedance pickup (DIY?). In any case, its hard to keep the strong driving
> signal separate from the outgoing sound signal. If you bring the supply 
>to
> the guitar, keep the ground separate. If you bring the driver signal to 
>the
> guitar from a external amp, shield it separately.
> 
> 3 The driver tends to feed back directly to the pickup. To avoid it, you
> need to limit its energy, make it more effective through filtering or 
>build
> it in a specific way so it does not stray the magnetic field.
> 
> But... go ahead and find out!
> 
> Matthias