[sdiy] Opamp ICs (slightly OT)

[Steven Allen]

Robotboy8 at aol.com wrote:
> 
> I'm tentatively working on a fretless 2-string drone bass guitar (not
> a synth... but i might add a lowpass filter whose cutoff is controlled
> by a ribbon controller under the fretboard).  I'm planning on not
> using a standard pickup but instead on using the strings as pickup
> with a strong magnet (from a car speaker) beneath them.  I do not
> know, however, whether the signal attained this way will be strong
> enough without using a magnet so strong that the strings tend to stop
> vibrating rather quickly (undesirable, as I intend this for drone
> use).  I'm thinking that I'll put an opamp IC right before the output
> (ratshack seems to have some for relatively cheap, if i recall
> correctly).  I've not used many ICs before, though, so can anyone
> recommend one for this use and explain where to connect which pins
> (okay, my rather incredible newbiness shows itself...)  Am I correct
> in assuming that I need basically just the + and - connections from
> the string and the + and - connections from the powersource (in this
> case batteries)?  Or are there many other connections to make
> (possibly a ground... any others?)
> 
> Also, does this make any sense?  Will the output voltage just be too
> low for suitable audio use?  Or will I not need an opamp anyway?
> 
> Thanks in advance

 Wow, + and - to where on the string..? One at each end of the string
should keep them warm for winter playing.
The magnetic field will dampen the vibration of the strings. The magnet
in a pickup is only there to create the field that the steel string
disrupts. So, you need a coil of wire to pickup these field
disturbances, that get amplified to produce a signal.
 You might be able to use an optical coupler, or why not just a few
oscillators tuned to the drone that you want to use?
 I'm sure others will have some real input on this. Check out some of
Craig Anderton's books and articles on the basics.
 Sounds like a cool idea. That's the important part, the idea!!
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