How an Ebow works..

[Charles Zwicky <cazwicky@earthlink.net>]

I've seen a lot of interesting misconceptions about how the ebow 
works and how "best" to use it since it was introduced in the late 
1970s...

Here's my simple explanation:

What an Ebow consists of:

The Ebow is a very simple device consisting of a pickup, an amplifier 
and an output coil.  The pickup is essentially the same as an 
electric guitar pickup, it uses a coil of wire and a magnetic pole 
piece.  The only difference is that the coil is wound on a single 
small round bobbin and designed only to pick up the vibration of a 
single string.

The pickup is connected to a very small amplifier which in turn 
drives the output coil.  The amplifier is not very powerful and is 
easily driven into square wave clipping, which is plainly audible in 
an electric instrument when the excitation coil is positioned above 
the instrument's own pickup.

The pickup coil and output coil are positions at opposite ends of the 
"string channel" along the bottom surface of the Ebow's body.

How an Ebow works:

The pickup in the Ebow operates exactly the same as the pickup in 
every ordinary electric guitar: The string vibrating in close 
proximity to the pickup causes fluxuations  in the permanent magnetic 
field around the pickup's coil.

These fluxuations  in the magnetic field induce a voltage into the coil.
This voltage is amplified and sent to the output coil, which operates 
in reverse of the pickup: The voltage sent to the output coil by the 
amplifier generates a changing magnetic field which excites the 
string.
Since the signal feeding the pickup and produced at the output are 
from the same string a feedback loop is created, allowing the string 
to ring indefinitely.

An Ebow will work on any vibrating magnetic object which is sensitive 
enough to be driven by the relatively weak excitation signal.

I hope that this clarifies a few things and opens the possibilities 
for all you loopers..

-Chuck Zwicky



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