[sdiy] EM radiation -- current or power ?

[Bob Weigel]

On 12/19/2010 1:46 AM, Magnus Danielson wrote:
>
> You do want the guitar cable to be twisted too. :)
>


And speaking of which.... there's a cool trick we can do (not sure if 
anyone mentioned it in this context) to reduce noise with unbalanced 
lines.  In many devices the unbalanced line has an op amp driving a 1K 
resistor or thereabouts to the output 1/4" jack for example.  If you can 
get a balanced input to run it to, you can noise cancel by simply 
putting pin 1 to shield as always and run the balanced cabling back to 
the 1/4" plug!  But instead of hooking pin 3 direct to ground, put a 
matching 1k or whatever resistance between it and the shield on the end 
of the device.  That way you have two lines running alongside each 
other.  Both will get the same amount of EM interference roughly.  And 
now BOTH have the same resistance to ground and virtual ground!!  So the 
mixer cancels most of the noise away.

Now what I haven't tried is doing this with a guitar.  I imagine it 
would work fine if you set the guitar up with a dual pot perhaps for 
volume.  Of course the tone control would come into play also...

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