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Ping Soundmind

I thought you might appreciate an anecdote on how a "high end" power cord can really screw things up.
A critic came by to visit some years ago and brought with him a Van Evers "tunable power cord" the power cord had a slider on the outside of the jacket that allowed one to "tune" their system.
So we plug this contraption into my pre amp and I put the slider at mid point on the cord. I get a relatively high amplitude bass note and I get gross distortion. The slider goes to the end of cord near one of the terminations and the gross distortion goes away. I do however note that something is not quite right with this contraption. I got the critic to leave it with me for a few weeks so I can take it into work for measurement.
I put it on an HP LRC analyzer and found nothing remarkable in terms of reactance or resistance. I then used the function that allowed me to meter the change in phase of the current at 100 Hz.
Note! with the slider near the cable terminations the change in phase of the current was approximately -7 degrees. At the middle of the power cord the phase shift of the current was approximately -25 degrees.
In discussion with another engineer we agreed that the change in the phase of the current could only be from the magnetic field from the "slider". In addition the gross distortion I was hearing was probably due to the phase of the current being changed enough to alter the charge cycle that normally happens on a standard linear power supply. In short: as the voltage peaked across the PS caps the current was far enough out of phase so the caps would not get charged as they normally would.
So: Now you have some idea on how high end line cords can screw up a standard linear power supply.
d.b.

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Topic - Ping Soundmind - Dan Banquer 13:57:55 11/04/06 (113)
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