Lune silver cable polarity
After a year of everyday usage my superfi EB cable has been broken. Living in Eastern Europe I was unable to buy a replacement cable, so I decided to make one for myself. Just after when I removed the two tiny conductor pieces from the broken cable, I realized that the polarity is not marked on the earphone. So I have a black box, and I must find out the correct polarity of the membranes. In the case of a common speaker it is easy to stress it by a simple low voltage battery, and then we can observe the polarity by the movement of the membrane. But in this case I cannot see the membranes; therefore this easy method was not viable.
So I did this: I feed a 400Hz sine signal to the first channel of my oscilloscope, the same signal was sent into the earphone. The sound of the earphone was picked up by a microphone, and the output signal of the microphone was connected to the second channel of my oscilloscope. When the polarity of the earphone was incorrect the two signals were out of phase, when the polarity was good the phases perfectly matched:
good polarity - in phase signal
reverse polarity - out of phase signal
measurement
Not long ago I purchased a lune silver upgrade cable, I found so that the blue and red dots must face outwards, to get the correct polarity as I described above. It is a surprise to me, because at first I assumed that the dots must face inward.
