Saturday, April 21, 2012

Polarity Testing the Oppo BDP-95

Above is the output of my Oppo BDP-95 player playing my SoftPolarityTest CD track one, through single ended stereo outputs, as viewed on a Tektronix scope.

A friend has been asking me to test the output polarity of the Oppo BDP-95.  Long ago I made a polarity test by recording a B&K analog function generator.  I started with a square wave at 400Hz and decreased the duty cycle so I had only a positive series of pulses at 400Hz.  I originally recorded this at a fairly high level, so it was dangerous to use.  Well this time I altered that by reducing the level 18dB.  I recorded the disc onto a T.Y. CD-R using a MacBook Pro.  I call this SoftPolarityTest.  You perform the test by playing the recording and watching the results on an oscilloscope.  If the visible pulses go positive, this is correct polarity, or at least it is correct compared with my reference standard for polarity, a Sony 507ESD high end CD player made in the 1980's and all other CD players I have tested so far.

Each track lasts 20 minutes so there is little chance of error.  I skipped ahead to the second track, which is the same recording in reverse polarity:

Here is the Sony 507ESD with the disc inserted.

It took about 11 minutes to get the scope hooked up to the sony because it is at the bottom of a pile of equipment in a tight space.  Here is what track one (I double checked) looks like on the Sony:

Here is the Denon 5900 playing track one:

So all three players have the same output polarity.  If I remember correctly, I previously tested a Samsung DVD player and a Toshiba 5700 (a model not made by Samsung like later Toshiba's were) and they had the same polarity also.  These are the only disc players I have ever tested for polarity, and none have been different.  I believe that is because all the ones I have tested are correct.

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