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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: RE: Every CD/SACD/DVD/Blue Ray player measures perfectly that I have measured. posted by georgelouis on January 28, 2012 at 21:58:43:
"How do you measure the polarity of a player?"
Carefully, using the appropriate calibrated tools. :-) The selection will depend on the equipment available. I would buy a test disk or else I would create one using an audio editor and CD burner. With a positive going impulse one can use a scope. One can verify that the scope and its probe have the correct polarity by using a battery. If one doesn't have a scope one can use a PC sound card and appropriate software, again using a battery for calibration.
If the CD player has DC response then one can use a test track that has a DC level. In this case one can use a VOM to check polarity. Again, the VOM wiring should be verified using a battery if there is any question.
There is the question of polarity of the output terminals. In the case of unbalanced (RCA) outputs then the center connector is measured with respect to the outside connector. When the center is positive with respect to the outside, the signal is positive. In the case of balanced (XLR) one must take care not to get the pins mixed up when connecting the test equipment and that consistent standards are used throughout one's system that agree with the standards used by one's test equipment. I use: Pin 1 - shield, Pin 2 - in phase (hot), Pin 3 - out of phase (cold). (A player that was in polarity and given a test track with positive samples would have Pin 2 more positive than Pin 3 for the duration of the test level if the player had DC response.)
If one has a scope one can use a periodic waveform that is asymmetric. This could be a sine wave at 440 Hz mixed with a sine wave at 880 Hz, see above. This waveform will have a rapid swing from one peak to the other in one direction and a wiggly swing in the opposite direction. This will enable you to recognize polarity. The waveform on the scope should match the waveform in the audio editor if the player has positive polarity.
If one has dyslexic tendencies as I do, one would be well advised to double or triple check the calibration of ones equipment and procedures and double or triple check any measurements.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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Follow Ups
- RE: Every CD/SACD/DVD/Blue Ray player measures perfectly that I have measured. - Tony Lauck 11:09:27 01/29/12 (0)
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