5. Phase alignment


Author: Karsten Hein

Category: High Fidelity

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In HiFi forums it is often suggested that the polarity of a 240V plug should not matter, because the polarity is oscillating at 50Hz. However, this is not the whole truth, as only the phase oscillates while the other remains neutral. In many countries, such as the US and Britain, an inversion of the poles is prevented wherever necessary through the use of directional plugs, either through a ground prong (UK) or through one pole being larger (US). The question of whether polarity matters is therefore essentially a German one, and as such, it will never go away.

There are many ways in which to determine the correct polarity of a unit’s plug. Oehlbach suggests we use their ‘Phaser’, others favour extensive measurements with the unit being turned on and off. Regardless of the method employed, the first step will be to use a phase tester, usually a screwdriver, and to check and mark the phase on the outlet socket. When using a power strip for distribution, the phase should be marked here as well, this can be done with a white or red marker or with adhesive dots, etc.

Although I have used the Oehlbach Phaser at times, I have found the most effective method to be trial and error, using my own ears. To do so, I took an empty power strip and plugged in the minimum units I need to play music, e.g. turntable, pre-amp, amp. If your phono preamp is not located inside your turntable but in your pre-amp, the polarity of the turntable does not matter, because the audio signal path is passive. This way I only had two plugs to phase: pre-amp and amp. This limits the number of combinations.

What to listen for: When phase alignment is done poorly, the music sticks to the speakers and the phantom center (the middle position resulting from mono signals in the recording, usually the voice) will be off. When phase alignment is done correctly, the music will extend into the room, with the phantom center being as discernible as a third speaker. Do the same for each new unit you bring in, until you reach this effect. This is called phasing your system and is an interesting stage of the setup that can take some time getting used to. Once you have it right, there is no going back.

When phasing a single unit, such as a receiver, with no other units attached during listening, the effect of phasing might be less pronounced. Phasing mostly has to do with differences in electric potential between devices.

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