Checking the AC polarity of your amplifier

On some components with advanced power supply designs, "balanced power" will lower the performance quite noticeably. Before investing in such a device, you should check with the manufacturer of each component to find out if is suitable for use with such a device.

Here's a post i made about Noise, Hum and AC Polarity a few years ago. It may explain a few things to those that have questions or are confused about what to do. Sean
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One of my friends was using a preamp that i was very familiar with. We discussed a few things over the phone and i told him that he had the polarity reversed on the preamp. I told him how to verify this and once he checked it, it was reversed as i had suspected.

After changing the polarity and listening for a while, he told me that he had never heard that big of a difference when playing with the AC on any component before. The reason why the differences were so obvious? This specific product has a built in noise trap / transformer damping circuit that requires specific polarization to work properly. Without the proper polarity OR using balanced power, that circuitry is completely negated and the preamp will never work or sound nearly as good as it can.

This is why i said that one should check with the manufacturer of the gear before investing big money in what could be a major step backwards in their AC systems. It is also the reason why i've touted high quality isolation transformers, as they will only strip away the noise without altering the polarity of the signal. Sean
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Running balanced AC to some gear and not to others within the same system is the same thing as introducing a ground loop. That's because the difference in voltage potential from hot to neutral varies with the way that each component is receiving their power.

In one method, you've got 120 volts of potential on the hot and the neutral tied to ground. In the other, you've got 60 / 60 volts divided between the hot and neutral. This is why filtering inside the gear becomes ineffective when used in balanced mode i.e. neutral is no longer at ground potential but has become an active part of the AC feed. Since most filters shunt the noise to neutral or ground, you've removed the "dumping ground" for the noise from the equation. This means that the noise remains in the gear and further contaminates the other components tied into that same balanced AC feed.

Once again, all of these types of systems introduce further non-standardized variables into the system. Rather than opening up the door for more problems, why not just optimize the standardized system that you've already got and we've been using for years? Using this approach, you're guaranteed that your components will work optimally with little chance for negating built-in design features and circuitry.

Until gear is actually designed and built to be run strictly on balanced power, introducing balanced AC as the source of power will provide rather unpredictable results in any given system. Sean
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