- Be careful what you add in series with equipment. Even an extra power cord, if not selected properly, can narrow the pipe feeding your equipment and sound worse.
- Most power filters are series devices. As such, they provide the most aggressive noise reduction, but, if not designed properly (and few are) they can rob your system of its life and dynamics. Assume the worse when you audition them. Filters should prove their merit or be removed.
- Some power filters are parallel devices. These have less negative impact on the sound, but struggle to provide any real benefit. Audition carefully, assume these are doing nothing and make them prove themselves before staying in the system.
- Isolation transformers are double edged swords. They lower common mode noise, isolate your system from the power line, but all that good stuff comes at a price. When you demand power from an isolation transformer, it struggles to deliver it and often times causes more power line distortion. It's the same as rule number One. Isolation transformers can benefit low power devices, like preamps and DACs, but generally should be avoided for power amplifiers. Isolation transformers cannot fix power line problems like voltage drops or wave shape, they only make them worse.
- AC regenerators are the only devices that can actually add missing energy back and fix problems, like voltage drops and wave shape. But be careful you don't use too small of one and that the design does not make things worse. Several AC regenerators actually create more distortion under the load of a power amplifier than what comes out of the wall. Assume the worse, use your ears as your guide.
Power, the last bit
My wife Terri thinks I am weird. In fact, she know I am. I like power and talking about such things. Power quality is fascinating to me, but not everyone gets the same charge out of it. So, let's end this series today and move on to other fun stuff. We learned in yesterday's post the difference between resistance and impedance (two subject of great fun in themselves). And we note that the wire in our home's walls has plenty of resistance, which means every time your power amplifier or projector takes a gulp of power, the voltage drops. This is like running out of gas every time you step on the car's accelerator. Adding an isolation transformer or power conditioner to your system only makes this problem worse. We also learned that a power filter uses impedance to clean the ever present noise of the power line; noise generated by all the radio waves and household electronics polluting the environment we live in. Impedance works because at low frequencies, like the 50 and 60Hz coming out of our wall, the filter has no more resistance than wire. But, at higher frequencies where the noise hangs out, its resistance is high and the noise can't get to our equipment. An excellent solution to lowering noise, but one we have to be careful is done properly. Designing the filter with skinny wire or overly aggressive components bleaches the sound we so desperately want only to improve. We also learned that while an AC regenerator solves the problems discussed, like flat top sine waves, voltage drops both long term and short term from power amplifiers, wave shape and noisy power, most power amplifier manufacturers recommend not using them - or filters - or anything they do not make. And I have never figured out quite why that is, though I suspect it is because power filters in general make their amps sound weak - and rather than saying "don't use any of these, but this one's ok" they find it safer and simpler to just say, "use nothing". The truth is that any properly designed AC regenerator that outputs pure, regulated, low impedance AC - and has enough power to not make things worse - will improve the sound of anything plugged into it. Dynamics are bettered, not lowered as some suggest from power filters. But there are models of AC regenerators out there that cannot deliver high power without making the wall power worse. So be careful. Here's the takeaways I would suggest are valuable for any Audiophile.
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