Power cords obey Ohm’s Law. Voltage drops across them can cause a very measurable loss of power in an amplifier. In that manner it can affect distortion and output impedance too.
The voltage drop is easy to measure with a regular digital voltmeter. So this isn’t anything mysterious.
A good power conditioner is helpful too. A glorified power strip that gets called a ’power conditioner’ is not. The latter forces all the equipment to obtain its power through the same power cord, FWIW.
A proper power conditioner will not limit current, it will be able to guarantee the AC sine wave distortion (you’ll see that in its specs) and should be able to regulate the AC line voltage. One of the more pesky AC line aberrations is the 5th harmonic, which can cause power transformers to become noisy, power rectifiers to become noisy and can affect synchronous motors found in turntables and tape machines.
There are very few power conditioners offered to high end audio that can do everything I’ve mentioned here.
That means that most people on this thread, in particular those that think power conditioners don’t make a difference, simply haven’t heard what a proper conditioner can actually do. Its not as if they are wrong; most of what they have heard simply doesn't work!
That is why there is controversy on this topic.
I know of only two power conditioners that seem to work. One is made by PSAudio. The other was made by a company called Elgar, who got out of the power conditioning market a long time ago, so if you find one of their conditioners (they show up on ebay) its likely it will have to be refurbished.
A proper power conditioner has to have active components- if passive (for example a choke or transformer is all that’s involved) it won’t work. To give you an idea of why, let’s take the Elgar as an example. It has a low distortion 60Hz oscillator that is synchronized to the incoming AC power. The AC power goes through an isolation transformer that also has windings to run the conditioner’s internal power supplies. Feedback is taken from the output and compared to the low distortion oscillator; this correction voltage is applied to the isolation transformer as correction (through a power amplifier built in); in addition it also is used to buck the output voltage so that voltage is thus regulated without current limiting.
That’s a bit of sophistication! If you don’t have that in your power conditioner, it can’t filter out the 5th harmonic, it won’t be able to correct line voltage, it won’t be able to provide a clean AC waveform to your stereo. Put another way, +90% of all ’high end audio’ ’conditioners’ are so much junk.
If y’all want to argue about this topic, at least have the facts available!
