THD IN value

Good morning,
I have a P20 and I noticed that the THD IN value changes when I switch on some components in my system, for istance the amplifier.
With all my components off, the THD IN is 1,1% and THD OUT is 0,1%
When I switch on the Diablo 300 integrated amplifier, the THD IN raises at 1,3% and THD OUT remains at 0,1%
Is it OK? I wonder why the components attached to the P20 affect the THD IN?

Hi @luigi61
To me the outgoing THD is what counts. Even 1.3 incoming THD is average for most of us. My explanation for the change is that the Diablo is loading the mains circuit feeding your P20. A dedicated circuit may reduce that effect but you’re still fine as is.

I’m with Serhan on this one. 1.1-1.3% in is darn good compared to my 5.5-6% in. The fact that you’re out is consistently .1%, you have nothing to worry about.


Just to confirm this is normal behaviour also on my P10.

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Thank you for your answer. I know that my values are perfect, this is not an issue.
I was curious to understand why the THD IN increases when I switch on the Diablo 300?
I understand that the load on the main line can affect this parameter.

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@Maniac Totally normal.

@luigi61 Still keep in mind it’s still a circuit with the amp plugged into the P20. As the demand on a circuit goes up, we tend to see an increase in incoming THD. Because your incoming is already so low, I’m guessing it is dedicated for your audio gear specifically.

This is really easy to test. Plug in something like a space heater to the same circuit that a PowerPlant is plugged into. You’ll notice the incoming THD go up a pretty fair amount. One of a couple reasons why dedicated circuits are so great for audio.

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Yes, I confirm that I have a dedicated line from my electrical panel to my hi-fi system