Review PS Audio PowerPlant 12 – Clean Machine

Measurements and conclusion

We measured the PS Audio PP12 particularly extensively. This is to get a complete picture of what the PS Audio PowerPlant is good at and not so good at. In the video you can get an idea of the setup we used. Later we made some additional measurements on the mains side and on ‘cross contamination’ with the PicoScope and the Tekbox LISN.

Common Mode and Differential Mode

We did quite a few measurements to gain insight into the noise characteristics of the PowerPlant 12. We initially tried to do these measurements with a differential probe. However, it gave too much distortion. So we took the 230 – 10V transformer and did the output in the splitter for common mode and differential mode noise. We do not know exactly the bandwidth of this transformer, but from the measurements it is enough to get an idea. The Splitter works from 30 KHz to 300 MHz.

As can be seen, the mains are not very disturbed and adding a dirty switchmode power supply does not add a huge amount of noise. If we look at the PowerPlant 12, we see that the noise image is slightly quieter, but differential mode does seem a bit higher. However, the average image is thus somewhat quieter.

However, what is noticeable is that if we add a switchmode power supply, the noise increases quite a bit. So there is substantial cross contamination after all. We honestly didn’t expect that. By the way, the same goes for noise to the mains: it too rises when we add a switchmode power supply. Apparently there is no filtering.

Low-frequency noise and distortion tests

If we are going to look at low frequency on the Prism dScope III, the story is a little different. Yes: sometimes the noise floor is slightly higher, but the harmonic distortion – which we do have the ability to measure with the Prism – is significantly lower.

For example, look at the THD N of our GW Instek AC generator. It’s at 0.3%. If we connect the PowerPlant 12 to it and then measure the PP12, we see 0.14%. The sine wave coming out of the PP12 is just cleaner. By the way, with multiwave, the distortion does increase significantly.

However, if you look at the “AC Generator – PS Audio PP12” picture, you will see that the noise floor of the PP12 is higher compared to the AC Generator. However, the distortion is lower and so is the overall THD+N. This is due to the much lower harmonic distortion of the PP12. The same thing happens with the LISN. If we connect the PP12 to it, the distortion drops from 3.4% to 0.88%.

So it’s not like the PS Audio PowerPlant 12 knows how to lower distortion of every input to a fixed value. It still depends in part on how clean the input is. But a factor of four lower distortion is neat.

This low distortion also seems to carry over into the test with the Bryston amplifier. The SINAD value improves when we use the PP12. It is subtle, but consistent and reproducible.