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To assess this mains noise further we visited our neighbor who is a trance and dance DJ with his own home recording studio. We plugged the Noise Analyser into his sockets. Not only to our but also his regret we got very high readings but no radio - and that even with wall sockets from his supposedly 'clean' groups for the studio. Later we would get more insight into various causes.

Still surprised we continued the plug’n’play session with our own audio setup. Here we have a PS Audio PPP regenerator. When we plugged the Noise Analyser into one of its outlets, we got a 000 reading. No noise or radio at all. This thing works great. That was interesting too as the PPP is not advertised as a power filter, just a regenerator. Somewhere along the line there must be a filtering stage. We suggest—but other opinions are welcome—that it has to do with the last stage. This is a stepup transformer since the PPP was initially built for the 110V US market but we needed 230V.

During our Blue Horizon experiments we had a visitor who brought along his new PS Audio P10 power regenerator. Curious as we are we of course treated the P10 to an analysis. Guess what? Noise and radio reception were our rewards. The P10 contains no line filtering. For many very enthusiastic owners of the P10—who even traded their PPP in for it—this lack of filtering apparently is no problem. Still curious we now cascaded the P10 behind the PPP from one of the PPP’s outlets. All remaining free outlets on the PPP continued to show 000 and were silent. All outlets on the P10 now showed readings around 280 and there was white noise though no radio.

In a follow-up email exchange with PS Audio’s Paul McGowan we tried to get these measurements explained. Apart from reassurances that the P10 does not filter in any way, the fact that all of a sudden there was high-frequency noise—that is noise above 60Hz—could not be explained. Somewhere the P10 must generate that noise (or act as its own antenna to receive it past its input which we knew to be perfectly clean). Here we have to emphasize that just like the PPP the P10 is not intended or advertised as a filter.

A major benefit of the P10 is its number of output sockets also in the EU version. In contrast the European version of the PPP is limited to 5 outlets, insufficient for our purposes. What to do? Add a power distributor. Cleaned-up power in, multiple clean power lines out. Logique, n’est pas?

Enter the Blue Horizon Noise Analyser. The output from the PPP was picture-perfect clean. So was the output from any socket on a Furutech passive TP60E power strip. We are supposed to know that dimmers and switching power supplies are evil AC power polluters. Here was a chance to catch them in flagrante. First we used a Hypex Ncore 1200-based power amplifier, a commercial evaluation unit with a switching PSU. Connected with a highly shielded Crystal Cable power cable, switched on the Ncore made the analyzer go to 038 whilst emitting a high-pitched sound. A spectrum analyzer on an iPad—we kept on analyzing—showed this frequency burst to sit around 7kHz. Swapping out the Ncore amp for a dimmer on a 300-watt halogen bulb, the reading went down to 003 without sound, proof that not all dimmers are noisy. This friendly dimmer was a transformer-based model that’s also mechanically quiet.

With just a PS Audio PWT CD transport on the power strip, the reading was 0000 without sound. The Devialet D-Premier with its switched PSU and loads of high-frequent parts inside caused a low 037 in standby mode without any sound from the analyzer. When we added the PWT the reading went down to 0000 and still no noise. Powering the D-Premier to active the reading went to 105 and noise, albeit of low output.