Audioquest PowerQuest 707 – 505 and 303

Measurements and conclusion

We measured the Audioquest PowerQuest 707 in our lab. We did those measurements directly in the wall and with the help of a programmable AC generator. And we used a LISN to see what goes back to the mains. Last but not least, we measurement at the output of the Bryston PowerPAC 300 amplifier. It turned out to be an interesting session with a somewhat unexpected outcome!

Filter test – in the wall

The test “in the wall” shows a similar outcome as with the generator. But here we can test well with and without an interference source. The PowerQuest shows that it really does push noise away after all. Is all the noise gone? No. But we now know that almost no filter does that. But the fact is: noise is reduced.

It is striking that the Low Current output seems to have higher noise than no filter. However, we see that the interference of the dirty amplifier between 1000 and 5000 Hz is much more suppressed than no filter. Above that we see it rear its head again.

The High Current output handles this a lot better. Overall it is really quieter than the Low Current. In the listening test this was also audible.

Filter test – at the generator

The generator was not so happy with the “battery” in the 707. We were getting some warnings and beeps. And the fan immediately went to fighter jet mode. Anyway: it kept working, so we quickly took measurements.

We see that High Current filters more than Low Current. Weird: we expected it the other way around. Low Current also has a “bulge” that we’ve seen before with the previous measurement. We can’t explain that.

The PowerQuests have no DC blocking circuit we see. The injected white noise is attenuated, but not completely eliminated. We see that the 707 does indeed filter very effectively from 30 KHz onward. There everything falls down quickly.

Filter test – amplifier output

Here we see the slight but constant impact on the speaker output. It is subtle, but constant. We can also see here that the Low Current filters differently than the High Current. Around 1500 Hz, the Low Current pushes out more noise than the High Current. But overall, the High Current is a bit more constant, we estimate.

Noise on the mains side

We see a clear shift in noise between the standard unfiltered socket and the PowerQuest 707. With the 707, overall the noise drops and we see less impact from the dirty switching amplifier. It’s not gone – nor can it be: a filter shifts noise – but it’s definitely less.