Power Plant and Noise

I’m curious about the noise my P12 injects into the line.

The following are typical measurements as taken with an Alpha Labs Line EMI Meter:

Wall 350 mV at 121 AC Volts
P12 1900 mV 118 AC Volts
Topaz Iso-Tran (after P12) 90 mV 121 AC Volts

Measurements from P12 front panel:

AC Volts In 125
AC Volts Out 120

THD In 1.9%
THD Out 0.1

So, there are contradictions in readings between Alpha Meter and P12. I do have another meter made by Entech which seems to correlate with the Alpha Meter.

This brings up questions for me:

Should we assume the P12 measurements are more accurate because of the cost difference to that of the Alpha meter?

If we are to assume the P12 is correcting Voltage (as its’ meter reads), is that Voltage correction deemed more important to audio than the line noise the P12 injects into the line?

My current set up uses the Topaz Iso Transformer (which runs downstream of the P12) to clean up High Frequency common mode noise and it clearly cleans up the wide band noise created by the P12.

All this being said, I’ve been evaluating the the sound between my amp coming straight from a dedicated wall line or from the P12 and I think I may prefer sq coming from the P12 (though it’s close.)

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Anyone have any thoughts about the line noise the power plant is injecting into the line?

I do think my system sounds better with the P12 and I am mitigating the noise by running all sources (Dac, Server, Switch) after the Iso Transformer. The amp is the only thing direct from the P12 (because it makes the Transformer hum).

Will also be curious to check system without the transformer in the mix.

Have you tried it without the ISO transformer? PS Audio recommends that you not use any other type of power filter.

Otherwise I would call or email tech support and get them to help you.

I do plan to take a listen without the Topaz ISO and see what my ears tell me.

I guess the concern with an iso trans in line is greater impedance and so loss of dynamics. But, I’m not putting a large load on the Topaz (only sources) and am running the amp straight from P12. My speakers are 107 db sensitive and I’m hearing plenty of dynamics from a 8 watt per channel SET tube amp.

So I wonder if this setup might be a good synergy: For Sources, use the Topaz to very effectively clean up AC noise generated by the P12. And use the P12 for voltage regulation in front of everything: 1. the sources after the Topaz and 2. the Amp directly after the P12.

Would love to hear comments from people who know a lot more about this stuff than me and maybe from someone at PSA?


Have you sent an email to tech support? I have a hard time believing a P12 generates that much noise. You are the first person I have seen post anything about it.

Because you have such sensitive speakers you are going to have noise issues with anything but the most quiet equipment.

I’m guessing most Power Plant owners haven’t measured the noise coming out of their units. But I am curious what PSA thinks about it. They probably view the noise as an inevitable result of a Regenerator and that the positives of Voltage and Sine Wave correction are more important.

But I’m curious if a hybrid use of a Regen and Topaz iso for Sources and a Regen alone for the Amp might make sense as I’ve described in my current set up.

When I have some time I’ll take a listen and report back.

Can this noise be observed on the amps outputs? I think most designs will reject anything over 100kHz, EMI is way above that range? Most mains transformers will naturally filter out HF nose as well, unless specifically designed to pass through such frequencies.
If to take voltage regulators analogy, they all inject noise into the output, hence the filtering after them to reduce noise, which is often in the range of MHz… It is usually not an issue unless that noise causes instability in the circuit.

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Nordic, I don’t have any way to measure noise on the amp outputs. The Alpha meter and Entech meter only connect through outlets. So I don’t know if my amp filters this noise coming out of the PP.

Are you saying the transformers in my amp should be expected to filter this noise? If that’s the case, why wouldn’t the transformers in the P12 filter it (rather than increase it)?

I know Shunyata makes a pretty big deal about how their conditioners reduce line noise as measured by the Entech. They believe the Entech is a better measuring device (better than the Alpha Lab) for meaningful audio noise as it measures a narrower band more significant to sound quality.(300 to 700khz). Their marketing tells us the elimination of this line noise to be essential.

And PSA marketing states the PowerPlants “eliminate noise.” What kind of noise or any other details aren’t mentioned as far as I can tell. I do know the noise coming out of the PP is far higher than that coming out of the wall. Interestingly, the Entech picks up an AM radio station from the wall, but not after the PP, even though noise measurement is higher.

So, for someone like me, with a Neanderthal knowledge of electricity, this is little mystifying.

I afraid I don’t have knowledge of how power plants work exactly, I did some basic modifications to the P3 as it didn’t sound to my expectations out of the box, it sounded different, but no better or worse than feeding devices directly out of the wall. However it did have this consistent flavour throughout evenings, while mains one evening would sound ok and other day quite awful or, sometimes, very good. To dig further the amp/sink assembly would need to be removed, perhaps another day.

In my head Pxx series are differential amplifiers. They have a precise signal generator that is synced and compared to the incoming mains signal and the difference is added or subtracted via the power amp, all these heatsinks are just for that. It all means power plants are active filters, that attenuate the signal and the ways they do it can be many. This is, perhaps, what can be characterized as noise, but it is a useful one. Multiwave is another feature, and unless measured it is hard to see what it generates, but it is considered a “good” noise, because it adds more energy to a certain range in sound spectrum, this way giving users a basic EQ option. The frequency response of the powerplant amp is not advertised, so we don’t know how much of noise range it can work against. There is also some passive filtering in the mains socket of the powerplant. I may be very wrong here, also they are expensive devices that most won’t touch. The price tag is kinda protecting them from anyone tinkering.

Sound is very hard to predict, calculate. It is very trial and error. If one was to build a perfect amplifier with perfect elements, it would most likely sound horrendous!

Well, I finally disconnected the Topaz Iso trans and put the sources and amp direct into the P12. I can’t detect any increase in noise. It may sound better, so no problem here.

I’m am still curious to hear from PSA what accounts for the measured increase in Rf/Emi noise on the line.

Have you emailed support directly to get answer?

Just did! Will post here when I hear back

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You may never get an answer. Any equipment that has inconsistent power consumption will result in noise in the line. Light dimmers, amplifiers, irons, led mains bulbs etc. It’s normal and manufacturers do not measure this, because grid and home setup differs from place to place. For example if you were to run a heavier gauge from the distribution box to P12, peak to peak noise in that line would change and may be smaller.
And even if you get an answer, what will you do with it?

They did get back to me and they’d like to replace the oscillator card in my P12 to see what happens.

I have to say, I’m pretty impressed that they want to do this. I think it shows they are always looking to improve their products.

I’ll report back on how it goes.


Please do so. I’m very interest in the results.

They replaced the oscillator card, but the P12 still doubles the noise coming out of the wall. But I think this is expected. The power plant is an amp and amps produce noise.

Has anyone tried connecting a balanced AC toroidal transformer (Equi=tech, PLiXiR, Torus, etc.) - between the output duplex of a PowerPlant and a source component as a power conditioner?

My two P20s “regenerate” wall duplex AC into low-distortion, low output-impedance AC to feed my system, but it’s evident from this thread that they generate idiosyncratic noise, and they’re sensitive to the quality of the input AC (as well as the characteristics of the input AC cable). So why not use a balanced toroidal conditioner to further filter out the residual DC and noise?

Did this for many years with my P10 (front end components) — I thought the improvement I got from this arrangement was worth it.

With the newer vintage PPs, I do not do this. I now use the balanced transformers on my monoblocks — does wonders on those, and I have dedicated 20A service to the audio system!

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Thank you for your reply! May I ask, did you encounter any issues plugging your balanced isolation toroidal transformers into your P10 - for example, inrush current (upon powering on) overloading and tripping the P10’s circuit breakers, or excessive inefficiencies through heat and power loss? What is the power rating of your isolation toroidal transformers, and are they the specially-wound “balanced” type?

The BITs are old Exact Power 1800w units that i stripped to its bare essentials (just the transformer please!). I plugged them into the high power outlets on the P10, which limited inrush. Off the P10, I used one for digital stuff and one for analog stuff.

Since I used the BITs well below capability (front end components only), I generally had no problem with heat or power loss. Using the BITs with power amps generates a barely audible buzz, however.