Puritan Audio PSM156 Review (AC Filter)

[amirm]

you can't translate FFT windows directly into actual noise, I don't know which FFT length you're using or how many averages are you taking.

What? You are comparing two measurements: before and after. It doesn't matter what the absolute value is. We are looking at the improvement from this device. All those variables factor out.

 

[amirm]

You mean the frequency and RMS level? I'm sorry but that doesn't tell me anything about the AC filter.

No, the bloody FFT as I showed you. Why is this so hard to understand?

This review is very shaky, I understand the convenience of using something on your bench already but i really don't think you did this device justice.

The only thing shaky is your arguments. People said in the last power filter review that tube amps with AC filaments could benefit. Well, this one is supposed to use that as well. Now you are complaining about this as well? It is not like I have 50 broken audio devices to pick from.

Go back to the understanding that all of these audio devices filter AC to DC. This is why they don't care about the AC box is doing. I do the measurements so people don't make up this and that scenario. But they don't matter at the end as we can plainly see in the first dashboard why such a device can't make a difference even if you didn't understand how DC is created in an audio device.

 

[amirm]

Good point !
BUT why is the company exhibiting on Hifi shows ?

For the same reason they talk about audio improvement in their spec sheet. They are opportunistic realizing consumer audio market's money is as good as any other.

 

[Toku]

I want to say
I'm very embarrassed that ASR makes completely wrong measurements for such products every time.
To evaluate such a product, create a situation that actually causes disturbance such as noise and affects the audio equipment, and measure how the target product is attached and how it works at that time. If you don't, it doesn't mean anything.
It is natural that measuring it in a normal state without any obstacles has no effect. "No effect" is the correct answer. If there is any change in the audio signal, it means a defective product.
Such products are similar to car seat belts and lightning arresters, and only show their effects in the event of an accident. It usually looks like a useless and disturbing entity.
Do not measure such products in the same way as audio equipment. Evaluation of these products requires a completely different and advanced measurement environment.

 

[Offler]

I purchased quite common surge protector. It has coils with ferrite cores, condensators which do similar kind of filtering, and varistors for the actual surge protection. There is also a claim it filters AC mains noise, but there is another claim they made.

Suppose a device you use dies, and it does it in "fancy" way with fireworks. One of my PC PSUs literally melted and all capacitors inside exploded...

Manufacturer of the surge protection made a claim that surge protector does not protect just from surges and noise from AC mains, but also in case of such catastrophic failure of a device connected to the powerstrip and from noise which might be generated from such device.

Well... since most devices have a ferrite core as a first component in their power supply, is such filter even justifiable in case you suspect your amp, PC or literally anything may generate audible noise and send it out through powercord and powerstrip to other devices?

 

[Count De Money]

Charlatan Audio


i was gifted a $15,000 isotek power mains conditioner

opened it up and it had $300 worth of parts from mouser

its only value to me were the neutrik power con connectors I could salvage for a future project

 

[Patrick1958]

That's expensive gear for a basic netfilter.
The Dynavox HiFi-netfilter X7000B does the same for 184 Euro

 

[ShinMolina]

I want to say
I'm very embarrassed that ASR makes completely wrong measurements for such products every time.
To evaluate such a product, create a situation that actually causes disturbance such as noise and affects the audio equipment, and measure how the target product is attached and how it works at that time. If you don't, it doesn't mean anything.
It is natural that measuring it in a normal state without any obstacles has no effect. "No effect" is the correct answer. If there is any change in the audio signal, it means a defective product.
Such products are similar to car seat belts and lightning arresters, and only show their effects in the event of an accident. It usually looks like a useless and disturbing entity.
Do not measure such products in the same way as audio equipment. Evaluation of these products requires a completely different and advanced measurement environment.

Completely agree, measurements featuring multiple types of interferences and such could be interesting.

Many people living in apartments face elevator noise issues as I do while other may encounter air conditioner noise and many other existing sources of RFI/EMI.

I understand that this measurements are mostly focused on checking the claims of the manufacturer. Nothing wrong with it, my main complaint is directed towards the marketing of these kind of devices, but the measurements could also be focused on noise mitigation as previous one have been.

 

[Mart68]

Completely agree, measurements featuring multiple types of interferences and such could be interesting.

Many people living in apartments face elevator noise issues as I do while other may encounter air conditioner noise and many other existing sources of RFI/EMI.

.

And Amir's home has none of these things? That seems unlikely.

 

[ShinMolina]

And Amir's home has none of these things? That seems unlikely.

I believe he has the equipment to induce such interferences. He even did include some artificial dimmer AC signals in a previous measurement.

He could even attach an used washer machine motor without filtering as a cheap way of inducing noise through the AC lines. No need for the home to be "noisy".

 

[Mart68]

I believe he has the equipment to induce such interferences. He even did include some artificial dimmer AC signals in a previous measurement.

He could even attach an used washer machine motor without filtering as a cheap way of inducing noise through the AC lines. No need for the home to be "noisy".

My point is he has a normal house with all the normal things that generate EMF and RFI in it, just like the rest of us. So doesn't this test represents a 'typical use' situation already?

 

[Vini darko]

I'd be intrested to see what effects its output impedance has on power amp output power. Thanks for the review Amir.

 

[AudioSceptic]

My mains are not clean. There is a ton of harmonic distortion in it as I showed in the review. The reason these devices don't do anything is because your audio gear consumes DC, not AC. The process of conversion from AC to DC already does this filtering and then some.

This device doesn't correct for voltage sag but even if it did, again, your audio device doesn't care. It is designed to work with wide variation in voltage.

Although the tech is very different, these mains filters are just the equivalent of all the useless USB and ethernet filter/regen devices, aren't they: products claiming to fix a problem that doesn't exist?

 

[pma]

My point is he has a normal house with all the normal things that generate EMF and RFI in it, just like the rest of us. So doesn't this test represents a 'typical use' situation already?

No. Typical use is that you connect more components to the filter outlets and you interconnect them with signal cables. So you get loops when especially SE cables are sensitive to shield currents and add the voltage drop into the signal. Depending on EMI emitted by the components to the power net the filter may reduce the shield circulating currents and thus improve S/N. This is the goal with AC filter. Not to measure single component in a clinical laboratory AP setup with balanced l/0, possibly with floating outputs.

 

[ShinMolina]

My point is he has a normal house with all the normal things that generate EMF and RFI in it, just like the rest of us. So doesn't this test represents a 'typical use' situation already?

He doesn't have inverter noise or motor noise for example which is very common in city apartments for example. Many people over this forum, Reddit and such show problems with GPU noises from their computers also.

There are multiple examples of noise that are not shown in these kind of measurements and are not probably present on his house by "default".

 

[AudioSceptic]

So, as opposed to other filters which do f*** all and do it badly, this does f*** all and does it well.

Ever since seeing 'Hatton Garden' (UK TV drama), I can't read "f*** all" without hearing Timothy Spall say it. ;-)

 

[Harmonie]

I want to say
I'm very embarrassed that ASR makes completely wrong measurements for such products every time.
To evaluate such a product, create a situation that actually causes disturbance such as noise and affects the audio equipment, and measure how the target product is attached and how it works at that time. If you don't, it doesn't mean anything.
It is natural that measuring it in a normal state without any obstacles has no effect. "No effect" is the correct answer. If there is any change in the audio signal, it means a defective product.
Such products are similar to car seat belts and lightning arresters, and only show their effects in the event of an accident. It usually looks like a useless and disturbing entity.
Do not measure such products in the same way as audio equipment. Evaluation of these products requires a completely different and advanced measurement environment.

No. Typical use is that you connect more components to the filter outlets and you interconnect them with signal cables. So you get loops when especially SE cables are sensitive to shield currents and add the voltage drop into the signal. Depending on EMI emitted by the components to the power net the filter may reduce the shield circulating currents and thus improve S/N. This is the goal with AC filter. Not to measure single component in a clinical laboratory AP setup with balanced l/0, possibly with floating outputs.

To both of you: your remarks are thoughtful and make a point.
Just how do you measure it "correctly" and does it "improve" the audio ?
Also:
Why don't the AC filter "box" manufacturers measure it objectively rather than claiming subjective audio heaven ?

Wouldn't the best solution to get cleaner AC from the start using shielded mains from the electrical board and wire the gear with correct phase?

 

[wwenze]

We need to find a bad situation which gets fixed by these products then.

I use a line filter to block the AC fan noise from reaching my mains so my powerline network can get faster speeds. What next?

Going back to the seatbelt analogy, we know how to recreate situations where the seatbelt is useful. Thus we know how to test the usefulness of the seatbelts. What about power conditioners? Surely there has to be some if there is so much support.

 

[CedarX]

I think Amir’s review is absolutely fair in regards to what the manufacturer claims about the product benefits… The thing is not completely useless—Amir is clear about that—but it is solution in search of a problem. It may solve some specific problems very well, but it does not appear those are of the audio type, and it seems not capable of improving the audio rendition chain…
Is there common-enough real life scenario causing an identifiable audio problem that this thing would solve? Even then, is it the best/cheapest solution vs. removing/changing one element in your problematic scenario?

 

[sarumbear]

Could it be that your mains are rather clean and have no effect on the AC filter as measured? Is there a way to distort the mains by adding voltage sag, over-voltage, ... etc and other forms of distortion?

Haven’t you read the review where @amirm displays the dirty mains?