Puritan Audio PSM156 Review (AC Filter)

[MrPeabody]

This Puritan unit also has a DC blocker in it. The designer speaks of it in the linked video at the point linked below. You can see the heatsinked bridge rectifier and the bank of electros for that purpose.

A noisy transformer from DC offset in an otherwise excellent amp or preamp can be infuriating.

So it incorporates the useful capability of a $150 DC blocker.

 

[MrPeabody]

I think if they did not claim that it 'Enhances clarity and dynamics' then they would get a pass.

Yes, the problem isn't that it is worthless, but rather that the manufacturer claims in essence that it will make anyone's audio system sound better in magical and mysterious ways. Even for anyone who has no problems of any significant sort on the mains and no matter the quality of the power supplies built in to your audio gear.

 

[MrPeabody]

You are writing long posts with philosophical content, @MrPeabody . I would rather appreciate facts and test results.

@pma, you have been a major pain to me for a long while. You have dismissed my comments previously because in your opinion it is "philosophical" and not facts and test results. Instead of taking such cheap shots, why not explain why you disagree with what I wrote? The point I'm making now is that audiophiles give manufacturers a free pass by not insisting that manufacturers back up their claims with test results, that it is largely because of this that there is need for Amir to do most of what he does, and that when Amir does what he does, very many people pile on him in looking for ways to criticize his tests when what they really should be doing is insisting that the manufacturers back up their claims with published test results. If you do not agree with this, please explain why you do not agree with it. In any case, please cease and desist from making jackhole comments such as the one you have made here and now, where you criticize me for "long posts with philosophical content". I think that between this post of yours and the others you have directed at me in the past, you have given me more than ample reason to say are an extremely rude person, with no tact or manners. I wouldn't say something like this except in extreme cases where it is well deserved, and this is an extreme case where it is well deserved. You are routinely rude and dismissive of other people, telling other people that they are "ignorant" and so one, and the minute that anyone is even a little bit critical of something you've written, you take great insult. I recall that I looked back through some of posts a few months ago and one thing that was conspicuous, forming an obvious pattern, is that even in a given thread you would argue with one person by taking a particular position, then less than a day later you would take the exact opposite position in order to argue with someone else. I've observed you do this on multiple occasions. Have a nice day.

 

[Billy Budapest]

So, the bottom line is that the Puritan box indeed does what they say it does, but what it does doesn’t matter.

It does something, which is a plus when comparing it to other similar devices. But what it does has little to none relation to what they say it does.

Well, they say it filters the AC, which it does. However, filtering the AC does not result in any audible benefit. That’s what I was communicating.

 

[Billy Budapest]

So, the bottom line is that the Puritan box indeed does what they say it does, but what it does doesn’t matter.

Have you read what the manufacturer says the box does?

I’m not talking about the silly audio claims. I am talking about the AC filtering. It does filter the AC coming in from the line, but who cares? That’s my point.

 

[sarumbear]

Because inductors.

Why would a current affect induction?

 

[Murray A]

Lots of uninformed speculation and discusion regarding power quality issues and its mitigation.

Here is a power utility view of the issues!

https://www.hydroone.com/businessse...s - HONI CEATI Report Summary - Sept 2014.pdf

https://www.hydroone.com/businessse...for Customers and Utility Representatives.pdf

 

[Yevhen]

It doesn't really. I showed you the filtering when feeding it with my AP and capturing it with the same with very low currents involved. Passive circuits like that don't care about current as far as filtering. Current specifications are there with respect to voltage drops and safety which is independent of performance.

Here is some simulation for the most simple filter:

From the video I can see they have 3rd order filter. If I look at the guts of the 16A similar filter from Schaffner, I get following:

So supression is load-dependent, although a bit less than I expected.

 

[pma]

So supression is load-dependent,

It must be, however Q is most affected, as also shown in your simulation.

 

[Yevhen]

Why?

Because the circuit L_filter + R_load behaves as the voltage divider. With the high-ohmic load, the inductor of the filter rejects less high-freq content.

 

[amirm]

Here is some simulation for the most simple filter:

That is a different thing and not related to current. It is the load impedance combining with the filter to change its transfer function. If I hook up an amplifier to this AC filter and I drive it at 5 watts or 50 watts, its action would not change even though current is changing.

 

[pma]

Because the circuit L_filter + R_load behaves as the voltage divider. With the high-ohmic load, the inductor of the filter rejects less high-freq content.

10 ohm is unrealistic, it would make 23A at 230V.

 

[Yevhen]

It must be, however Q is most affected, as also shown in your simulation.

They also show these resonances in the datasheet:

Funny, but at some frequencies these filters actually boost amplitude of that crap from AC mains.
https://asset.conrad.com/media10/ad...-250-vac-3-a-l-x-b-48-mm-x-225-mm-1-stuks.pdf

 

[Yevhen]

That is a different thing and not related to current. It is the load impedance combining with the filter to change its transfer function. If I hook up an amplifier to this AC filter and I drive it at 5 watts or 50 watts, its action would not change even though current is changing.

Not sure, the amp should behave more or less as an active load (resistor) if the cos Phi of the power supply is close to 1

 

[amirm]

It's not immediately clear if Amir's insertion loss measurement used the industry standard input and output termination impedance of 50Ohms? If not, it is not really useful.

It is almost that. The differential probe I use has 50 ohm input impedance (output of it is high impedance so don't get confused by that). The input to the AC filter is 40 ohm because that is the closest impedance AP has for balanced mode. For the purposes of what we are doing, this is more than good enough. Indeed you can see its correctness when I use it in situ.

 

[amirm]

Funny, but at some frequencies these filters actually boost amplitude of that crap from AC mains.

That's why I called the peaks a resonance. Go high enough in frequency and you get that. A bit of poison is provided with that medicine.

 

[sarumbear]

Because the circuit L_filter + R_load behaves as the voltage divider. With the high-ohmic load, the inductor of the filter rejects less high-freq content.

Why the resistance will change with load. You have not answered that.

 

[ShinMolina]

I don't agree at all. I think that people who challenge Amir's findings should stop nitpicking and do tests of their own. If you think that there is a different type of noise+distortion that will affect typical audio equipment and that a power conditioner such as this one will have the superior ability to cope with that type of noise+distortion, then it seems to me that the onus is on you to (1.) identify exactly what that type of noise+distortion is, then (2.) demonstrate via testing that typical audio gear really is unable to cope with that type of noise+distortion, then (3.) demonstrate that when a power conditioner such as this one is used, the problematic noise+distortion is eliminated such that it no longer presents a problem with which the typical audio gear can't cope.

The thing is, when it is thought appropriate for complaints of this sort to be registered at all, i.e., "you didn't test with the right kind of noise and distortion", it can go on forever, with no end in sight. Surely this is apparent to everyone, and as such, everyone ought to understand that if they want to assert that the test wasn't done with the right kind of noise and distortion, that they need to do what I explained in the previous paragraph.

I see that you have come here like a storm! Just joking.

First of all, I don't challenge Amirm's measurements. I find them quite valuable and have motivated me to star doing my own measurements. I consider myself a "deaf" person, in the sense that I unable to hear some things that people could consider obvious (compressed/uncompressed, tube warmth, digital filters...).

I also don't consider that Amirm is measuring the wrong parameters or that his measurements point us to a wrong direction. I believe that these kind of measurements help people understand that not all claims by the manufacturer should be true by default. By no means I am someone who would consider buying something like this, my most precious and most expensive device I have is a SMSL DA-9 I bought a month ago (250$). I can't think about buying something like this because of money reasons, and even if I could I wouldn't.

And about the noise I have between my AC line and interconnects, I have also measured it with an oscilloscope and the noise is there. It comes from the elevator of my building, when it is moving the noise appears. I can assure you the I have minimal 50 Hz noise in my setup as I always try to use balanced cables and avoid ground loops. I started noticing the 8 kHz tone while using some "audiophile grade" RCA cables that were unshielded, even with Mogami RCA cables the noise appears although much lower.

What I was selfishly thinking was for a setup to introduce these kind of noises into a test setup. Everyone can dream, I just brought possible scenarios to the table. By no means I want Amirm to change his measuring system, I have learned a lot from his findings and the comments of many people around this forum.

 

[Yevhen]

That is a different thing and not related to current. It is the load impedance combining with the filter to change its transfer function. If I hook up an amplifier to this AC filter and I drive it at 5 watts or 50 watts, its action would not change even though current is changing.

Sorry, maybe I'm trying to go too much into details. Still, I fully agree with you, these filters are only useful against some particular pollution sources and, probably, in 99.9% of the cases just doing nothing.

On top of it, you can get a 10$ industrial AC mains filter with the same performance.

In my case with the noisy LAN via AC mains adaptor leaking into my power amp, I could solve the issue by simply switching to another socket (feeding the amp from the socket on another wall)

 

[amirm]

I am thinking of creating an FAQ for future reviews:

1. If you have real, audible noise, pops and glitches caused by other AC devices, these filters *may* help you (there is huge variation here between them and I am not testing them for this purpose).

2. If you are not experiencing such interferences, then my measurements are completely applicable and show that these filters do not improve your audio performance.